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ECPD 2023 Timetable

ECPD 2023 Program

Poster Presentation

CA21128 PROBONO Meeting Program




09:00 - 10:55
Session 1 learn more
Chair: Tsuyoshi Akiyama - Vice Chair: Ioannis Fitilis
Diagnostics For Fusion Reactors
Presenter: Rejean Boivin (General Atomics)
Authors: Rejean Boivin
Abstract: With ITER’s design and construction entering final stages, and with a renewed effort in designing and constructing the next step fusion devices, a new emphasis on the role of diagnostics is emerging. The next steps, being demonstration fusion reactors or full-scale power plants, will require a dedicated set of diagnostics and monitors serving primarily in control loops. This stands in contrast to the current role as both control and physics measurements in present-day devices. Design of these diagnostic systems will encounter many challenges, such as radiation effects (prompt and accumulated), surface degradation (deposition and erosion), reduced access and maintenance, very high required reliability, availability and inspectability, as well as long pulse operation. In addition, they will experience complications due to relativistic effects and lack of neutral beam-based measurements. Many of these challenges have been addressed for ITER and will be experienced during its operation, which will provide valuable knowledge for overcoming these issues. In some cases, however, the conditions expected in a reactor will require further developments beyond those achieved for ITER. New approaches such as RF/microwave-based techniques and the use of proxy measurements are showing excellent promise in fulfilling the needs of a reactor. A review of these needs, the impacts of the expected harsh conditions, and prospects for new approaches will be discussed and illustrated.
Multispectral Advanced Narrowband Tokamak Imaging Systems (MANTIS)
Presenter: Artur Perek (Ecole Polytechnique Fédérale de Lausanne)
Authors: Ivo Classen, Artur Perek, Bryan Linehan, Tijs Wijkamp, Curdin Wuethrich, Emanuel Huett, Yanis Andrebe, Jean-Daniel Landis, Marco de Baar, Basil Duval
Abstract: Quantitative imaging is rapidly gaining interest within the tokamak community. Multispectral imaging systems such as MANTIS can simultaneously provide integrated emission line intensity along half a million chords through the plasma for up to ten narrow spectral bands. This wealth of information allows for simultaneous hydrogen and helium spectro- scopic analyses providing an unprecedented level of insight into the edge tokamak plasmas. This work presents the working principles of the MANTIS system, together with the requirements for the narrowband interference filters that enable the system to maintain image quality in all ten cameras. The optimized filters facilitated the design of a compact iteration of the system allowing for the installation of two more six-camera systems for a more complete coverage of the poloidal cross-section in TCV. The stereoscopic tomographic inversion process is shown, highlighting the utility of multiple MANTIS systems in combating the inversion artefacts. The 2D emissivity maps are presented with their use cases; first, as the emission profiles localizing the emission-weighted spectroscopic analysis; second, for the atomic density inference in the SOL utilizing the Thomson Scattering. Then, the 2D maps of plasma parameters inferred using collisional-radiative models are shown. Finally, diverging from plasma edge application, the system’s utility in the runaway electron synchrotron emission imaging is presented.
Visible imaging diagnostics for high-performance plasmas on the HL-2M tokamak
Presenter: Liang Liu (Southwestern Institute of Physics)
Authors: Liang Liu, Deliang Yu, Fan Xia, Shiqin Wang, Wenjin Chen, Xiaoxue He, Yanling Wei, Zhongbing Shi
Abstract: The main missions of HL-2M are to support the operation of International Thermonuclear Experimental Reactor (ITER) and the design of future fusion devices in integrating both the technological and physics aspects. HL-2M features ultrahigh vacuum, large current, strong magnetic field, and intense radiation. Therefore, design of the imaging systems should be ingenious enough to make them run normally on the HL-2M. Three visible imaging diagnostics, including a tangential view, an extreme wide-angle view and a downward-looking diagnostic, are installed on the HL-2M tokamak for the high-performance plasmas. The entire field of view (FOV) covers up to 80% of the vacuum vessel. They aim at meeting the requirements of safe machine operation, plasma position control, MHD instabilities study, etc. The field of the extreme wide-angle view reaches 112°, which is the widest for regular operation among large tokamaks. Without showing the distortion of conventional wide angle lenses, it opens up new opportunities for the high-temperature plasma studies, as shown in Fig. 1(a). The multifaceted asymmetric radiation from the edge (MARFE) phenomenon is specially observed by the extreme wide-angle view, as shown by the bright radiation around the central column in Shot 1525 in Fig. 1(b). It is a nearly toroidally symmetric and poloidally asymmetric band at high field side near the plasma boundary, which starts to grow up (in this case of Shot 1525, beginning at about 1000 ms) as the electron density exceeds a high value. Two types of motion behaviors have been observed: (a) remaining fixed in poloidal position and (b) moving downwards poloidally just before the plasma disruption.
Development of the electron cyclotron emission diagnostics on EXL-50 spherical torus
Presenter: Yumin Wang (Hebei Key Laboratory of Compact Fusion, ENN Science and Technology Development Co., Ltd.)
Authors: Yumin Wang, Weiqiang Tan, Minsheng Liu, Qifeng Xie, Renyi Tao, Xiaokun Bo, Xiuchun Lun, Hui Zhang, Lin Chen, Xiaomin Tian
Abstract: The electron cyclotron emission diagnostic (ECE) system has been developed on ENN Spherical Torus (EXL-50). EXL-50 is a solenoid-free spherical tours with the major and minor radius at 0.58 and 0.39m, and the ECRH at 28 GHz is used to drive plasma current [1]. The ECE system aims to detect radiation from energetic electrons in the frequency range between 4 to 40 GHz. The system is composed of five subsystems with different frequency bands, i.e., C-band (4-8 GHz), X-band (8-12 GHz), Ku-band (12-18 GHz), K-band (18-26.5 GHz) and Kα-band (26.4-40 GHz), and it uses heterodyne detection. K-band and Kα-band subsystems are located horizontally in the EXL-50 equatorial plane while C-band, X-band and Ku-band subsystems are vertically located under EXL-50 tours. A local oscillator (LO) at 28 GHz is used to lower the frequency of the detected microwaves for K- and Kα-band subsystems. The quasi-optical system has been developed to direct the microwaves from plasma to the antennas for horizontal detection subsystems, and the beam width at the magnetic axis during the whole K- and Kα-band is less than 20 cm. The antennas for vertical detection are attached directly to the port beneath the torus at R=700mm, i.e., the magnetic axis of the torus. The system integration, bench test and the initial experimental results will be given in detail. Reference: [1] Shi, Y., et al. (2022). Nuclear Fusion 62(8): 086047.
11:30 - 13:40
Session 2 learn more
Chair: Rejean L. Boivin - Vice Chair: Artur Perek
Laboratory Atmosphere Model of the Hottest White Dwarf H1504+65
Presenter: Dieter H.H. Hoffmann (Xi'An Jiaotong University)
Authors: Dieter H.H. Hoffmann
Abstract: H1504+65, a bare stellar nucleus, is an unusual white dwarf with a Carbon- and Oxygen-dominated atmosphere. The composition cannot be explained by current stellar evolution models. The analysis of the elemental abundance and the improvement of stellar atmospheric models depends heavily on spectral measurements and accurate spectral data. We used soft x-ray emission from a laser heated hohlraum to irradiate a foam target and obtained a Carbon-Oxygen plasma emission spectrum with temperature T=195 000K±10 000K and mass fraction ratio C/O=0.85, similar to that of H1504+65. We performed a detailed comparison of our spectra with the H1504+65 Chandra spectrum, and do observe the same O VI emission lines.
Angular-resolved Thomson Parabola Spectrometer for Laser-Plasma Ion Accelerators
Presenter: Carlos Salgado (CLPU)
Authors: Carlos Salgado, Jon Imanol Apiñaniz, Alessandro Curcio, Diego de Luis, José Luis Henares, José Antonio Pérez-Hernández, Luca Volpe, Giancarlo Gatti
Abstract: Since the experimental demonstration of laser-plasma based ion acceleration [1,2], several diagnostics have been applied to measure simultaneously both angular and spectral properties of the beams and their correlation. Thomson parabolas (TP) spectrometers, radiochromic film stacks and nuclear track detector are commonly used, but somehow all are limited in angular or spectral resolution and/or in ion specie discrimination [3]. We report on the design and construction of a high-repetition rate compatible, angle-resolved TP spectrometer for laser-accelerated mutli-MeV ion beams, fully developed at CLPU [4]. Thanks to an entrance array of pinholes, which chops the ion beam into beamlets with different emission angles and an analysis procedure capable of accounting for crossing particle traces, this detector combines the spectral and ion charge-to-mass ratio resolution for each beamlet detected, with very few restrictions for all parameters. We describe as well the first test of the device at the 1 PW VEGA 3 laser facility at CLPU. Furthermore, employing the same device, we present a technique for fully energy-resolved emittance measurement for laser-generated proton beams. By means of a combined methodology between magnetic spectrometer and pepper-pot diagnostic [5] we performed a discretized and spectrally resolved study of the trace-space of the proton beam driven by VEGA 3. [1] H. Daido et. al., Rep. Prog. Phys. 75 (2012). [2] A. Macchi et. al., Rev. mod. Phys. 85 (2013). [3] P. Bolton et. al., Physica Medica 30 (2014). [4] C. Salgado-López et. al., Sensors 22 (2022). [5] S. Humphries, Charged Particle Beams (2002).
Characterization of optically shaped gas-jet target profiles for proton acceleration experiments in the near-critical density regime
Presenter: Ioannis Tazes (Institute of Plasma Physics & Lasers - IPPL, Hellenic Mediterranean University center for research and innovation, Rethymnon, Greece. Department of Electronic Engineering, Hellenic Mediterranean University, Chania, Greece)
Authors: Ioannis Tazes, Georgia Andrianaki, Anastastios Grigoriadis, Stylianos Passalidis, Christos Karvounis, Evridiki Vrouvaki, Donaldi Mancelli, Evangelos Kaselouris, Ioannis Fitilis, Alexandros Skoulakis, Makis Bakarezos, John Chatzakis, Emanouil Benis, Vasilis Dimitriou, Nektarios Papadogiannis, Michalis Tatarakis
Abstract: Laser-induced proton acceleration has attracted increasing attention due to its numerous potential applications such as in Inertial Fusion Energy (IFE) for the proton-driven fast ignition scheme and in biomedical applications (i.e., hadron therapy). Laser-plasma accelerators are often based on the interaction of an intense laser pulse with a solid target, in the over-dense plasma regime. The targets are destroyed upon irradiation, not allowing their use for high repetition rate (HRR) proton sources. Extreme-pressure gas-jet targets, able to reach the near-critical (NCR) density plasma regime, can be used as HRR, debris-free proton sources. State-of-the-art simulations predict hundreds of MeV protons by Magnetic Vortex Acceleration (MVA). MVA remains experimentally challenging for super-intense, short wavelength, femtosecond laser pulses due to the steep density gradient plasma profiles required. Here we present an experimental characterization of high-pressure, supersonic gas-jet density profiles performed using Mach-Zehnder interferometry. The NCR density profiles are delivered by 3D printed specially designed nozzles with a solenoid valve along with an air-driven hydrogen gas booster, able to support up to 1000 bar of backing pressure. We further present their optical shaping through multiple, laser-generated blastwaves (BW) using ns pulses from an 840 mJ Nd:YAG laser. The counterpropagating BWs compress the gas-jet targets, upon their shock fronts’ collision, achieving steep density gradient slabs of a few microns thickness. These profiles are considered suitable candidates for laser-induced proton acceleration experiments, using the 45 TW, fs laser system ZEUS, hosted at the Institute of Plasma Physics and Lasers (IPPL). Finally, we present MagnetoHydroDynamic simulation results on the optical shaping of the gas-jet target profiles by multiple laser pulses geometrical set-ups.
First experimental measurements of the scintillator-based Fast-Ion Loss Detector in the MAST-U spherical tokamak
Presenter: Juan Francisco Rivero Rodriguez (United Kingdom Atomic Energy Authority)
Authors: Juan Francisco Rivero Rodriguez, Lina Velarde, Tristram Williams, Manuel García-Muñoz, Ken McClements, Daniel Dunai, Joaquin Galdón-Quiroga, José Rueda-Rueda, Rory Scannell, Eleonora Viezzer
Abstract: The first scintillator-based Fast-Ion Loss Detector (FILD) in MAST-U is equipped with a fast scintillator material, a high-resolution camera and an avalanche photo-diode camera that enable the inference of the fast-ion loss velocity space and fast-ion loss fluctuations at frequencies up to 2 MHz. The probe is installed on a rotary and reciprocating system that makes it possible to adapt the probe orientation to the plasma magnetic field pitch and radial position, respectively. The first measurements have revealed a clear dependence of the losses with the distance between the probe and the separatrix. The measured velocity-space of the neutral beam injection (NBI) prompt-losses agrees with estimates made using the ASCOT5 Monte-Carlo full-orbit code. Fourier analysis of the FILD signal revealed fast-ion losses from both on-axis and off-axis beam correlated with a wide variety of plasma instabilities, as can be observed in figure 1, such as toroidal Alfvén eigenmodes (TAE) and long-lived modes (LLM). Moreover, fast-ion losses in the range of 1 – 2 MHz have been revealed for the first time. These losses are correlated with fast-ion driven instabilities identified as either Compressional Alfvén Eigenmodes (CAEs) or Global Alfvén Eigenmodes (GAEs): their frequency is 0.3 – 0.45 times the cyclotron frequency of deuterium at the magnetic axis. Other plasma instabilities, such as sawteeth, fishbones and edge localized modes are seen to cause fast-ion losses. Measurements with a neutron camera and solid-state neutral particle analyser confirm the drops in the confined fast-ion population when the fast-ion losses are observed. These results show the unique capability of the MAST-U FILD to provide high-resolution measurements of fast-ion losses enabling a detailed physics investigation of wave-particle interactions in a spherical tokamak.
Observation of the Geodesic Acoustic Modes (GAM) density fluctuations in H-mode on EAST
Presenter: Hui Lian (Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China)
Authors: Hui Lian
Abstract: A geodesic acoustic mode (GAM) is observed in H-mode plasma on EAST tokamak. With the POlarimetry-INTerferometry (POINT) system on EAST, the density fluctuation arising from the GAM is obtained. Electron density fluctuation is measured to have an m=1 structure where m is poloidal number. Density fluctuation amplitude in the edge measurement chords is higher than central chords as expected from GAM. The mode frequency increases from 15kHz in L-mode plasma to 25kHz in H-mode. Turbulence fluctuations decrease in H-mode but GAM is still sustainable during entire H-mode discharge phase. For the first time on EAST, the GAM density fluctuation both in L and H-mode plasma with POINT measurement is reported in this paper. GAM fluctuation frequency increases from 15kHz to 25kHz in L-mode and keeps at around 25kHz in H-mode till the end of discharge. The poloidal number m is obtained from the correlation between ne1 and ne11, it is supposed to be 1 as their phase difference is pi, and it keeps m=1 both in L and H-mode plasmas, it is further confirmed by the correlation between magnetic signal and POINT 11 chords. The GAM density fluctuation of 11 measurement chords is also demonstrated. Amplitude of edge chords is high while the chords in middle are low, which is consistent with the theoretical expectation. The fluctuation amplitude decreases significantly after the L-H transition, which is because the confinement suppresses the turbulence. However, the understanding of GAM in H-mode is still not fully clear, which needs more study in the future. The driving force of GAM in H-mode is under experimental investigation.
Primary results of EAST edge TV Thomson scattering system
Presenter: Mengfang Ren (Chinese Academy of Sciences)
Abstract: A new TV Thomson scattering (TVTS) system has been developed to provide high accuracy electron temperature (Te) and density (ne) profiles for the study of the Experimental Advanced Superconducting Tokamak (EAST) edge physics. A 532 nm high energy and high frequency laser was invented based on a new frequency doubling and amplification technology. A modified Littrow structure spectrometer working at 532  50 nm with the stray light suppression ratio greater than 106 was involved to provide high S/N scattering spectrum. The custom lenses enable the spectrometer has the ability to analyze 15 measurement points simultaneously with the spectral resolution of 5 nm at the slit width of 1.5 mm and the transmission efficiency greater than 50%. A high sensitive detector coupled to the high effective scattering light collection, transmission and spectral analysis systems ensure that the TVTS has the measurability at electron temperature of 20–1000 eV in the edge plasma with spatial resolution as low as 3 mm. The details of the diagnostic system as well as the measurement results are presented in this talk. The preliminary results have confirmed the feasibility of the TVTS system based on 532 nm laser for the research of steady-state long-pulse operation.
14:40 - 15:40
Poster Session 1 learn more
poster session 1
Gamma-ray Diagnostics for High-time Resolution Measurement in the Large Helical Device
Presenter: Kunihiro Ogawa (National Institute for Fusion Science)
Authors: Kunihiro Ogawa
Abstract: A high-time resolution gamma-ray spectrometer based on a LaBr3(Ce) scintillation detector characterized by high-time resolution was installed in the Large Helical Device (LHD) as a complemental diagnostic for energic particle studies. The 1-inch diameter 1-inch height LaBr3(Ce) scintillator coupled with a 1-inch photomultiplier tube is immersed into the radiation shield whose total weight is 500 kg. The radiation shield composed of 10 cm thick lead and more than 10 cm thick 10% borated polyethylene was designed using the Monte Carlo three-dimensional radiation transport code MCNP6 to suppress unwanted signals due to gamma-rays from the surrounding material as well as fast-neutron because a LaBr3(Ce) detector has a sensitivity to fast-neutron. The pulse signal was transferred by a 60 m co-axial cable and fed into the 1 GHz sampling rate analog to digital converter equipped with a field programmable gate array implemented with an offline pulse height analysis function. The high voltage of the detector is applied by an externally controllable high voltage module having the logging function. After in-situ energy calibration of the LaBr3(Ce) detector using a 137Cs gamma-ray source was performed, we clarified that the unwanted pulse counts induced by neutrons created by thermal deuterium-deuterium fusion reactions do not inhibit gamma-ray spectroscopy measurement. The detailed design of the diagnostics and initial result of gamma-ray spectroscopy will be presented.
Study of beam ion anisotropy using multi-sightline CLYC7-scintillator-based compact D-D neutron spectrometers
Presenter: Longyong Liao (The Graduate University for Advanced Studies, SOKENDAI)
Authors: Longyong Liao
Abstract: Studying fast-ion physics in fusion plasmas plays an important role in making effective plasma heating and achieving high-performance plasmas. Neutron spectrometry is one of the superior methods to diagnose fast-ion’s velocity distribution in a fusion plasma core because in a neutral-beam (NB)-heated plasma, fusion neutron is dominated by neutron resulting from so-called beam-plasma reaction. Therefore, neutron spectrometry can contribute to deeper understanding of the excitation mechanism of beam-ion-driven magnetohydrodynamic (MHD) instability which is one of the key topics for magnetic confinement fusion. In this work, we applied the novel compact neutron emission spectrometer (CNES) to deuterium plasmas in the Large Helical Device (LHD). Anisotropy of beam ion’s velocity is of great concern in the LHD since fast-ion-driven MHD modes are often destabilized due to high-energy NB injection based on negative-ion source (N-NB). Three new CNESs based on novel inorganic scintillator Cs2LiYCl6:Ce with 99% 7Li-enrichment (CLYC7) having different tangency radii were installed in the LHD. It should be noted that the CLYC7 scintillator can directly measure the D-D neutron energy through the 35Cl(n,p)35S reactions unlike a conventional organic liquid scintillator, e.g. EJ-301. In this LHD campaign, we observed the Doppler shift of the D-D neutron energy resulting from the anisotropy of fast ions injected by tangential N-NB injection by the CNESs with multiple lines of sight at 6-T, 8-O, and 10-O ports. We also have compared the D-D neutron spectra observed in the experiment and that predicted by a numerical simulation. The detailed experiment setups of the CNESs in the LHD and the results of D-D neutron spectroscopy during N-NB injection heating will be presented.
Characterization of Liquid Scintillator-based Compact Neutron Emission Spectrometers for D-D Neutron Emission Spectroscopy in the Large Helical Device
Presenter: Siriyaporn Sangaroon (Mahasarakham University, Maha Sarakham, Thailand)
Authors: Siriyaporn Sangaroon
Abstract: D-D neutron emission spectroscopy in the neutral beam (NB) heated plasma provides a deeper understanding of slowing-down of injected energetic beam deuterons through measurement of Doppler broadening of beam-driven D-D neutrons. Works can contribute the systematic understanding of fast-ion confinement in stellarator/helical systems and excitation mechanism of magnetohydrodynamic (MHD) instability by fast-ions. In the Large Helical Device (LHD), D-D neutron emission spectroscopy is well advanced by three compact neutron emission spectrometers (CNESs) based on conventional liquid scintillator (EJ-301). A tangential sightline CNES was installed at LHD 6-T port to observe a significant Doppler shift of the neutron energy due to the high-energy tangential negative-ion-source-based perpendicular NB injections (N-NB) [1]. Two perpendicular sightline CNESs were installed at LHD 1.5-L port to observe a helically-trapped beam ion, created by the perpendicular positive-ion-source-based perpendicular NB (P-NB) and/or ion cyclotron range of frequency wave heating [2]. This work focuses on the characterization of three liquid scintillator-based CNESs at the neutron source facility and in the LHD experiments. Prior the installation of CNESs in the LHD, three 1-inch in diameter and 1-inch in length liquid scintillator coupled with a conventional 1-inch photomultiplier tube are characterized at fast neutron source facility, i.e., Fast Neutron Laboratory (FNL) of Tohoku University. The EJ-301 scintillation detector was placed at different position from the beam axis, where the D–D neutron energy peak at the detector position was expected to be up to ∼6 MeV. The charge comparison method is used for neutron/gamma-ray pulse shape discrimination. The simple derivative unfolding technique is used to unfold the neutron energy spectra from the recoiled proton energy spectra. To further understanding of detector response to the fast-neutrons, the deuteron beam’s energy spectra in the D2 gas target and the neutron transport in the FNL experiment hall was calculated by TRIM code and Monte Carlo N-Particle transport (MCNP) code. In the LHD experiments, the operational capability of the CNESs in the pulse counting rate is investigated. D-D neutron emission spectroscopy in various approaches during the N-NB and P-NB heated plasma using liquid scintillator-based CNESs in the LHD are characterized and compared with the numerical simulation based on the orbit following model. [1] S. Sangaroon et al., AAPPS Bulletin 32, 5, 2022. [2] S. Sangaroon et al., Review of Scientific Instruments 93, 093504, 2022.
Overview of DD fusion product diagnostics at the Gas Dynamic Trap facility
Presenter: Egor Pinzhenin (Budker Institute of Nuclear Physics, Novosibirsk, Russia)
Authors: Egor Pinzhenin
Abstract: Gas dynamic trap (GDT) is an open magnetic mirror trap for plasma confinement. Diagnostics of fusion reaction products for GDT should solve the following scientific problems. Measurement of the absolute values of the intensity of the deuterium fusion reaction in the system in each experiment. Observation of the fast particle accumulation with NBI plasma heating and the loss of fast particles as a result of MHD instabilities. Study of fusion reaction spatial distributions and rebuilding of profiles as a result of micro instabilities. The entire system operates under conditions of gamma ray and hard X-ray radiation, which occurs when superheated electrons are lost from the plasma. The diagnostic system consists of the following main elements. Fusion reaction intensity monitor based on a scintillator and PMT. The detector is located outside the vacuum chamber and operates in current mode. It provides 25 µs time resolution. The main task is a survey measurements, observation of the accumulation of fast particles and global events associated with MHD plasma activity. A set of 3.02 MeV proton detectors local inside the vacuum vessel. They work in the count mode. The detectors make it possible to measure the absolute values of fusion reaction intensity the system, to observe the spatial profiles of the reaction intensity and the temporal evolution of the reaction intensity profiles as a result of micro instabilities. A neutron and gamma spectrometer based on a stilbene scintillator and a PMT is designed for fast neutron spectrometry under the conditions of gamma and X-ray background. It can be used to analyze superheated electrons that appear in the GDT because of additional microwave (ECRH) heating.
ECE diagnostics at the Wendelstein 7-X stellarator
Presenter: Matthias Hirsch (Max-Planck Institut für Plasmaphysik)
Authors: Matthias Hirsch, Melina Arvanitou, Neha Chaudhary , Céline Dyhring, Udo Höfel, Mathias Stern, Hans Oosterbeek, Gavin Weir, Robert Wolf
Abstract: The ECE diagnostic at the Wendelstein 7-X stellarator (B=2.5T) comprises a radiometer system and a Michelson interferometer sharing the same Gaussian optics with slim sightline for maximum resolution across the plasma center. Both systems use notch filters to cope with the strong ECRH stray-radiation background of the 140 GHz gyrotrons. The 32 channel radiometer covering the 2nd harmonic X-mode (126 to 162 GHz) is used for the study of various plasma dynamics. Absolute calibration enables profile inference that applies Bayesian forward analysis using the radiation transport code TRAVIS. A standard branch aims on overnight or even intershot availability of the Te profile evolution by Maximum a Posteriori methods. On top of that and for individual cases a full Markov Chain Monte Carlo analysis allows to assess the probability distribution of the priors as well as enables integrated data analysis that addresses the pressure- and some extent the density profile as well. ECRH power switching is used to measure the power deposition zone of individual gyrotrons via a break-in-slope analysis of the ECE signals. This is in support of advanced W7-X scenarios with the ECRH plant providing at present 8 MW - e.g. for high-density O2 heating, or for off-axis heating and current drive allowing profile and configuration control, respectively. The spatial resolution of ECE is improved for this by an additional zoom radiometer with 16 channels densely spread over a 4 GHz wide band that can be tuned to vary the radial position of the measurement by means of an additional tunable local oscillator. Broadband ECE analysis with the Michelson interferometer covers also higher harmonics where the optically grey 3rd harmonic allows to track core Te and even provides profile information in high-density plasmas (n> 1.2 1020 m-3) where classical ECE fails as the optically thick X2 mode is in cut-off. This is of particular relevance for high-density discharges heated by O2-ECRH where microwave absorption depends critically on Te. A continuously measuring radiometer for the 3rd harmonic X3 is in preparation for this purpose.
High pressure miniature plasma focus characterization for efficient plasma emission
Presenter: Christos Karvounis (Institute of Plasma Physics & Lasers - IPPL, Hellenic Mediterranean University Research Centre, Rethymnon, Greece. Department of Electronic Engineering, Hellenic Mediterranean University, Chania, Greece)
Authors: Christos Karvounis, Alexandros Skoulakis, Ioannis Tazes, Donaldi Mancelli, John Chatzakis, Vasilis Dimitriou, Nektarios Papadogiannis, Michalis Tatarakis, Ioannis Fitilis
Abstract: The field of high current generated plasma has been well studied over the past years. The secondary emissions (neutrons, X-rays etc.) have numerous possible applications, among others, in neutron activation analysis and x-ray lithography and the study of the robust fundamental physics involved. Here we present a Mather-type miniature plasma focus machine that was used for the plasma generation. The scope of this study was the characterization of this machine as a neutron source. We further present the optimal gas pressure values, under voltage charge operation of 19 kV, for achieving pinching conditions, resulting to a highest neutron production yield. The experiments were conducted in the Institute of Plasma Physics and Lasers (IPPL) facility of the Hellenic Mediterranean University (HMU). Snapshots with different pressure values of the plasma evolution, using shadowgraphy diagnostic technique, are presented before, during and after pinching. Additionally, results of the neutrons and the hard X-rays emission using a diagnostic set-up consisting of a plastic scintillator and a photomultiplier, which signal recording in a fast oscilloscope are presented. In order to measure the production number of neutrons at different pressure values, a calibrated bubble-type detector (BD-PND) was used and the results are presented. Finally, we present the calculation of the neutron’s speed and the comparison with the results that was obtained by using Lee’s simulation model.
Runaway Electrons Instability Measurement and Analysis at the COMPASS and FTU Devices
Presenter: William Bin (Institute for Plasma Science and Technology, National Research Council (ISTP-CNR))
Authors: Jaroslav Čeřovský, Francesco Napoli, Paolo Buratti, Jakub Čaloud, Alessandro Cardinali, Andrea Casolari, Carmine Castaldo, Ondrej Ficker, Martin Jerab, Jan Mlynar, Eva Tomesova, William Bin
Abstract: Kinetic instabilities can be excited in a tokamak plasma by free energy available from the distribution function of runaway electrons (RE) in the momentum space, owing to its anisotropy, in particular for high RE momentum parallel to the static magnetic field, or due to the presence of a local maximum. The wave-particle interaction, which is the pumping process underlying the instability growth, can occur by means of the Cherenkov and/or anomalous Doppler resonance. The very first direct observation of unstable waves in a laboratory plasma was performed a few years ago at DIII-D [1], by means of in-vessel radio-frequency (RF) measurements. Further experimental measurement of emissions from RE scenarios then followed, right after, at the COMPASS [2] and Frascati Tokamak Upgrade (FTU) [3, 4] devices, where several families of instabilities have been recorded, in the entire range of toroidal magnetic fields available in these two tokamaks: from the lowest ones, attainable at COMPASS, to the highest ones, typical of FTU. Such a wide range of fields (applied in discharges with different plasma densities) allows covering the overall scenarios expected at ITER, for what the dispersion relation of RE-driven unstable plasma waves is concerned. From a diagnostic point of view, the instability processes are related to the RE dynamics and, therefore, the study of these phenomena can bring to light aspects of the dynamics otherwise hidden and hardly investigable using other diagnostics. Even when the RE density and energy are low, RF emissions are very sensitive to the presence of fast electrons and this holds true also during the early phase of the discharge, when the capabilities of the other diagnostics are generally still limited. In the present work, a number of results from detection of RE waves are presented. The experiments have been performed at both the COMPASS and FTU devices, under different RE plasma conditions, by means of either ex-vessel or in-vessel antenna systems designed and constructed ad-hoc for this purpose. [1] D. A. Spong et al., Phys. Rev. Lett. 120, 155002 (2018) [2] E. Macusova et al., Proc. 47th EPS Conference on Plasma Physics, I2.106 (2021) [3] W. Bin et al., Phys. Rev. Lett. 129, 045002 (2022) [4] W. Bin et al., Rev. Sci. Instrum. 93, 093516 (2022)
Conceptual design of a visible spectroscopy diagnostic for DTT
Presenter: Andrea Belpane (Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova, Italy - Department of Economics, Engineering, Society and Business Organization, University of Tuscia, Largo dell’Università, 01100 Viterbo, Italy;)
Authors: Alessandro Fassina, Andrea Belpane, Lorella Carraro, Luca Senni, Marco Cavedon
Abstract: The project of the diagnostics for the Zeff radial profile measurement and for the divertor visible imaging spectroscopy, designed for the new tokamak DDT (Divertor Tokamak Test), is presented. To deal with the geometrical and functional constrains of DTT and to minimize the diagnostics occupancy inside the access pipe, an integrated and compact solution hosting the two systems has been proposed. The Zeff radial profile will be evaluated from the Bremsstrahlung radiation measurement (in a wavelength region free of line emissions) in the visible spectral range acquiring emission from the upper part of the poloidal plan (from the equatorial line up to the separatrix). The plasma emission will be focused on optical fibers which will carry it to the spectroscopy laboratory; one more toroidal line of sight crossing the plasma center and laying on the equatorial plane will measure the averaged Zeff on a longer path. The divertor imaging system is designed to measure impurity and main gas influxes, to monitor the plasma position and kinetics of impurities, to follow the plasma detachment evolution. The project aims to obtain the maximum divertor region coverage and to set instruments outside the torus hall, in order to share light among different spectrometers and interferential filter devices and easily change their setup. The system is composed by two mirrors inside a protective head, which protrudes from the diagnostic box where the divertor image transfer optics and the Zeff telescopes are collocated.
Velocity-space analysis of the first fast-ion losses measured in MAST-U using a high-speed camera in the FILD detector
Presenter: Lina Velarde (University of Seville)
Authors: Lina Velarde, Juan Francisco Rivero Rodriguez, Tristram Williams, Joaquin Galdón-Quiroga, José Rueda-Rueda, Pilar Cano-Megías, Ricardo Chacartegui, Manuel García-Muñoz, Ken McClements, Lucía Sanchís, Eleonora Viezzer
Abstract: A Fast-Ion Loss Detector (FILD) was installed for the first time at MAST during its upgrade in 2021 [1]. FILD consists of a probe near the plasma edge on the low field side that acts as a magnetic spectrometer, collimating the ions and dispersing them onto a scintillator plate. The acquisition system comprises two cameras, one CMOS camera providing enough spatial resolution (up to 1.1 MPx), and one APD camera providing temporal resolution (up to 4 MHz) to infer both the velocity space and the frequency of the fast-ion losses, respectively. For the second MAST-U experimental campaign (2022), the CMOS camera has been upgraded (from 23 Hz to up to 3.5 kHz acquisition frequency), in order to properly capture the temporal variation in velocity-space. In addition, the reciprocating probe of the diagnostic has been commissioned. The velocity-space of the losses observed in MAST-U has been inferred with the FILDSIM code [2]. The first results show that the low NBI injection energy, plasma current and toroidal magnetic field used in the first campaign have led to larger gyro-radii than expected during the design phase (16 cm versus the maximum design value of 12.5 cm) [1]. In addition, the orbit-following Monte-Carlo code ASCOT [3] has been used to simulate fast-ion losses in a wide range of scenarios, with Bt = [0.4, 0.6] T and Ip = [450, 750] kA to analyse the dependence of the fast-ion loss distribution with the plasma safety factor (q). This has shown that lower q values help bring the losses closer to the probe’s head. The NBI has been modelled in ASCOT5 to generate realistic particle inputs. The modelling of first orbit losses with ASCOT5 has enabled the benchmark of the experimental data measured by FILD, and the numerical simulations of the velocity-space are in good agreement with the experimental results. Furthermore, a scan of the probe’s radial position with respect to the separatrix (17 to 8 cm) has shown an inverse correlation between the number of particles hitting the detector and its proximity to the separatrix. This correlation agrees with the experimental measurements obtained in the second campaign. [1] J. F. Rivero-Rodríguez et al 2018 Rev. of Scientific Instruments 89, 10I112 [2] J Galdón-Quiroga et al 2018 Plasma Phys. Control. Fusion 60 105005 [3] E. Hirvijoki et al 2014 Computer Physics Communications 185 1310-1321
Thermal cycling of prototype bolometer sensors for ITER
Presenter: Sina Jahanbakhsh (Max Planck Institute for Plasma Physics (IPP))
Authors: Sina Jahanbakhsh, Hans Meister, Christian Ingesson, Ulrich Walach
Abstract: In order to evaluate endurance and compatibility of the prototype bolometer sensors to ITER relevant environment, various tests are being conducted on the sensors. The prototype sensors include two different sensor types, namely self-supporting substrate (Au absorbers on 20-μm thick yttria-stabilized ZrO2 (YSZ) substrates - Pt meanders and tracks) and supported membrane (Au absorbers on 3 μm thick SiN membranes supported by a Si frames - Pt meanders and tracks). The results for calibration of the sensors at temperatures up to 325 °C were presented in a previous contribution [1]. The aim of the current study was to investigate the effect of several thermal cycles on the prototype bolometer sensors. In addition, the failure statistics obtained will contribute to determining the adequacy of the sensors for the use in ITER. The main objectives were mechanical stability of the sensors and also potential changes of sensor calibration parameters due to thermal cycles. In each thermal cycle the sensors were calibrated before starting the heating, and then were heated with a rate of 2.5 K/min up to 350 °C. The sensors were kept for 20 minutes at this temperature, then the setup was cooled down overnight. This was repeated 19 times. Additional 5 cycles up to 400 °C were done by manufacturers. From eight supported-membrane sensor channels, seven survived till end of the test. One channel lost its electrical connection during the 9th cycle. There was a significant increase in meander resistances of all channels in the first five cycles. The total increase of the resistances was approximately 30 percent. The calibration parameters of the sensors with heat conduction layer (HCL) also changed considerably during thermal cycling. This was not observed in the sensor without HCL. The self-supporting sensor, which was put inside a sensor holder and calibrated during the test, survived only nine cycles; although material of the holder (Al2O3) was chosen so that its thermal expansion coefficient was close to sensor substrate. The significant resistance increase was also observed in this sensor. This sensor had an HCL and the sensor parameters were changed by thermal cycling. The self-supported membrane sensors, which were put inside the vacuum chamber without a sensor holder and thus it was not possible to calibrate them during the test, survived the tests. This indicates the importance of the optimization of the sensor holders for this type of bolometer sensors. References [1] Jahanbakhsh, S. et al., “Calibration and evaluation of prototype bolometer sensors for ITER,” 32nd Symposium on Fusion Technology (SOFT), September 19-23, 2022, Dubrovnic, Croatia.
Ionization dynamics in ultra-relativistic laser plasmas using X-ray free electron lasers
Presenter: Mikhail Mishchenko (European XFEL GmbH)
Authors: Mikhail Mishchenko
Abstract: The dynamics of bulk heating and ionization determines the crucial plasma parameters such as plasma temperature and density in ultra-short relativistic laser-solid target interactions. We have experimentally demonstrated (resonant) time-dependent probing of radiative K-transitions in a mid-Z model system (copper plasma) as a convenient method for the simultaneous study of spatial and temporal ionization and relaxation dynamics. Experimental data on relaxation dynamics and recombination rates are in high demand to improve particle-in-cell simulations. We have no direct information on the actual recombination rates, as the widely applied Thomas-Fermi approximation lacks the reaction rate information and thus usually overestimates the ionization degree. [1,2,3] Opportunities at HED instrument at the European XFEL with its 25-fs x-ray pulses, together with the demonstrated 20-30 fs timing synchronization to the sub-petawatt class ReLaX short-pulse laser, allows unprecedented studies of relativistic laser plasmas with few-fs precision. [4] In the course of this project, we managed to measure the characteristic lifetime for oxygen-like ionization states of a copper for plasma obtained from flat foils irradiated by ultra-relativistic laser radiation, and also to demonstrate the effectiveness of resonant X-ray pumping for the simultaneous study of the temporal and spatial dynamics of ionization in laser plasma.
Development of GaAs and GaN passive millimeter-wave imaging diagnostics on the DIII-D tokamak
Presenter: Ying Chen (UC Davis)
Authors: Yilun Zhu, Xianzi Liu, Guanying Yu, Yu Ye, Johan Yu, Gerrit Kramer, Neville Luhmann, Ying Chen
Abstract: Millimeter-wave imaging diagnostics provide 2D/3D fluctuation structures of density and temperature in tokamak, which are essential for dangerous disruption prediction and better plasma physics understanding. The passive visualization radiometer, Electron Cyclotron Emission Imaging (ECEI), has been developed and applied on tokamaks throughout the world since 1995. Based on the rigors to which fusion plasma diagnostics are subjected, the innovative system-on-chip generation diagnostics have been developed and demonstrated epoch-marking breakthroughs, including over 400x signal level gain, over 85% electronics noise suppression, and extremely high integration level. The W-band (75-110 GHz) gallium arsenide (GaAs) receiver chip (size 3 x 3 mm2) has been developed and applied to the DIII-D ECEI system since 2017. It provides both 2D equilibrium temperature profiles and temperature fluctuations. While facing several orders of magnitude stronger neutron radiation on burning plasma reactor, radiation tolerance is the most urgent requirement to all diagnostics. The employment of wide bandgap semiconductors provides one promising solution for millimeter-wave measurement by virtue of its wider bandgap, which allows the sensitive detector to operate at higher voltages, temperatures, and frequencies. In 2022, a W-band gallium nitride (GaN) passive receiver chip (5 x 3 mm2) has been developed by the University of California at Davis, for further improvement against the radiation (auxiliary heating, neutron, X-ray) harsh environment. The system-on-chip millimeter-wave detectors are developed as general modules for amplitude and phase measurements, which could be widely applied to radiometers, reflectometers, interferometers, scattering, and polarimeters for present and future diagnostics.
Development of a Vertical Edge Thomson Scattering Diagnostic on HL-2M Tokamak
Presenter: Shaobo Gong (Southwestern Institute of Physics)
Authors: Shaobo Gong
Abstract: A vertical edge Thomson scattering diagnostic system on HL-2M tokamak has been developed recently. A Nd: YAG laser (1064 nm, 0.6 ~ 2 J, 30 Hz, 15 ns) is used as the probe beam. The laser beam propagates vertically through the plasma region and the scattered light is observed horizontally. The combination of a half-wave plate and a polarized beam splitter is used for stray light suppression. Characteristics of the non-ideal Gaussian laser beam is studied in detail. A group of collection lens is designed to image the 400 mm scattered region onto the rectangular fiber arrays. The laser beam waist and vertical spatial resolution are 2 mm and 10 mm, respectively. Scattered light is imaged on the 2.20 mm × 2.86 mm (10 × 13) fiber optic bundle. The development of in-vessel collection optics with a special designed safety shutter ensures a reliable scattered signal, where the solid angle at central field of view is 0.018 sr. A compact polychromator (Width 482 cm × Height 8.8 cm) is developed to measure the scattered light. The noise level of each channel is less than 5 mV. Relative calibration of the filter response (1060 nm, 1052 nm, 1029 nm and 982 nm) and absolute calibration by nitrogen Raman scattering have been completed. In the 2022 plasma campaign of HL-2M, the measured plasma density is as low as 1.2×1018 m-3 at E0 = 1.2 J, confirming the capability of the system for pedestal measurement in the future H-mode campaign.
Space and Time resolved plasma density estimated from Hα/OI atomic lines generated by nanosecond discharge in liquid water.
Presenter: Garima Arora (Department of Pulse Plasma Systems, Institute of Plasma Physics of the Czech Academy of Sciences (IPP CAS))
Authors: Garima Arora, Petr Bílek, Vaclav Prukner, Petr Hoffer, Milan Simek
Abstract: Non-equilibrium plasmas in liquids generated by nanosecond high voltage pulses have found use in various applications such as water treatment, electrolysis, or biomedicine [1]. The dynamics of such discharges are very complex and highly dependent on experimental conditions such as electrode geometry, high voltage (HV) polarity, HV pulse rise time and duration, impedance matching, liquid conductivity, and the presence of vapor bubbles [2]. Understanding the complex dynamics and chemical kinetics of this highly non-equilibrium discharge requires the knowledge of plasma parameters with high spatial and temporal resolutions. In this work, the optical emission from nanoseconds pulsed plasma generated by a 175 kV HV pulse applied to the tungsten anode tip is monitored and analyzed. Electron number densities are estimated from the broadening and shifts of hydrogen and oxygen atomic lines measured by a fast imaging ICCD spectrometer. The initial spectra show a broad band continuum followed by hydrogen Balmer and atomic oxygen lines during later phases. The line profiles are extracted from the modeled continuum to get the spectral line shape. Temporal and spatial electron number densities notably evolve with time 2.1 X 1020 cm-3 – 6 X 1018 cm-3 from 30 ns to 450 ns with only slight density variation with the distance from the anode tip for a particular time. The results are consistent with images taken with high temporal (ns) resolution using either an ICCD spectrometer (0th diffraction order) or a 4-channel ICCD imaging device. References 1. Šunka, P. (2001). Pulse electrical discharges in water and their applications. Physics of plasmas, 8(5), 2587-2594. 2. Hoffer, P., Bílek, P., Prukner, V., Bonaventura, Z., & Šimek, M. (2022). Dynamics of macro- and micro-bubbles induced by nanosecond discharge in liquid water. Plasma Sources Science and Technology, 31 (1), 015005.
Design and component testing for a new steady-state multi-channel dispersion interferometer at Wendelstein 7-X
Presenter: Jakob Brunner (Max-Planck-Institute for Plasma Physics)
Authors: Jakob Brunner, Jens Meineke, Jens Knauer, Andrew Moreau, Beate Kursinski, Matthias Hirsch, Robert Wolf
Abstract: The Wendelstein 7-X stellarator is designed to demonstrate steady-state operation to show the feasibility of the Helias concept for fusion reactors. The experiments conducted so far indicate that high performance can only be maintained with good control over the plasma density profile, for which a reliable density profile diagnostic is required. Dispersion interferometry has proven itself as a reliable steady-state capable density measurement, which can deliver real-time density profile information via inversion with low latency. The original plan for Wendelstein 7-X already foresees the implementation of a multi-channel interferometer, which was on hold until now. Here we present the current design of the multi-channel dispersion interferometer (MCDI), which will be built in the next 2-3 years. The results of various hardware component tests are presented, which have been incorporated into the design. Notable are damage threshold tests for orientation-patterned gallium arsenide frequency doubling crystal (the non-linear crystal limiting signal to noise ratio), high-frequency electro-optical modulation (determining the temporal resolution) and laser stabilization. The presented design incorporates various advances from previous interferometers as well as the test results to yield a space efficient and cheap yet powerful interferometer for fast measurement of the density profile evolution. The system is designed to yield a temporal resolution in the mega-Hertz range to contribute to Alfvén mode studies, whilst maintaining a sub-millisecond latency using FPGA-based processing.
Ultrafast diagnostics of a pulsed barrier discharge in argon
Presenter: David Prokop (Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic)
Authors: David Prokop, Lukáš Kusýn, Zdeněk Navrátil, Tomáš Hoder
Abstract: A time-correlated single photon counting (TCSPC) based optical emission spectroscopy and an electrical diagnostics utilizing an equivalent circuit theory [1] have been used for investigation of a volume barrier discharge in atmospheric pressure argon. Micro discharges were produced by applying high voltage nanosecond pulses to a pair of metallic electrodes, with one electrode covered in aluminum oxide. From the highly resolved TCSPC optical emission spectra, we have obtained a spatiotemporal evolution of different phases of argon discharge, namely the transition from rapid electron avalanching to streamer to transient glow discharge, which ended with surface discharge upon reaching the lower electrode. From the obtained data we have also determined the approximate velocity of propagating streamers. In this contribution, motivated by the detailed spectroscopic analysis of the nanosecond pulsed coplanar discharge in argon as done in [2], we present detailed spatiotemporally resolved measurements of light intensities originating from all ten Ar 2p1-10 radiative states. The quantified relative 2p1−10 densities for identified discharge phases enable a well-resolved insight into the ultra-fast discharge kinetics and open a possibility for the development of future detailed diagnostics of the rapidly ionized argon plasmas. These measurements are then crucial and serve as a cornerstone for further development of new optical emission spectroscopy methods for local and time resolved plasma diagnostics of highly transient plasmas.
Updates of Coherence Imaging Spectroscopy at Wendestelstein 7-X for scrape-off layer measurements
Presenter: Valeria Perseo (Max Planck Institute for Plasma Physics)
Authors: Valeria Perseo, David Matt Kriete, Oliver Patrick Ford, David Andrew Ennis, Dorothea Gradic, Ralf König
Abstract: Coherence Imaging Spectroscopy (CIS) is a camera-based polarization interferometer [1]. Given its capability of delivering 2D measurements of plasma parameters with high spatial resolution, it has proven itself suitable for studying the complex 3D scrape-off layer (SOL) of the Wendelstein 7-X (W7-X) stellarator [2]. The fusion experiment is equipped with two CIS systems, one featuring a broad overview of the SOL thanks to a toroidal field of view, the other focusing on one divertor module and overlapping with dispersive spectroscopy lines of sight. After successful impurity flow measurements acquired during the last operational campaign (OP1.2b in 2018) [3] [4] [5], the two W7-X CIS systems have undergone upgrades to either cope with the W7-X steady state operation or to deliver additional physics information. The toroidal system, measuring routinely impurity flow velocities thanks to a well-established calibration technique, now features new plasma facing components capable to withstand the 18 GJ operation foreseen for W7-X. A combination of a water cooled front plate and a movable shutter with copper straps dissipates the heat loads expected from the plasma. On the other hand, the divertor viewing system is used to implement at W7-X the recently developed multi-delay CIS technique [6], in order to obtain reliable SOL ion temperature measurements in addition to the well-known velocity measurements. The multi-delay technique utilizes a micropolarized camera and multiple birefringent crystals, which have been optimized to deliver information about the non-negligible contributions of Zeeman splitting and bremsstrahlung to the measured line broadening and wavelength shift. This new CIS implementation is characterized with fine-tuned laser scans and is validated by exploiting the overlap of lines of sight with dispersive spectroscopy. References [1] J. Howard, Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 43, 2010. [2] V. Perseo et al., Review of Scientific Instruments, vol. 91, 2020. [3] V. Perseo et al., Nuclear Fusion, vol. 59, 2019. [4] V. Perseo et al., Nuclear Fusion, vol. 61, 2021. [5] D.M. Kriete et al., Nuclear Fusion, vol. 63, 2023. [6] J.S. Allcock et al., Review of Scientific Instruments, vol. 92, 2021.
Alkali Beam Emission Spectroscopy for absolute electron density radial profile measurements for NSTX
Presenter: Mate Lampert (Princeton Plasma Physics Laboratory)
Authors: Mate Lampert, Ahmed Diallo, Ors Asztalos
Abstract: Alkali beam emission spectroscopy (ABES) is a well-established diagnostic technique for absolute electron-density profile measurements [1]. This diagnostic technique was successfully applied to the measurement of the absolute ne radial profile on numerous devices including ASDEX Upgrade, JET, and W7-X. Fulfillment of the scientific objectives (1. and 2.) of the NSTX-U (National Spherical Torus Experiment Upgrade) 5-year plan [2] requires fast scrape-off layer (SOL) and edge electron density profile measurements which cannot be provided by the currently available diagnostics. Our study shows that high temporal and spatial resolution absolute electron density profile measurements would be feasible on the NSTX-U tokamak by means of alkali beam emission spectroscopy. We propose a Sodium beam setup with 1 mA ion equivalent beam current, 2.5 cm beam diameter and 60 keV beam energy. This beam setup perturbs the plasma negligibly with approximately 100 W deposited heat and 10^16 m-3 Na impurity in the SOL. The proposed observation geometry consists of 32 by 2 radial by poloidal pixels each covering approximately a 5 mm x 20 mm (radial  poloidal) area. The combined beam-observation geometry provides high estimated photon current (≈ 7 · 10^10 s-1) and high estimated signal-to-noise ratio (130 at the pedestal and 20 in the far-SOL for 500 kHz analogue bandwidth). Our simulations show that the combined smearing of the atomic physics and the misalignment of the magnetic field to the line of sight gives an overall estimated radial resolution of 12 mm in the far-SOL, 10.5 mm at the separatrix and 7.5 mm in the pedestal.
First measurements of an imaging heavy ion beam probe at the ASDEX Upgrade tokamak
Presenter: Joaquin Galdón-Quiroga (University of Seville)
Authors: Joaquin Galdón-Quiroga, Gregor Birkenmeier, Pablo Oyola, Hannah Lindl, Alfonso Rodriguez Gonzalez, Gabor Anda, Manuel García-Muñoz, Albrecht Herrmann, Joey Kalis, Karl Kaunert, Tilmann Lunt, Daniel Refy, Volker Rohde, Manfred Sochor, Balazs Tal, Markus Teschke, Eleonora Viezzer, Elisabeth Wolfrum, Sandor Zoletnik
Abstract: The imaging heavy ion beam probe (i-HIBP) diagnostic [1-3] has been successfully commissioned at ASDEX Upgrade. The i-HIBP injects a primary neutral beam into the plasma, where it is ionized leading to a fan of secondary (charged) beams. These are deflected by the magnetic field of the tokamak and collected by a scintillator detector, generating a strike-line light pattern which encodes information on the density, electrostatic potential and magnetic field of the plasma edge. The first measurements have been made, demonstrating the proof-of-principle of this diagnostic technique. A primary beam of Rb has been used, opposed to the 133Cs beam used in the prior campaign, with energies ranging between 35-70 keV and extracted currents up to 1.2 mA. The neutralization efficiency is up to 80% and the typical beam diameter is of the order of 5 mm, without using any additional collimator. The first signals have been obtained in experiments covering a wide range of parameter space, with plasma currents (Ip) between 0.2-0.8 MA and on-axis toroidal magnetic field (Bt) between 1.9-2.7 T. Low densities appear to be critical for the performance of the diagnostic, as signals are typically observed only when the line integrated density is below 2.0-3.0⋅10^19 m^(-2) in the central interferometer chord, depending on the plasma shape. The toroidal orientation (β) of the beam is found to be critical. Signals have been obtained only in the range of β=4.00-〖4.66〗^o. It is observed that stray light from the plasma, as that provoked by edge localized modes, can mask the beam signal in the scintillator detector. To alleviate this problem, a filter centered at the scintillator wavelength emission (500-580 nm) is included in the optical setup. The signal-to-noise ratio is observed to degrade during the campaign due to the impact of neutron fluence on the transmissivity of the image guide. This is partially healed by exposing the image guide to heating cycles up to 220 ºC. The typical pattern observed in the scintillator detector consists of a strike-line of 30 mm width. The strike-line moves as expected when either Bt or Ip are ramped, as well as when the beam is deflected. Additionally, clear dynamics in the intensity of the strike-line are often observed, which might be linked to filamentary activity in the plasma edge. Finally, simulations have been carried out to investigate the sensitivity of the expected signals to plasma density and temperature. The results are in qualitative agreement with the experimental observations, suggesting that the diagnostic is almost insensitive to fluctuations in the temperature profile, while the signal level is highly determined by the density profile due to the beam attenuation. [1] J.Galdon-Quiroga et al., JINST 12 C08023 (2017) [2] G.Birkenmeier et al., JINST 14 C10030 (2019) [3] G.Birkenmeier et al., FED 168 112644 (2021)
Validation of the synthetic diagnostic model for the imaging Heavy-Ion Beam Probe
Presenter: Pablo Oyola (Universidad de Sevilla)
Authors: Joaquin Galdón-Quiroga, Pablo Oyola, José Rueda-Rueda, Manuel García-Muñoz, Eleonora Viezzer, Joey Kalis, Tilmann Lunt, Daniel Refy, Balazs Tal, Hannah Lindl, Gregor Birkenmeier, Alfonso Rodriguez-Gonzalez, Gabor Anda
Abstract: First measurements with the imaging Heavy Ion Beam Probe (iHIBP) [1-4] have been carried out in recent dedicated experiments at the ASDEX Upgrade tokamak. In this work, we aim to compare against first experimental results and validate the synthetic diagnostic framework, i-HIBPsim [5], that simulates the evolution of the heavy-ion beam through the plasma until it hits a scintillator detector placed in the limiter shadow. The created light pattern (so-called strikeline) contains information on the plasma potential, magnetic field and the plasma density at the plasma edge. The numerical code of the synthetic diagnostic has been upgraded to fully include a realistic finite beam width, beam divergence and a 3D model of the optical head, which allows the simulation of the beam blocking by the optical head, as observed in experiments. The optical model of the diagnostic, including magnification, photon emission and distortion has been included, allowing a more realistic comparison between experimental measurements and simulated signals. Dedicated plasma pulses were carried out at the ASDEX Upgrade tokamak consisting of a ramp in the plasma current ranging from 200 kA to 700 kA. Changes in the plasma current translate into a visible shift of the strikeline pattern on the scintillator images up to one centimeter, that are reproducible by the synthetic model. Filaments propagating in the Scrape-Off Layer (SOL) may have an important impact on the scintillator signals, generating blob-like patterns on the strikeline. A realistic model of the filaments has also been implemented and tested in the synthetic model. We show the 3D effects of the filaments on the simulated signals and compare them to experimental measurements, which show blob-like structures.
On the injection, wave breaking and filamentation of electrons in LWFA
Presenter: Rareș Iovănescu (ELI-NP/Politehnica University of Bucharest)
Authors: Rareș Iovănescu, Radu Petru Daia, Emil Ioan Slușanschi, Cătălin Mihai Ticoș
Abstract: We study the origin of filamentation of the accelerated electrons in LWFA and their behavior in dependence to the plasma density. Several 2D PIC simulations were performed for different plasma densities, while keeping the other parameters constant. A filamentation is observed for lower plasma densities ~9×1017 cm-3 and a0>10 up to a limiting threshold density at around 2.5×1018 cm-3 and then vanishes. Moreover, with the growth of density, at around 4×1018 cm-3 the electrons on the edge of the bubble start to counter propagate and separate from the bubble margin, thus reaching each other behind the rear of the bubble, significantly reducing the self-injection. Depending on the plasma density the bubble has a different dimension and shape, being bigger for lower densities. The filamentation appears when the bubble closes at its rear and depends on the closure angle of the bubble wall. If the angle of closure of the bubble is less than π (it closes from the beam direction), the filamentation does not set in from the beginning and is limited as the electron bunch is travelling towards the laser pulse. However, if the closure angle of the bubble wall exceeds π (it closes from the rear part), which means that the wall edges turn towards the laser, the electron bunch travels inside the bubble and forms the filaments. This is related to the fact that the constant phase surface of a broken wave in plasma follows such curves that close differently at the rear of the bubble. We present the energy distribution for the different plasma density and the evolution of the filaments in time. Besides, we measure the maximum electron energy for each plasma density at intervals of 250 fs, and obtain lower values in the cases with filamentation.
Investigation of inward particle flux formation in the PKU Plasma Test (PPT) device
Presenter: Tianchao Xu (Peking University)
Authors: Tianchao Xu
Abstract: Turbulent particle transport causes the loss of particle in the magnetic confinement plasma devices, which degrades the confinement of plasma. The inward particle transport is conducive to transport barrier formation and confinement improvement. The inward particle flux is associated with the formation of peaked density profile, which could improve the fusion rate and contributes to the realization of steady-state discharge. And understanding the formation mechanism of inward particle flux could achieve its control, which is helpful to solve the challenge of fusion plasma fuelling. The PKU Plasma Test (PPT) device is a linear plasma device in Peking University, China. It has a vacuum chamber with 2000mm length and 500-700mm diameter. Recently, the inward particle flux has been observed in this linear plasma device. Combining both a high-speed camera and probe diagnosis, inward particle flux and outward particle flux are observed simultaneously at certain experimental parameters. Based on the theoretical and experimental analysis, the nonlinear interaction of streamers could drive the inward particle flux in the region without the boundary effect where the density fluctuation saturated. The magnetic field impacts the distribution of the inward particle flux and the power of helicon source has an effect on the amplitude of the outward particle flux.
Reconstruction method of laser-driven ion-beam trace probe diagnosing the poloidal magnetic field in spherical tokamak
Presenter: Zuyu Zhang (Peking University)
Authors: Zuyu Zhang
Abstract: The poloidal magnetic field (B_p) is a critical factor for plasma equilibrium and stability, and multiple diagnostics are in need for a more accurate profile of B_p. The laser-driven ion-beam trace probe (LITP) has been proposed recently to diagnose the poloidal magnetic field (B_p) and radial electric field (E_r) in tokamak.[1-3] It measures the displacements of laser-driven ion beams which directly depend on electromagnetic field along the beam traces, and tomography methods are employed for the reconstruction. Based on the three properties of laser-driven ion beam: large energy spread, short pulse lengths, and multiple charge states, the two-dimensional profile of both B_p and E_r can be diagnosed by LITP. Spherical tokamak (ST) is a promising compact device with high plasma beta and increased vertical stability. When applying LITP to diagnose B_p in ST, the larger B_p comparable to the toroidal magnetic field, turns the reconstruction problem into solving the nonlinear equations. In this presentation, an iterative reconstruction method is proposed to solve the nonlinear equations and a model to reconstruct B_p profile in ST is built. The schemes of ion traces are designed for EXL-50 (a middle-sized ST in Langfang) and simulated reconstruction has been conducted. The relative errors of reconstructed B_p are mostly under 10%. The effects of measurement error and system error have been evaluated, suggesting LITP can reconstruct B_p in ST for practical purposes.
Designing active spectroscopy on Magnum-PSI to characterize neutral particles in detached conditions
Presenter: Ivo Classen (DIFFER)
Authors: Ivo Classen, Hennie van der Meiden, Kaden Loring, Kay Schutjes, Jordy Vernimmen
Abstract: Divertor detachment is the leading candidate for solving the heat exhaust problem in future fusion reactors. Key to understanding detachment is the interaction of the plasma with a background of neutral particles in the divertor region. Collisions of the plasma with these neutral background particles result in a rich range of physical and chemical processes, causing the plasma to dissipate its energy and momentum, and finally to recombine, preventing damage to the wall. Whereas charged particles are routinely diagnosed, information on neutral particles is often missing. The properties of neutral particles can be measured using active spectroscopy. At Magnum-PSI, a linear plasma generator that can simulate the high heat and particle flux conditions of future fusion reactors, three types of active spectroscopy will be installed in the coming years: TALIF, CARS and VUV-LIF. With this combination of diagnostics one can measure the (ground-state) densities of both atomic and molecular Hydrogen, as well as the ro-vibrational state distribution of H2 and its isotopologues. The ground state densities are important parameters in many of the detachment processes, and are also needed as input for scrape-off layer modelling. The ro-vibrational state distribution is important as it determines the reaction rate of MAR (Molecular Assisted Recombination), one of the dominant recombination processes in divertor plasmas. TALIF: Two photon Absorption Laser Induced Fluorescence At high enough laser intensity, TALIF can be used to measure the density of H atoms in the electronic ground state. The needed laser wavelength of 205.14 nm (for Lyman  absorption with 2 photons) is in the UV range. The resultant fluorescent Balmer  emission (in the visible range) is a measure for the density of the ground state Hydrogen atoms. CARS: Coherent Anti-Stokes Raman spectroscopy CARS is a four wave mixing process in which the plasma is simultaneously illuminated by two laser frequencies in the visible range, tuned to be resonant with the various ro-vibrational state transitions of H2 molecules. The resulting emitted CARS signal is also in the visible range and is a measure for the density of the resonant ro-vibrational states, including the H2 ground state density. VUV-LIF: Vacuum Ultraviolet Laser Induced Fluorescence For higher vibrational states (>2) the sensitivity of CARS is too low. The higher ro-vibrational states will hence be measured with VUV-LIF. The main challenge of this technique is the need for laser light in the VUV wavelength range, which will be obtained by frequency shifting via a Raman gain process called Stimulated Anti-Stokes Raman Scattering. The beamlines for both the laser and the fluorescence signal (detected using a VUV monochromator) need to be in vacuum. Preliminary designs for all three active spectroscopy methods will be presented.
X-Ray Emissivity Models as a Tool for Benchmarking Steady-State ECR Plasma Simulations
Presenter: Bharat Mishra (Università degli Studi di Catania, Italy; INFN-LNS, Catania, Italy)
Authors: Bharat Mishra, Alessio Galata, Giorgio Finocchiaro, Angelo Pidatella, Eugenia Naselli, Richard Rácz, Sándor Biri, Giuseppe Torrisi, Giorgio Mauro, David Mascali
Abstract: Electron cyclotron resonance (ECR) plasmas are systems where electrons are energised through resonance heating with microwaves and magnetically confined using min-B profiles. They contain cold ions diffused in a cloud of hot and dense electrons that frequently collide with each other and with radiation through collision-radiative (CR) processes, leading to sequential ionisation and excitation of the neutrals to high charge states [1]. Owing to the strong anisotropy and inhomogeneity of the system, simulation models developed for predicting space-resolved properties of plasma constituents are quite complicated [2,3], and benchmarks with suitable experimental data are the only way to assure their correctness. Soft X-ray spectra and fluorescence maps are not only a powerful non-invasive tool to extract density and temperature of warm electrons in ECR plasmas, but also validate simulation models based on them [4,5]. We present here space-resolved X-ray emissivity models developed to generate synthetic bremsstrahlung spectra and fluorescence maps, starting from ECR plasma simulation outputs. The predicted spectra are compared with experimental measurements, and discrepancies thereof are analysed to improve the 3D PIC-MC codes in use. Consequent updates to the simulation toolkits are useful not only for fundamental research into the operation of these ECR ion sources but also for applications making use of magnetised plasmas like the upcoming PANDORA facility [6]. References [1] A. Girard et al. Rev. Sci. Instrum. 75, 1381 (2004) [2] A. Galata et al, Front. Phys. Special issue (2022) [3] B. Mishra et al. Front. Phys. Special issue (2022) [4] R. Racz et al. Plasma Sources Sci. Tech. 26(7) (2017) [5] B. Mishra et al. Physics of Plasmas 28, 102509 (2021) [6] D. Mascali et al. Universe, 8(2), 80 (2022)
Oxygen plasma diagnostic for a negative ion beam source
Presenter: Jia Han (UNIL)
Authors: Jia Han, Joey Rubin, Philippe Guittienne, Ivo Furno
Abstract: Negative ion beams have broad applications and are of particular interest in the fields of fusion and accelerators. Previous studies have focused on H- or D- ions with beam diameters on the centimeter scale or larger. However, there is less research on other ion species and beam sizes in the millimeter range or smaller, which are critical for Secondary Ion Mass Spectroscopy (SIMS) applications. Radio frequency plasmas have been shown to be effective in generating ion beams for SIMS instruments, but a highly collimated and stable ion beam is required for achieving high spatial resolution on the target. To address the need for a highly collimated and stable ion beam for SIMS applications, we have developed a negative oxygen ion source capable of producing long-term steady-state operation using inductively coupled plasmas. The source can generate positive or negative ion beams with a few millimeters diameter. Ions are extracted from the plasma using a 2-grid system with a bias up to 10 kV. A filter magnetic field (up to 1000 Gauss) is applied at the beam exit to deflect electrons. To enhance plasma density, an additional DC magnetic field (up to 100 Gauss) is installed along the axis of the chamber. A Faraday cup with a secondary-electron suppressor plate is used to measure the ion beam current. The compactness of the beam source imposes great challenges on measuring any plasma parameters inside the chamber. The cylindrical chamber has one end dedicated for beam extraction, with electric and magnetic connections. The other (far) end of the chamber has space for only one small window. An optical fiber is placed looking into this window, and connected to a spectrometer that measures visible lines of the oxygen plasma. Previous literatures have not provided ways to interpret line ratio of visible light emission from Oxygen plasma without additional information. We therefore built a separate plasma chamber with similar operating regime to allow proper plasma diagnostic access. An experimental setup that includes a microwave interferometer and Langmuir probe is being developed to measure plasma density. One objective of this study is to establish a correlation between visible spectra line measurement and plasma density under identical collision conditions (same neutral pressure and electron temperature). This approach enables the estimation of plasma density in the source chamber that generates the ion beam. Additionally, this experimental setup can facilitate other diagnostic studies in the future.
15:40 - 17:40
Session 3 learn more
Chair: Ioannis Fitilis - Vice Chair: Mengfang Ren
Active and Passive Balmer-α Measurements in Magnetic Confinement Experiments
Presenter: Shaun Haskey (Princeton Plasma Physics Laboratory)
Authors: Shaun Haskey, Brian Grierson, Colin Chrystal
Abstract: Spectrally resolved Balmer-α measurements offer a plethora of information about magnetically confined plasmas that can be used to provide profiles of the bulk main-ion properties (temperature, rotation, density), hydrogenic isotope fractions in mixed isotope plasmas, and details about the fast ions and neutral energy distribution. In addition the spectrally resolved Stark split beam emission can be used to characterize the neutral beam injector energy fractions, provide information about |B| and the bootstrap current, and assist in aligning ion and electron pedestal profiles. Whether an operating neutral beam injector is viewable (active vs passive measurements) determines which measurements are possible at a particular time along with the location of the measurement. For example, information on the bulk ions is available when a neutral beam injector in the line of sight is on (active) while neutral energy distribution information is available when it is off (passive). While a large number of measurements are possible, they are not simultaneously available and interpretation can be challenging due to atomic physics effects that can distort the measurements, and the complexity of multiple overlapping features in the spectrum. Despite these challenges, significant progress has been made using collisional radiative modeling to correct the measurements and comprehensive models to fit the spectrum, allowing these measurements to form the cornerstone of a variety of physics investigations. An overview of the measurements available from the Balmer-α spectrum along with the challenges associated with atomic physics corrections and fitting the spectrum will be presented with a focus on their application at DIII-D as well as other tokamaks and stellarators. This work was supported in part by the US Department of Energy under DE-FC02-04ER54698, and DE-AC02-09CH11466.
Diagnostic challenges for the JET DTE2 Campaign
Presenter: Scott Silburn (1United Kingdom Atomic Energy Authority, Abingdon, UK)
Authors: Scott Silburn
Abstract: In 2021 the Deuterium-Tritium (D-T) Experiment campaign 2 (DTE2) was conducted at the Joint European Torus (JET), achieving a new fusion energy world record and performing experiments to address key physics issues to inform ITER D-T operations. Availability of a comprehensive diagnostic set compatible with D-T plasmas was crucial to these achievements, with DTE2 benefitting from substantially increased diagnostic capabilities compared to the previous JET D-T campaign (DTE1) in 1997. DTE2 posed challenges for diagnostics not faced during operations with other fuel species, and a unique opportunity to evaluate solutions to these challenges. This talk will give an overview of the challenges faced by diagnostics for DTE2 and the work carried out to address them. The principal diagnostic challenges faced for DTE2 included: DT-specific measurement requirements, particularly for fusion products and plasma composition; greatly increased deleterious radiation effects on components in the machine hall; reduced opportunities for maintenance, calibration & repair; effects of tritium ingress to vacuum-coupled diagnostics; and a greatly increased complexity of coordinating diagnostic requirements and operational resources with the experiment planning due to strict Tritium and 14 MeV neutron budgets. An extensive programme of preparation was undertaken prior to DTE2, including significant upgrades to neutron & gamma-ray spectroscopy and tomography systems; installation of two new long track (~40m) optical image relay systems to re-locate several camera diagnostics to a shielded area outside the machine hall; re-locating or shielding radiation-sensitive diagnostic components where practical; and development of data analysis tools and techniques to be able to meet the D-T specific requirements. New control room tools were implemented to help coordinate and confirm diagnostic setup and readiness for each D-T pulse. During the experimental campaign, while many diagnostics operated with high availability and little or no performance degradation, a minority suffered degradation or failures, as anticipated when operating in the D-T environment. Radiation-induced transmission loss was observed in optical components, for example loss of ~40% in the unheated optical fibres used in the motional Stark effect diagnostic (although with relatively minor impact on the diagnostic operation). Malfunction of data acquisition electronics in the machine hall caused some ultraviolet spectroscopy and soft X-ray detection systems to become inoperable during the campaign, as expected. Ongoing work to quantify, and where possible mitigate, such effects will be discussed.
Design of a wide-angle infrared visible viewing system using reflective optics on EXL-50 spherical tours
Presenter: Dong Guo (Hebei Key Laboratory of Compact Fusion)
Authors: Dong Guo, Qifeng Xie, Dong Guo
Abstract: EXL-50 is a solenoid-free spherical tours with its major and minor radius 0.58 and 0.39 m. A high-resolution imaging system, consisting of mid-IR and visible cameras along the same line of sight, has been installed for the EXL-50[1-2]. This diagnostic system has a wide field of view with 70°×70°, which can provide imaging of the entire poloidal cross-section during a shot. The visible camera V1212 has a system capability of 5 mm spatial resolution at the ROI (region of interest) and a maximum 10kHz full resolution frame rate. The IR camera Telops M120 can operate between 3.5 and 5 μm waveband and up to sampling frequency of 210 Hz with a resolution of 640×480 pixels. In order to improve the resolution limit of the optics in the visible range, the Cassegrain telescope design is implemented like the design of JET and W7-X stellarator [3]. The reflecting mirrors are composed of a flat mirror with a 10 mm diameter aperture and an aspherical concave mirror. After a full-band ZnS sealed lens, the back-end transmitting lenses are adapted to the different detectors for mid-IR and visible observations, with their optical light paths separated by in-air dichroic beam splitters. By comparing the IR-measured temperature with those from the thermocouples which were installed beneath the surface of divertor target tiles during vacuum vessel baking, the key parameters of IR thermography have been calibrated. At the forefront of the optical path, a modified mechanical iris shutter with 18 blades is installed in the vacuum chamber. It not only has excellent space utilization but also can withstand up to 200℃ high temperature baking.
Diagnostic overview for the first operational phase of the SMART tokamak
Presenter: Diego Jose Cruz Zabala (University of Seville)
Authors: Diego Jose Cruz Zabala, Eleonora Viezzer, Manuel García-Muñoz, Alfonso Rodriguez-Gonzalez, Fernando Puentes del Pozo, Juan Sanchez Gamino, Pablo Vicente Torres, Jesus Salas Suarez-Barcena, Joaquin Galdón-Quiroga, Manjit Kaur, Luis F. Delgado-Aparicio, Alessio Mancini, Jorge Segado Fernandez, Stefano Munaretto, Jack Berkery, Mario Podesta, Ahmed Diallo
Abstract: In order to characterize the plasmas obtained in the Small Aspect Ratio Tokamak (SMART), a set of diagnostics is being developed for the first years of operation. SMART is a new spherical tokamak (ST) currently being assembled at the University of Seville. This new machine aims to explore a new possible path to compact fusion reactors: STs operating in negative triangularity (NT). NT plasmas in low confinement mode (L-mode) present positive triangularity (PT) high confinement mode (H-mode) like core confinement without edge localized modes (ELMs) [1,2]. The reduced heat loads achieved in NT relax the requirements for the heat exhaust, lowering the cost of the machine. STs can accommodate plasmas with high beta, and they are more compact than standard tokamaks, which also helps to reduce the cost of the reactor. This contribution presents an overview of this set of diagnostics composed by the magnetics suite, a gas puff-based Charge eXchange Recombination Spectroscopy (CXRS) diagnostic, an interferometry system, a Thomson Scattering (TS) diagnostic, radiated power density (Prad) measurements as using fast Si diodes, as well as visible spectrometers for impurity monitoring. The magnetics suite will allow us to reconstruct plasma equilibria and measure plasma instabilities. It is composed of Rogowski coils, Mirnov coils, poloidal flux loops, and diamagnetic loops. Impurity temperature, rotation and density measurements will be provided by the gas puff-based CXRS diagnostic [3]. A poloidal array of these systems is planned such that the poloidal variation of the impurity properties can be studied in NT and PT plasmas (see figure 1) with a radial resolution of ~ 3 mm and a temporal resolution of ~ 2 ms. To measure the line integrated electron density, a heterodyne interferometer will be implemented with three radial and three vertical chords using mm microwaves as its source. A synthetic model has been developed to aid in the study of time and density resolution. A 16-channel Thomson scattering (TS) diagnostic will be employed to measure local electron temperature and density in the mid-plane. The diagnostics measurement locations for TS, Prad and visible spectrometer are arranged such that the edge pedestal can be resolved on the high-field and low-field sides in both PT and NT plasma scenarios. The design of the diagnostics above mentioned will be described and synthetic signals will be presented
X-Ray Phase-Contrast Imaging of Imploding Strong Shock Waves
Presenter: Wolfgang Theobald (Focused Energy)
Authors: Wolfgang Theobald, Duc Cao, Luke Ceurvorst, John Ruby, Matthew Khan, Nigel Woolsey, Victorien Bouffetier, Alexis Casner, Dimitri Batani, Francesco Barbato, Olena Turianska, Robbie Scott
Abstract: The application of phase-contrast imaging to diagnose laser-induced shock waves is a powerful technique to determine the shock-front position in both the high- and low-density region of the target. It is an ideal tool to detect multiple shocks, shock-front asymmetries, and to study hydrodynamic instabilities in the context of inertial confinement fusion and high-energy density physics. The platform was first developed in planar geometry on OMEGA EP by applying a short pulse backlighter and a cylindrical CH target. High-quality radiographs of the shock front with phase-contrast enhancement were obtained for single-shock and double-shock experiments. A follow-up experiment applied the platform to spherical implosions. The 60 OMEGA UV laser beams compressed a 1-mm-diam CH sphere with a 1-ns square pulse; the IR short-pulse beam from OMEGA EP (100 ps, ~5 x 10^16 W/cm^2) was focused onto a Cu wire with a of 10-micron diameter producing x rays in the 8- and 9-keV range, which were detected by either an image plate or a time-gated x-ray framing camera. Radiographs with phase-contrast enhancement of the imploding shock wave were captured at different probing times by shifting the timing between drive and backlighter in subsequent shots.
18:10 - 20:00
Session 4 learn more
Chair: Shaun Haskey - Vice Chair: Scott Silburn

Chair: Shaun Haskey - Vice Chair: Scott Silburn

High Resolution Radiography Researches Based on Picosecond Laser: A Review of Experiments at Shenguang II Upgraded Facility
Presenter: Yuqiu Gu (professor)
Authors: Yuqiu Gu
Abstract: High spatial resolution X-ray radiography has widely applications in inertial confinement fusion (ICF) and high energy density physics (HEDP) experiments. Generally, the X-ray sources used in ICF and HEDP experiments are produced by high energy nanoseconds laser heating a planner target, with which a high resolution radiography must been with the aid of imaging elements. Unlike long-pulse laser drive X-ray sources with large size and nanosecond orders pulse duration, the short-pulse laser drive X-ray sources with short pulse and higher X-ray energy, thus higher penetrating power, but no imaging elements, its imaging diagnostics generally work in point projection mode. In this talking, the x-ray source characters and imaging diagnostic researches at Shenguang II upgrated facility based on short pulse laser will be reviewed. Time-resolved radiographic images of the ICF targets were obtained with hard X-rays generated by irradiating a short-pulse laser on a metal microwire. High-resolution X-ray flash radiography of Ti characteristic lines with a multilayer Kirkpatrick–Baez microscope was also developed on the Shenguang-II (SG-II) Update laser facility. The optical design, multilayer coatings, and alignment method of the microscope and the experimental result of Ti flash radiography of the Au-coned CH shell target on the SG-II Update are described. References 1) Radiography of direct drive double shell targets with hard x-rays generated by a short pulse laser. Chao Tian, Minghai Yu, Lianqiang Shan, Yuchi Wu, Tiankui Zhang,Bi Bi, Feng Zhang, Qiangqiang Zhang, Dongxiao Liu, Weiwu Wang,Zongqiang Yuan, Siqian Yang, Lei Yang, Weimin Zhou, Yuqiu Gu* and Baohan Zhang, Nucl. Fusion 59 (2019) 046012 2) Enhanced energy coupling for indirect-drive fast-ignition fusion targets. F. Zhang, H. B. Cai* , W. M. Zhou, Z. S. Dai, L. Q. Shan, H. Xu, J. B. Chen, F. J. Ge,Q. Tang, W. S. Zhang, L. Wei, D. X. Liu, J. F. Gu, H. B. Du, B. Bi S. Z. Wu, J. Li, F. Lu, H. Zhang,B. Zhang, M. Q. He, M. H. Yu, Z. H. Yang, W. W. Wang, H. S. Zhang, B. Cui, L. Yang, J. F. Wu,W. Qi1, L. H. Cao, Z. Li1, H. J. Liu, Y. M. Yang, G. L. Ren, C. Tian, Z. Q. Yuan, W. D. Zheng, L. F. Cao1,C. T. Zhou, S. Y. Zou, Y. Q. Gu*, K. Du1, Y. K. Ding, B. H. Zhang, S. P., Nature Physics.04(2020) 3) High-energy X-ray radiography of laser shock loaded metal dynamic fragmentation using high-intensity short-pulse laser. Genbai Chu, Tao Xi, Minghai Yu et al. Rev. Sci. Instrum. 89, 115106 (2018). 4) High-resolution X-ray flash radiography of Ti characteristic lines with multilayer Kirkpatrick–Baez microscope at the Shenguang-II Update laser facility. Shengzhen Yi, Feng Zhang, Qiushi Huang, Lai Wei, Yuqiu Gu, and Zhanshan Wang, High Power Laser Science and Engineering, (2021), Vol. 9, e42
Modelling and Design of a Hard X Ray Spectrometer for TCV
Presenter: Luke Simons (Swiss Plasma Center)
Authors: Luke Simons, Umar Sheikh, Joan Decker, Basil Duval, Mathias Hoppe, Eva Tomesova, Ondrej Ficker, Jaroslav Čeřovský
Abstract: Fast electron populations in tokamak plasmas are vulnerable to runaway acceleration up to relativistic energies as the collisional drag decreases with increasing velocity. These Runaway Electrons (REs) are anticipated to pose a threat to ITER in post-disruption scenarios [1], as they have the potential to cause significant damage that may halt operation [1, 2]. A path to benign termination of RE beams has recently been developed [3, 4] and preliminary experimental findings suggest that it may be related to changes in RE energy [5]. It is therefore necessary to measure these energy distributions to investigate the underlying physics. In this work, the design and modelling of a Hard X-Ray spectrometer for the Tokamak à Configuration Variable (TCV) is presented. The optimisation of the design for an ITER relevant, LaBr3 scintillator based, Hard X-Ray spectrometer is evaluated under constraints related to calibration, shielding, collimation, signal processing and modelling with the aim of recovering information about the initial energy distribution. This scheme is informed in part by recent measurements made using CeBr3 scintillator detectors on loan from the GOLEM tokamak [6] as well as by simulations performed using Geant4 [7] that are used to build synthetic detector response functions. In this work, favorable shielding and collimation geometries are demonstrated that attenuate the photon flux without adversely affecting the reconstructed spectrum. The inversion of the simulated, detector response to reconstruct the photon energy spectrum is successfully validated using calibration data and test exponential distributions by regularization with Minimimum Fisher Information. This detection method is therefore demonstrated to provide useful reconstructions of the photon energy distribution from measured spectra that may constrain physical models of the electron velocity distribution function. References [1] Boozer, A. H. (2017). Nuclear Fusion, 57(5). [2] Matthews, G. F., et al. (2016). Physica Scripta, 2016 (T167). [4] Paz-Soldan, et al. (2019). Plasma Physics and Controlled Fusion, 61(5). [5] Reux, C., et al. (2021). Physical Review Letters, 126(17), 1–7. [4] Sheikh, U. (2022). Second Technical Meeting on Plasma Disruptions and Their Mitigation Contribution. [5] Esposito, B., et al. (1996). Plasma Physics and Controlled Fusion, 38(12), 2035–2049. [6] Cerovsky, J., Ficker, et al. (2022). Journal of Instrumentation, 17(1). [7] Agostinelli, S., et al. (2003) Nuclear Instruments and Methods in Physics Research, 506(3), 250–303.
TALIF diagnostic for atomic hydrogen density in divertor-relevant plasmas
Presenter: Kaden Loring (Dutch Institute for Fundamental Energy Research (DIFFER), SLAC National Lab, Stanford University )
Authors: Kaden Loring, Kay Schutjes, Hennie van der Meiden, Jordy Vernimmen, Ivo Classen
Abstract: Detachment is a mandatory operating condition to maintain power loads well below 20 MW/m^2 in the ITER divertor. However, experimental data for validation of the SOLPS-ITER fluid-kinetic code is missing. Namely, atomic density and the ro-vibrational distribution during detachment are not known. For this reason, a Two-photon Absorption Laser Induced Fluorescence (TALIF) diagnostic has been developed for measuring spatially-resolved atomic density profiles of ground-state hydrogen in Magnum-PSI; a linear device uniquely capable of producing ITER-divertor relevant plasma conditions. The TALIF diagnostic is based on a Sirah Cobra-Stretch dye laser (10 Hz, pulse width 8 ns), pumped by an Nd:YAG, which generates ~205 nm light (8 mW) by third-harmonic generation. Using the two-photon transition, ground-state atoms are excited to the n=3 level. The fluorescence (H-alpha) from n=3 to n=2 is detected by a gated ICCD camera and is a measure for the atomic density. The diagnostic has been successfully implemented on the Upgraded Pilot PSI (UPP) linear plasma device, where density measurements were made over a range of plasma parameters (ne < 8x10^19 m^-2, Te < 3.5 eV). Both the diagnostic design and density measurements from UPP are discussed. The diagnostic will be subsequently installed on Magnum-PSI in early 2023 and thereafter experiment-code benchmarking will take place.
Progress of high spatial and temporal resolution diagnosis for inertial confinement fusion experiments In ShengGuang 100KJ laser facility
Presenter: Feng Wang (Laser Fusion Research center, China Academy of Engineering Physics, Mianyang 621900, China)
Authors: Feng Wang
Abstract: In the laser driven inertial confinement fusion (ICF) experiment, it is necessary to compress the mm scale hollow target more than 30 times in a spherically symmetric and low entropy manner, forming a core of about 50μm high temperature and high density plasma hot spot, and then ablate the peripheral fusion fuel to support combustion. ICF implosion compression and fusion combustion are in a physical process of rapid contraction of space scale and accelerated evolution of time scale. However, due to driving symmetry, mixing of shell interface and hot spot caused by fluid instability growth, high-order mode of hot spot interface, asymmetry of hot spot and other factors, implosion performance is often significantly lower than theoretical design expectation, and it is necessary to develop high time-space resolution diagnostic technology and diagnostic instruments, The state evolution of ICF target in each stage of the implosion process in the experiment is precisely characterized to judge the physical and engineering factors affecting the implosion performance. In the implosion loading stage, factors such as the loading symmetry of the shock wave and the flatness of the wave front will become the seeds of the growth of the implosion compression symmetry and fluid instability. The research team has developed the three-axis velocity interferometer system for any reflector (VISAR) technology to characterize the driving symmetry of the multi angle shock wave, and has developed the 2ps resolution two-dimension VISAR to diagnose the non-uniformity of the wave front velocity field, At present, compressed ultrafast photography (CUP) VISAR technology is being developed and it is expected to realize the time evolution measurement of shock wave front with more than 50 frames. In the internal protection retardation and combustion stage, recently, a variety of high spatial and temporal resolution imaging diagnostic technologies have been developed mainly around the mode of retardation hot spot and hybrid analysis. The research team has established an ultra-high spatial and temporal resolution X-ray microscopic imaging method based on Wolter like microscopic imaging and magnetic drift time broadening camera, which can achieve 3μm space resolution and 10ps time resolution X-ray imaging in the 8keV energy region is expected to realize the imaging analysis of the eighth order mode and the following high mode of the hot spot interface; Developed a resolution of 6 μ M's toroidal curved crystal imaging technology, and the fluorescence imaging diagnosis method of missing elements has been established, and the diagnosis of fluid disturbance growth caused by isolated defects such as gas filled tubes has been carried out; The design of multi energy point KB imaging microscope and the diagnosis method of spatial distribution of hot spot bremsstrahlung intensity are proposed, which are used to measure the spatial distribution of hot spot electron temperature and diagnose the spatial distribution of mixing zone; A new method of variable cone curved crystal spectrum measurement is designed, which can increase the X spectrum sensitivity by more than 100 times in the energy range of 1-10 keV, and realize the high signal noise ratio measurement of the emission spectrum of trace mixed elements.
Diagnosis Integrated Control and Intelligent Operation in Inertial Confinement Fusion
Presenter: Bolun Chen (Laser Fusion Research Center, CAEP)
Authors: Bolun Chen, Feng Wang, Peng Wang
Abstract: For Inertial Confinement Fusion experiments, different kinds of diagnosis with hundreds of channels are used to inspect the target area. The whole fusion process and abundant of physics information would be measured by these diagnoses which are important to understand the physics phenomenon and to achieve the ignition. The application of the integrated computer control system (ICCS) will enhance the experiment efficiency, safety, and reliability, especially for the huge laser facility. Compare to the laser facility, the diagnostic configurations are more flexible and will be adjusted for different experimental design, which is a big challenge for the design of the diagnosis integrated control system. A novel diagnosis integrated control system has been designed for ShenGuang laser facility. The system adopts BS architecture, and the novel micro-service framework is used to improve the scalability, maintainability, and reliability of the system. For system service layer, a visual drag-and-drop programming tool has been developed. The diagnostic operation process can be quickly edited and packaged according to the experimental requirements. The system runs in a process-driven way. Coupling to the operation nodes of the laser facility, the sub-processes of each diagnosis are automatically implemented. Tango-controls middleware is used in the device service layer. The diagnosis units are abstracted and secondary developed according to the process control requirements. Except the hardware of the diagnosis, the image recognition and data statistics modules, as virtual units, are developed under the tango-controls framework and coupled to the corresponding device. These AI techniques are used for the diagnosis aiming, parameters setup and data pre-analysis. In the future, the 3D visualized virtual diagnosis will also be coupled to the control system, like ‘digital twiner’, to show the real-time status of the diagnosis and to improve the safety of the experiments. At present, the system V1.0 has been released and applied to the experiments
09:00 - 10:55
Session 5 learn more
Chair: Marco Feroci - Vice Chair: Nektarios Papadogiannis
High-Resolution Laboratory Measurements Advancing Diagnostics of Astrophysical and Fusion Plasmas
Presenter: Chintan Shah (NASA Goddard Space Flight Center | Max-Planck-Institut für Kernphysik)
Authors: Chintan Shah
Abstract: The latest generation of high-resolution UV and X-ray spectroscopic instruments available onboard current and future satellite observatories present exciting opportunities to investigate processes occurring in astrophysical plasmas, particularly those found in galaxy clusters and near active galactic nuclei. However, the insights that can be gained from analyzing the observed spectra are currently limited by the availability and quality of atomic data, which are crucial for developing plasma diagnostic models. This limitation is particularly acute for highly charged ions (HCI) that are ubiquitous in hot astrophysical environments as well as magnetically confined fusion plasmas. Laboratory measurements are essential for providing atomic data, such as transition energies, and excitation and ionization rates. We use electron beam ion traps and synchrotron light sources to resonantly excite electronic transitions in trapped HCI. This enables us to gather and benchmark spectroscopic data with unprecedented accuracy, leading to new insights into astrophysical plasma diagnostics.
PROTO-SPHERA: a magnetic confinement experiment which emulates the jet + torus astrophysical plasmas
Presenter: Franco Alladio (PROTO-SPHERA )
Authors: Franco Alladio
Abstract: The phenomenon of magnetic reconnection is ubiquitous in astrophysical plasmas, from the terrestrial Magnetosphere, to the solar Corona, to the Pulsar-wind Nebulae until to the AGN jets. These phenomena can be so summarized: near a point, or a curve, where two magnetic field lines touch each other, but have opposite field direction (so-called X-points), a "tearing" of those lines occurs, followed by a different "stitching" between them; the new resulting magnetic field configuration has a lower energy and so this leads to thermal plasma heating as well as to super-thermal particles acceleration. In magnetic reconnections magnetic flux and electric current are transferred as well. The PROTO-SPHERA experiment was built at the CR-ENEA in Frascati as an innovative configuration of plasma magnetic confinement, in view of Controlled Fusion research, and it is quite different from the confinement experiments studied so far. PROTO-SPHERA attempts to emulate in the laboratory the jet + torus astrophysical plasmas; an internal magnetized plasma centerpost (jet) on the axis of symmetry of the configuration, surrounded by a magnetized plasma torus orthogonal to the plasma centerpost. The confined plasma geometry is simply connected: no metal conductor is topologically linked to the plasma torus and the vacuum chamber is a simple cylinder. The plasma centerpost is sustained by a DC voltage, applied between electrodes internal to the vacuum vessel, and a confined plasma torus is formed by self-organization around the plasma centerpost: the lines of force that wind around the centerpost are broken and reconnected into lines of force winding along the torus. The experiment is capable of sustaining the confined torus as long as the centerpost is kept running, provided that magnetic reconnections are recurring and that the magnetic flux transfer from the jet to the torus is efficient enough. The first difference between PROTO-SPHERA and its cosmical examples is that in Astrophysics the virial theorem is fulfilled by the gravitational force, whereas in the case of a laboratory experiment it is fulfilled by magnetic fields produced by poloidal field coils external to the plasma. The second difference is that in the Pulsar Wind Nebulae models the current in the plasma jet has opposite directions in the 2 emispheres, whereas in PROTO-SPHERA the plasma current goes through the center of the magnetic configuration without changing direction. The final difference is that in non-relativistic Astrophysics the solenoidal condition for the plasma current density is always satisfied; instead in a laboratory experiment the plasma charges all nearby metallic conductors present inside the vacuum vessel. But these charged metal surfaces cause an rotation of the overall plasma around its symmetry axis: recent observation of the tilted azimuthal rotation of the plasma and of the non-axisymmetric nature of the recurring magnetic reconnections, show that in PROTO-SPHERA the production of closed toroidal flux surfaces is associated with a plasma that acts as a slightly oblique rotator, which is an unexpected similarity to the oblique plasma rotators present in Pulsar Wind Nebulae.
Space Resolved Electron Density and Temperature Evaluation by X-Ray Pinhole Camera in ECR Plasma
Presenter: Giorgio Finocchiaro (Università degli Studi di Catania, Italy; INFN-LNS, Catania, Italy)
Authors: Giorgio Finocchiaro, Eugenia Naselli, Bharat Mishra, Sándor Biri, Maria Mazzaglia, Angelo Pidatella, Richard Rácz, Giuseppe Torrisi, David Mascali
Abstract: X-ray space-resolved emission characterization can provide relevant features of plasmas in terms of local distribution of electron density and temperature. In the PANDORA project [1] framework and in the context of the collaboration between ATOMKI and INFN-LNS laboratories, a high resolution full-field X-ray pin-hole setup was developed. It consists of a 400 μm hole in a lead disk coupled with a 1 MP X-ray CCD camera (sensitive in~ 1 – 20 keV energy range) and a multi-layered Pb collimator. Advanced analysis techniques for single-photon-counted (SPhC) and high-dynamical-range (HDR) analysis [2] were developed, allowing X-ray imaging and space-resolved spectroscopy at high energy and spatial resolution (560 μm and 230 eV @ 8.1 keV respectively). We here present the first quantitative evaluation of local warm electron density and temperature of an Electron Cyclotron Resonance (ECR) Argon plasma heated by 200 W microwave power in the 14 GHz ECR ion source (ATOMKI, Debrecen). Thermodynamic parameters have been extracted by the analysis of the local fluorescence and bremsstrahlung spectra, according to the theoretical emissivity model [3,4] in the approximation of local Maxwell-Boltzmann distribution of electron energies (LTE – local thermodynamic equilibrium). The technique is then supported by the comparison with a properly developed theoretical model [4], which gives a further constraint on fitted parameters by considering the fluorescence emission from plasma ions. Several regions of interest (ROIs) of the image were selected, studying the non-homogeneity of plasma parameters inside the ECR plasma volume, comparing temperature and density maps in the plasma core ROI vs the peripheral regions. The analysis method is a powerful tool to investigate the confinement of magnetic plasmas and heating dynamics, with relevant implications about R&D of ECR Ion Sources as well as for fundamental plasma physics and nuclear physics research in these setups. References [1] D. Mascali et al. Universe, 8(2), 80 (2022) [2] E. Naselli et al JINST 17 C01009 (2022) [3] A. Gumberidze et al. Rev. Sci. Instrum. 81, 033303 (2010) [4] B. Mishra et al. Physics of Plasmas 28, 102509 (2021)
Development and Commissioning of Upgraded Microwave Radiometer for CTS Diagnostics at W7-X Stellarator
Presenter: Sergiy Ponomarenko (Max-Plank Institut für Plasmaphysik, D-17491 Greifswald, Germany)
Authors: Sergiy Ponomarenko, Dmitry Moseev, Torsten Stange, Paul Stordiau, Harald Braune, Gerd Gantenbein, Jelonnek John, Laurent Krier, Alexei Kuleshov, Heinrich Laqua, Carsten Lechte, Stefan Marsen, Stefan Nielsen, Hans Oosterbeek, Burkhard Plaum, Riccardo Ragona, Jesper Rasmussen, Tobias Ruess, Jonas Zimmermann
Abstract: In this paper, we present the design of the upgraded microwave CTS receiver at Wendelstein 7-X. This is a heterodyne radiometer designed to perform measurements of collective Thomson scattering radiation around frequencies of both 140 GHz and 174 GHz. The key aspect of this upgrade is the additional operation frequency range around 174 GHz characterized by low electron cyclotron emission background and reduced refraction. This allows receiving the scattering radiation with improved signal-to-noise ratio and extends the set of possible scattering geometries. We have characterized the transmission losses of the passive microwave components of the receiver and the performance of down-converter units for both operation frequency ranges. The noise factor of the system has been defined. Finally, we present and discuss initial measurements.
11:30 - 13:40
Session 6 learn more
Chair: Karl Krushelnick - Vice Chair: Franco Alladio
Temporally and spatially resolved characterization of capillary discharge plasma density profile using emission spectroscopy
Presenter: Alamgir Mondal (Extreme Light Infrastructure ERIC, Za Radnici 835, 25241 Dolni Brezany, Czech Republic)
Authors: Alamgir Mondal, Konstantin O. Kruchinin, Petr Zimmermann, Eugene Vishnyakov, Sebastian Niekrasz, Srimanta Maity, Alexander Molodozhentsev
Abstract: Study of a plasma produced by an electrical discharge in a gas filled capillary is one of the crucial aspects in the development of modern, state-of-the-art Laser Wakefield Accelerators. In such capillaries, generated plasma provides a specific radial electron density profile that effectively creates a guiding plasma channel. The formation of a plasma channel allows for creation of tailored wake fields and for the efficient transport of the driver laser beam over long distances by avoiding the laser diffraction. The target plasma is generated via a capacitive discharge circuit designed to provide a discharge voltage of up to ~25 kV and current of up to ~350 A over 1--3 cm long square-shaped sapphire capillary with varying edge length from 300 $\mu$m to 500 $\mu$m with a total discharge duration of a few hundreds nanoseconds. For achieving required gas pressure inside the capillary a continuous hydrogen gas flow is controlled via multiple input channels with separate mass flow controllers. The use of other gasses or gas mixtures is also possible. Plasma density is measured by analyzing the Stark broadening of hydrogen Balmer lines in the visible wavelength range (mainly Hα and Hβ lines). Estimation of plasma temperature is also possible by applying Boltzmann equation. The experimental setup allows for both longitudinal and transverse plasma density profiles to be reconstructed with a very high spatial resolution. The evolution of the plasma density profiles is measured with 10–20 ns steps by utilizing fast gated, intensified scientific Complementary Metal–Oxide–Semiconductor camera. Here we present an overview of the plasma diagnostics laboratory designed for a comprehensive plasma target characterization. The setup is built in the frame of laser-driven Free Electron Laser development project - LUIS at ELI-Beamlines in Czech Republic. Design features and a description of all the instrumentation used to characterize the plasma target and diagnostic systems will be presented.
Recent progress of Thomson scattering diagnostics at the 100kJ-level laser facility in China
Presenter: Hang Zhao (Laser Fusion Research Center, China Academy of Engineering Physics)
Authors: Hang Zhao
Abstract: The ultraviolet Thomson scattering diagnostics at the 100kJ-level laser facility in China has been upgraded by 2022. This upgraded diagnostic system allows simultaneous measurement of both time-resolved and space-resolved Thomson scattering spectra, with up to 7 measurement branches in 3 scattering angles (42-degree forward scattering, 90-degree side scattering, and 138-degree backscattering). Multiple plasma parameters can be obtained by flexibly choosing and combining Thomson scattering signals from different angles and different wavelengths (i.e. ion spectra around 263nm and electron spectra in 200nm-250nm). Experiments are conducted based on this diagnostic system to study the plasma conditions in gas-filled hohlraums for inertial confinement fusion. Besides obtaining more accurate plasma parameters (electron/ion density, temperature, flow velocity etc.) for benchmarking radiation hydrodynamic models, a wider range of physical issues can be studied further, including hydrodynamic instabilities (Rayleigh-Taylor instability and Kelvin-Helmholtz instability) and mixing at the interface of gas and wall plasma, return current instability in the hohlraum coronal region, two plasmon decay instability, etc.
1D Space-Time & 2D Space Resolved Hot Electron Generation At Shock Ignition Relevant Laser-Matter Coupling Parameters
Presenter: Oldrich Renner (Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic)
Authors: Oldrich Renner, Dimitri Batani, Gabriele Cristoforetti, Michal Červeňák, Roman Dudzak, Evgeny Filippov, Pavel Gajdoš, Leonida A. Gizzi, Libor Juha, Philipp Korneev, Petra Koester, Miroslav Krůs, Artem Martynenko, Philippe Nicolai , Sergey Pikuz, Tadeusz Pisarczyk, Sushil Singh, Alessandro Tentori , Stefan Weber
Abstract: The detailed investigation of HE production and their interaction with matter is of paramount interest for fundamental directed research in the fields of laboratory astrophysics and in general high-energy-density physics. The more practical applications refer to the HE role in a development of diverse scenarios for inertial confinement fusion, where the laser coupling to fast electrons and their transport inside the ICF capsules affects the efficiency of the energy delivery to the ignition region. This is particularly true for the shock ignition scheme anticipating the ignition by the sub-ns-laser spike with intensity close to 10^16 W/cm2. The kinetics of HE generation and their impact on formation of strong shocks however have not been fully understood yet. The aim of experiments conducted at the Prague PALS laser facility is to collect precise data needed for development of theoretical models describing the HE formation, transport, and energy deposition inside targets which affect the dynamics of strong shocks. Here we report x-ray measurements characterizing HE generation via 1D space-time and 2D space-resolved imaging of HE-induced Kα emission inside the cold target material. The experiments were performed at the PALS iodine laser facility with intensities up to 2×10^16 W/cm2, i.e., at parameters of the laser-plasma coupling suitable to address the physics of the laser spike induced shock wave igniting the fusion reaction. The principal part of the experimental setup consisted of the imager which combined the spherically bent crystal of quartz (422) with the Hamamatsu x-ray streak camera or with the absolutely calibrated imaging plate detector to obtain magnified monochromatic images of the HE-induced K-shell emission from the laser irradiated Cu containing targets. The experimental limits of the HE measurements are derived, the algorithms used for reconstruction of raw images via application of the ray tracing procedure and the Geant4 code are described. The HE characteristics observed at different geometry flat and spiral-shaped targets are presented and discussed in detail.
Gain evaluation for low-density np/nB >1 proton- Boron fusion plasmas
Presenter: Stavros Moustaizis (Technical University of Crete)
Authors: Stavros Moustaizis, Chrysovalanti Daponta, Shalom Eliezer, Zohar Henis, Paraskeuas Lalousis, Noaz Nissim, Yonatan Svhweitzer
Abstract: Fusion energy power plans based on compact magnetic fusion devices are funded in the USA and China [1, 2, 3]. For this type of devices, p-11B fuel is attractive, not only because of its corresponding aneutronic nuclear fusion reaction, which produces three (3) charged alpha particles of 8.7 MeV total energy that can directly be converted into electricity, but also because it is not necessary to be equipped with breeding technologies for the production of the necessary components of the fusion fuel (p, 11B plenty abundant in nature). The last few years, power plans based on laser ignited fusion, have proposed the use of the p-11B fuel [4]. The disadvantages of the p-11B fuel are the Bremsstrahlung radiation losses and the fact that p-11B nuclear reaction presents a maximum at approximately 670 keV, which is high compared to the 10 keV of D-T fuel. Theoretical works [5,6] investigate the interpretation of the relatively high alpha particle generation (1011) of the recent laser-based p-11B fusion experimental results [7, PALS facility], through the introduction of the chain reaction and the avalanche effect. The latter effects are responsible for the energy transfer from the fusion born alphas to the p, 11B fusion species and the improvement of the reaction rate (RR). The use of a multi-fluid code enables us to evaluate the temporal evolution of the fusion medium parameters, the necessary time for the reaction rate (RR) maximization, the energy transfer from the produced alpha to the fusion species (p, 11B), which results to an important increase of the energy of the latter to values corresponding to the optimum p-11B cross section and the contribution of the produced alphas density on the rapid rise of the RR [8, 9, 10, 11].. The numerical simulations concern initial densities of 10 19 – 10 20 m-3, which are close to magnetic confinement fusion, and initial temperatures of the order of 80 keV or lower, that are relatively low, compared to the energy corresponding to the maximum of the p-11B fusion cross section. In the present work, the initial density conditions are selected with a ratio of np/nb > 1, favorable for the Bremsstrahlung losses optimization. The numerical results show the importance of the chain reaction and the avalanche effect, that contribute to the feasibility of p-11B fusion ignition for relatively low initial medium temperatures. The gain evaluation for two distinct cases with density ratio of the fusion species np/nΒ > 1 will be explored and compared: i) A p-11B fusion medium with initial temperature typically at 80 keV and ii) The interaction of a Boron plasma of 80 keV initial temperature with protons (proton fluid with energy lower than 1 MeV). These numerical results could be applied for potential experiments, using magnetic mirror-like configuration. Potential experimental set up with the related diagnostics will be presented and discussed. References [1] T. J. Mcguire, “Heating plasma for fusion power using magnetic field oscillation”, US Patent 2014/0301519, 2014. [2] N. Rostoker, M. W. Binderbauer, H. J. Monkhorst, “Colliding Beam Fusion Reactor”, SCIENCE, VOL. 278, p. 1119, 1997, [3] ENN Compact Fusion Technology, [4] H. Hora, S. Eliezer, G. J. Kirchhoff, N. Nissim, J. X. Wang, Y. X. Xu, G. H. Miley, J. M. Martinez-Val, W. McKenzie, and J. Kirchhoff, “Road map to clean energy using laser beam ignition of boron-proton fusion,” Laser and Particle Beams, vol. 35, no. 4, p. 730–740, 2017. [5] S. Eliezer, H. Hora, G. Korn, N. Nissim, and Jose ` Maria Martinez-Val, “Avalanche proton-boron fusion based on elastic nuclear collisions”, Physics of Plasmas, vol. 23, p. 050704, 2016. [6] F. Belloni, D. Margarone, A. Picciotto, F. Schillaci, and L. Giuffrida, “On the enhancement of p-11B fusion reaction rate in laser-driven plasma by a→p collisional energy transfer”, Physics of Plasmas, vol.25, no. 020701, 2018. [7]C. Labaune, S. Deprierraux, S. Goyon, C. Loisel, G. Yahia, and J. Rafelski, “Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma”, Nature Communications, vol. 4, Article ID 2506,, 2013. [8] S. Moustaizis, C. Daponta, S. Eliezer, Z. Henis, P. Lalousis, N. Nissim and, Y. Schweitzer, “Alpha heating and avalanche effect simulations for low density proton-boron fusion plasma”, Presentation in the 2nd International Workshop on proton-Boron fusion, Catania, Sicily, 5-8 September 2022. [9] S. Moustaizis, C. Daponta, S. Eliezer, Z. Henis, P. Lalousis, N. Nissim and, Y. Schweitzer, “Alpha heating contribution to the different stages of the p-11B fusion process and the temporal appearance of the avalanche effect”, Oral presentation at CHILI2022 (Conference on High Attosecond Laser Science in Israel), 5-8 December 2022. [10] N. Nissim, Z. Henis, C. Daponta, S. Eliezer, S.D Moustaizis, P. Lalousis and, Y. Schweitzer, “Parametric scan of plasma parameters for optimization of the avalanche process in p11B fusion”, Oral Presentation in the 2nd International Workshop on proton-Boron fusion, Catania, Sicily, 5-8 September 2022. [11] C. Daponta, S. Moustaizis, S. Eliezer, Z. Henis, P. Lalousis, N. Nissim and, Y. Schweitzer, “Numerical evaluations indicating p-11B high gain fusion due to important alpha heat transfer- avalanche effect, Poster presentation at CHILI2022 (Conference on High Attosecond Laser Science in Israel), 5-8 December 2022.
Hybrid Garfield++ simulations of GEM detectors for tokamak plasma radiation monitoring
Presenter: Michał Jagielski (Institute of Plasma Physics and Laser Microfusion)
Authors: Michał Jagielski, Karol Malinowski, Maryna Chernyshova
Abstract: Extreme conditions in fusion reactors necessitate development of new Soft X-Ray (SXR) diagnostic systems, which are able to withstand high radiation environment. Such a system, among the others, should assure safe operation of the machine by monitoring the level of plasma radiation. As high neutron fluxes preclude application of semiconductor-based technologies at future fusion devices, the use of relatively new micropattern gas detectors is being considered instead. The detectors of this type, based on Gas Electron Multiplier (GEM) technology, are being developed for use in tokamak plasma monitoring. The constructed working systems were already tested at the WEST project and other devices. Long term plans may envisage usage of gaseous detector based SXR diagnostics in ITER and in DEMO for real time plasma monitoring and control. For this use case a full-detector simulation software was created based on the already existing interface and previous results obtained so far within the group. It takes into account interactions of high energy photons and neutrons with the detector parts with proper handling of primary ionization electrons tracks, gas mixture fluorescence and collisions with detector materials. Software combines Geant4 package for interactions with solid parts of the detector, Garfield++ for electron avalanching, Heed for X-ray interaction with gas, Gmsh and Elmer for meshing and electrostatics and introduces a hybrid approach to the simulation of electron drift in different regimes. For further optimization the developed software employs precomputation algorithms in later stages of the electron cascades, where individual electron tracks can be substituted with statistical density distributions. The simulated response profiles of the detector, exposed to $^{55}$Fe calibration source radiation, were simulated and verified by comparing them with experimental data. This contribution will present details of hybrid simulator implementation as well as simulation results.
X-ray polarimetry as a plasma physics probe in accreting pulsars
Presenter: Victor Doroshenko (IAAT/EKUT)
Authors: Victor Doroshenko
Abstract: Physical conditions within emission regions of X-ray pulsars are truly extreme: high temperatures (T ∼ 10^8 K), strong magnetic fields (B ∼ 10^12 G), and gravity (log g∼14) make them unique natural laboratories for fundamental physics under extreme conditions. To fully exploit this potential, one needs, however, to understand the astrophysics of these objects, i.e. how the observed emission is produced, and while the basic emission mechanism, i.e. accretion, was understood early on, a clear and coherent understanding of the physical processes at work in the emission regions of accreting pulsars has not yet been reached. In the talk I will present an overview of the IXPE mission which has recently opened a new observational window in terms of X-ray polarimetry, and first observation results obtained during its first year of operation in context of studies of plasma physics in vicinity of accreting neutron stars.
14:40 - 15:40
Poster Session 2 learn more
Poster Session 2
Impact of window temperature changes on ITER toroidal interferometer and polarimeter (TIP) measurements
Presenter: Tsuyoshi Akiyama (General Atomics)
Authors: Tsuyoshi Akiyama, Michael A. Van Zeeland, Daniel Finkenthal, Michael LeSher, Ryan Finden, Peter Trost, Anthony Gattuso, Sebastian Miranda, Marc-Andre De Looz, Christopher Watts
Abstract: The Toroidal Interferometer and Polarimeter (TIP) is the primary electron density diagnostic on ITER. For long pulse operation, the interferometer is challenged by phase offsets due to environmental changes such as temperature, humidity, etc. [1,2]. To improve measurement accuracy and provide reliable electron density data to fueling control, it will be essential to minimize and monitor ambient environmental changes. A key element of this will be consideration of temperature changes in window and transmissive optics materials since the index of refraction depends on the temperature. In TIP, BaF2 and ZnSe are used for vacuum and secondary windows, as well as lens and beam splitter/combiners [1]. Though previously published data on the dependence of the index of refraction on the temperature [3] exists for these materials, the quoted error bars are too large to reliably characterize the expected phase drifts, nor have actual measurement been made yet. Hence, this work experimentally measured the phase shift caused. The TIP prototype, operating at 10.59 and 5.22 microns, was used to measure the phase shifts by temperature changes of BaF2 and ZnSe over typical operating ranges. 3 cm-long BaF2 and ZnSe specimens were placed in an oven in the TIP beam path and the temperature increased up to > 80 °C (ITER vacuum window temperature ~ 70 °C). The temperature dependent vibration compensated phase shifts of BaF2 and ZnSe are +0.012 and -0.27 deg./°C/cm, respectively. The measured phase shift is the sum of two terms: the index of refraction change and the thermal expansion. While signs of these two terms are opposite in BaF2, they are the same in ZnSe. Hence the phase shifts in BaF2 are largely cancelled resulting in smaller temperature dependent vibration compensated phase shift errors. The primary vacuum window material for TIP is planned to be ZnSe, which has been chosen over BaF2 because it can meet ITER’s strict vacuum window requirements; ZnSe has better resistance to steam ingress and satisfies the mechanical strength required for the helicoflex vacuum sealing. Due to double passage of double 1.4 cm-thickness windows, the total path length of TIP beams in ZnSe is 5.6 cm. Allocating 1 deg. error budget to the vacuum window (10% of TIP’s total error budget), a temperature change of <0.7 °C during a discharge will be required. For temperature changes beyond that value, careful monitoring of the window temperature would be required to remove phase offsets. This work is supported by US DOE Contract No. DE-AC02-09CH11466. All US activities are managed by the US ITER Project Office, hosted by Oak Ridge National Laboratory with partner labs Princeton Plasma Physics Laboratory and Savannah River National Lab-oratory. The project is being accomplished through a collaboration of DOE Laboratories, universities and industry. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization. [1] M.A. Van Zeeland, Plasma Phys. Control. Fusion 59, 125005 (2017). [2] T. Akiyama et. al., JINST 15, C01004 (2020). , K.J. Brunner et. al., JINST 14, P11016 (2019). [3] “Optical Materials Characterization Final Technical Report”, NBS technical note 993, 1978
High-speed imaging for the diagnostics of rotating cluster in radio-frequency (RF) plasma
Presenter: Maria-Luiza Mitu (National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest, Romania)
Authors: Maria-Luiza Mitu, Dorina Ticos, Adrian Scurtu, Nicoleta Udrea, Catalin Mihai Ticoş, Mihai Oane
Abstract: Dusty plasma diagnostics is mainly performed by means of high-speed imaging techniques [1]. The sequences of images acquired by a high-speed camera are further processed through Particle Tracking Velocimetry (PTV) analysis technique to investigate the cluster dynamics. Here by we show the dusty plasma diagnostics of a cluster rotating under the influence of an electron beam [2]. In the experiment the dust cluster composed of spherical dust particles with radius r_d=5.9 μm and made of melamine-formaldehyde with density ρ=1.5 g 〖cm〗^(-3) is levitated in the sheath of a radio-frequency (RF) plasma. The experiments were performed in a RF discharge in argon at pressure p=90 mTorr and discharge power of 3 W. The microparticles are illuminated by a laser sheet from a diode laser of 20 mW and irradiated by a pulsed electron beam (EB) with energy in the range 8-12 keV and peak current of 4 mA. The electron beam used to irradiate the cluster has pulse frequency of 56 Hz and pulse duration of 40 µs. The images of the dust microparticles trajectories were acquired in time by a Photron CCD camera. For the analysis of the cluster rotation the image data is used to construct Voronoi diagrams, to calculate inter-particle spacing and to obtain pair correlation functions.
Imaging Neutral Particle Analyzer Measurements of Mode-Induced Fast Ion Distribution Function Fluctuations in the DIII-D Tokamak
Presenter: Xiaodi Du (General Atomics )
Authors: Xiaodi Du
Abstract: Imaging neutral particle analyzers (INPA) provides precise measurements of the radial, energy and pitch angle of confined fast ions in the DIII-D tokamak [1, 2] including the local fast ion distribution function via tomographic inversion [3] and fast ion phase space flow induced by multiple small-amplitude Alfvén eigenmodes (AE) [4,5]. Recently, two significant improvements have been made to the DIII-D INPA system. Photomultiplier tubes (PMT) are now used to monitor the phosphor light emission of the INPA with large bandwidth. To reduce the electromagnetic noise, the emitted photons are transferred out of machine hall via ~100 m optical fibers. Local fluctuations of the fast ion density with frequencies up to ~250 kHz are observed, which are caused by neoclassical tearing modes, ellipticity-induced AE modes and beta-induced AE modes. This new capability to measure the steady and fluctuating fast ion density of fast ions locally in phase space will shed light on the understanding of diffusive and convective transport during resonant interactions between energetic particles and waves. The second improvement is the development and installation of a new INPA. Complementing the initial DIII-D INPA system [1,2] which probes passing fast ions, this new INPA provides energy-resolved radial profiles of local trapped fast ion density. It measures the counter-Ip (co-Ip) leg of trapped particles, when the plasma current is in the counter-clockwise (clockwise) direction. The new system images a broad radial range from the plasma core to the edge and deuterium energies up to >100 keV at a pitch of about 0.45, with energy resolution of ~10 keV, radial spatial resolution of ~10 cm and pitch resolution of ~4 degree. The initial data demonstrates that the system has exceptionally good signal to noise. This new trapped INPA system also provides the opportunity to extend previous studies of AE-induced fast ion flow to the phase space occupied by fast ions on trapped orbits.
Diagnostics for, and of, the open large volume TCV divertor transiting from attached to detached regimes
Presenter: Basil Duval (SPC, EPFL, Lausanne, Switzerland)
Authors: Luke Simons, Marcelo Baquero, Artur Perek, Basil Duval, Bryan Linehan, Curdin Wuethrich, Emanuel Huett, Yanis Andrebe, Christian Theiler, Olivier Février, Holger Reimerdes, Lorenzo Martinelli, Dmytry Mykytchuk, Sophie Gorno, Claudia Colandrea, Nicolas Offendu, Diego Oliveira, Harry Han, Golfinopoulos, Guang-Yu Sun, Cedric Tsui, Yinghan Wang, Martim Zurita, Umar Sheikh, Keneth Lee
Abstract: TCV has an up/down symmetric open vacuum chamber where diverted configuration’s legs may be placed near anywhere within the capabilities of its 16-element, independently powered, poloidal coil array. Diagnosing such a range of poloidal magnetic configurations originally relied upon a generous array of tile-surface Langmuir probes, floor and high-field-side IR cameras and surveillance imaging. In recent years, diagnostic needs have extended to partially and deeply detached configurations with and without in-vessel neutral gas baffles and this for the widest range of divertor configurations that include a range of two, four (and more) strike points, ranges of divertor leg flux expansion and, in TCV tradition and a wide range of core shapes that include high negative triangularity. TCV has an up/down symmetric open vacuum chamber where diverted configuration’s legs may be placed near anywhere within the capabilities of its 16-element, independently powered, poloidal coil array. Diagnosing such a range of poloidal magnetic configurations originally relied upon a generous array of tile-embedded Langmuir probes, floor and high-field-side IR cameras and surveillance imaging. In recent years, diagnostic needs have extended to partially and deeply detached configurations with and without in-vessel neutral gas baffles and this for the widest range of divertor configurations that include a range of two, four (and more) strike points, ranges of divertor leg flux expansion and, in TCV tradition and a wide range of core shapes that include high negative triangularity. Furthermore, to make physics progress, results from all these configurations are to be compared with edge plasma physics modelling. Two more factors are required: systems that can simultaneously diagnose a large part of the diverted plasma and surrounding, and some direct experimental data validation. This paper describes a wide slew of novel diagnostics that include inversions of images from arrays of spectrally filtered cameras (MANTIS), reciprocating Langmuir Probe arrays (RDPA and fastRP), neutral pressure valves (Baratrons and AUG-in-field types), a highly complete visible spectroscopy array (DSS: survey to high resolution), edge turbulence characterisation (though edge GPI), edge radiation intensities (AXUV and blackened Bolometer Arrays) and Thomson Scattering spectrometers able to measure temperatures to below 1eV. To understand the results of extensive SOLPS simulations, TCV’s magnetic control system was programmed to scan the divertor leg positions across the diagnostics’ positions permitting 2D divertor comparisons/validations both in space and time with model-everything codes (SOLPS-ITER) for detachment relevant conditions. Although each of these diagnostic systems is the subject of both diagnostic and physics publications, their combined, validated, usage provides the basis for a leap forward in diagnostic/modelling comparisons. Finding the physical processes, missing in such models, that are required to generate better experimental agreement will greatly improve extrapolation to upcoming fusion-grade devices.
Latest developments of SDD detectors for the neutron/gamma sensor for DEMO
Presenter: Enrico Perelli Cippo (Istituto per la Scienza e Tecnologia dei Plasmi-CNR, Milan, Italy)
Authors: Enrico Perelli Cippo, Federico Caruggi, Marica Rebai, Davide Rigamonti
Abstract: In this poster, we present the latest development of neutron/gamma multi-LOS sensor for DEMO. Aim of this sensor is the measurement of fusion power and other relevant plasma parameters (like for instance position or fuel ratio nD/nT) for the control of the future DEMO fusion plant through the monitoring of 14 MeV neutrons and 16.7 photons form the deuterium-tritium reaction in burning plasma. Present plans envisage the use of Single-crystal Diamond Detectors (SDD) as neutron detectors, due to their compactness and well-known characteristics. However, they still need a wide R&D approach to make them completely competitive to other state-of-the-art neutron detection techniques. Moreover, they are affected by gradual degradation due to radiation damage and high temperature. In particular, in this poster we discuss a method to monitor the characteristics of the SDD during its use as a neutron spectrometer. It is known that the good characteristics of SDD as a 14 MeV neutron detector are due to its spectroscopic capabilities, and in particular the presence, in the response function, of a well-defined peak due to the 12C(n,)9Be reaction. However, the radiation damage can cause broadening of such a peak (with loss of energy resolution), reduction of the counting rate and, in definitive, to a failure of the whole detector. During long plasma discharges like the ones envisaged in DEMO, it is impossible to make specific tests on the functionality of neutron detectors; it is thus of paramount importance to develop a monitoring method able to recognize the degradation of the SDD from the same data collected by the detector during its standard use (i.e. neutron spectra from burning plasma). At present, the method is performed off line, but possible developments are discussed that may lead to the implementation of it into an FPGA for real time monitoring of the different SDD in the sensor.
Real-time Electron Temperature and Density Measurement by Thomson Scattering for Plasma Control on LHD
Presenter: Hisamichi Funaba (National Institute for Fusion Science)
Authors: Hisamichi Funaba, Ichihiro Yamada, Ryo Yasuhara, Naoki Kenmochi, Yuya Morishita, Sadayoshi Murakami, Jong-ha Lee, Hideya Nakanishi, Masaki Osakabe
Abstract: The real-time measurement of the spatial profiles of the electron temperature (Te) and density (ne) is required from the ASTI system, a data assimilation system for integrated transport simulation of fusion plasma [1], on the Large Helical Device (LHD). It is intended to predict and control the temporal development of the plasma parameters, such as Te and ne, through the transport simulation in the ASTI system. Moreover, the real-time information of Te and ne profiles can be used for evaluating or controlling of the heating profiles, the magnetic configurations, the divertor detachment, and so on. The real-time data processing is realized by applying the fast digitizers, which were installed for the measurement with the high-repetition-rate Nd:YAG laser [2], for the main Thomson scattering system [3, 4] on LHD. These fast digitizers acquire the signals from the 70 polychromators, each of which has 5 or 6 spectral channels. The laser in the main Thomson scattering system is operated in 30 - 50 Hz. The data are transferred from these fast digitizers to the acquisition computer. The analyzing computer, which derives Te and ne, receives the data through the "RTRetrieve" system from the acquisition computer [5]. The frequency of this data transmitting is operated in 10 Hz because it takes almost 70 ms to transfer all the data of 350 channels for the 70 spatial positions. Although the most data are transferred within almost 30 ms, the data in some channels come a few tens of milliseconds later. The time for the signal processing and calculation of Te and ne by the X^2-method is almost 12 ms. Therefore, the delay time in this real-time system is within 100 ms. The Te and ne profiles are transmitted to a vector engine server SX-Aurora TSUBASA in real-time by the socket communication and used as inputs of the ASTI system. In the recent experiment of LHD, Te was controlled by changing the power of the electron cyclotron heating (ECH) under the prediction of ASTI. The delay time within 100 ms is enough for the ASTI operation at present. This work is supported by NIFS20ULHH005, NIFS22KIPT008, JSPS KAKENHI Grant Numbers 15KK02451 and JSPS KAKENHI 21K13901. References [1] Y. Morishita, et al., Comput. Phys. Commun., 274 (2022) 108287. [2] H. Funaba, et al., Sci. Rep., 12 (2022) 15112. [3] K. Narihara, et al., Rev. Sci. Instrum., 72 (2001) 1122. [4] I. Yamada, et al., Fusion Sci. Tech., 58 (2010) 345. [5] H. Nakanishi, et al., IEEE Trans. Nucl. Sci., 63 (2016) 222.
Proposal for measurement of p-11B reaction in the EHL-2 spherical torus
Presenter: Bing Liu (1 Hebei Key Laboratory of Compact Fusion, Langfang 065001, China 2 ENN Science and Technology Development Co., Ltd., Langfang 065001, China)
Authors: Bing Liu, Zhi Li, Tiantian Sun, Xinchen Jiang, Di Luo, Yingying Li, Yuejiang Shi, Huasheng Xie, Shaodong Song, Yuankai Peng
Abstract: EHL-2 is the next generation of spherical torus under design in the ENN Energy Research Institute towards proton-boron fusion energy. One of the important missions of EHL-2 is to achieve proton-boron (p-11B) reaction in a magnetized plasma possibly driven by external heating systems. A big challenge is the measurement of the reaction rate of these low reactivity events in the magnetic fusion environment. Here, we propose to a strategy for measuring p-11B reaction rate in EHL-2 through integrated modeling. Preliminary analysis shows that considering the H-B plasma in EHL-2, with electron density of , ion temperature of and , more than alpha particles could be produced. Such a number of alpha particles is able to be detected and measured by varies types of detectors (i.e. FILD, NPA, GRS, class of CR39, etc.). A further simulation on the distribution of p-11B reaction in a magnetic environment which considers both the effect of neutral beams and background plasma is in progress, as well as a detector simulation which provides the detection efficiency. Here we would like to discuss the feasibility of the varies types of detectors, which could tell energetic alpha particles from proton.
Real-time correction of modulator in dispersion interferometer on HL-2M
Presenter: Haoxi Wang (Southwestern Institute of Physics)
Authors: Haoxi Wang
Abstract: To meet the requirement of electron density measurement on HL-2M, a single channel CO2 dispersion interferometer based on second harmonic generation technology has been developed and commissioned on HL-2M Tokamak. In series of discharge experiments, a slowly varying delay of reference signal provided by the modulator caused a phase drift and introduced an extra error of up to 10 degrees. An extra phase correction method is applied on the data processing system to calculate the delay and to eliminate the extra phase drift. An additional phase-tracking method is introduced to eliminate unexpected phase flip in phase correction. These methods are included in data analyzing code and FPGA. The FPGA can derive the phase of delay every 0.1 ms to provide real-time phase drift correction in density feed-back signals. The phase drift occurs no more in 10 seconds measurement with the phase correction method.
Runaway electron studies via HXR spectroscopy at Golem, COMPASS and TCV
Presenter: Jaroslav Čeřovský (Institute of Plasma Physics, Prague, Czech Republic)
Authors: Jaroslav Čeřovský, Ondrej Ficker, Eva Tomesova, Luke Simons, Vojtěch Svoboda, Jan Mlynar, Umar Sheikh, Mathias Hoppe, Joan Decker, Jakub Čaloud, Vladimír Weinzettl, Martin Hron
Abstract: The research on runaway electrons in tokamaks continues to be important for safe and reliable operation of large fusion devices due to the potential risk of impact of so called runaway electron beams on plasma facing components which could cause a serious damage and lead to putting the machine out of operation. In order to investigate the properties of runaway electrons and provide useful information about their behavior under different experimental conditions (e.g. efficiency of various mitigation techniques or exploration of runaway electrons free regimes) many dedicated diagnostics has been utilized. One way of inferring features of runaway electrons is a measurement of their bremsstrahlung radiation which is generated by collisions with plasma ions or by their impact on the first wall when runaway electrons are deconfined and lost. Recently, diagnostic capabilities at GOLEM [1] were upgraded by installation of two scintillation detectors with CeBr3 crystals (1” x 1”), which were also successfully tested during the dedicated runaway electron campaigns at the COMPASS tokamak [2]. Moreover, both scintillation detectors were also installed at the TCV tokamak to extend for the first time the hard x-ray radiation diagnostics and provide an estimates of the maximal energy of runaway electrons. The aim of this contribution is to describe the diagnostic used and experimental conditions of the different devices. Additionally, illustrative examples of experiments from these three different devices are presented and acquired data by the diagnostic system for HXR spectroscopy is discussed and put into the context. The comparison with other relevant diagnostics is shown. At the GOLEM tokamak the spectroscopy system was used to observe the influence of the initial pressure of the working gas and maximal energy of HXR photons was estimated about 300 keV. On the other hand at the COMPASS tokamak [3], the data recorded in experiments focused on characterizing runaway electron beams properties and the efficiency of various mitigation techniques (e.g. graphite pellet injection). At TCV [4], the installed set of scintillation detectors proved to be useful as a source of complementary information to standard radiation diagnostics and helped to characterized generated runaway electrons beams. This contribution also briefly shows a progress in modeling the radiation transport using FLUKA [5], carried out in order to better interpret the obtained data. References [1] V. Svoboda et al. 2019 Jour. Fus. En. 38.2 253-261 [2] J. Cerovsky et al. 2022 JINST 17 C01033 [3] J. Mlynar et al. 2019 Plasma Phys. Control. Fusion 61 014010 [4] J. Decker et al. 2022 Nucl. Fusion 62 076038 [5] C. Ahdida et al. 2022 Front. Phys. 705 * See the author list in M. Hron et al 2022 Nucl. Fusion 62 042021 ** See the author list of H. Reimerdes et. al., 2022 Nucl. Fusion 62 042018
Conceptual design of the visible / near-infrared camera system for the COMPASS Upgrade tokamak
Presenter: Jordan Cavalier (Institute of Plasma Physics of the CAS, Za Slovankou 3, 182 00 Prague 8, Czech Republic)
Authors: Jordan Cavalier, Miroslav Kral, Vladimír Weinzettl, Matej Tomes, Peter Vondracek, Petra Bilkova
Abstract: This contribution describes the visible and near-infrared (~1 μm) camera systems which are planned to observe the interaction between the plasma and the first wall in the first phase of the COMPASS Upgrade operation. The COMPASS Upgrade tokamak is a compact mid-size (R = 0.9 m) device being designed and assembled at the Institute of Plasma Physics in Prague [1]. Extensive auxiliary plasma heating power is foreseen (several megawatts of NBI and ECRH), therefore, extreme heat fluxes of order of tens MW/m 2 towards the plasma facing components are expected in 1-3 s long discharges [2]. Consequently, some of these cameras will also be used as interlocks, protecting the first wall against overheating by monitoring the material temperature. The requirements for the camera systems to be met are introduced, e.g. temperature range of the first wall to monitor, large field-of-views and spatial and temporal resolutions to be reached. Issues raised with selection and technical implementation of the chosen visible and near-infrared cameras are described in detail, including optical design for visible and infrared spectral regions. Because the first (plasma facing) mirrors have to withstand high operating temperature of the first wall (up to 500oC), the concept is a compromise between the occupied port space (compact tokamak) and the diagnostic requirements. Pros and cons of three different considered concepts [3,4.5] will be discussed. The systems placement and their expected field-of-view and coverage will then be shown. References [1] P. Vondracek et al. Fusion Engineering and Design 169 (2021) 112490 [2] V. Weinzettl et al. Fusion Engineering and Design 146 (2019) 1703-1707 [3] K. Kamiya et al. Fusion Eng. Des. 89 (2014) 3089–3094 [4] E. Gauthier et al. Fusion Eng. Des. 82 (2007) 1335 [5] A. Huber et al 2018 Nucl. Fusion 58 (2018) 106021
Designing a Midplane Turbulence Probe for MAST-U
Presenter: Will Fuller (The University of Warwick)
Authors: Will Fuller, Scott Allan, Bogdan Hnat, John Omotani, Peter Ryan
Abstract: Throughout the first MAST-U campaign there was focus on investigating the Super-X divertor and how alternative divertor configurations impact the dynamics of the scrape-off layer. Key phenomena born from turbulence, such as profile broadening and filamentary transport must be investigated to avoid possible damage to the first wall in future fusion reactors, including STEP. One way to study such phenomena is by probing edge and SOL plasma with a new probe head of the midplane reciprocating probe system installed on MAST-U. The system allows direct measurement of plasma properties producing a radial profile of the scrape-off layer. Current diagnostics are not specifically designed for the variety of measurements required to fully characterise SOL turbulence. This new probe head design was first synthetically iterated through a variety of models to reach the current design and includes several arrays of probes targeting different turbulence measurements. We include a logarithmically spaced probe array sampling a range of length scales. A five-pin balanced triple probe array has been included to gather fluctuation statistics of temperature and density simultaneously. We incorporated ball-pen probes designed for direct measurements of the plasma potential. There is a linear array of probes including a radial offset to calculate velocity statistics. Along with probes in other arrays, an additional radially offset probe is included to operate a mach probe setup, allowing plasma flows to be measured. This work will present the synthetic approach we used to design our turbulence probe, and the data presented will be compared to experimental and synthetic results from the existing Mach probe head and other diagnostics to determine the turbulence probe’s suitability for purpose. Unique results and future work will also be discussed to fully exploit the diagnostic subsequently.
Machine-learning correction of misalignment effects in density profiles from Thomson scattering
Presenter: Golo Fuchert (Max-Planck-Institut für Plasmaphysik (IPP), Greifswald, Germany)
Authors: Golo Fuchert, Jule Frank, Shan Chen, Andrea Pavone, Marcus Beurskens, Sergey Bozhenkov, Jakob Brunner, Matthias Hirsch, Ekkehard Pasch, Robert Wolf
Abstract: A number of effects can negatively impact the quality of experimental density profiles measured with laser Thomson scattering. Examples are laser misalignment, coatings on windows or detector drifts. At Wendelstein 7-X (W7-X), it was observed that vibrations and temperature changes along the beam-path lead to laser misalignment, which was the dominant error source for the electron density profiles during the first experimental campaigns. Countermeasures that are being implemented include mechanical improvements and a new calibration method, in which the laser position is monitored, both for the calibration measurements and for the actual experiments. This, however, requires a scan of laser positions during calibration, which has not been performed in the first experimental campaigns of W7-X. In order to correct existing data, the impact of laser misalignment had to be deduced from the density profiles themselves. The machine-learning based solution for this task is described in this contribution. The first step to correct the impact of laser misalignment is to determine the laser position for the existing data, even though it has not been measured. It is not required to find the laser position in actual lab coordinates, but rather it is sufficient to distinguish different laser positions and to be able to tell which of those positions are close to each other. This is facilitated by the fact that that the laser misalignment does not impact every spatial point of the density profile (scattering volume) in the same way and, hence, leaves a characteristic fingerprint in the point-to-point variation between neighboring points in the profile. A special type of neural network, called an autoencoder, is used to classify these fingerprints and to represent them as an abstract laser position. It was shown experimentally that this abstract laser position is correlated with the actual laser position in lab coordinates. This also means that positions close to each other in one coordinate system can be assumed to also be close in the other. Consequently, the density profiles themselves contain enough information about the laser position to group profiles of similar laser positions together. In the second step, transformations between different laser positions are determined. With these transformations, profiles that have been measured at one abstract laser position can be mapped to a different one to see how the profile would look like, had it been measured at that other laser position. Finally, the abstract laser position that corresponds to the laser position during the absolute calibration has to be identified. Since in magnetically confined toroidal plasmas, density and temperature profiles are symmetric in magnetic coordinates, profiles measured close to the calibration position are more symmetric than profiles that have been measured far away from it. The reference position can be identified by ranking profiles by their symmetry. The transformation from a profile’s position to this reference position is the best estimate for the appropriate correction. Error bars can be estimated by transforming to neighboring positions. In this contribution, we apply this procedure to both synthetic data (for illustrational purpose) and experimental data.
X-ray radiography of a titanium wire isochorically heated by laser-accelerated electrons
Presenter: Olena Turianska ( 1)Focused Energy, 64291 Darmstadt, Germany 2)1) Universitè de Bordeaux, CNRS, CEA, CELIA, UMR 5107, F-33405, Talence, France)
Authors: Olena Turianska
Abstract: We performed an experiment using the laser Phelix at GSI to isochorically heat a wire and study its following expansion using time resolved X-ray radiography. A mm-long titanium wire (50 µm in diameter) was irradiated on its tip by the laser pulse with duration τ=0.5 ps, energy E=50 J and intensity I~ 10^18 W/〖cm〗^2. Hot electrrosn were gereated innteh interaction and propagated along the wire isochorically heating the titanium material. X-ray emisison spectroscopy (FSSR) of the titanium K- line was performed to retrieve the wire temperature along the wire, i.e. T=T(z) where z=0 corresponds to the wire tip [1, 2]. After this initial quasi-instantaneous heating, the expansion of the wire was followed using time-resolved X-ray radiography. Backlighter target was 5um tungsten wire illuminated by a second laser beam with similar characteristics. Measurement of wire expansion was done at different time by changing the delay between the two laser beams. X-ray radiography was successfully used to measure plasma expansion and sound velocity cs = cs (z). We observed how local plasma expansion velocity along the wire is consistent with the temperature extracted from FSSR data [2]
A fast Thomson scattering system for the transient plasma physics phenomena in LHD
Presenter: Ryo Yasuhara (National Institute for Fusion Science)
Authors: Ryo Yasuhara, Hisamichi Funaba, Hiyori Uehara, Daniel Den Hartog
Abstract: A fast Thomson scattering system is very powerful and has successfully measured various high-speed phenomena such as hydrogen pellet ablation dynamics and a partial plasma collapse phenomena. Also, we plan to challenge repetition rates of 100 kHz or higher by improving the power supply, increasing the thermal shock resistance of a laser medium, and increasing the efficiency of the pump source.
Feasibility study of a Coherence Imaging Charge Exchange Recombination Spectroscopy diagnostic for Wendelstein 7-X
Presenter: Ramón López-Cansino (Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain)
Authors: Ramón López-Cansino, Valeria Perseo, Eleonora Viezzer, Oliver Patrick Ford, David Matt Kriete
Abstract: A feasibility study of a Coherence Imaging Charge Exchange Recombination Spectroscopy (CICERS) diagnostic has been carried out for the Wendelstein 7-X stellarator (W7-X). This diagnostic, based on Coherence Imaging Spectroscopy (CIS) [1] and Charge Exchange Recombination Spectroscopy [2], is expected to measure charge exchange radiation of the main impurity species present in the plasma. The spectral information of the radiation is encoded in a 2D fringe pattern, which is generated by birefringent plates, in order to obtain 2D maps of relevant impurity ion parameters such as rotation velocity, temperature and density after a demodulation procedure is applied to the fringe pattern. A synthetic diagnostic has been developed, which enables the optimization of the design and components of the system, based on the already existing CIS diagnostic in W7-X [3], the latter optimized for impurity flow measurements from passive lines in the edge of the plasma. The CICERS system has been set up and characterized in the laboratory, finding good agreement in its behaviour when compared to the simulation results. This also increases the confidence of using the synthetic simulations in the calibration process of the diagnostic, which will be routinely calibrated with a laser before and after every measurement [4]. [1] J. Howard 2010 J. Phys. B: At. Mol. Opt. Phys. 43 144010 [2] R. J. Fonck 1985 Rev. Sci. Instrum. 56 855 [3] V. Perseo et al 2020 Rev. Sci. Instrum. 91 013501 [4] D. Gradic et al 2019 Fusion Eng. Des. 146 995–998
CVD Diamond Tomography for the DTT Fusion Device
Presenter: Silvia Palomba (“Tor Vergata” University of Rome, Italy)
Authors: Claudio Verona, Gianluca Verona-Rinati, Marco Marinelli, Maurizio Angelone, Matteo Iafrati, Francesca Bombarda, Silvia Palomba, Silvia Cesaroni
Abstract: The DTT tokamak [1] presently under construction at Frascati (Rome, Italy) is a relatively large device of major radius R= 2.19 m, minor radius a= 0.70 m, toroidal field on axis BT= 6 T, plasma current Ip= 5.5 MA. Even if designed to operate with Deuterium fuel, the neutron and gamma radiation flux will pose very substantial challenges for any diagnostic system required to operate in the proximity of, or inside the vacuum vessel, as in the case of typical Si diodes used for Soft-X-ray Tomography. For this reason, a different kind of UV-SX photon detectors diodes is envisaged, namely the single crystal, Chemical Vapor Deposition (CVD) diamond detectors being produced at the laboratory of Industrial Engineering Department of the University of “Tor Vergata” in Rome. These have been successfully tested on JET [2] and FTU [3], but never in full tomographic layout (in fact only two detectors were installed on each machine), and their locations so removed from the torus that both radiation and heat were not a concern. The CVD diamonds exhibit a number of attractive features: they are sensitive to radiation from 5.5 eV up to tens of keV but are visible blind and much more radiation resistant than silicon, especially the thin samples suitable for photon detection. They can also operate at room temperature with very high S/N ratios, are very small in size and, most importantly, they can be placed in the machine high vacuum, without need for Be windows. Furthermore, considering the geometry of DTT port ducts, the coverage of the plasma poloidal section required for a proper tomographic inversion is allowed only by placing the diodes very close to the plasma itself, but no vacuum breaks are permitted at such location: this essentially rules out the possibility of using standard Si or CdTe diodes, in addition to their poorer resistance to neutrons that would make them very short lived. The main features of the CVD diamond tomography systems proposed for DTT are presented, with the results of the simulations used to guide the design of the optical layout and the various detector configurations adopted for different applications. The main technical issues associated with the mounting of a large number of diodes in close proximity to the plasma, insulation, cabling, heat and radiation loads, and front-end electronics will be discussed. [1] R. Ambrosino et al, Fus. Eng. & Des.167 (2021) 112330 [2] M. Angelone et al., Nucl. Instrum. Methods A 623 (2010) 726 [3] F. Bombarda et al., Nucl. Fusion 61 (2021) 116004
Application of a sparse sensor placement technique to the limited diagnostic set in DEMO
Presenter: Joost Raukema (DIFFER - Dutch Institute for Fundamental Energy Research)
Authors: Joost Raukema, Thomas Bosman, Ivo Classen, Tijs Wijkamp, Artur Perek, Gijs Derks, Jesse Koenders, Roger Jaspers
Abstract: In DEMO, a demonstration fusion power plant, the amount of diagnostics will be reduced compared to current experimental nuclear fusion reactors. A sparse sensor placement technique [1] is used to deal with the limited diagnostic set for the case of spectroscopy, required for wall heat load control. Experimental camera data from the MANTIS system [2] at TCV [3] is used to create and verify a synthetic diagnostic approach. The synthetic diagnostic consists of a set of lines of sight looking at the divertor leg, with the aim of identifying the CIII emission profile. However, the method is expected to be applicable to other diagnostics as well. The sparse sensor placement algorithm takes as input the radiation measured for a large set of lines of sight, resolved over a range of timesteps. A singular value decomposition (SVD) is performed to obtain a number of eigenmodes, or “eigen-emission profiles”. Then a pivoted QR-factorization is done to obtain the optimal sensor locations for reconstruction of the emission profile. Using the measurements of this limited set of sensors, the whole emission profile along the leg is reconstructed by multiplying the measured radiation of only those few lines of sight with their corresponding eigenmode. We demonstrate that it is feasible to use a calibration based on either data from previous experiments or simulated data from SOLPS. For DEMO, this means that a line of sight selection and set of eigenmodes can already be calculated before experiments are performed. This method can also be applied to reconstruct other profiles from emission measurements by adding them in the SVD, if they have sufficient relationship to the shape of the emission profile. For example, the peak target current density obtained with Langmuir probes can be reconstructed using the synthetic spectroscopy measurements. [1] Manohar, K., et al. "Data-driven sparse sensor placement for reconstruction: Demonstrating the benefits of exploiting known patterns." IEEE Control Systems Magazine 38.3 (2018): 63-86. [2] Perek, A., et al. "MANTIS: a real-time quantitative multispectral imaging system for fusion plasmas." Review of Scientific Instruments 90.12 (2019): 123514. [3] Reimerdes, H., et al. "Overview of the TCV tokamak experimental programme." Nuclear Fusion 62.4 (2022): 042018.
The first results of the HCN interferometer measuring atmospheric pressure air plasmas
Presenter: Jibo Zhang (Institute Of Plasma Physics Chinese Academy Of Sciences)
Authors: Jibo Zhang
Abstract: A HCN heterodyne interferometer has been designed for measuring electron densities of Experimental Research Apparatus for Electromagnetic Science (ERAES) for hypersonic vehicle plasma in near space, whose density is from 1×1015 to 3×1019/m3 and the pressure is from 50Pa to 1500Pa. The light source is hydrogen cyanide (HCN) laser with wavelength of 337m, which has high spatial resolution compared with microwave interferometer. The interferometer is configured as a Mach-Zehnder interferometer, which intermediate frequency (IF) is generated by the Doppler shift with a rotating grating. The spatial and temporal resolution of the HCN interferometry is reach to about 14mm and 100s respectively. The antenna-coupled ALGaN/GaN-HEMT have been used as detectors which have more high sensitivity— typical RF responsivity is around 900 V/W — than VDI planar-diode Integrated Conical Horn Fundamental Mixers. The first results of the HCN interferometer designed for ERAES have been obtained in the recent experimental campaign, with phase resolution up to 0.04π, corresponding to a minimum detectable change of the line integral density 1.32×1013cm-2, which is sufficient to measure the electron density in the range of 1×1012-3×1013cm-3.
Clippers ESTER Metrology Results
Presenter: Patrice Bertelli (CEA-DAM)
Authors: Patrice Bertelli
Abstract: The LASER MEGA JOULE (LMJ) is a high power laser facility used and operated by the CEA. Located in the south of France, this facility provide an extrordinary instrument to study High Energy Density physics. The experimental LMJ require the installation of several hundred measurement channels connected to high bandwidth digitizers whose inputs channel are regularly damaged by high amplitude parasitic pulses circulating in the facilty The ESTER Limiters (Limiteurs Electronique de Surtensions Transitoires Electriques Rapides Electronic Clippers Fast Transient Electric Surge), presented in this article, are the result of studies carried out by CEA teams for several years. In 2022, they made it possible to design and provide, a reliable and robust solution to ensure the protection of digitizer inputs (protection function) while ensuring the integrity of high-frequency experimental signals (integrity function). This article aims at presenting the technology used and afterwards at providing the results obtained that are related to the protection function for two transient pulse shapes (Amplitude: 600V/LMH: 200 ns; Amplitude: 1 kV/LMH: 6 ns). The integrity function is also addressed. The results show that the ESTER Limiters ensure the passage of 3 GHz HF signals without degradation in an amplitude range between -8 and +8V. Several tests on long experimental links (10, 20, 30 and 40 meters), typical of LMJ coaxial links used, are also presented. The results show that after appropriate digital processing, the original signal is perfectly reconstructed, without distortion, even in the presence of limiters. All the metrological results are presented on a sample of 20 limiters in order to check the homogeneity of the characteristics and the absence of manufacturing default processing.
Impact of ambient temperature on the filter polychromators performance and accuracy of Thomson scattering diagnostics
Presenter: Tongchuan Zhang (
Authors: Tongchuan Zhang
Abstract: Thomson scattering is one of the most important diagnostic methods for measuring plasma electron temperature and electron density. However, the performance of the avalanche photodiodes (APD) used in polychromators is greatly affected by the ambient temperature, and subsequently the change of ambient temperature will seriously affect the accuracy of Thomson scattering diagnostics. With the increase of ambient temperature from 17.7 to 21 degrees, the signals of all measuring channels of the polychromator are significantly reduced by ~30% (Fig. 1). Using the relative spectral response measured at different ambient temperatures, the electron temperature and electron density can be obtained. When the ambient temperature rises from 17 ℃ to 27 ℃, the electron temperature changes within ± 2%, while the electron density decreases by about a factor of 2. In general, the ambient temperature has little influence on the measurement of electron temperature, but has a greater influence on the electron density. These measurement and modeling results show that tight control and monitoring of the ambient temperature is required for high quality Thomson scattering diagnostic measurements.
Novel multi-energy soft x-ray camera in the WEST tokamak: first data and synthetic diagnostic
Presenter: Oulfa Chellai (Princeton Plasma Physics Laboratory)
Authors: Oulfa Chellai, Luis F. Delgado-Aparicio, Didier Vezinet, Tullio Barbui, Rémi Dumont, Kenneth Hill, Philippe Malard, Novimir Pablant, Brentley Stratton
Abstract: During the C6 campaign, the tungsten (W) Environment in Steady-state Tokamak (WEST) tokamak was operated for the 1st time with a water-cooled full tungsten divertor -similar to that of ITER- and long-pulse scenarios, making it an ideal environment for high-Z impurity transport studies. In that context, a compact multi-energy (  2-30 keV) soft x-ray diagnostic (MESXR) [1] was deployed by PPPL in WEST for high-Z impurity transport studies and electron temperature profile measurements. The ME-SXR consists of the PILATUS3 photon-counting detector manufactured by DECTRIS Ltd. mounted on a pinhole camera with a temporal and spatial resolution of 2 ms and 1-2 cm, respectively. The novelty of this soft x-ray diagnostic lies in the fact that the lower-energy threshold is set independently on each one of the   100k pixels with a high energy resolution (< 1 keV). The design, capabilities and engineering challenges of the ME-SXR diagnostic are briefly presented here. This contribution mainly presents the first data of the ME-SXR diagnostic acquired during C6. A tentative comparison of the experimental x-ray emissivity with predictions made using the synthetic diagnostic based on the FLYCHK suite [2] for the computation of the charge-state distribution and x-ray emissivity of the plasmas as well as the ToFu [3] open-source python library will also be presented. This work is supported by the U.S. DOE-OFES under Contract No. DE-AC02-09CH11466. References [1] O Chellai, LF Delgado-Aparicio, P VanMeter, T Barbui, J Wallace, KW Hill, N Pablant, B Stratton, C Disch, B Luethi, et al. Calibration of a versatile multi-energy soft x-ray diagnostic for west long pulse plasmas. Review of Scientific Instruments, 92(4):043509, 2021. [2] H-K Chung, MH Chen, WL Morgan, Yu Ralchenko, and RW Lee. Flychk: Generalized population kinetics and spectral model for rapid spectroscopic analysis for all elements. High energy density physics, 1(1):3–12, 2005. [3] D Vezinet. "".
CCD Direct Detection on a SPRED Spectrometer
Presenter: Umar Sheikh (SPC, EPFL, Lausanne, Switzerland)
Authors: Umar Sheikh, Basil Duval
Abstract: Spectroscopic measurements are critical for tokamaks as they provide information on a range of plasma parameters such as composition, power loss channels, impurity content and plasma-wall interaction. The vacuum ultraviolet (VUV) spectral range is of particular importance due to the photon energies emitted by ions in the core and hot divertors. The standard diagnostic used on tokamaks in this spectral range is a grazing incidence “survey, poor resolution, extended domain” (SPRED) spectrometer [1]. This spectrometer is combined with a microchannel plate (MCP) image intensifier, fiber-optically coupled to a Reticon photodiode array. The high voltage and vacuum requirements of the MCP led to reliability issues on the SPRED system installed on the TCV tokamak. Currents induced during plasma disruptions, and increases in vacuum pressure during divertor experiments, were enough to cause arcing and trips on the power supply. These issues were more prevalent on TCV due to the proximity of the system to the tokamak (~3m). It was therefore decided to simplify the system using a direct detection CCD camera. A thinned, back-illuminated CCD from GreatEyes® was selected due to its sensitivity in the VUV, camera design flexibility and price. A camera design modification was required to offset CCD chip itself from the camera base in order to place it in the focal plane. Once installed, the system was aligned and calibrated using a hollow cathode lamp and visible light sources. As the CCD could operate at atmospheric pressure, a new alignment procedure using zeroth order reflections was developed and will be outlined in this paper. The spectral resolutions achieved were 2.5A and 0.7A for the 450g/mm and 2105g/mm gratings respectively. This represented a 2-3x increase in spectral resolution over the legacy MCP detector system. The CCD detector system has now worked reliably on TCV for over 20,000 plasma discharges. It has been routinely used to assess plasma core content variations due to impurity seeding or the sputtering of material, and provide long term stability analyses that have led to the identification of events which produced impurity injections into the machine. References [1] Fonck, R. J., A. T. Ramsey, and R. V. Yelle. "Multichannel grazing-incidence spectrometer for plasma impurity diagnosis: SPRED." Applied Optics 21.12 (1982): 2115-2123
Investigation of the released p-11B fusion energy from proton beam interaction with 11B target
Presenter: Chrysovalanti Daponta (Technical University of Crete)
Authors: Chrysovalanti Daponta, Stavros Moustaizis, Paraskeuas Lalousis
Abstract: Between the so-called “advanced fusion fuels”, p-11B nuclear fusion reaction is of interest, due to the production of three (3) iso-energetic charged alpha particles with 8.7 MeV total energy, which can directly be converted into electricity [1, 2, 3]. In the present work, we examine the possibility of exploiting the energy of these three (3) fusion produced alpha particles, considering the interaction of a beam of accelerated protons with a solid 11B target. During this kind of interaction, protons with a kinetic energy between 650 keV and 1MeV are of particular interest, as in this energy range, the exploitation of the 675keV resonance is possible. As the protons move through the solid 11B target, they lose gradually their initial kinetic energy EK(0), in the context of a Continuous Slowing Down Approximation (CSDA). Stopping power expresses the specific energy loss rate per unit path length of the protons inside the 11B target and can be used for the determination of their range – penetration depth (RCSDA) in the solid 11B material, through the integration of the Bethe-Bloch formula. Protons deposit the biggest part of their energy in the Bragg peak. However, until the end of their range in the 11B target, where they have eventually lost all of their initial kinetic energy and stop, p -11B nuclear fusion reactions are induced. In a specific position z inside the 11B target, the production of alphas depends on the number of protons, the solid 11B target particle density and the cross section corresponding to the residual energy of protons. As it is observed through our numerical evaluations, when the protons initial kinetic energy is higher, the production of alpha particles increases significantly, while the maximum production of alpha particles occurs at a greater depth within the 11B target. The alpha particles produced from p-11B nuclear fusion reactions inside the 11B target, can either exit its two sides (in a straight line or at an angle θ), or remain inside it, if the distance to be travelled is greater than their range in solid 11B. The use of the Bragg-Kleeman rule enables us to determine the alpha range in the 11B target. Determining a suitable 11B target thickness and considering a uniform alpha particle energy loss across their path, we calculate the energy spectrum and the angular distribution of the alphas exiting the 11B target. This evaluation could be useful for the determination and the development of a potential experimental diagnostics configuration, concerning the alpha particles production detection. The study of two schemes, one electrical and one thermal, for the conversion of alpha energy into electrical energy, shows that the configuration of the proton beam interaction with the 11B target is not effective for energy production. The number of protons in the beam remains relatively small, regardless of whether it is produced using a high-intensity laser beam [4, 5, 6] or high current pulsed power technology [7]. As an example, it is noteworthy to mention that a compact pulsed power device, operating at 800 kV-1MV, with a pulse duration between 100ns - 1 μs, produces a proton beam current of 15 kA [7], that is able to deliver ~ 10 17 protons to the Boron target. Considering a repetition rate of a 10Hz, a 100% conversion efficiency of the proton beam to three (3) 2.9 MeV fusion born alphas and no input power losses for the operation of the pulsed power device, the output p-11B fusion power would be of the order of 1.5 MW. However, in a more realistic case, the alpha production efficiency is 10-3–10-4, the input electric power losses are ~20% for the proton beam generation and the remaining alphas in the Boron target reduce the useful electric output power to the range of kWatt, which is much lower than the input power of the proton beam. Thus, in the context of more efficient schemes, recent efforts concern a hybrid configuration, in which a proton beam interacts with a plasma [8] or with a relatively low temperature 11B medium (~< 100 eV) [9]. These two schemes allow the determination of the stopping power and the fusion probability (as a function of the electron density), as well as of the contribution of potential related processes, such as the chain reaction and the avalanche effect [9, 10]. References [1] H. Hora, S. Eliezer, G. J. Kirchhoff, N. Nissim, J. X. Wang, Y. X. Xu, G. H. Miley, J. M. Martinez-Val, W. McKenzie, and J. Kirchhoff, “Road map to clean energy using laser beam ignition of boron-proton fusion,” Laser and Particle Beams, vol. 35, no. 4, p. 730–740, 2017. [2] H. Hora, “Clean boron fusion using extreme laser pulses: A laser-driven technique to ignite proton-boron fuel offers the possibility of nuclear fusion for clean, Sustainable energy generation”, SPIE, The international society for optics and photonics, httpt://, 14 July 2015. [3] [4] A. Picciotto, D. Margarone, A. Velyhan, P. Bellini, J. Krasa, A. Szydlowski, G. Bertuccio, Y. Shi, A. Margarone, J. Prokupek, A. Malinowska, E. Krouski, J. Ullschmied, L. Laska, M. Kucharik, and G. Korn, “Boron-Proton Nuclear-Fusion Enhancement Induced in Boron-Doped Silicon Targets by Low-Contrast Pulsed Laser”, Phys. Rev., vol. X 4, p. 031030, 2014. [5] D. Margarone, A. Picciotto, A. Velyhan, J. Krasa, M. Kucharik, A. Mangione, A. Szydlowsky, A. Malinowska, G. Bertuccio, Y. Shi, M. Crivellari, J. Ullschmied, P. Bellutti, and G. Korn, “Advanced scheme for high-yield laser driven nuclear reactions”, Plasma Physics Controlled Fusion, vol. 57, p. 014030, 2015. [6] D. Margarone, J. Bonvalet, L. Giuffrida, A. Morace, V. Kantarelou, M. Tosca, D. Raffestin, P. Nicolai, A. Piccioto, Y. Abe, Y. Arikawa, S. Fujioka, Y. Fukuda, Y. Kuramitsu, H. Habara, and D. Batani, “In-Target Proton-Boron Nuclear Fusion Using a PW-Class Laser”, Applied Sciences, vol. 12, p. 1444, 2022. [7] K. Perrakis, S. D. Moustaizis and P. Lalousis, “Numerical investigations on high flux neutron production from a high-current pulsed ion device”, Proceedings of the 47th Conference on Plasma Physics, 2021. [8]Thomas. A. Mehlhorn, L. Labun, B. M. Hegelich, et al., "Path to Increasing p-B11 Reactivity via ps and ns Lasers", LPB, 2022, 2355629, 16 p, (2022). [9] N. Nissim, Z. Henis, C. Daponta, S. Eliezer, S.D Moustaizis, P. Lalousis and, Y. Schweitzer, “Parametric scan of plasma parameters for optimization of the avalanche process in p11B fusion”, Presentation in the 2nd International Workshop on proton-Boron fusion, Catania, Sicily, 5-8 September 2022. [10] S. Moustaizis, C. Daponta, S. Eliezer, Z. Henis, P. Lalousis, N. Nissim and, Y. Schweitzer, “Alpha heating and avalanche effect simulations for low density proton-boron fusion plasma”, Presentation in the 2nd International Workshop on proton-Boron fusion, Catania, Sicily, 5-8 September 2022.
First results of a multi-energy hard x-ray camera on the WEST tokamak
Presenter: Tullio Barbui (Princeton Plasma Physics Laboratory)
Authors: Tullio Barbui, Luis F. Delgado-Aparicio, Brentley Stratton, Oulfa Chellai, Rémi Dumont, Kenneth Hill, Novimir Pablant
Abstract: The WEST tokamak recently completed its first experimental campaign with the new water-cooled full tungsten divertor, which enables long pulse operation. Heating is provided by radiofrequency systems, including lower hybrid current drive (LHCD). In this context PPPL has operated for the first time a compact multi-energy hard x-ray camera (ME-HXR) for energy and space-resolved measurements of the electron temperature, the fast electron tail density produced by LHCD and runaway electrons, and the beam-target emission of tungsten at the edge due to fast electron losses interacting with the target. The diagnostic is a pinhole camera based on a 2D pixel array detector equipped with a CdTe sensor. The novelty of this diagnostic technique is the detector capability of adjusting the threshold energy at pixel level. This innovation provides a great flexibility in the energy configuration allowing simultaneous space, time and energy resolved x-ray measurements. This contribution presents first measurements of the new diagnostic on the WEST tokamak. Line-integrated measurements of hard x-rays were acquired during LHCD discharges along ~80 lines-of-sight covering most of the plasma cross section including the lower divertor. 4-6 discreet energy threshold settings were used over the range of 10-100keV. Radial position of LH power deposition was identified from the slope of the HXR profiles. Beam-target emission was observed along the lines-of-sight intersecting the lower divertor.
Motional Stark effect modelling for CASPER
Presenter: Péter Balázs (Institute of Nuclear Techniques, Budapest University of Technology and Economics, Budapest, Hungary ; Centre for Energy Research, Budapest, Hungary)
Authors: Péter Balázs, Aleksei Shabashov, Matej Tomes, Mireille Schneider, Maarten De Bock, Gergő Pokol
Abstract: The motional Stark effect (MSE) describes the spectral splitting of the light emitted by neutral atomic beams traversing a strong magnetic field. The degree of splitting is dependent on the magnitude of the magnetic field, while the polarization is determined by the direction of the field. Therefore, observing this effect in the heating or diagnostic beams of fusion devices allows for local magnetic field measurements inside the plasma. The splitting itself is rarely resolvable in todays’ machines, leaving the method for only field direction measurements. However, in a machine like ITER, with a stronger magnetic field, the splitting will be stronger and the spectrum is expected to be resolvable. With this capability, the planned MSE system on the machine will primarily be used to measure the q-profile, but it will also be useful for plasma current and toroidal field measurements. CASPER (CAmera & SPectroscopy Emission Ray-tracer) is the code responsible for the modelling of several optical plasma diagnostics for ITER, such as charge exchange or visible spectroscopy. CASPER uses the Integrated Modelling and Analysis Suite (IMAS) [1], making it generic to simulate the light spectrum for various synthetic diagnostics in the visible range. It is designed to build scenes for Raysect & Cherab [2], a framework tailored for the ray-tracing simulation of fusion environments. With this method, it is possible to simulate the observed spectrums realistically, burdened by background emissions and reflections. CASPER has been designed to be progressively extended with new physics processes and new diagnostics. So far CASPER lacked the ability to also simulate the emission of neutral beams with the MSE accurately taken into account, however, with plans of multiple dedicated MSE diagnostics observing the heating and diagnostic neutral beams in the machine, this is a serious requirement that the code has to fulfill. This issue has been recently addressed and accurate beam emission calculation has been added to CASPER. The spectrum calculation was adopted from the MSESIM [3] code, and has a quantum mechanical basis. This has been integrated into CASPER together with a branch of Cherab still under development, allowing for flexible beam modelling. The first test results produced by the improved code are presented here. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization. References: [1] F. Imbeaux et al, 2015 Nucl. Fusion 55 123006 [2] M. Carr, et al, Rev. Sci. Instrum. 89, 083506 (2018) [3] M. F. M. De Bock, et al, Rev. Sci. Instrum. 79, 10F524 (2008)
Simultaneous measurement of co- and counter-current ions with a Fast Ion Loss Detector on the TCV tokamak
Presenter: Jesús Poley (Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland.)
Authors: Jesús Poley
Abstract: Supra-thermal ions play an essential role in the plasma’s heating, current drive, and production of the fusion reactions. The supra-thermal ion confinement is critical to prevent degradation of the fusion performance and damage to the plasma-facing components [1]. To study the supra-thermal ion confinement on tokamaks, a wide range of diagnostics can be used, such as Neutral Particle Analyzers (NPA), Fast Ion Deuterium Alpha detectors (FIDA) and Fast Ion Loss Detectors (FILD) [2]. To this end, a new FILD has been designed, installed, and used for the first time on the TCV tokamak. The diagnostic has a high-resolution medium-speed (up to 10 kHz) camera to characterise the velocity space parameters of the supra-thermal ion losses and a fast acquisition system (up to 2MHz) based on a Photo Multiplier Tube (PMT) to characterise the supra-thermal ion losses frequency spectra. However, recently the PMT has been replaced with a 128-avalanche photodiode matrix camera which allows a fast response (up to 4MHz) with a medium spatial resolution (~ 5-10 keV in energy and ~ 0.1-0.15 in pitch, 𝑣∥/𝑣). A double collimator has been installed to simultaneously measure co- and counter-current supra-thermal ions for the first time. A fast removal system was also installed, which retracts the FILD if the temperature in the head (measured by means of a pyrometer) reaches more than 300 degrees Celsius. This allows respectively measuring the FI losses in both plasma current directions and inserting the detector closer to the plasma without the risk of damaging the FILD head. A synthetic characterization of the diagnostic using the e-FILDSIM code [3] has been developed, allowing the data interpretation and possibly the implementation of reconstruction techniques currently under development. Measurements over a wide range of equilibria have already been taken to explore the detector’s capabilities showing the FI first orbit losses of both NBI beams installed on TCV, as well as the FI interaction with MHD activity at frequencies up to 100kHz, which appear correlated with the magnetic perturbations, the neutron measurements, and the soft X-ray emission. Modelling using the orbit following code ASCOT5 agrees qualitatively with the experimental observations of the first orbit losses on the FILD. With the already installed NPA, FIDA, and fast neutron detector, the FILD extends the FI studies on the TCV tokamak.
Novel approach to proton-boron fusion using protons generated through laser-induced thermonuclear DD reaction
Presenter: Przemysław Tchórz (Institute of Plasma Physics and Laser Microfusion)
Authors: Przemysław Tchórz, Tomasz Chodukowski, Marcin Rosiński, Maciej Szymański, Stefan Borodziuk
Abstract: Majority of current research related to proton-boron approach of laser fusion employ hundreds of TW and PW-class laser systems to increase yield of alpha particles produced during p+(_^11)B reaction [1][2]. Recently, such laser systems became much more accessible, however the importance of enabling as many research groups as possible to contribute in the laser-fusion field requires seeking alternative approaches that could be implemented using moderate laser intensities. In this work we report generation of energetic (E_max>4 MeV), intense and directed proton beam during Cavity Pressure Acceleration (CPA) scenario of laser-matter interaction, where CD_2 foils were used inside the target cavity [3][4]. The origin of these protons is one of deuterium-deuterium fusion reaction channels, in which (_1^3)H and p^+ are produced. The measurements of proton energy spectra carried out during this experiment served as an input for preliminary Monte Carlo simulations (FLUKA) [5]–[7] of proton beam colliding with boron targets of different thickness, which suggest potential for few-TW laser systems to generate alpha particle flux comparable to these achieved using the most powerful laser beamlines. References [1] J. Bonvalet et al., “Energetic α-particle sources produced through proton-boron reactions by high-energy high-intensity laser beams,” Phys Rev E, vol. 103, no. 5–1, May 2021, doi: 10.1103/PHYSREVE.103.053202. [2] D. Margarone et al., “In-Target Proton-Boron Nuclear Fusion Using a PW-Class Laser,” Applied Sciences 2022, Vol. 12, Page 1444, vol. 12, no. 3, p. 1444, Jan. 2022, doi: 10.3390/APP12031444. [3] T. Chodukowski et al., “Neutron production in cavity pressure acceleration of plasma objects,” AIP Adv, vol. 10, no. 8, Aug. 2020, doi: 10.1063/5.0005977. [4] S. Borodziuk, A. Kasperczuk, and T. Pisarczyk, “Cavity pressure acceleration: An efficient laser-based method of production of high-velocity macroparticles,” Appl. Phys. Lett, vol. 95, p. 231501, 2009, doi: 10.1063/1.3271693. [5] V. Vlachoudis, “FLAIR: A POWERFUL BUT USER FRIENDLY GRAPHICAL INTERFACE FOR FLUKA,” 2009. [6] G. Battistoni et al., “Overview of the FLUKA code,” Ann Nucl Energy, vol. 82, pp. 10–18, Aug. 2015, doi: 10.1016/J.ANUCENE.2014.11.007. [7] C. Ahdida et al., “New Capabilities of the FLUKA Multi-Purpose Code,” Front Phys, vol. 9, p. 705, Jan. 2022, doi: 10.3389/FPHY.2021.788253/BIBTEX.
15:40 - 17:40
Session 7 learn more
Chair: Nektarios Papadogiannis - Vice Chair: Victor Doroshenko
Time resolved spectroscopy of proton-heated targets relevant to proton fast ignition
Presenter: Farhat Beg (University of California)
Authors: Farhat Beg
Abstract: Recent demonstration of ignition on the National Ignition Facility has generated significant interest worldwide in the use of inertial confinement fusion for future fusion power plants. However, to make thermonuclear fusion a reality for energy applications, one needs to significantly increase gain of the target. Fast ignition (FI) of inertial confinement fusion concept promises high gain compared to conventional hot spot ICF. FI is also attractive due to less stringent symmetry requirement because of separate compression and heating phases [1]. The heating of compressed fuel could be done using energetic electrons or protons/ions. Particularly, heating by protons is attractive due to their heavier mass, which makes them less prone to instabilities and provides a more localized energy deposition. We have carried out a series of experiments on the Omega EP laser to understand proton focusing and energy deposition. We, for the first time, used time-resolved X-ray spectroscopy to investigate heating of a copper foil by laser generated proton beam using the High-Resolution Streaked X-ray Spectrometer (HiResSpec). The EP laser (450-900 J, 5-10 ps) was focused onto a cone-enclosed partial hemisphere to generate and focus an intense proton beam onto a 10 µm- or 25 µm-thick solid copper sample. HiResSpec diagnosed the Cu Kα1 and Kα2 line emissions with a time resolution of a few picoseconds, allowing us to resolve temperature-dependent shifts of the lines; these correspond to sample temperatures up to ∼50 eV within ∼35 ps, according to atomic kinetics simulations. We compared these results with hybrid-PIC simulations and find consistent temperature evolution, when accounting for the temporal spreading of the proton beam as it traverses the cone.
Measurements of the seed of runaway electrons and its core transport and growth using a novel multi-energy SXR pin-hole camera
Presenter: Luis F. Delgado-Aparicio (PPPL)
Authors: Luis F. Delgado-Aparicio
Abstract: New observations of the seed formation and dynamics of the birth conditions of runaway electrons (REs) have recently been carried out at the Madison Symmetry Torus (MST). The use of a newly developed versatile multi-energy soft x-ray (SXR) pinhole camera provides unprecedented improvement in throughput and signal-to-noise-ratio thus enabling early-detection, imaging (r/a~2%, t~1 ms) and energy discrimination at Ephoton~20-300×Te,0; the latter is of great advantage over conventional REs studies conducted in large tokamaks with electron temperatures of few keV and electron energies up to 1-60 MeV with Ephoton~(1-60)×103 ×Te,0. The formation of an off-axis seed with an initial linear growth at E/ED~0.1-0.2 (ED being the Dreicer field) has been clearly resolved for photon energies Ephoton~20-40×Te,0; the emergence of the seed population in the plasma periphery instead of that in at the magnetic axis is consistent with a lower electron-density and Dreicer fields. Spatially dependent exponential growth rates have also been resolved for the first time and are consistent with a “hot-component” increasing its characteristic energy up to 103×Te,0. Seed calculations using a newly developed Backward Monte Carlo code computing the RE generation in space- and time-dependent dynamic scenarios including radial transport - with a forward synthetic ME-diagnostic capability - will also be presented. New data will also showcase the radial time-history effects of resonant magnetic perturbations (RMPs) with poloidal mode number m=3 in the suppression of runaway electrons.
Development of a multifunctional real-time data processing system for interferometers on EAST
Presenter: Yuan Yao (ASIPP)
Authors: Yuan Yao
Abstract: Due to the disadvantages of the old interferometer with high voltage drive, such as instability during long-pulse discharge and unsafety of personnel operation, interferometers for electron density measurements are gradually being replaced by interferometers built with smaller, more stable sources. In the latest campaign of EAST experiments, two new interferometers were installed, a dispersive interferometer (DI) based on a Carbon Dioxide laser and a solid source interferometer (SSI) based on microwave multiplier sources. In order to make them available for the Plasma Control System (PCS) system, each of them needs to be provided with a real-time processing system to extract the detector output signal and afterward obtain the electron density information through signal processing. To obtain interferometer data quickly and reliably, a unified hardware template was applied to both interferometers. Three main parts are included in this hardware template - digitization, digital signal processing, and output modules. In particular, the digitization section uses a multi-channel Analog-to-Digital Convertor to acquire the signals that need to be calculated. The digital signal processing part is implemented by an FPGA, which is the hardware basis of this multifunctional template that can be used for multiple interferometers. This section includes two main parts, wrapped density signal extraction and signal unwrapping. For DI it is a phase calculation based on the intensity ratio, while for SSI it is a phase calculation by means of FFT or phase demodulation. Both computational approaches form independent IP cores to build systems quickly, while these IP cores provide parameter interfaces to adapt to different application scenarios. The output module provides a variety of data transmission methods, including fiber optic transmission and Digital-Analog-Convertor-based analog transmission, to interface with PCS or other subsequent systems. This data processing system template has been applied to each of the above two interferometers and valid data were obtained in a recent EAST experiment campaign. It demonstrates the usefulness of the template and provides a reference for the design of data processing systems on future devices.
Synthetic X-ray Phase Contrast Images using the GREENER Code
Presenter: Calum Freeman (University of York)
Authors: Calum Freeman, Nigel Woolsey, Robbie Scott, Luca Antonelli
Abstract: The National Ignition Facility's landmark results over the last two years were in part made possible by effective diagnostics supporting improvements in experimental design. Improved diagnostics and diagnostic modeling capabilities could result in further improvements in understanding, which could lead to higher gain experiments. This talk will discuss one potential diagnostic improvement: X-ray Phase Contrast Imaging (XPCI); and the GREENER code which can model this diagnostic. Inertial Fusion experiments generate plasmas with material interfaces and strong shocks. Understanding interfaces and the growth of instabilities like Rayleigh Taylor instability, as well as how laser imprint seeds mixing and instabilities could help reduce ablator mix into the core. Better diagnostics showing shocks could improve hydrodynamic simulations and test new experimental designs. XPCI is particularly sensitive to shocks and interfaces, so is well suited to this task, and has benefits over purely absorption based x-ray imaging. XPCI has already been used to image static cold objects, and some objects undergoing shock compression. The GREENER code, based on extensions to the Geant4 Monte Carlo particle tracking code, can be used to aid the analysis of these experiments, and to design new experiments. This code can generate synthetic absorption and refractive images of the output from hydrodynamic simulations, and is moving towards generating synthetic images of hot plasmas through including bremsstrahlung emission. This work is part funded by the EPSRC.
Coherent XUV Multispectral Diffraction Imaging for dense plasma diagnosis
Presenter: Emanouil Benis (Institute of Plasma Physics and Lasers, Hellenic Mediterranean University Centre for Research & Innovation, & Department of Physics, University of Ioannina)
Authors: Stylianos Petrakis, Alexandros Skoulakis, Yannis Orphanos, Anastasios Grigoriadis, Georgia Andrianaki, Dimitrios Louloudakis, Nathanail Kortsalioudakis, Athanasios Tsapras, Costas Balas, Dimitrios Zouridis, Efthymios Pachos, Makis Bakarezos, Vasilis Dimitriou, Michalis Tatarakis, Nektarios Papadogiannis
Abstract: Interest in fast imaging at the nanoscale using coherent XUV and/or X-ray radiation has received increased attention nowadays primarily due to the rapid growth of nanotechnology. Such coherent, directional, and high-brilliance X-ray radiation sources are currently provided by X-ray free-electron laser facilities. However, these facilities are scarce worldwide with limited access, since they require large financial investments for development, maintenance, and manpower. Recently, we suggested an alternative path, reporting on an automated table-top system for multispectral XUV coherent diffraction imaging (CDI). [1]. The coherent XUV radiation is generated in a semi-infinite gas cell via high harmonic generation of the near-infrared femtosecond laser pulses ensuring high-stability conditions and supporting operation at high repetition rates. The XUV spectral selection is performed by specially designed multilayer XUV mirrors that do not affect the XUV phase front and pulse duration. Several pairs of multispectral mirrors can be automatically interchanged, thus providing different narrowband XUV spectral regions for CDI applications, employing either transmission or reflection. Here we examine the option of applying the multispectral coherent XUV CDI method for plasma diagnosis. Considering (a) the higher frequency of the XUV radiation with respect to the plasma frequency (b) the ns time scale of the plasma dynamics and (c) the option of performing IR-pump–XUV-CDI-probe measurements, the detailed dynamical evolution of the plasma formation becomes viable.
18:10 - 20:00
Session 8 learn more
Chair: Luis Felipe Delgado-Aparicio - Vice Chair: Tomas Hoder
Specificities of plasma diagnostics using ultrashort laser induced fluorescence techniques
Presenter: Gabi Daniel Stancu (Laboratoire EM2C, CentraleSupelec, France)
Authors: Gabi Daniel Stancu
Abstract: Non-equilibrium high-pressure plasmas are often confined with characteristic dimensions of less than a millimeter (e.g. capillary microwave discharges), and can exhibit transient behaviors (e.g. nanosecond discharges) with characteristic times below one nanosecond. Spectroscopic diagnostics such as fluorescence techniques functioning with cw to ultrashort lasers are employed for in situ species density measurements of key plasma radicals. Focusing laser beams at micrometer scale for spatially resolved measurements or using ultrashort lasers (e.g. pico & femtosecond lasers) for temporal resolved measurements tremendously increases the photon flux (up to PW/cm2) and induces several phenomena (e.g. power saturation, photolytic effects, Stark detuning, Rabi oscillations), which must be taken into account for a correct evaluation of the plasma parameters. In this contribution, the phenomena, principles and peculiarities of laser induced fluorescence techniques (e.g. quenching, photolysis, photon statistics) will be discussed. Using the two-photon absorption laser induced fluorescence technique (TALIF) as example, the classical and the VUV calibration methods applied for femtosecond TALIF will be presented along with temporal and spatial plasma characterizations.
First Measurements with an Imaging Neutral Particle Analyzer in the ASDEX Upgrade tokamak
Presenter: José Rueda-Rueda (University of Seville)
Authors: José Rueda-Rueda, Manuel García-Muñoz, Eleonora Viezzer, Philip Schneider, Javier Garcia-Dominguez, Pablo Oyola, Joaquin Galdón-Quiroga, Micaela Videla-Trevin, Albrecht Herrmann, Xiaodi Du, Michael A. Van Zeeland, Tilmann Lunt, Javier Hidalgo-Salaverri
Abstract: A new Imaging Neutral Particle Analyser (INPA) [1-2] diagnostic has been installed and commissioned at the ASDEX Upgrade (AUG) tokamak. The AUG INPA diagnostic measures fast neutrals escaping the plasma after CX reactions. The neutrals are ionised by a 20 nm carbon foil and deflected towards a scintillator by the local magnetic field. The use of a neutral beam injector (NBI) as active source of neutrals provides radially resolved measurements while the use of a scintillator as active component allows us to cover the whole plasma along the NBI line with good phase-space resolution (~ 10 keV and 8 cm); making it suitable to study localized fast-ion redistribution in phase-space. The diagnostic explores pitch angles ( λ=v||/ v ) close to 0.5 at the magnetic axis and close to 0.7 at the plasma edge in the low field side. First measurements taken in MHD-quiescent plasmas are compared with neoclassical simulations to validate the synthetic diagnostic, showing a good agreement within errorbars. Energy and position localised redistributions of FI were found during phases with strong FI driven modes such as BAE and TAE, showing the capability of INPA to measure localized fast-ion transport. * See author list of U. Stroth et al. 2022 Nucl. Fusion 62 042006 [1] X.D. Du et al., Nucl. Fusion 58 082006 (2018) [2] J. Rueda-Rueda et al., RSI 92, 043554 (2021)
Laser-driven quasi-static magnetic fields for magnetized high energy-density experiments
Presenter: Christos Vlachos (Université de Bordeaux, CNRS, CEA, Centre Lasers Intenses et Applications, Talence, France/Hellenic Mediterranean University)
Authors: Valeria Ospina Bohorquez, Philip Bradford, Gabriel Perez-Callejo, Michael Ehret, Pierre Guillon, Morgane Lendrin, Xavier Vaisseau, Bruno Albertazzi, Sussane Eitan, Michel Koenig, Sophia Malko, Robert Fedosejevs, Channprit Kaur, Matthew Gjevre, Mathieu Bailly-Grandvaux, Christopher Alexander Walsh, Ricardo Florido, Francisco Suzuki Vidal, Christopher Mcguffey, Farhat Beg, Jacob Saret, Marco Antonio Gigosos, Tomasz Chodukowski, Tadeusz Pisarczyk, Zofia Rusiniak, Jan Dostal, Roman Dudzak, Annette Calisti, Sandrine Ferri, Luca Volpe, Laurent Gremillet, Joao Jorge Santos
Abstract: The use of seed magnetic-fields (B-fields) in laser-driven target-compression experiments is expected to lead to > 10 kT B-fields across the compressed core due to advection of the in-flow plasma. B-fields exceeding 10 kT are promising for magneto-inertial fusion since they reduce electron thermal conduction. Studying the formation of these compressed B-fields may also improve our understanding of magnetized astrophysical plasmas or extended magnetohydrodynamics. To reach compressed B-fields exceeding 10 kT, one important challenge is to generate strong seed B-fields on major laser facilities. Where external pulsed power hardware is not available, it is possible to use laser-driven coil (LDC) targets to generate a multi-tesla field. We have tested LDCs on several nanosecond laser facilities under laser drive conditions similar to those at the Laser MegaJoule (LMJ). The goal was to predict the B-fields that might be achieved on LMJ by benchmarking a laser-driven diode model of B-field generation. At the LULI2000 and OMEGA facilities we used comparable laser intensities, ~1015-1016 W/cm2, at 1.06µm and 0.35µm wavelengths respectively. We generated discharge currents of ~20 kA and ~8 kA yielding B-fields of ~50 T and ~6 T respectively, with targets of different size. Where possible, magnetic fields were measured using proton deflectometry directed along two axes of the target. Comparing our experimental deflectograms with proton tracking simulations enables us to identify various deflection features that can be linked to the looping current or static charging of the coil’s wire surface. Measured discharge currents are consistent with predictions from our model for all the experimentally tested conditions, which give grounds for the successful use of LDCs on large-scale facilities like LMJ.
The Progress of ITER Divertor Langmuir Probe final design
Presenter: Lin Nie (Southwestern Institute of Physics)
Authors: Lin Nie
Abstract: Divertor Langmuir probe (DLP) system is one of ITER diagnosis used to measure the divertor parameter profiles such as ion saturation current, electron temperature, density and loaction of strike point, for ITER advanced control and physics analysis. The system consists of three components: 1) 400 Langmuir probes installed on the side of monoblack in 5 cassettes. It should sustain 10MW/m2 Steady heat load or 20MW/m2 Transient heat load. With the thermal analysis and mechanical analysis, the structure design of probe has gone through 3 versions, and now the full tunsten design was reviewed and accepted. The Final machining and welding processes research is on going. 2) the Electronics System, includeing power supply, mode switching and signal conditioning components, will be used for 3 kinds of probe operational mode: Single probe voltage scanning mode, double probe voltage scanning mode and ion saturation current mode. 3) Instrumentation and Control system is used to provide scan waveform output for power supply and measured data to CODAC for calculation of Te, ne and ion flux. The work of DLP finished preliminary design and now is in the final design stage. we will start our final design review (FDR) in this year.
The Development of a Pulse Dilated Wolter-like X-ray microscope for the Imaging of the Hot Spot in a High-modes Asymmetry
Presenter: Xing Zhang ( Laser Fusion Research Center, China Academy of Engineering Physics)
Authors: Xing Zhang, Feng Wang
Abstract: In the laser driven inertial confinement fusion, the fuel filled capsule will converge rapidly in a high implosion velocity. The slight driven asymmetry or the small defects in the shell may form the seeds of the Rayleigh-Taylor (R-T) instability growth. The R-T instabilities will grow rapidly during the stagnation phase, and form the structure of “spike-bubble” in different amplitudes around the hot spot. As a result, the symmetry of the hot spot degenerates, and the mix in the hot spot increases. Diagnostics of the high-modes asymmetries of the stagnated hot spot is crucial, but the reliable tools are under development. Considering the size of the hot spot and the motion blur, the imaging diagnostics needs a spatial resolution less than 3μm and a temporal resolution of about 10ps. It is out of the capability of the Kirkpatrick-Baez (KB) microscope with an X-ray framing camera (XFC), which has the resolution of about 7μm and 80ps. In this work, a pulse dilated Wolter-like X-ray microscope is presented. It consists of a Wolter-like microscope and a pulse dilated XFC. The microscope has the Wolter-I type mirror configurations in the sagittal and meridian directions respectively. The object distance is about 20cm. The imaging aberrations are suppressed by the combination of the hyperbolic and elliptical mirrors. The static imaging resolution is less than 2μm in a field-of-view of 400μm. The mirrors use the Pt film and the filter package is set as 30μm Ni and 50μmAl. The maximum reflectivity X-ray energy is around 8keV. To overcome the low resolution of the XFC, the magnification is set as about 25. A pulse dilated XFC is also developed. In the present prototype camera, two CsI cathode chips with a width of 10mm are coated in the center. The exposure time of the pulse on the MCP is about 500ps. So the pulse dilation is set as 50 to decrease the length of the dilation tube. In the test with a fs pulsed ultraviolet laser, the temporal resolution of the pulse dilated XFC is about 10ps and the spatial resolution is about 20lp/mm. The prototype pulse dilated Wolter-like X-ray microscope is installed on the Shenguang-III prototype laser facility. The comprehensive spatial resolution is about 3μm in a field-of-view of 400μm, and the temporal resolution is able to be about 10ps. The performance of the stagnated hot spot imaging will be tested in the following work.
09:00 - 10:55
Session 9 learn more
Chair: Milan Simek - Vice Chair: Emmanouel Benis
A critical overview of Optical Emission Spectroscopy for plasma diagnostics
Presenter: Giorgio Dilecce (Institute for Plasma Science and Technology - CNR)
Authors: Giorgio Dilecce
Abstract: Optical Emission Spectroscopy (OES) is perhaps the most flexible plasma diagnostic technique, from the hardware point of view. Non-invasive collection of light and its spectral analysis can be done on virtually any plasma device at any plasma condition. Utilization of the spectral information for the measurement of plasma parameters is much less straightforward. Light emission at optical or VUV wavelengths originates from unstable atomic/molecular electronic states. These are someway excited in the plasma and then undergo a collision/radiative kinetics during their short lifetime. In non-equilibrium plasmas, then, a correct interpretation of the OES outcomes is possible only if the excitation and loss kinetics is well known, together with the relaxation properties of the vibrational and rotational manifolds of molecules. Furthermore, inferring plasma parameters is possible only if particular conditions are fulfilled. It is therefore of paramount importance to address the issue of how to recognize and assess the dominant, if any, process producing the molecular excitation to a radiative state. Starting from a survey of the most common excitation mechanisms, not always the mere electron impact with the ground state, and of the collision kinetics of excited states, we shall address the measurements by OES analysis of the translational and vibrational temperatures, of the electric field in a gas discharge, of the concentration of species, in a variety of non-equilibrium plasma conditions, from low to high pressure, including plasma processing devices, negative ions sources and cold edge plasmas. With a focus on common mistakes arising from the misuse of bad assumptions in the analysis of spectra.
Non-steady state collision-radiative models for atmospheric pressure plasma diagnostics
Presenter: Tomáš Hoder (Masaryk University)
Authors: Tomáš Hoder, Lukáš Kusýn, David Prokop, Zdeněk Bonaventura, Petr Bílek, Aleksandar Jovanovic, Marjan Stankov, Detlef Loffhagen, Markus M. Becker
Abstract: The discharge mechanisms generating atmospheric pressure plasmas lead to their highly transient behavior with steep gradients on sub-millimeter and sub-nanosecond scales. These plasmas, generated by barrier, corona, or spark discharges, or in nanosecond pulsed or jet discharges, are useful in many application-oriented fields of research. Particularly, the interest is focused on plasmas in gases like air or argon, which have an exclusive position both in nature and technology. For proper understanding of such plasmas, closely linked diagnostics and computer modelling approaches are necessary. We summarize the use and basic principles of these approaches in the past and present recent methods for development of non-steady state collision radiative models for such plasma investigations and their results for relevant gas-mixtures. Applying these models, we unravel the changes in a local electric field parameter with high spatiotemporal resolution, using linked experimental and theoretical efforts. The experimental part comprises the utilization of usual (ICCD cameras) as well as less common (time-correlated single photon counting systems) devices for detailed plasma diagnostics. The theoretical part uses procedures of sensitivity analysis, uncertainty quantification, enhancement of reaction kinetics models or fluid modelling of discharges selected for the case studies. Only such joint procedure can lead to the knowledge clarifying in detail the underlying plasma physical mechanisms and plasma chemical processes on aforementioned small temporal and spatial scales. This work is supported by the Czech Science Foundation project no. GACR 21-16391S and by the project LM2018097 funded by the Ministry of Education, Youth and Sports of the Czech Republic.
Energy-resolved Thomson parabola spectrometer for laser-driven low energy multi-ion measurement
Presenter: Alma Kurmanova (INFN Laboratori Nazionali del Sud)
Authors: Alma Kurmanova, Giada Petringa, Roberto Catalano, Giuseppe Antonio Pablo Cirrone
Abstract: Laser-driven tabletop accelerators have paved the way for multi-ion sources with ultra-high energies and well-defined beam divergence. Real-world applications need to be preceded by robust beam diagnostics, which are challenging due to the operating conditions and beam complexity. One possible dosimetric solution is the Thomson parabola spectrometer (TPS), which scatters ions according to their kinetic energy and charge-to-mass ratio (q/m) thanks to the combination of electric and magnetic fields. A new compact TPS has been designed and is under development at INFN Laboratori Nazionali del Sud based on realistic beam simulations performed using the Monte Carlo based toolkit TOPAS. The spectrometer is specially designed for low energy ion beams composed of 0.5-5 MeV protons and 1-10 MeV alpha particles, to distinguish then with high energy resolution ΔE/E <1%. Overlapping ion traces in a certain energy range are consequently avoided, through careful choice of pinhole diameter, field parameters, and drift lengths. The proposed TPS has been designed to be merely 30 cm in size while retaining full functionality, to allow for direct placement in the target-laser interaction chamber. The compact design can be readily deployed in proton-boron fusion experiments with low reaction rates where particle flux is expected to be small.
Reconstruction of beam emission spectra produced by a large negative ion beam for fusion
Presenter: Riccardo Agnello (EPFL)
Authors: Riccardo Agnello
Abstract: Heating Neutral Beams (HNBs) for ITER will be based on large beams of hydrogen/deuterium atoms, about 1m x 2m in cross section, with a current up to 350 A/m2, and an acceleration energy up to 1 MeV [1]. These beams, made of 1280 individual beamlets, must fulfill strict requirements in terms of current uniformity and divergence to maximize their transmission through beam ducts. The plasma source SPIDER, an intermediate technological step towards the full-scale HNB prototype MITICA, has achieved the first phase of experimentation by testing source performances in caesium and investigating the physics of single isolated negative ion beamlets (28 out of 1280) by multiple beam diagnostics [2]. Upcoming SPIDER experimental activities foresee the extraction of a few hundred beamlets, as a midway goal to full beamlets (1280) extraction. In this configuration, the signal acquired by optical diagnostics will consist of the overlapping of many beamlets along the line of sights, with a consequent difficulty in distinguish the features of the individual beamlets, required to study the beam optics. To overcome the ambiguity due to volume-averaged data, beam emission models are required. In this contribution, we present a numerical tool based on a Monte Carlo model to synthesize the spectra observed by the diagnostic of beam emission spectroscopy (BES), starting from the interaction of a single beamlet with the background gas. The preliminary results suggest that, despite the beamlets space mixing, the BES diagnostic is expected to provide useful information on the criss-cross effect and the mutual beamlet repulsion. In the case of MITICA, where beamlet groups have different directions converging to the plasma, separating the beam components will be essential. These studies are crucial to characterize the beam performances, while approaching ITER HNBs requirements.
11:30 - 13:40
Session 10 learn more
Chair: Michael Tatarakis - Vice Chair: Farhat Beg
Overview of ITPA Diagnostics R&D: recent Activities in Support of ITER
Presenter: Didier Mazon (CEA)
Authors: Didier Mazon
Abstract: Diagnostic systems are essential for safe machine protection, reliable machine operation and comprehensive understanding of burning plasma behavior in ITER [1]. In order to achieve the above aims, more than fifty sub-systems will be developed for measurement of plasma and plasma facing components in the harsh ITER environment, e.g. higher neutron/-ray irradiation and lower accessibility/maintainability compared to that of existing fusion devices. The International Tokamak Physics Activity (ITPA) Topical Group (TG) on Diagnostics has been conducting continuous R&D activities to support improved ITER diagnostic performance. In this paper, highlights of some of the recent TG activities are overviewed
Development of a new helium imaging system to measure the edge two-dimensional turbulence and profiles simultaneously on EAST
Presenter: Shaocheng Liu (Institute of Plasma Physics, Chinese Academy of Sciences)
Authors: Shaocheng Liu, Letian Li, Liujun Zhong, Wei Wei, Ning Yan, Yinlong Xing, Ran Chen, Guanghai Hu, Xiaoju Liu, Qing Zang, Liang Wang, Rui Ding, Guoqiang Li, Guosheng Xu, Xianzu Gong, Xiang Gao
Abstract: Since plasma turbulence is driven by free energy source for micro-instabilities, edge turbulence plays an essential role in the energy and particle transports due to the radial gradient of plasma temperature and density in the boundary region [1]. Understanding the interaction between edge turbulence and cross-field transport could be beneficial to controlling radial transport and divertor heat load, which is a key issue in magnetically controlled plasmas. Therefore, the measurements of edge turbulence and the corresponding plasma profiles could provide a means to identify the edge turbulence pattern and its contribution to transport. A new helium imaging system is under development based on the gas puff imaging (GPI) system in EAST, aiming to measure the evolution of two-dimensional edge turbulence structure and plasma profiles simultaneously with high temporal and spatial resolution. Recently, the GPI system on EAST has been upgraded by applying a new relay optical system [2]. In contrast with the previous optical system of GPI in which a coherent glass fiber bundle is used to transmit the image from the end of a telescope inside the vacuum vessel to the outside, the new relay optical system has much lower light loss, i.e., the emission intensity on the image plane of the new GPI is at least 15 times higher than the previous one. The temporal resolution of the GPI system is 530 kHz, and the spatial resolution is 2 mm. Based on the GPI system, the new optical system of helium imaging system contains two optical branches through a light-splitting optical system, with one branch operated as the standard GPI system, and the other operated as a four-color optical system. In the latter branch, four wavelengths (587.6 nm, 667.8 nm, 706.5 nm and 728.1 nm) are extracted and focused on a thin image surface. The 2D electron temperature and density can be derived from the ratio of I_728.1/I_706.5 and I_667.8/I_728.1 as the standard helium beam diagnostic [3]. Consequently, the new helium imaging system can measure the edge turbulence evolution and 2D plasma profiles simultaneously, which is of great significance to identifying edge turbulence and its contribution to transport. References [1] Doyle E. J. et al Chapter 2: Plasma confinement and transport, Nucl. Fusion 47 (2007) S18 [2] Liu S. C. et al Upgrade and application of the gas puff imaging system in EAST, Fusion Eng. Des. 179 (2022) 113156 [3] Schmitz O. et al Status of electron temperature and density measurement with beam emission spectroscopy on thermal helium at TEXTOR, Plasma Phys. Control. Fusion. 50 (2008) 115004
Calibration techniques for Thomson scattering diagnostics on large fusion experiments
Presenter: Golo Fuchert (Max-Planck-Institut für Plasmaphysik (IPP), Greifswald, Germany)
Authors: Golo Fuchert, Marcus Beurskens, Sergey Bozhenkov, Jakob Brunner, Shan Chen, Federico d'Isa, Jule Frank, Leonardo Giudicotti, Matthias Hirsch, Udo Höfel, Tobias Jesche, Jens Knauer, Ekkehard Pasch, Andrea Pavone, Robert Wolf
Abstract: Measuring the electron density and temperature with laser Thomson scattering requires an accurate calibration of the entire diagnostic. For the temperature, a relative spectral calibration is required, for the density additionally an absolute calibration (e.g. using rotational Raman or Rayleigh scattering). In practice, these calibrations change over time (drift of beam path, coating on observation windows, etc.), which requires frequent recalibrations. On larger fusion experiments, this is particularly challenging. Longer beam paths are more sensitive to alignment drifts, calibration measurements have to be arranged with a tight experiment plan and torus hall access may be restricted for longer periods due to radiation safety or during operation of a superconducting magnet system. At Wendelstein 7-X (W7-X), a number of techniques are developed to make existing calibration methods more resilient against alignment changes, to reduce the time required for calibration measurements, and to prolong the time between recalibrations. An in-situ spectral calibration is developed using a tunable OPO laser for Rayleigh scattering. As it is often the case for Rayleigh scattering, stray light is an issue. However, this also offers the possibility for an “emergency calibration” using only the stray light when a quick recalibration is required during an experimental campaign. Furthermore, it is investigated if the accuracy of the spectral calibration can be improved by using an additional Nd:YAG laser with a different wavelength for the Thomson scattering measurements (dual wavelength Thomson scattering). For the absolute calibration, a position-sensitive Raman calibration has been developed, in which the laser alignment is monitored and included in the resulting calibration factors. For large experimental devices, the beam position is controlled automatically. However, these control systems can fail temporarily and for pulsed lasers, like the ones used for laser Thomson scattering, the beam pointing stability alone leads to a scatter in the beam position that cannot be mitigated and that becomes important for long beam paths. Including the beam position in the calibration improves the density profile quality and allows for longer times between calibrations. For experiments in which the position monitoring failed (e.g. due to data acquisition issues or hardware failures), a machine-learning algorithm has been developed which determines the impact of laser misalignment on the density profiles and allows for a correction. We believe that the techniques developed at Wendelstein 7-X may be essential for other large fusion experiments like, for example, ITER.
JET Far Infrared (FIR) Interferometer/Polarimeter Diagnostic System – 40 years of lessons learned
Presenter: Alexandru Boboc (UKAEA)
Authors: Alexandru Boboc
Abstract: The first-generation burning plasma devices such as ITER, STEP or DEMO will operate in a very challenging environment for diagnostic systems due to the special operating conditions and these can be found only to a certain extent in some of the existing fusion devices around the world. Some of these conditions are high ambient temperatures, strong electro-dynamic forces due to high magnetic fields, long pulse lengths and uninterrupted periods of operation and, most notably, very low or zero access to some parts of diagnostics. With that in mind one must develop a system with enough redundancy and robustness to survive the reactor-relevant plasma conditions for many years to come. Originally designed for five years of plasma operations, the JET Far Infrared diagnostic system is still operating at its full capabilities nearly forty years later and in ITER relevant conditions (4.5MA plasmas, 30MW additional plasma heating power, albeit with significantly lower neutron fluences) and under extreme environment of several D-T campaigns. The original design changed substantially over the years, just to give two examples: the introduction of the divertor significantly reduced access and the number of laser beams; D-T readiness required double vacuum windows greatly reducing the laser signal level to 5% but the diagnostic still worked, due to the excellent dynamic range of the detectors. On JET, complete alignment of the FIR system is required only once in a decade, like the timescale for fusion reactor maintenance shutdowns. The FIR system operates as a hybrid interferometer and polarimeter system, nearly automated, with state of the art electronics for phase counting using FPGA technologies, improved redundancy in both optical hardware (multiple lasers) and data acquisition and control (parallel acquisition systems based on PowerPC and FPGA straight from detectors), real-time integration of measurements with the JET plant (active plasma control and additional heating system interlocks) but also with other physics diagnostics& systems such as High Resolution Thomson Scattering (for offline data validation) and magnetic reconstruction codes such as EFIT++ (where polarimetry information is in the default input data set) are just some of the upgrades and optimisations done in many years. One notable completed enhancement (in 2014) was the integration and use during experiments of the line-integrated density from polarimetry for plasma density control and machine protection. This was the first-time when polarimetry was used for this type of application in a fusion plant and was replicated in most of the current polarimeter developments recently. Also, during the recent D-T campaign on JET the FIR system was the single point failure device for density control on JET with nearly 100% reliability 16hrs/day, 5 days a week. This presentation will discuss invaluable lessons learned designing, operating, optimising, and enhancing such a complex system and how these can these used for developing the new class of laser-based diagnostics for the next generation reactor grade machines. Acknowledgement This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. *See the author list of ‘Overview of JET results for optimising ITER operation’ by J. Mailloux et al 2022 Nucl. Fusion 62 042026
Improving the time resolution of Thomson scattering via machine learning on reflectometry data
Presenter: Diogo R. Ferreira (IST, University of Lisbon)
Authors: Diogo R. Ferreira, Andreas Gillgren, Andrei Ludvig-Osipov, Pär Strand
Abstract: When measuring the electron density profile at JET, the preferred diagnostic is usually HRTS (high resolution Thomson scattering), which provides good accuracy in terms of radial position (on the order of 1 cm) but has a low sampling rate (20 Hz). This makes it infeasible to analyze pedestal dynamics in detail, especially for phenomena such as ELMs (edge localized modes), which occur on faster time scales, and would require at least a sampling rate in the range of 100 Hz to 1 kHz to capture the transient processes associated with ELM crashes. On the other hand, the reflectometry system at JET provides a high temporal resolution (on the order of 1-10 kHz) but is not as accurate in terms of the radial position of the density measurements, which led to the development of new reconstruction methods. In this work, we develop a virtual diagnostic which combines the spatial accuracy of HRTS with the temporal resolution of the reflectometer diagnostic. For this purpose, we train a neural network to predict HRTS-like profiles from reflectometry data. Once trained, we observe that the model agrees closely with HRTS, and is able to overcome some problems that occur in reflectometry-based reconstructions. In addition, the model estimates the density values at the same positions as HRTS, but with a much higher time resolution, which enables the analysis and visualization of ELM dynamics throughout a pulse. We illustrate the results on the pulse that achieved the current energy record in the recent D-T (deuterium-tritium) campaign at JET.
Experimental diagnostic systems for the new 3 PW laser facility at the University of Michigan
Presenter: Karl Krushelnick (University of Michigan )
Authors: Karl Krushelnick
Abstract: The past two decades have witnessed the development of revolutionary light sources having the unprecedented ability to probe new physical regimes and control matter with atomic scale precision. The ongoing development of multi-Petawatt lasers around the world will allow exploration of fundamental yet unanswered questions regarding non-linear Quantum Electrodynamics in relativistic plasmas, including non-perturbative quantum radiation reaction and electron-positron pair production mechanisms. Further experiments enabled by such lasers will include pump-probe experiments using femtosecond x-rays as a probe of material dynamics on ultra-short timescales, the production of GeV ion beams, the generation of instabilities in electron-positron jets, the exploration of vacuum polarization effects, relativistic shocks and the production of “exotic” particles such as pions and muons. I will describe the new NSF funded ZEUS facility under construction at the Center for Ultrafast Optical Science (CUOS) at the University of Michigan. ZEUS will be a dual-beamline 3 PetaWatt laser system that will provide unique capabilities for research. This will be a new high power laser user facility for US scientists as well as for the wider international research community, and will have an open and transparent external review panel for facility access and 30 weeks per year dedicated to external user experiments. After completion in late 2023, the ZEUS laser system will be the highest-power laser system in the US. The development of diagnostic systems for the commissioning experiments at ZEUS will be discussed. Acknowledgments ZEUS construction funded through US National Science Foundation Mid-Scale Infrastructure Award: NSF PHY-1935950
09:00 - 10:50
Session 11 learn more
Chair: Dimitri Batani - Vice Chair: Vasilis Dimitriou
Diagnostics for Fusion Gain > 1 Experiments on the NIF
Presenter: Dave Schlossberg (Lawrence Livermore National Laboratory)
Authors: Dave Schlossberg
Abstract: In December 2022, the National Ignition Facility (NIF) accomplished one of its core missions, which was to achieve controlled fusion ignition – when more energy is released by fusion reactions than energy required to drive the experiment. This scientific milestone was surpassed when 3.15 MJ of fusion energy was generated by a target driven with 2.05 MJ of laser energy (target gain = 1.5), using inertial confinement fusion (ICF). Fusion ignition by inertial confinement requires compression and heating of the deuterium-tritium fuel to temperatures >5 keV, densities >100 g/cc (>1024 particles/cc) with durations ~100 ps. On the NIF this is achieved through laser indirect drive ICF in which the fusion capsule is surrounded by a high-Z enclosure (“hohlraum”) used to convert incident laser energy into x-rays that symmetrically compress the capsule at ~400 km/s. Fundamentally, this extreme environment presents a challenge for plasma diagnostics; recent advances in fusion performance have even more so increased these challenges. On the pathway to ignition on the NIF several key advances in understanding have been supported by diagnostic measurements. This talk will highlight those key measurements and summarize the enabling diagnostic techniques. These include diagnoses of: plasma degradation mechanisms due to engineering features (e.g., “fill tube”) and high-Z impurities mixed into the plasma; reduction of compression due to residual kinetic energy of the plasma; and 2D shock velocity measurements to characterize the impact of ablator material structure on implosion quality. These are just a few examples of physics understanding underpinned by diagnostic advances. Upon achieving an ignited plasma there are several unique diagnostic signatures which clearly indicate the plasma exceeds the Lawson Criterion. A basic metric is provided by neutron diagnostics measuring the number of fusion reactions per implosion. Additional signatures are the time of peak neutron emission, the duration of the plasma “burn,” the plasma spatial size – as imaged by neutrons and x-rays – averaged over its lifetime, and average number of downscattered neutrons. Fascinatingly and somewhat unexpectedly, additional diagnostics measuring drive temperatures and even laser beam energy also observed signatures of ignition. Finally, we will also discuss next-generation diagnostics needed to explore this new, ignited-plasma regime. As heating from alpha-particles dominates plasma temperature profiles and more significant fractions of DT fuel is burned up, new diagnostics must be developed to explore and understand these dynamics. We will also touch upon the diagnostic upgrades necessary to radiation-harden and ruggedize instrumentation. A few forward-looking diagnostic options are explored and discussed. *This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-847465.
Advanced 3D time resolved imaging of streamers and comparison with numerical model results
Presenter: Sander Nijdam (Eindhoven University of Technology)
Authors: Sander Nijdam, Zhen Wang, Siebe Dijcks, Shariar Mirpour, Yihao Guo, Martijn van der Leegte, Anbang Sun, Ute Ebert, Jannis Teunissen
Abstract: Streamer discharges are self-organizing discharges which occur when a fast high voltage pulse is applied, leading to a local, but not global electric field above the breakdown field. These ionization waves can then penetrate areas below the breakdown field. Streamers occur as a precursor to sparks and lightning, but also as separate discharges. In recent years, both simulations and diagnostics of streamer have made great steps, so great that they allow us to compare simulation results now directly to experiments and see that their results agree very well. Here, we will show some examples of recent diagnostics which help us to bridge the gap between experiment and simulation even further. We will show details of inception of discharges, both from electrodes as from suspended dielectric particles representing hail stones. Results are obtained from measuring statistics of inception delay times with respect to a high voltage pulse. This leads to surprising distributions of delays that can give great insights in the mechanisms involved, but also brings up many new questions. Next to this, we will show how we can use a combination of stereoscopic and stroboscopic imaging to determine the path of a propagating and branching streamer discharge. We have developed a semi-automatic routine to reconstruct this path from the images, giving us a complete picture in 3D of streamer velocity, diameter and branching properties. This data will be compared to numerical streamer simulation results obtained using the 3D Afivo streamer model.
Recent highlights of diagnostics and their port integration at ITER
Presenter: Roger Reichle (ITER Organization)
Authors: Maarten De Bock, Michael Walsh, Victor S. Udintsev, Mikhail Turnyanskiy, Bruno Coriton, Thibaud Giacomin, Julio Guirao, Martin Kocan, Daniel Nagy, Takeshi Nishizawa, Sunil Pak, Raphael Tieulent, Jim Palmer, Roger Reichle
Abstract: Recent highlights of diagnostics and their port integration at ITER R. Reichle, M. De Bock, B. Coriton, T. Giacomin, J. Guirao, M. Kocan, D. Nagy, T. Nishizawa, S. Pak, J. Palmer, R. Tieulent, M. Turnyanskiy, V.S. Udintsev, M.J. Walsh ITER Organization, St Paul Lez Durance, France ITER has 26 diagnostic ports which house about 50 diagnostic systems. They are procured through 7 different DAs (CN, EU, IN, JA, KO, RF and US) and by the ITER Organization. Manufacturing has started for many of these systems. For some of the in-vessel diagnostics or diagnostics in the buildings, the first parts have already been installed. New solutions had to be found in response to the numerous challenges posed by ITER to the design of the diagnostic systems. Here we report on the status of some port-based diagnostics (covering the Visible, VUV and X-ray Diagnostics, the Fusion Product Diagnostics and the Heat and Imaging Diagnostics) and of the ports in the form of recent development highlights which are examples of such cases. Many ITER specific systems and subsystems adapted to the various harsh environment aspects of ITER have been developed and/or manufactured such as radiation hard components (sensors for bolometers, low voltage ionization chambers for X-ray cameras), erosion resistant mirror materials (single crystal molybdenum mirrors), various shutters (e.g. linear or rotating electrical) steam resistant devices (obligatory test for all in vessel components), ECRH reflecting or absorbing coatings, remote handling or human assisted handling tools, shielding materials (B4C and others) and collimation solutions for neutrons (e.g. in the Neutral Particle Analyzer), robust mounting of optical components under high thermal mechanical and electrical constraints (e.g in the H-alpha diagnostic). R&D related risks were often minimized by initially parallel developments and diversity followed by selection of the best options and cost control by standardization e.g. for detectors (e.g. common detectors for all VUV systems), port integration, common infrastructure etc.. In the area of assembly, testing, commissioning, calibration and alignment much work has been carried out with the more mature areas being those that are planned for the early campaigns (Equatorial Port 11 and 12). Specific solutions comprise onboard mirror cleaning, onboard alignment and calibration devices and agile in vessel calibration tools. Some novel diagnostic systems were developed e.g. for measuring the divertor flow, the core ion temperature or for the in vessel lighting to account for new demands and/or the tight integration space. Presently one of the main directions of work is to reduce remaining maturity differences between diagnostics and ports to meet the tight and complex installation schedule. The biggest progress and largest number of tangible achievements can be seen in the first plasma ports and the diagnostics to be installed therein, setting the scene for the others to follow. The continued support of the Plasma Diagnostic community is important and highly welcome for ITER. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.
Recent Results on Proton-11Boron Reaction obtained in Accelerator and Laser-Plasma Experiments
Presenter: Dieter H.H. Hoffmann (Xi'An Jiaotong University)
Authors: Dieter H.H. Hoffmann
Abstract: Intense ion- and laser beams are complimentary tools to induce High Energy Density in matter. The development of this field is intimately connected to technological advances of the field. We will give an overview of the projects in High Energy Density science related to inertial fusion with emphasis on the recent results obtained for the Proton-11Boron reaction.
11:30 - 13:40
Session 12 learn more
Chair: Dieter H.H. Hoffmann - Vice Chair: Sander Nijdam
Advanced Optical Diagnostics for Low Temperature Plasmas at PCRF
Presenter: Arthur Dogariu (Texas A&M University)
Authors: Arthur Dogariu
Abstract: The talk will present recent developments and results using advanced optical diagnostics in Low Temperature Plasmas (LTP) at the Princeton Collaborative Research Facility (PCRF).[1] PCRF provides expertise and instrumentation for comprehensive characterization of LTPs with goal of advancing methods of predictive control of LTP. Some of the collaborative research highlighted include measurements of neutrals densities (such as O, N) using femtosecond Two-Photon Laser Induced Florescence (fs-TALIF) and velocimetry using Femtosecond Laser Electronic Excitation Tagging (FLEET) in an arc jet plasma as well as in magnetized RF heated low density plasmas, imaging atomic species induced in a liquid by an impinging plasma jet via fs-TALIF, and mapping the spatial and temporal profile of the electric field in plasmas using E-FISH. The Princeton Collaborative Research Facility was established under Contract No. DE-AC02-09CH11466 by the U.S. Department of Energy (DOE).
Status of the EUROfusion Enabling Research Project "Advances in real-time reflectometry plasma tracking for next generation machines."
Presenter: Filipe da Silva (Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Lisbon, Portugal)
Authors: Filipe da Silva, Jorge Santos, António Silva, Jorge Ferreira, Emanuel Ricardo, Stéphane Heuraux, Roland Sabot, Frédéric Clairet, Yassir Moudden, Gianluca De Masi, Roberto Cavazzana, Giuseppe Marchiori, Rennan Bianchetti Morales
Abstract: One of reflectometry’s expected major roles for DEMO will be plasma positioning, shaping and tracking, complementing or effectively substituting magnetic diagnostics. The first steps to achieve this goal have already been taken experimentally, theoretically and with simulations but a great amount of groundwork remains to be done. An Enabling Research (EnR) Project was built involving a team of experts and developers of reflectometry systems in Europe aiming to tackle many of the still remaining open questions and come out with a coherent and unified approach allowing to implement a reflectometry system able to provide control inputs not only in steady-state operation (flattop) but also during the initial stage of the discharge (ramp-up phase) and, in the sequence of the ErR project, at the end of the discharge (ramp-down phase). The objectives and associated outcomes are divided in two main branches with its own specificities and requiring different approaches: (i) The ability to track and monitor the position and shape of the plasma in the initial stage of the discharge, in the start-up phase and also at the ramp-down phase; (ii) To improve the capabilities of operation in the stationary phase (flattop) in order to provide an accurate and precise substitute to the positioning magnetic diagnostics in real time. An important issue that must be addressed is the synchronization between all reflectometers. An experimental validation on the tokamak WEST will prove the concepts of synchronizing several reflectometers sharing the same clock and synchronizing triggering events. The project also contemplates advances on hardware with a prototype of a compact coherent fast frequency sweeping radio frequency (RF) back-end being developed using commercial Monolithic Microwave Integrated Circuits (MMIC) with Direct Digital Synthesis (DDS), which allows for full control of the signal’s frequency and phase, both with very high precision and resolution.
Development of Fibre Optics Current Sensor synthetic diagnostic for ITER
Presenter: Andrei Gusarov (SCK CEN)
Authors: Andrei Gusarov
Abstract: The Fibre Optic Current Sensor (FOCS) is a diagnostic system, to be installed on ITER as a part of Diagnostic upgrades beyond the 2016 Baseline and to be enabled for PFPO-1. In the present-day magnetic fusion devices, tokamaks, including the biggest European machines JET and Tore-Supra (in the framework of the WEST project) the plasma current measurements rely on the inductive type sensors: Rogowski coils, saddle lops, etc. Coil based sensors provide a signal which is proportional to the time derivative of the magnetic flux through the sensor loop. In case of a nearly stationary operation the magnetic flux is also nearly constant and the useful signal is close to zero. To obtain accurate data in case of a long plasma discharge with weakly changing current sophisticated integration-based signal processing is required. This situation may result in non-linear drifting of the signal. Moreover, in case of burning plasma experiments, like ITER, the presence of strong nuclear radiation fields should result in a high level of parasitic currents in electromagnetic sensors and may generate a significant error of the plasma current estimation. To mitigate the risk of the measurement drift of the inductive sensors, FOCS was proposed as a back-up option. Important knowledge on using FOCS for plasma current measurements is already available thanks to FOCS implementation at JET. However, the operation conditions of ITER FOCS will be different from that at JET. In this regards, it is important to develop a FOCS model relevant for ITER environment in order to predict the measurement performance of the diagnostics and to support both ITER plasma operation and research activities. In the presentation we will describe development of the FOCS synthetic diagnostics which will be a part of the ITER Integrated Modelling & Analysis Suite (IMAS). The model takes into account constrains related with the ITER implementation. The physical background of simulation approach based on the Jones matrix formalism will be outlined and results of the FOCS operation simulation for several scenarios will be presented. The simulations show that the stability of the optical link between the sensing fibre placed on the vacuum vessel and the data acquisition hardware is important to satisfy the measurement accuracy requirements.
Multilayer time-of-flight detector for real-time particle detection in laser-matter experiments
Presenter: Fabrizio Consoli (ENEA)
Authors: Fabrizio Consoli, Giorgio Di Giorgio, Pierluigi Andreoli, Mattia Cipriani, Giuseppe Cristofari, Riccardo De Angelis, Martina Salvadori, Massimiliano Scisciò, Massimo Alonzo, Francesco Filippi, Claudio Verona
Abstract: The detection of accelerated particles is a powerful method for getting information on the physics of intense laser-matter interaction, in both Inertial Confinement Fusion and Laser-Plasma Acceleration schemes. One of the important requirements nowadays is the capability to run diagnostics in real-time mode. Time-of-Flight (ToF) methodologies may allow accurate characterization of incoming accelerated ions, and are intrinsically real-time schemes. Unfortunately, they cannot supply discrimination on the species of the incoming ions, but only on their velocities. In some conditions, this limitation can be overcome by theoretical considerations or by the use of specific filtering foils. A promising technique can exploit the different ranges of ion species, as discussed in reference [1], for a scheme of several active ToF sensors placed in cascade. There, a single ion will undergo energy attenuation depending on both its energy and its species, traveling from one layer to the following one. The energies collected on each sensor can give real time characterization of number, energy and type of the incoming particles. In this work we describe a high-sensitivity ToF prototype detector that we have developed, consisting of three sensitive diamond sensors placed in cascade, in a structure with robust shielding to laser-generated electromagnetic pulses [2]. The sensors have different thicknesses and for each a different foil filter can be mounted, allowing for a high degree of adaptability of the structure to several possible experimental conditions and regimes of laser-matter interaction. The sensor thicknesses chosen for this first prototype took into account diamond robustness and device realization ease to demonstrate the actual capabilities of the adopted scheme. This choice is related to the energy range of incoming particles where the multilayer structure principles can be applied, as it will be discussed. This opens the field for future multilayer active structures for different particle energy ranges. In particular, details on the design, realization and test of the full structure on high intensity laser-matter experiment, will be given. a [1] M. Salvadori, F. Consoli et al, Scientific Reports 11, 3071 (2021) [2] F. Consoli et al, High Power Laser Science and Enginering 8, e22 (2020) a This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.
EDICAM camera for runaway electron detection in JT-60SA disruptions
Presenter: Gergo I. Pokol (Centre for Energy Research, Budapest, Hungary)
Authors: Mathias Hoppe, Tamás Szepesi, Kensaku Kamiya, Gergo I. Pokol, Soma Olasz
Abstract: Runaway electrons are highly energetic particles which are generated in tokamaks whenever strong electric fields are present, such as disruptions. In high-current devices a large fraction of the plasma current can be converted into runaway electron current and the subsequent runaway beam might cause significant damage to the plasma facing components. Visible cameras, like the EDICAM camera system installed on the JT-60SA tokamak, are often used to detect the synchrotron radiation from runaway electron beams in fusion devices. In this work we present runaway electron simulations in JT-60SA disruptions and investigate the applicability of the EDICAM system for the detection of the synchrotron radiation of runaway electrons. The DREAM disruption runaway electron simulation code was used to model a massive material injection induced disruption. The runaway electron distribution function from the kinetic DREAM simulation was given to the SOFT synthetic synchrotron diagnostic framework and the visible radiation was calculated for the parameters of the EDICAM camera system. The key properties of the runaway electron beam affecting the detectability by EDICAM have been identified.
Millimeter-wave scattering measurement system for verifying anisotropy and interactions between scales in microscale turbulence
Presenter: Tokihiko Tokuzawa (National Institute for Fusion Science)
Authors: Tokihiko Tokuzawa
Abstract: Confinement of high-temperature plasmas is believed to be limited by so-called microscale turbulence, such as ion temperature gradient (ITG) mode, trapped electron mode (TEM), and electron temperature gradient (ETG) mode, etc., which have scales about the Larmor radius of ions and electrons. In order to characterize these turbulences and verify the interaction between them, it is necessary to observe each turbulence at the same time and place. We have installed two types of millimeter-wave scattering systems to observe ion-scale and electron-scale turbulence at the same location and time in LHD plasmas. For the electron-scale turbulence measurements, a scattering system using 90 GHz millimeter waves have been applied [1] and recently 150 GHz has been added. The incident wave is injected into the plasma along a horizontal axis in a horizontal cross section. The scattered waves are received by three antennas: one receives backscattered waves at about 160 degrees, while the second and third receive scattered waves at nearly 90 and 110 degrees, respectively. This allows multiple wavenumbers to be observed simultaneously. In addition, because of the different angles of reception of the scattered waves, turbulent wavenumber components in different directions can be observed, and the anisotropy of turbulence can be investigated. For further investigation, we have constructed a system that can also observe turbulence of the same magnitude but in different directions using electromagnetic waves of different frequencies. For ion-scale turbulence measurements, multi-channel Doppler back-scattering (DBS or Doppler reflectometer) has been applied [2-4]. Especially, since the measurement position of DBS varies with the plasma density, a frequency comb was introduced to achieve a position measurement equivalent to that of the above 90 GHz millimeter-wave scattering system by performing simultaneous multi-point measurement. References [1] T. Tokuzawa et al., Rev. Sci. Instrum. 92, 043536 (2021). [2] T. Tokuzawa et al., Plasma Fusion Res. 9, 1402149 (2014). [3] T. Tokuzawa et al., Appl. Sci. 12 (9), 4744 (2022). [4] T. Nasu et al., Rev. Sci. Instrum. 93, 113518 (2022).
14:40 - 15:40
Poster Session 3 learn more
Poster Session 3
Development of the FIR laser interferometer for the HL-2M tokamak
Presenter: Yonggao Li (Southwestern Institute of Physics,CHINA)
Authors: Yonggao Li
Abstract: A five-channel Michelson-type far-infrared (FIR) laser interferometer has been developed on HL-2M tokamak for the electron density measurement in 2022. Two CO2 laser pumped formic-acid lasers (HCOOH, λ=432.5μm) are used as the probe sources. Two waveguides as long as 18.0 meters are employed for the laser beams transmission from the laser room to the interferometry tower. Five metallic retro-reflectors with 50mm aperture are mounted in the vacuum vessel for favourable wave reflection. In the 2022 experimental campaign, five channels of line-integrated electron densities can be measured, with a temporal resolution of 1.0μs and a spacial resolution of 10cm, corresponding the geometric positions of -20, -10, 0, 10, 20cm along the vertical direction, here 0 indicates the geometrical center of HL-2M. In the near future, up to 13 probe channels will be developed for the HL-2M tokamak, and the monofunctional interferometer will be upgraded to three-wave based polarimeter/interferometer. Thereupon, both the electron density and Faraday rotation angle can be simultaneously measured for the same probe channel.
Ion and neutral particle diagnostics in Radio Frequency discharges in the upgraded TOMAS device
Presenter: Luis Daniel López Rodríguez (Laboratory for Plasma Physics, LPP-ERM/KMS, Brussels, Belgium)
Authors: Luis Daniel López Rodríguez, Kristel Crombé, Andrei Goriaev, Johan Buermans, Yuri Kovtun, Laura Dittrich, Per Petersson, Sunwoo Moon, Tom Wauters
Abstract: The upgraded TOroidal MAgnetized System (TOMAS) is a device used to complement studies of wall conditioning techniques for superconducting devices like W7-X and ITER [1]. The magnetic field of TOMAS is toroidal and has a maximum intensity of 0.125 T on axis. The flexible system allows the use of both microwaves and radio frequency (RF) waves for plasma production. An ion cyclotron radio frequency (ICRF) system made of a single strap antenna generates the RF discharges, it operates with an adjustable frequency in the range of 10–50 MHz and can couple up to 6 kW of power to the plasma [1]. The study and optimization of the ion and neutral fluxes and energy distributions in RF discharges is necessary to properly describe the conditions used during sample analysis experiments, performed using a sample load lock system built for material samples exposure. The aim of the research is to study the ion cyclotron wall conditioning (ICWC) technique, foreseen for magnetic confinement devices like ITER [2]. The characterisation of RF plasmas is performed using several diagnostics present at TOMAS: a Time-of-Flight Neutral Particle Analyzer (ToF-NPA), employed to measure neutral particles fluxes and the low energy (10–725 eV) neutrals distribution [3]; a Retarding Field Energy Analyser (RFA) integrated into the sample load lock system, used to measure local ion fluxes and their energy distribution (10–1000 eV) [4]; and a set of movable Langmuir probes, utilized to determinine plasma quantities like the electron temperature and density at different positions inside the vessel [5]. For this research, the measurements of plasma parameters, ion and neutral fluxes and their energy distributions are performed for hydrogen plasmas as a function of different values of pressure during the discharges, frequency of the RF waves launched into the plasma, and intensity of the magnetic field. 1. A. Goriaev et al., Review of Scientific Instruments, 92, 023506 (2021). 2. T. Wauters et al., Plasma Physics and Controlled Fusion, 62, 034002 (2020). 3. S. Moon et al., Physica Scripta, 96, 124025 (2021). 4. A. Goriaev et al., 24th Topical Conference on Radio-Frequency Power in Plasmas, Annapolis, USA (2022). 5. Yu. Kovtun et al., Plasma Physics and Controlled Fusion, 63, 125023 (2021).
Laser Diagnostics for Low-Temperature Plasma Characterization: E-FISH and Laser Induced Fluorescence
Presenter: Lorenzo Ibba (EPFL-SPC Lausanne, Switzerland)
Authors: Lorenzo Ibba, Fabio Avino, Ivo Furno, Domenico Aceto, Giorgio Dilecce, Marianna Ambrico, Paolo Ambrico, Igor Adamovich
Abstract: Low-Temperature Plasma (LTP) applications for medicine, sterilization and agriculture are rapidly increasing. A deep understanding of the physics and chemistry of LTPs is still missing because of the multitude of parameters involved, especially in air at atmospheric pressure. A comprehensive characterization, electrical and chemical, of LTPs is necessary to optimize the devices to better suit the application. Electric field characterization is often overlooked as trivial, despite being one of the possible key factors in direct plasma treatments. Optical Emission Spectroscopy (OES) is used to measure indirectly the electric field, however only in the plasma phase. Advanced laser diagnostic such as Electric-Field Induced Second Harmonic (E-FISH) generation can measure the electric field inside the plasma discharge locally, with better space and time resolution during the whole operation of the device. To better understand the dynamics of the ionization wave and the electric field evolution during and after the plasma discharge, E-FISH measurements are needed. Here, we perform direct E-FISH measurements in a Volume Dielectric Barrier Discharge (VDBD) nanosecond-pulsed plasma at atmospheric pressure, showing the electric field evolution, due to ion and electron dynamics, is quite different in humid air with respect to other gases. Concerning the chemical characterization of LTPs, Fourier Transform Infrared Spectroscopy (FTIR) is often used to measure different relevant molecules but it is limited in sensitivity, as well as in space and time resolution. Laser Induced Fluorescence (LIF), on the contrary, can measure the concentration of different key molecules like NO, O, OH and N, at the nanosecond timescale. The dynamic of these molecules in LTPs is of major importance in the understanding of interaction mechanisms with biological substrates. Absolute measurements of NO concentration by picosecond LIF are performed in a nanosecond-pulsed Surface Dielectric Barrier Discharge (SDBD) plasma at atmospheric pressure, resolving the time evolution and the 2D distribution of NO concentration. The results also call attention to relative humidity to be an important parameter, often underestimated, but critical in real life scenarios.
Design and fabrication of the CER microwave proton ion source
Presenter: Gábor Anda (Senior research fellow)
Authors: Gábor Anda, Sándor Bató, Balázs Leskó, Dénes Oravetz, András Zsákai, Imre Katona
Abstract: A new medium current (20mA max), low normalized beam emittance (< 1 π mm.mrad) ECR microwave H+ source is currently have been built at the Centre for Energy Research, Budapest, Hungary. The design is intended to be a high stability (energy ripple below 1%) ion source capable of delivering a 20 mA continuous or pulsed (0.1-10ms @ 0.01-25Hz) proton beam with 35 keV beam energy. The proton source is part of the compact neutron research laboratory will be built in Martonvásár, Hungary. The design is based on the most commonly used arrangement [1]: MW generator followed by a four stub tuner, E-bend, DC-break, window (vacuum boundary), E-bend, and at last a four section matching transformer [2] connected to a 90/100mm (diameter/length) cylindrical chamber. Magnetic field is generated by permanent magnets (6 magnet bars surround the chamber axially). Among the magnet bars 15 pieces of 2 mm holes are placed (at 5 section, 3 in a row) to have the possibility to observe the discharge at different parameter settings, measure the vacuum in the chamber and for hydrogen gas inlet. Simulations are conducted to determine the parameters of the permanent magnet bars (sizes, grade) and ferromagnetic components to ensure the desired magnetic field inside the cylindrical chamber. High voltage insulators are installed vertically instead of horizontally. This way the distance between the extraction slit and the entrance of the ion optic can be extremely short. References [1] Rev. Sci. Instrum. 81, 02B313 (2010); [2] Rev. Sci. Instrum. 85, 063301 (2014);
Wisconsin In Situ Penning (WISP) neutral partial pressure gauges in view of the quasi steady-state operation at Wendelstein 7-X
Presenter: Stepan Sereda (Department of Engineering Physics, University of Wisconsin - Madison, Madison, USA)
Authors: Stepan Sereda, Barret Elward, Jessica Hoffman, Dirk Naujoks, Dirk Pilopp, Georg Schlisio, Oliver Schmitz
Abstract: Wisconsin In Situ Penning (WISP) neutral partial pressure gauges in view of the quasi steady-state operation at Wendelstein 7-X S. Sereda1, B. Elward1, J. Hoffman1, D. Naujoks2, D. Pilopp2, G. Schlisio2, O. Schmitz2, 1 Department of Engineering Physics, University of Wisconsin - Madison, Madison, USA 2 Max-Planck-Institut für Plasmaphysik, Greifswald, Germany Helium exhaust is one of the most important problems for a future magnetic fusion confinement device in the case of deuterium-tritium fuel mixture. Helium, originating in the main plasma region as a product of deuterium and tritium fusion, must be effectively exhausted, otherwise causing fuel dilution and cooling of the main plasma. Eventually the neutralized helium must be pumped out from a device through the corresponding pumping ducts. The Wisconsin In Situ (WISP) neutral partial pressure gauges were developed [1] to measure neutral partial pressures of different species in the ambient magnetic field of magnetic fusion devices. The Penning gauges are equipped with spectroscopy to measure line emission of different species (mainly hydrogen and helium), allowing neutral partial pressure study. During the first operational phase (OP1.2) of Wendelstein 7-X the first set of WISP gauges was commissioned. This contribution is focusing on the recent updates of the WISP system at Wendelstein 7-X in the view of the quasi steady-state operation. Water cooling was added in order to withstand the heat flux from the plasma, allowing the gauges to operate continuously at the 10 MW heating rate of the main plasma. In addition, a new compact line emission detector system was implemented. Moreover, 4 additional gauges will be installed at the high-iota part and pumping gap of the divertor target. These locations will allow to better understand helium exhaust at Wendelstein 7-X, including up-down asymmetry effects and high-iota part of the pumping system. By performing so-called puff/pump studies the effective helium confinement time τ_(p,He)^* and helium enrichment η_(gap/div)^enrich are being studied during the ongoing experimental campaign (OP2.1) at Wendelstein 7-X. [1] T. Kremeyer et al., Rev. Sci. Instrum. 91, 043504 (2020)
A comprehensive spectroscopic diagnostic suite for the C-2W field-reversed configuration device
Presenter: Marcel Nations (TAE Technologies)
Authors: Marcel Nations, Erik Granstedt, Thomas Roche, Hiroshi Gota
Abstract: In TAE Technologies’ current experimental device, C-2W (also called “Norman”) [1], record breaking, advanced beam-driven field-reversed configuration (FRC) plasmas are produced and sustained in steady state utilizing variable energy neutral beams (15 – 40 keV, total power up to 20 MW), advanced divertors, end-biasing electrodes, and an active plasma control system. An extensive suite of advanced spectroscopic diagnostic systems has been developed and deployed on C-2W enabling shot-to-shot as well as ensemble measurements of key plasma parameters from emitted radiation. The suite consists of 20+ individual systems including PMT-based Bremsstrahlung and Balmer-alpha arrays for Z-effective and neutral density measurements, VUV/VIS survey spectrometers, active charge-exchange recombination spectroscopy for main/impurity ion temperature and velocity profiles, high-resolution Doppler spectroscopy for impurity dynamics studies and isotope fraction monitoring, laser-based Doppler-free saturation spectroscopy for internal magnetic field vector measurements, multiple filtered fast-imaging cameras for plasma visualization, X-ray energy spectrometer, etc. [2-5] These diagnostic systems work together to provide a comprehensive picture of the FRC and allow TAE to advance physics understanding of its fusion concept and improve prediction models required for designing future machines. Here, we shall provide an overview of the spectroscopic diagnostic suite in C-2W and present key results inferred by these systems. [1] H. Gota et al., Nucl. Fusion 61, 106039 (2021) [2] E. M. Granstedt et al., Rev. Sci. Instrum. 92, 043515 (2021) [3] M. Nations et al., Rev. Sci. Instrum. 92, 053512 (2021) [4] M. Nations et al., Rev. Sci. Instrum. 93, 113522 (2022) [5] T. Roche, Rev. Sci. Instrum. 92, 033548 (2021)
Overview of C-2W Diagnostic Systems and Experimental Results
Presenter: Thomas Roche (TAE Technologies, Inc.)
Authors: Thomas Roche, Hiroshi Gota, Erik Granstedt, Martin Griswold, Marcel Nations, Kan Zhai
Abstract: TAE Technologies, Inc. (TAE) in the pursuit of an alternative approach to magnetic confinement fusion, has developed field-reversed configuration (FRC) plasmas composed of mostly energetic and well-confined particles. The high-energy particle population is produced by a state-of-the-art tunable energy neutral-beam (NB) injector system. TAE’s current experimental device, C-2W (a.k.a. Norman) [1], is the world’s largest and best performing compact-toroid system. The plasma parameters of the FRC, high temperature (Ttot > 5 keV), high density (ne ~ 1-4 x 1013 cm-3), etc are sustained in steady state for up to 40 ms (limited only by the energy storage on-site) and measured by an extensive array of plasma diagnostic systems (> 70 individual systems), including: magnetics, interferometry, Thomson scattering, a variety of spectroscopic techniques, fusion product detection, neutral particle detection, fast ion detection, fast imaging, bolometry, end-loss analyzers, thermal sensors, etc [2,3]. Active feedback control, driven by the multiple diagnostic systems, is utilized in C-2W to produce repeatable and performance-pushing FRC plasmas. This presentation will give an overview of the various C-2W diagnostic systems and some details about of the results measured by the same. [1] H. Gota et al., Nucl. Fusion 61, 106039 (2021). [2] M.C. Thompson et al., Rev. Sci. Instrum. 89, 10K114 (2018). [3] T. Roche, Rev. Sci. Instrum. 92, 033548 (2021)
Ablator - laser preheating simulations for diagnostic optimization
Presenter: Helen Papadaki (Institute of Plasma Physics & Lasers - IPPL, Hellenic Mediterranean University center for research and innovation, Rethymnon, Greece)
Authors: Helen Papadaki, Evangelos Kaselouris, Alexandros Skoulakis, Yannis Orphanos, Ioannis Fitilis, Nektarios Papadogiannis, Michalis Tatarakis, Vasilis Dimitriou
Abstract: Laser preheating of the solid ablator is of major importance for inertial confinement fusion studies. Ablator coatings are preheated to increase the mass ablation velocity and thus to reduce the growth of the developed Rayleigh-Taylor instability. In this study, to simulate the initial phases of solid-to-plasma transition, a ns pulsed laser interacts with a monocrystalline solid Si target-sample. The 532 nm laser pulse used, has a duration of 6 ns. Multiphysics finite element simulations are performed to explore the influence of the thermoelastoplastic (TEP), melting and ablation phases, during the ablator’s heating, considering its intrinsic TEP properties. For the TEP mechanical response of the heated solid a strength material model is adopted coupled with a suitable equation of state that considers the hydrodynamic response of the Si target. Simulation results provide key insights on the thermomechanical behavior of the irradiated target, which changes phases from solid to plasma. The resulting data may provide the initial conditions for further studies of hydrodynamic/magnetohydrodynamic simulations for the plasma evolution and the shock wave dynamics. Such studies are crucial not only for the ablator dynamics at early times but also for the optimization of nm scale diagnostic devices for monitoring the ablator’s surface spatiotemporal dynamics.
A Neutron Spectrometer for General Fusion
Presenter: Ryan Underwood (General Fusion/TRIUMF)
Authors: Ryan Underwood
Abstract: General Fusion is a company based in British Columbia, Canada, aiming to bring commercial fusion energy to market by the 2030s. General Fusion is designing a Magnetized Target Fusion (MTF) machine, the Fusion Demonstration Plant (FDP), that mechanically compresses a deuterium plasma with a liquid lithium liner. The compression will take place on timescale of 5 ms, leading to a very short, but intense burst of fusion neutrons. A key metric to measure the success of the FDP is by achieving a plasma temperature that reaches 10 keV during compression. In order to measure this, we design a time-of-flight neutron spectrometer diagnostic system composed of two layers of plastic scintillator. Due to the extremely high rate of neutrons emitted and the relatively short compression window, the design of the neutron spectrometer will have to reach time resolutions better than 150 ps, and position resolution of better than 1 cm, both challenges that will require state of the art technology and optimized design. This poster will discuss the proposed design of General Fusion’s neutron spectrometer, including the current state of simulations, the plan to use photon-to-digital converter (PDC) technology, and the challenges that will have to be overcome to make the diagnostic successful.
EUROfusion Diagnostic Enhancements in support of ITER research plan priorities
Presenter: Joao Figueiredo (EUROfusion)
Authors: Joao Figueiredo
Abstract: EUROfusion fusion devices, JET, ASDEX Upgrade and WEST have technical characteristics that make them a group of unique devices worldwide to address specific ITER research plan priorities. A set of diagnostic enhancements is in different stages of progress, from design to installation and commissioning, covering the implementation of a state of the art Laser Induced Desorption (LID) diagnostic and a Laser Induced Breakdown Spectroscopy (LIBS) at JET, a divertor Thomson Scattering system for the new upper divertor at ASDEX Upgrade and a vertical endoscope for a fast IR camera at WEST. These efforts specifically focus on tritium retention monitoring using laser induced desorption combined with mass spectrometry, on demonstrating LIBS mounted on a remote handling arm as a technique for T retention quantitative measurement in Be codeposits on main wall, on providing measurements expected to have a high impact on the interpretation of the physics of power and particle exhaust and at measuring the ELMs and disruption loads on the divertor target plate. An overview of the scope of these projects is presented.
Diagnostics upgrades for the RFX-mod2 facility for multi-magnetic-configuration exploration
Presenter: Matteo Zuin (Consorzio RFX / ISTP CNR Padova Italy )
Authors: Andrea Belpane, Giuseppe Marchiori, M. Moresco, M. Bonotto, S. Dal Bello, D. Fiorucci, L. Grando, N. Pomaro, M.E. Puiatti, A. Rigoni, P. Scarin, C. Taliercio, Matteo Zuin, Lorella Carraro, D. Abate, P. Agostinetti, M. Agostini, D. Aprile, M. Barbisan, G. Berton, Matteo Brombin, Roberto Cavazzana, S. Ciufo, G. Croci, L. Cordaro, M. Fadone, P. Franz, Gianluca De Masi, A. Fassina, M. La Matina, N. Marconato, I. Mario, L. Marrelli, R. Milazzo, A. Muraro, Enrico Perelli Cippo, S. Peruzzo, Davide Rigamonti, A. Rizzolo, S. Spagnolo, M. Spolaore, M. Tardocchi, D. Terranova, M. Ugoletti, M. Valisa, N. Vianello, B. Zaniol
Abstract: The RFX-mod2 device [1], the upgraded version of RFX-mod, will start its operation in 2024 with improved magnetic boundary and diagnostic capabilities. The main device modification is the enhancement of the passive stabilizing shell to plasma proximity. This, coupled to the advanced active feedback control system, is predicted to significantly improve plasma performances in a variety of magnetic configurations, including the reversed-field pinch (RFP), the tokamak and the ultra-low q. For a better characterization of plasma dynamics in all the accessible experimental conditions, several significant diagnostics improvements have been proposed and are presently under implementation. These include the installation of >1000 in-vessel high frequency coils for the characterization of long and very-small scale magnetic fluctuations, of about 500 edge electrostatic probes, distributed throughout the toroidal and poloidal directions, for the analysis of the electron density, temperature, plasma potential and flow in the edge and of plasma-wall interaction and turbulence. A higher repetition rate Thomson scattering system and a strengthened Soft X-ray diagnostics based on the double filter technique, will provide better reconstruction of the topology and the dynamics of the core thermal barriers, which form in helical RFP equilibria. Multiple lines of sight neutron diagnostics based on fast inorganic and organic scintillators and a new Compact Neutral Particle diagnostic system are dedicated to the analysis of anomalous ion heating phenomena in RFP plasmas. A diagnostic neutral Beam (50keV) will investigate the evolution of the ion temperature profile. The electron distribution function will be energy, time and space resolved by means of a soft X-ray imaging system based on a GEM detector in a pinhole configuration. A fast-reciprocating manipulator, housing systems of magnetic and electrostatic probes, will allow the exploration of the edge radial plasma profiles and turbulence even in high current RFP regimes and to characterize SOL and pedestal regions in H-mode tokamak shaped and circular plasmas. An innovative reflectometric technique for plasma position in the tokamak will be tested. The 3D pattern of the plasma wall interaction will be studied with a set of 7 cameras (500 fps) measuring the emission and the Carbon influx. The poloidal distribution of low Z impurities will be obtained with the Light Impurity Tomography (LIT). A cavity-based imaging polychromator designed to resolve 2D absolute intensity images of different emission lines with < 5mm resolution, named MANTIS [2], will gain information on the 2D pattern of electron density and temperature [3]. The edge radial profiles of ne and Te, will be studied with the Thermal Helium Beam [4,5]. The edge characterization is completed by measuring the edge fluctuations due to turbulence [6] thanks to the Gas Puff Imaging diagnostic, already present in RFX-mod. The complex arrays of magnetic coils, along with a system of distributed halo sensors, will allow to validate the electromagnetic modelling of the sideway forces during rapid transients in the tokamak. 1 L. Marrelli et al., Nucl. Fusion 59 (2019) 076027 2 A. Perek et al., Nuclear Materials and Energy 26 (2021) 100858 3 B. Schweer et al., Journal of Nuclear Materials 196–198 (1992) 174-178 4 S. Kajita and N. Ohno, Rev. Sci. Instrum. 82 (2011) 023501 5 M. Agostini et al., Rev. Sci. Instrum. 91 (2020) 113503 6 M. Agostini et al., Rev. Sci. Instrum. 81 (2010) 10D715
Time-integrated measurements of the X-ray source size using a Pin-hole camera
Presenter: Alexandros Skoulakis (HMUTime integrated measurements of the X-ray source size using a Pin-hole camera )
Authors: Alexandros Skoulakis, Donaldi Mancelli, Ioannis Tazes, Ioannis Fitilis, Nektarios Papadogiannis, Michalis Tatarakis
Abstract: Imaging X-rays with pinholes has long been the diagnostic method of choice in the inertial confinement fusion program ICF [1, 2]. X-ray pinhole cameras are imaging devices that provide two-dimensional views of laser heated targets. Utilizing foil filtration to select x-ray energies per individual channels provides valuable information on target symmetry, laser pointing and other implosion dynamics [3]. Such diagnostic system is also used in cyclotron facilities where they provide crucial information about the electron beam size [4], as well as on high current Pulsed-power plasma devices loaded as Z-pinch or X-pinch [5, 6]). The detailed X-ray source-detector geometry makes it possible to reconstruct the size of the projected source on a selected observed plane. Image processing methods are applied for the reconstruction of the X-ray pinhole camera data from laser-produced plasma as well as plasma generated using an X-pinch device. Numerically determined point-spread functions are utilized to calculate the modulation transfer function of the pinhole camera, while the optimal Wiener filter is applied to suppress the spatial noise.
ITER-like Thermal sensors for the Beam Line Components in MITICA and ITER HNB
Presenter: Matteo Brombin (Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4 –35127 Padova, Italy; CNR- Istituto per la Scienza e la Tecnologia dei Plasmi, CNR, Padova, Italy)
Authors: Matteo Brombin, Mauro Dalla Palma, Paolo Tinti, Moreno Maniero, Federico Bittanti, Alessandro Saracino, Roberto Pasqualotto
Abstract: MITICA, the full-scale prototype of the NBI for ITER, is under procurement and is going to be installed and operated in Padova at the Neutral Beam Test Facility at Consorzio RFX. MITICA will be equipped with several diagnostics to assess and optimize the beam production in the beam source and the beam transport in the beamline components of the ITER HNB injectors, which will have a reduced set of these diagnostics. Among this set, the thermal diagnostic is the main in vessel measurement for the protection and calorimetry of the Beam Source (BS) and the beam line components (BLCs). About 700 thermal sensors will be mounted in MITICA with different technologies: thermocouples for distributed measurements on the in vacuum components, fiber Brag gratings (FGSs) as thermal sensors on high voltage biased panels of the BLCs. The full set of the thermocouples can be split into two groups: one foreseen only in MITICA and another one, called ITER-like and subject of this paper, common to both HNB and MITICA. In fact, the requirements about the vacuum compatibility and the radiation hardness to be satisfied in ITER NBIs are more constraining than in MITICA and hence the technical solutions adopted in the design of such sensors have been severely investigated. The ITER-like thermocouples with isolated junction are Type N (Nicrosil-Nisil) without ferromagnetic materials to avoid errors due the strong magnetic fields expected in ITER. Accuracy tolerances are in compliance with ASTM E230 special class. Mineral Insulated Cables (MICs) with MgO as insulating material and Inconel 600 for the metal sheath are mandatory to survive to the high neutron and gamma fluxes. These thermocouples are realized with an Ultra High Vacuum (UHV) compatible termination with ceramic/metallic bushing leak tight tested through helium bombing technique accordingly to 10-9mbar l/s, consistently with the large number of sensors and in accordance with the ITER requirements. The diameter of the MIC is 0.5mm with a sheath thickness of 0.08mm to get a reliable mechanical robustness, compact cabling and compliance with the requirements for remote handling operations. The paper reports the technical specifications for the procurement of the full set of ITER-like sensors. All the manufacturing details are presented and all the tests carried out by Metrologie Srl, an accredited testing and calibration laboratory, are widely described and the results reported demonstrating that the majority of the ITER requirements are satisfied.
Characterization of ultrafast cameras for the plasma diagnostics of the Laser Megajoule
Presenter: Théophile Chirac (CEA)
Authors: Théophile Chirac
Abstract: The Laser MegaJoule (LMJ) facility near Bordeaux in France is designed to study high-energy-density physics. Plasma diagnostics surrounding the implosion chamber are designed to quantitatively measure the evolution of the target during the experiment. X-ray spectrometers, optical & x-ray imagers or VISAR require ultra-fast cameras. For each family, framing cameras and streak cameras are available. We provide an overview of the current performances of these cameras and the ongoing work to improve and harden them. Four types of ultra-fast cameras are currently operated at LMJ: framing and streak camera for X-ray diagnostics, gated optical imager and streak camera for optical diagnostics. Each one of them is routinely calibrated to provide LMJ physicists with accurate results. Here, we present the approaches we have to dealing with artifacts and improving the performances of the ultrafast cameras thanks to their fine characterization.
Heat flux and ion temperature measurements with the Multi-Purpose Manipulator at Wendelstein 7-X
Presenter: Philipp Drews (Forschungszentrum Jülich, IEK-4)
Authors: Philipp Drews
Abstract: Measurements of edge plasma parameters of Wendelstein 7X (W7-X) have been conducted with reciprocating probe heads on the Multi-Purpose Manipulator (MPM) [1][2]. Typically, electron temperature and density are obtained from Langmuir probes, where the data evaluation requires an assumption of the ion temperature. Usually, in the edge of magnetic fusion plasmas, is assumed. However, modelling and experiments have shown that the ion temperatures can by far exceed measured electron temperatures [3]. Retarding field analyzers (RFA) are widely used for the measurement of the ion temperature [4]. RFAs are technically demanding and the necessary size and placing of the RFA limits the design and the operation of the probe heads. These limitations of the RFA probe, mean also that the coverage of ion temperature measurements is limited to specific probe heads. Thermocouples have been used to measure heat fluxes on limiters and divertors and compared well to Langmuir probe measurements of the electron heat flux in response and magnitude [5]. The total heat flux measured with the thermocouples can be used together with the electron heat flux measured with the Langmuir probes to estimate the ion temperature Measuring the total heat flux on a Langmuir pin by two thermocouples offers a simple alternative to the RFA system for an estimation of the ion temperature in the plasma edge. Measurements of the electron temperatures and densities with Langmuir probe and estimations of the ion temperature with thermocouples will be compared to RFA ion temperature measurements. [1] P. Drews, Nuclear Fusion 57, 126020 (2017), [2] C. Killer, JINST17 P03018, (2022), [3] P. Drews, Nuclear Materials and Energy Volume 19, 2019, P. 179-183 [4] M. Henkel, Fusion Engineering and Design Volume 157 (2020), 111623, [5] D. Brunner, Review of Scientific Instruments 83, 033501 (2012);
Reconstructions of Global Plasma Oscillations on C-2W via 300-channel Bolometry System
Presenter: Anton Bondarenko (TAE Technologies)
Authors: Anton Bondarenko
Abstract: In TAE Technologies’ current experimental device, C-2W (also called “Norman”) [1], record breaking, advanced beam-driven field reversed configuration (FRC) plasmas are produced and sustained in steady state utilizing variable energy neutral beams (15 – 40 keV, total power up to 20 MW), expander divertors, end bias electrodes, and an active plasma control system. FRC plasmas in C-2W are stable to MHD modes due to a combination of end biasing and neutral beam injection [2] and can even remain stable to the tilt mode past the traditional empirical stability boundary of S*/E < 3 [3]. There is an ongoing effort to study the stabilization mechanisms as well as low-amplitude MHD modes which remain in stable plasmas. A 300-channel bolometer system installed on C-2W utilizes photodiode arrays to collect broadband radiation (SXR to NIR) along 180 unique lines of sight that intersect a toroidal plane of the FRC near the mid-plane, providing a diagnostic for bulk plasma motion and MHD activity [4]. Automated scripts process the raw photo-signals after each plasma discharge, yielding time-resolved tomographic reconstructions and centroid trajectories of the near-midplane emissivity profile. Both 1D and 2D tomographic reconstructions are achieved via pixel-based methods with Phillips-Tikhonov regularization, while the centroids are derived via a custom view chord intersection algorithm. The reconstructions reveal stable, annular emission profiles with low-amplitude MHD mode structure. Application of singular value decomposition (SVD) to the reconstructed profiles successfully resolves toroidal mode numbers n=0, n=1, and n=2. Both the tomographic reconstructions and the centroid trajectories indicate that the n=1 toroidal mode reverses from the electron diamagnetic direction to the ion diamagnetic direction and grows in amplitude immediately after termination of end biasing, qualitatively consistent with the expected stabilizing effect of the electrodes. Diagnostic considerations for improving signal-to-noise and accounting for photodiode sensitivity degradation are also addressed. [1] H. Gota et al, “Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device,” Nuclear Fusion 59, 112009 (2019). [2] M. Tuszewski et al, "Field Reversed Configuration Confinement Enhancement through Edge Biasing and Neutral Beam Injection," Physical Review Letters 108, 255008 (2012). [3] T. DeHaas et al, “Magnetic Field-Shaping Effects on Tilt Stability in C-2W Field Reversed Configuration.” Poster presented at: 64th Annual Meeting of the APS Division of Plasma Physics; October 20th, 2022; Spokane, WA. [4] A. S. Bondarenko et al, "Tomographic and centroid reconstructions of plasma emission on C-2W via enhanced 300-channel bolometry system," Review of Scientific Instruments 93, 103517 (2022).
Study of effects influenced to the sub-THz unambiguous interferometer probing waves in plasma expected on COMPASS-Upgrade
Presenter: Mykyta Varavin (Institute of Plasma Physics of the Czech Academy of Sciences)
Authors: Mykyta Varavin
Abstract: The COMPASS-U tokamak (ne=5x1020m-3, R = 0.9 m, a = 0.27 m, Bt = 5 T, Ip = 2 MA) [1] is under construction in the Institute of Plasma Physics in Prague. Combination of high temperature vessel 300-500oC, high plasma densities, toroidal magnetic fields and plasma current is a big call for the diagnostic design [2]. Based on simulation the differential (“unambiguous”) interferometer concept for real-time line-integrated electron density measurements [3] was proposed. Combination of simulation methods of the wave propagation in the hot plasmas is used. Raw estimation was done based on WKB method. The more precise simulations of the wave propagation were done by the 2D full-wave COMSOL code. The plasma profiles are simulated by METIS. The information about attenuation given by defocusing effect of probing beam propagated through the plasma and the reached phase of the probing waves depending on plasma profile and vertical position was also provide by the COMSOL code. The raw estimations of the correction coefficient for a non-linear dependence of the refraction index on plasma density were done based on WKB method. The unique study of phase measurement inaccuracy caused by O-X-mode parasitic interference was performed. The special analytical approach was developed for the mentioned study. Method of correcting such error was proposed. The study of influence of different plasma shapes, plasma density profiles and other parasitic impacts to the density measurement is presented. Based on these simulations the special technical solution design was proposed. This solution includes the conceptual design of the quasi-optical focusing system and the in-vessel reflection mirror placed on the central column. The study of compatibility of chosen solution with the estimated charged particle heat fluxes was done. The introduced concept allows the precise phase measurements in a wide density range and compatible with a real-time density feedback system. The proposed solution is compatible with the expected COMPASS-U parameters
Characterization of ion beam generated by an anode layer ion source
Presenter: Andrey Kaziev (National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia)
Authors: Andrey Kaziev, Dobrynya Kolodko, Mikhail Novikov, Yaroslav Kiryukhin
Abstract: Plasma technologies are widely applied in the processes of coating and modification of surface properties in many areas of industry and science, including electronics, mechanical engineering, and optics. Among the most versatile devices for the implementation of ion-plasma technologies are ion sources of various types, e.g. anode layer sources [1, 2]. The main parameters of such sources are the energy and mass distributions of ions in the generated beam. In most applications, a narrow energy spectrum of the beam is preferable, and a well-defined ion mass composition is necessary. To characterize a custom anode layer ion source, we used a combination of separate mass-analyzer (MA) and energy-analyzer (EA). MA was an in-house magnetic sector equipped with specially designed extraction and detection systems [3]. The energy analyzer was a retarding field one, composed of three single-orifice diaphragms and collector. Prior to implementation, electric field distributions, ion trajectories, and instrument function of EA were modeled in COMSOL Multiphysics to optimize its dimensions and aperture sizes. With an initial ion energy in the range from 1500 to 2500 eV, the width of the instrument function of designed EA remains less than 10 eV, which we consider suitable. The mass and energy spectra of ion beam were measured by both instruments. The experiments revealed presence of three groups of extracted argon ions: low-energy background plasma ions, ions with initial energy of ~ 100 eV, and the ions accelerated in the ion source, with peak energy corresponding roughly to half of the discharge voltage (~ 600–700 eV). The origin of ions groups and the energy spectra are discussed in detail.
Characterization of arcs occurring on nanostructured tungsten surfaces under ion irradiation in an ICP
Presenter: Andrey Kaziev (National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia)
Authors: Margarita Kukushkina, Maksim Kharkov, Dobrynya Kolodko, Georg Rykunov, Andrey Kaziev, Mikhail Tsventoukh
Abstract: The effect of nanostructure (fuzz) growth on the surface of tungsten when it is exposed to helium ion bombardment from plasma draws much attention both from the nuclear fusion community and from the low-temperature technological plasma researchers. The latter is because of a wide range of potential applications of such nanostructured surfaces [1]. Formation of W fuzz in fusion facilities might lead to easier initiation of unfavorable electrical discharges (arcs) on the wall elements [2]. However, up to now, little is known about the overall correlations between the real structural characteristics of W fuzz, the parameters of He+ irradiation that results in its growth, and the arc triggering modes. Here, we study the dynamics and statistics of arcing on the surface of tungsten while its surface becomes nanostructured under irradiation with helium ions. Experiments on the irradiation of tungsten samples with helium ions were carried out at the Bella facility that is an inductively coupled plasma (ICP) reactor with a planar radiofrequency (RF) coil mounted inside a vacuum chamber. The operating frequency of the RF power source was 13.56 MHz. In the experiments, bias voltage (pulsed or DC) was applied to W samples during the growth of the nanostructured layer. In order to enable arc detection, a special electric circuit was implemented, which made it possible to reduce the current and increase the lifetime of arc discharges on the sample. We demonstrate preliminary results of analysis of current and voltage waveforms that presumably correspond to arcing events.
Status of the Development and Testing of Port-Plug and ECH-Protection Components for the ITER Low-Field Side Reflectometer
Presenter: Christopher Muscatello (General Atomics)
Authors: Christopher Muscatello
Abstract: We report the status of various microwave components of the vacuum and ECH-protection sub-systems of the ITER Low-Field Side Reflectometer (LFSR). These components consist of: 1. Antenna array: The array consists of 6 antennas for simultaneous profile, fluctuation, and Doppler measurements. High accuracy of the aiming of the profile antennas is required for sufficient monostatic coupling of the reflection. The coupling versus aiming, as measured in the laboratory and with full-wave modeling with an ITER plasma, is used to specify the pointing direction and associated error of the LFSR antennas. 2. Vacuum windows: Windows produce unwanted reflections that can cause noise and clutter in the reflectometer signals, as well as frequency-dependent loss. Dual, redundant windows are used at the vacuum boundary for safety-protection that further exacerbate these issues. Broadband transmission improvement can be achieved with an anti-reflective layer, corroborated by modeling and measurements. 3. Phase calibration mirror: For absolute phase calibration of the LFSR profile reflectometer, an embossed mirror is incorporated into an in-vessel miter bend. Demonstration of real-time phase measurements using the in-situ calibration technique is performed with the DIII-D profile reflectometer. The field tests successfully demonstrate the feasibility of the calibration technique for LFSR; real-time calculations of the phase profiles agree well with the standard DIII-D post-processing analysis. 4. ECH protection mirror and monitor: The stray-ECH protection system for LFSR consists of both passive and active components. Passive diffraction gratings are the system’s first line of defense, rejecting 20 dB of power at 170 GHz. Another layer of defense is a waveguide-integrated power monitor that shutters the back-end electronics in the case of a high-power event. The current design and initial measurements of these components will be described.
The single crystal diamond-based diagnostic suite of the JET tokamak for 14 MeV neutron spectroscopy measurements in DT plasmas
Presenter: Davide Rigamonti (Institute for Plasma Science and Technology, National Research Council of Italy, Milan, Italy)
Authors: Davide Rigamonti, Andrea Dal Molin, Gabriele Croci, Joao Figueiredo, Giuseppe Gorini, Andrea Murari, A. Muraro, Massimo Nocente, Marica Rebai, Zamir Ghani, Vasily Kiptily, Enrico Perelli Cippo, M. Tardocchi
Abstract: In the recent year the EUROfusion enhancement program has allowed to significantly improve the JET nuclear diagnostics in view of the Deuterium-Tritium (DT) campaign. In particular, the set of the 14 MeV neutron spectrometers has been expanded with single crystal diamond-based detectors. A diamond matrix has been installed looking radially the plasma at a distance of about 20 m. In order to increase the counting statistics of the detector, it is made by 12 identical single crystal pixels working independently. Other two diamond spectrometers are single pixel diamond samples, both installed tangentially at 47 and 52 degrees with respect to the magnetic axis of the torus. The idea to using the same technology along different lines of sight allows for measuring the anisotropicity of the neutron emission which is a feature in case of use of external heating systems. Diamond detectors have been selected for their compactness, enhanced energy resolution (<1% at 14 MeV), very high count rate operation (up to 1 MHz) and high radiation hardness. They are prone to be installed on already existing fusion devices or where there are space limitations, such as on multi-lines of sight of neutron cameras. In this paper, the suite of the diamond diagnostics will be described together with the electronics and data acquisition system, besides the detector response function to monenergetic neutrons. Typical example of measured 14 MeV neutron spectra collected during the DTE2 campaign will be also presented.
X-ray imaging based temperature estimates of warm dense matter of a thin Ti wire heated by laser-accelerated relativistic electrons
Presenter: Artem Martynenko (GSI Helmholtzzentrum fur Schwerionenforschung, 64291 Darmstadt, Germany)
Authors: Artem Martynenko, Paul Neumayer, R. A. B. Alraddadi, E. Hume, K. Lancaster, A.P.L. Robinson, L. Wegert, L. Antonelli, Francesco Barbato, G. Boutoux, D. Khaghani, D. Mancelli, S.A. Pikuz, Joao Jorge Santos, G. Zeraouli, Dimitri Batani
Abstract: In a recent experimental campaign at the PHELIX laser facility at GSI (Darmstadt, Germany), we isochorically heated a thin titanium wire to a warm dense matter (WDM) state using laser-accelerated relativistic electrons. To characterize the temperature profile and emission properties of the WDM, we used an approach based on radiographic "imaging" of the expansion and "traditional" X-ray emission spectroscopy. Here we discuss this approach and obtained results. We performed an experiment in which we irradiated a 50 μm thick titanium wire with a 0.5 ps laser pulse with an intensity of ~1019 W/cm2 and a power of 0.1 PW. This resilted in acceleration of hot electrons (HE) at laser-matter interaction area. These HE propagated along the wire isochorically heating it. We also irradiated a 5 μm W wire with a 0.5 ps laser pulse. The resulting plasma served as a “backlighter” to obtain X-ray images of the hydrodynamic expansion of the target. To estimate the temperature profile, we used a 1D radiation hydrodynamics code, HELIOS. This showed that WDM temperature at a depth of 100 µm from the laser-matter interaction point was about 30 eV and at a depth of 500 µm was about 5 eV. We also used a 3D macroparticle-based hybrid particle-in-cell simulation code, ZEPHYROS, to support our experimental results and draw conclusions about the heating mechanisms. This work continues our previous research on this topic [1,2]. [1] A. Schönlein, G. Boutoux, S. Pikuz, L. Antonelli, D. Batani, A. Debayle, A. Franz, L. Giuffrida, J. J. Honrubia, J. Jacoby, D. Khaghani, P. Neumayer, O. N. Rosmej, T. Sakaki, J. J. Santos, and A. Sauteray, EPL (Europhysics Lett. 114, 45002 (2016). [2] A. S. Martynenko, S. A. Pikuz, L. Antonelli, F. Barbato, G. Boutoux, L. Giuffrida, J. J. Honrubia, E. Hume, J. Jacoby, D. Khaghani, K. Lancaster, P. Neumayer, O. N. Rosmej, J. J. Santos, O. Turianska, and D. Batani, Opt. Express 29, 12240 (2021).
Presenter: Dimitri Batani (University of Bordeaux)
Authors: Dimitri Batani
Abstract: MEASURING THE EQUATION OF STATE OF BORON NITRIDE IN EXTREME CONDITIONS K. Batani1, D. Singappuli2, M. Huault2, P. Nicolaï2, D. Raffestin2, D. Batani2, T. Buriuan3 R. Dudzak3, M. Krůs3, S. Pikuz4, W. McKenzie4, A. Martynenko5, L. Giuffrida6, Y.I. Chen7, S. Mateti7, Q. Cai7 1) Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland 2) CELIA, University of Bordeaux, France 3) Prague Asterix Laser System, Prague, Czech Republic 4) HB11 Energy, Australia 5) GSI, Darmstadt, Germany 6) ELI Beamlines, Prague, Czech Republic 7) Institute for Frontier Materials, Deakin University, Australia The study of the equation of state of boron compounds in extreme pressure conditions is important for several fields of physics. In particular, boron nitride has been proposed as alternative ablator in Inertial Confinement Fusion experiments thanks to its high tensile strength [1] and also because boron and nitrogen, which both undergo reactions with neutrons and protons, offer the potential for using additional nuclear reactions to better constrain the shell areal density and ablator mix at burn time [2]. From the point of view of material science, boron compounds are also very interesting. In particular, the phase diagram of boron nitride is similar to that of carbon, incorporating phases at high temperatures and pressures whose structures and physical properties resemble diamond [3]. However, there are at today only a few experimental data on boron nitride. Results obtained with the Omega laser, using the direct-drive approach, cover the range 10 to 20 Mbar. It is therefore interesting both to increase the statistics in this range and to explore higher pressures [4]. In this context,we are performing a series of experiments at the PALS laser facility with the goal of obtaining new EOS data along the principal Hugoniot for boron nitride targets in the pressure range 10 to 35 Mbar. In the experiment, we use the PALS laser beam converted to third harmonic (E= 150 J in 300 ps at wavelength 0.44 µm) to create a strong pressure shock travelling in targets which include a base (plastic ablator and aluminum pusher) and two steps of quartz (reference material) and boron nitride. These have been produced at Deakin University. The shock propagation is diagnosed using a streak chronometry diagnostic (SOP) and a velocity interferometer (VISAR). Due to the short duration of the laser pulse the shock pressure will decay in time allowing in the same laser shot to obtain and measure several states of the samples at decreasing pressure [5]. In the poster, the preparation of the campaign and of the diagnostics, and some preliminary results obtained with the SOP diagnostics will be presented. 1. Heather D. Whitley, et al. “Comparison of ablators for the polar direct drive exploding pusher platform” 2. Probing the Physics of Burning DT Capsules Using Gamma-ray Diagnostics, A. C. Hayes-Sterbenz, G. M. Hale, G. Jungman, and M. W. Park, LA-UR-15-20627. 3. Elise Knittle, Renata M. Wentzcovitch, Raymond Jeanloz & Marvin L. Cohen “Experimental and theoretical equation of state of cubic boron nitride” Nature volume 337, pages 349–352 (1989) 4. Shuai Zhang, et al. “Equation of state of boron nitride combining computation, modeling, and experiment” PHYSICAL REVIEW B 99, 165103 (2019) 5. “High-Pressure Equation-of-State Studies Using Laser-Driven Decaying Shocks” J. E. Miller, University of Rochester Laboratory for Laser Energetics, 48th Annual Meeting of the American Physical Society Division of Plasma Physics Philadelphia, PA 30 October–3 November 2006
Analysis of scattered light from multiple blades and V-grooved laser dumps in Thomson scattering diagnostic
Presenter: Xiaofeng Han (Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences)
Authors: Shumei Xiao, Qing Zang, Mengfang Ren, Xiaofeng Han, Liqun Hu, Jian Zhou
Abstract: The measurement of the Thomson scattering signal and the absolute calibration of the system are both easily disturbed by the stray light. Stray light mainly comes from the end of the laser beam, especially for the system with the laser beam terminated inside the vacuum vessel of the device. A laser dump is essential optics of this system for terminating the laser beam. The multiple blades and V-grooved structure on laser dump have an advantage of reducing the heat through multiple wall surfaces, yet the wall edge of dump is easy to produce scattered light. So, the distribution and intensity of escaping scattered light from these two dumps are analyzed and simulated. Firstly, based on the optical theory, the characteristic of beam transmission and the intensity of escaping specularly reflected light in these two structures are analyzed. And then based on an optical-mechanical simulation model of the laser dump, the distribution and intensity of escaping scattered light from these two dumps and the scattered light on the wall surface are simulated. The results indicate that (i) as the depth of the laser beam entering the dump increases, the intensity and the distribution of escaping scattered light decrease for these two structures, (ii) the intensity and the maximum irradiance of escaping scattered light from the V-groove structure is less than that from the multiple blades structure, (iii) the intensity and the maximum irradiance on the wall surface are similar for the two structures, but the heat will focus on the bottom for the V-groove structure, (iv) there is a suitable number of wall edges for the dump to obtain the lowest intensity of escaped light. The research has important implications for the dump design of Thomson scattering diagnostic system.
Spectroscopic Temperature Determination of a Hydrogen Plasma
Presenter: Sahar Arjmand (LNFN-LNF)
Authors: Sahar Arjmand
Abstract: We report the theoretical and experimental activity on the plasma-discharge capillary for plasma-based accelerators (PBAs) at the SPARC_LAB test facility. Nowadays, in the particle accelerators field, plasma-based accelerators are highly demanded to reduce the barriers of the conventional accelerator structures. In fact, one of the essential characteristics of plasma- based accelerators is their compactness due to small-scale (mm to cm) plasma modules, providing extremely high accelerating gradients up to hundreds of GV/m. In this experiment, a gas-filled plasma-discharge capillary is tested, ionizing Hydrogen gas with a high-voltage electrical discharge (HVDC). The principal target of this innovative technique is monitoring and characterizing the produced plasma, which depends on the qualities of the particle bunch to be accelerated via an intense laser pulse technique (LWFA) or an energetic electron beam scheme (PWFA). The plasma characterization plays a fundamental role in determining the neutral gas distribution inside the capillary; therefore, the generated plasma in a Hydrogen-filled capillary is targeted by spectroscopic technique to investigate the plasma electron density and temperature. The plasma electron density and electron temperature have been studied as functions of time through the Stark broadening profiles for several ionic species. The line intensities of subsequent ionization stages of the Oxygen element have also been considered for electron temperature analyses.
15:40 - 17:40
Session 13 learn more
Chair: Vasilis Dimitriou - Vice Chair: Tokihiko Tokuzawa
Overview of Bayesian plasma diagnostic modelling at W7-X
Presenter: Sehyun Kwak (Max Planck Institute for Plasma Physics)
Authors: Sehyun Kwak, Jakob Svensson, Udo Höfel, Andrea Pavone, Oliver Ford, Maciej Krychowiak, Andreas Langenberg, Jonathan Schilling
Abstract: Scientific data analysis in a large-scale modern nuclear fusion experiment is a formidable challenge. Extracting information on the fusion plasma from a few hundred plasma di-agnostics requires the capability of modelling not only individual diagnostics but also interdependencies between global physics parameters and heterogeneous measurements from different diagnostics. This work demonstrates a well-established method of deliv-ering consistent inference of physics parameters by modelling diagnostics and their in-terdependencies within the Minerva scientific modelling framework. A number of appli-cations from consistent profile inferences accounting for multiple diagnostic data to ad-vanced tomographic techniques for the bolometers, soft-X ray and bremsstrahlung diag-nostics at Wendelstein 7-X are presented. Furthermore, these Minerva applications can be accelerated by deep learning surrogate models for real-time inferences.
Diagnostics for high-power helicon plasmas: from lasers to magnetic probes
Presenter: Ivo Furno (EPFL-SPC Lausanne, Switzerland)
Authors: Marcelo Baquero, Philippe Guittienne, Remy Jacquier, Lyes kadi, renat karimov, alan howling, christine stollberg, Ivo Furno
Abstract: The Resonant Antenna Ion Device (RAID) [1, 2] is a linear device (1.5 m length, 20 cm radius) at the Swiss Plasma Center in which high-power (up to 20kW), steady-state helicon plasmas are created by helicon wave excitation using twin resonant antennas (10 kW each, birdcage-geometry, 13.56 MHz). A modular set of copper magnetic coils, surrounding the vacuum vessel, is currently used to produce an axial magnetic field up to 700 G on-axis and a divergent magnetic field in the source region. Many gases can be used such as H2, D2, Ar and He, and typical electron densities of 1018 m-3 and 1019 m-3, respectively, in hydrogen and argon can be attained with electron temperature in the range 1-10 eV. RAID is equipped with an extensive set of diagnostics for plasma profiles and wave fields allowing to advance the physics understanding of helicon plasmas as well as validating novel theories of electrostatic probes. Here, I will discuss the technical implementation of diagnostics on RAID and the experimental challenges in a high-power helicon plasma environment as well as selected physics results. Detailed two-dimensional plasma profiles in RAID are obtained using in-situ double Langmuir probes, which provide electron temperature Te and plasma density ne measurements. We developed a novel probe theory, based on a two fluid solution for isothermal and collisionless plasma sheaths, which allows to compute Te and ne, as well as the ion temperature Ti from double-probe I-V characteristics. This new theory is tested on RAID using data from a Thomson Scattering system and laser-induced fluorescence system in argon plasmas. To investigate the physics of helicon waves, we have equipped RAID with a set of in-situ three-dimensional magnetic probes, which reconstruct the magnetic field associated with the helicon wave. By measuring the phase and amplitude of each magnetic field component along the axial and radial direction, the structure of the helicon wave is reconstructed and compared with numerical simulations, confirming that RAID plasmas are mainly sustained by the propagation of helicon waves, with a minor contribution from Trivelpiece-Gould modes and other modes depending on the plasma density profile. [1] I. Furno, et al., EPJ Web Conf. 157, 03014 (2017). [2] R. Jacquier, et al., Fusion Engineering and Design 192, 11361(2023).
HED science with intense heavy-ion pulses at GSI/FAIR
Presenter: Paul Neumayer (GSI)
Authors: Paul Neumayer
Abstract: The facility FAIR, currently under construction at the GSI Helmholtzzentrum für Schwerionenforschung, will deliver short heavy-ion pulses at unprecedented fluences. Within the framework of the HED@FAIR collaboration we are preparing an experimental station where such pulses can be used for volumetric heating of mm-scale samples to electron-volt temperatures, providing a novel path to generating matter at extreme conditions. Comissioning of the infrastructure and early proof-of-principle experiments are currently being carried out at an existing irradiation area at GSI. We will present first results testing ion beam focusing and heating with >4e9 Pb-ion pulses, as well as diagnostic schemes based on intense x-ray sources driven by GSI's high-energy laser facility PHELIX.
Experimental study of sub-atmospheric streamers in pure N2 with implications for nitrogen kinetic models
Presenter: Petr Bílek (Institute of Plasma Physics of the Czech Academy of Sciences, Prague, Czech Republic)
Authors: Petr Bílek, Tiago C. Dias, Vaclav Prukner, Petr Hoffer, Vasco Guerra, Milan Simek
Abstract: Fast ionization waves (streamers) initiate most of the discharges in different gases. A study of streamers can be performed at various pressures and the increase of the gas pressure causes the reduction of the streamer's lifetime. Therefore, the investigations of streamers at close to atmospheric pressures are highly challenging for diagnostics due to their sub-nanosecond time evolution. We investigate the streamers in pure N2 at the pressure of 200 Torr. The investigated monofilament streamer develops in a dielectric barrier discharge configuration with point-to-plane electrode geometry. Our experimental investigations include electrical characteristics, time-resolved images obtained using four 4-Picos ICCD cameras and N2/N+2 emission spectra, all acquired with sub-nanosecond temporal resolution. Time-resolved images and emission characteristics provide clear evidence of the formation of a cathode-directed streamer and allow the determination of the streamer propagation velocity. Using the intensity ratio of the first negative and second positive system of molecular nitrogen [1], we determine the reduced electric field at the first nanoseconds after the streamer onset. Subsequently, the electric field profile serves as an input parameter for 0D state-to-state kinetic model. Using the model, we aim to explain the evolution of experimentally observed species N(4S) and N2(A3Σ+u) [2-3] as well as the vibrational distribution function of excited states of N 2. The conclusions of our work are significant for plasma-chemistry models of nitrogen plasmas.
Single shot, non-resonant, four-wave mixing laser diagnostics for low temperature plasmas
Presenter: Alexandros Gerakis (Luxembourg Institute of Science & Technology)
Authors: Alexandros Gerakis
Abstract: We experimentally demonstrate the use of single shot coherent Rayleigh-Brillouin scattering (CRBS) for the measurement of the velocity distribution function (VDF) of neutral species in a glow discharge, from which macroscopic quantities, such as the flow velocity, density and translational temperature can be extracted. In CRBS, a four-wave mixing technique, a high energy optical lattice of precisely tailored chirped frequency interacts with the medium, such as neutral or ionized gas. The variation of the CRBS signal intensity at different optical lattice phase velocities allows for the restoration of the VDF and the resulting CRBS lineshape is a direct mapping of the medium's VDF. CRBS has already been demonstrated to be the coherent analogue of spontaneous Rayleigh-Brillouin scattering and has already been demonstrated in the measurement of nanoparticles in an arc discharge1. Single-shot CRBS is applied to measure simultaneously the temperature and density of neutral species in a weakly ionized DC glow discharge plasma. The DC glow discharge is generated at a pressure range of 15 Torr using xenon gas. For this application, we employ a newly developed dual-color CRBS scheme2,3 where the frequency doubled 532 nm beam serves as a probe beam to achieve a higher signal-to-noise ratio at the low-pressure environment versus the most employed single color CRBS approach. The temperature and density of neutral xenon particles inside the DC glow discharge is evaluated simultaneously by analyzing the resolved single-shot CRBS lineshapes and is characterized as a function of the discharge current, successfully demonstrating the use of CRBS in a partially ionized plasma environment. A simulation model of the glow discharge is also developed and there is good agreement between the simulation and the experimental measurements in the glow discharge.
18:10 - 20:00
Session 14 learn more
Session 14

Chair: Dimitri Batani - Vice Chair: Michael Tatarakis

Diagnostics of a Laboratory Platform for studying Electron Beam Driven Turbulence in Dusty Plasma
Presenter: Dorina Ticos (National Institute for Laser, Plasma and Radiation Physics)
Abstract: The diagnostics of a novel laboratory platform [1] dedicated to study turbulence in plasma crystals, induced by an electron beam of 8 to 15 keV is presented [2]. High-speed imaging [4] is used for visualizing the plasma crystal made of dielectric microparticles levitated in plasma. A Faraday cup is used to determine the electron beam current while the beam profile is seen on Ph screens. The image sequences acquired by a fast CCD, while illuminating the microparticles with a 20 mW laser diode, are further processed through Particle Image Velocimetry technique to obtain the velocity field of the microparticles. The platform, seen in figure 1, consists of three units connected in-line and vacuumed at different pressure levels. A hollow- anode plasma source is used to produce the free electrons [5]. The second unit is the electron extraction and focusing made by electromagnetic circular coils at pressures below 10-4 Torr and the third unit is an RF-driven dusty plasma in plane-parallel electrodes geometry where the plasma crystals are obtained at 10-1 Torr . The pulsed electron beam with a profile of a few millimeters is aimed at the plasma crystal that is made of dielectric microparticles levitated in the RF plasma chamber thus setting the microparticles in chaotic motion and creating turbulent flows in the plasma crystal.
Mass-spectrometric measurements of ion flux at a substrate in reactive HiPIMS processes
Presenter: Dobrynya Kolodko (Kotelnikov Institute of Radio Engineering and Electronics RAS, Fryazino, Russia)
Authors: Dobrynya Kolodko, Andrey Kaziev, Vladislav Lisenkov, Maksim Kharkov
Abstract: Reactive high-power impulse magnetron sputtering (HiPIMS) process is characterized by a rich spectrum of interesting effects that on the one hand require sophisticated experimental investigations and in-depth modeling, while on the other hand have significant influence on its technological applications. Among these effects, the most notable are features of process hysteresis that are different from that of conventional magnetron discharges (DC, or mid-frequency) [1, 2]. Using a hot-target magnetron increases the number of effects that one needs to account for to build a reliable model of the target state, even in DC mode [3]. However, besides detailed investigations of magnetron target conditions, the characteristics of substrate region are highly important as they are directly connected with properties of growing film [4]. We have measured the mass-resolved flux of ions originating from hot-target reactive HiPIMS plasma and arriving at grounded substrate. Magnetron targets were made from Cu, Cr, and Si. HiPIMS discharge was operated in O2/Ar mixtures for Cu and Si targets, and in N2/Ar mixture for Cr target. For these target/gas pairs, the composition of ion fluxes from plasma was measured by a custom magnetic mass-analyzer as a function of the reactive gas flow. The behavior of different fractions is analyzed and discussed.