Fusion Plasmas group

Concentric cylindrical striations in air at low pressure in the presence of an external magnetic field

Fine structures of the magnetic field during a turbulent reconnection simulation

Testing a new cathode concept, using CC Héré technology, in the IJL's ALINE machine

Last publications

Mutual interactions between plasma filaments in a tokamak evidenced by fast imaging and machine learning
Sarah Chouchene, Frédéric Brochard, Nicolas Lemoine, Jordan Cavalier, Mikael Desecures, Vladimir Weinzettl
Physical Review E , 2024, 109 (4), pp.045201. ⟨10.1103/PhysRevE.109.045201⟩
Improved accuracy and robustness of electron density profiles from JET’s X-mode frequency-modulated continuous-wave reflectometers
R B Morales, A Salmi, P Abreu, C H S Amador, L Appel, P Carman, J Fessey, J Flanagan, M Fontana, L Frassinetti, C Giroud, S Hacquin, S Heuraux, L Meneses, G Ronchi, R Sabot, A Silva, A Sirinelli, G Szepesi, D Taylor, D Terranova
Review of Scientific Instruments, 2024, 95 (4), ⟨10.1063/5.0176696⟩
An overview of the evolution of the modeling of reflectometry diagnostics in fusion plasmas using finite-difference time-domain codes
F da Silva, Stéphane Heuraux, T Ribeiro E C, E Ricardo, J Santos, A E Silva, Jorge Ferreira, J Vicente, G De Masi, O Tudisco, R Cavazzana, G Marchiori, R Luís, Y Nietiadi
Fusion Engineering and Design, 2024, 202, pp.114354. ⟨10.1016/j.fusengdes.2024.114354⟩

Presentation

A plasma is one of the four fundamental states of matter. It is a fluid made up of ions and electrons. There are natural plasmas, such as the stars, the solar wind, the magnetosphere, or lightning, and others that are produced artificially, by heating a gas or subjecting it to an electric field: neon signs, Hall-effect thrusters, material-processing reactors, etc.

Thermonuclear fusion is a process by which two atomic nuclei join to form a heavier nucleus. This process occurs naturally in stars. The mass of the product(s) of the fusion reaction is less than the sum of the masses of the initial nuclei. Thus, the difference is converted into energy according to Einstein's formula E = mc². Achieving thermonuclear fusion of hydrogen on Earth is one of the avenues being considered for the provision of electricity over the next few decades, as a complement to other renewable energies.

Thermonuclear fusion of hydrogen presents considerable advantages, such as the availability of fuel and the fact that it is a decarbonized energy and essentially a clean process. Nevertheless, several steps remain to be taken before the process can be industrialized. Several fusion reactor concepts are being explored by the international community. The team participates in research exploring 3 configurations: the tokamak (configuration of the ITER project), the stellarator (Wendelstein 7-X machine) and inertial fusion (Laser MegaJoule). This research is carried out in the framework of collaborations with groups from the Fédération de Recherche Fusion par Confinement Magnétique, especially l’Institut de Recherche sur la Fusion Magnétique of the Cadarache CEA, and many foreign laboratories: Instituts Max-Planck de physique des plasmas of Garching and Greifswald, IPP Prague, the Universities of Ghent, Basle, Kyushu, IST-IPFN Lisbon, Ioffé Institute of Saint Petersburg, UCSD San Diego, Hefei Institutes of Physical Science, Ecole Polytechnique Fédérale de Lausanne to name but a few.

Keywords

Thermonuclear Fusion

Plasma Turbulence

Plasma-wall interactions

Modeling

Plasma diagnostics

Tokamak

Research Topics

Transport and Turbulence in magnetized plasmas

The optimal implementation of thermonuclear fusion as a major energy source requires a better understanding of turbulence and particle and energy transport in magnetized plasmas. The group focuses in particular on methods for controlling turbulence that describe this transport. The TERESA code developed by the group has been used to study resonant interactions between zonal flows and TIM and TEM turbulence for the generation of a self-consistent internal transport barrier. This model can be seen as an extension of the modified Hasegawa-Wakatani model. The group is also developing experimental methods for turbulence characterization, notably in ultrafast imaging and reflectometry. These are put into practice during measurement campaigns on different tokamaks.

Project:

ANR GRANUL, 2020-2024

Thesis:

CEA/Région Grand-Est 2018-2021, Kyungtak Lim

Articles:

Test particle dynamics in low-frequency tokamak turbulence, J. Médina, M. Lesur, E. Gravier, T. Réveillé, and P. Bertrand, Phys. Plasmas 2019, 26, 102301.
Diffusive impurity transport driven by trapped particle turbulence in tokamak plasmas, E. Gravier, M. Lesur, X. Garbet, Y. Sarazin, J. Médina, K. Lim, and M. Idouakass, Phys. Plasmas 2019, 26, 082306.
Transport Barriers associated to the resonat interaction between trapped particle modes triggered by plasma polarization injection, A. Ghizzo, D. Del Sarto, F. Palermo, A. Biancalani, Euro. Phys. Lett. 119 (1) 2017

Plasma wave heating

RF wave heaters for frequencies in the vicinity of the ion cyclotron frequency are the only such heating systems that increase the energy of ions efficiently. However, antenna-plasma coupling is complex due to the excitation of several modes. One of them, the slow mode, can generate high DC potentials, via the rectification process induced by the RF sheaths. In turn, these high DC potentials induce transport phenomena, overheating of the antenna structure and production of impurities, which can be localized or not. It is therefore necessary to study the propagation of such modes to predict their effects. These "upstream" studies take the form of modelling work and laboratory experiments. They are required to understand experiments in tokamaks. Fundamental studies of RF sheaths in magnetized plasma also help to build interpretive models for different types of RF electrostatic plasma probes.

Project:

ANR SHEAR, 2020-2024

Thesis:

Doctoral attribution 2017-2020, Jordan LEDIG
Experimental measurements of the RF sheath thickness with a cylindrical Langmuir probe E. Faudot, J Ledig, J. Moritz et al., Physics of Plasmas 26, 083503, 2019, ⟨10.1063/1.5096018⟩. ⟨hal-02171939⟩
Experimental and theoretical study of bumped characteristics obtained with cylindrical Langmuir probe in magnetized Helium plasma, J Ledig, E. Faudot, J. Moritz et al., Plasma Sources Sciences and Technology 29 (3), 035007 (2020) ⟨hal-02171921⟩

Magnetized plasma-wall transition

The plasma facing material components of fusion reactors are subjected to extreme flows of heat, particles and neutrons from the plasma. These plasma facing material components are subject to changes, whether in terms of erosion or deformation or changes in their properties. The group conducts research to better understand plasma-wall interactions (or plasma-surface interactions). In particular, it studies the flow of particles and heat on a plasma facing material component, and the triggering of electric arcs and their effects on different surfaces, through experimental and modelling studies.

Project:

ANR SHEAR, 2020-2024

Thesis:

Chabha DJERROUD, “Mechanisms and dynamics of unipolar arcs in plasmas”, doctoral grant 2018-2021

Articles:

Intrinsic dust transport in ASDEX Upgrade studied by fast imaging, F. Brochard, V. Rohde, T. Lunt et al., Nuclear Materials and Energy 18, 268 (2019).
The plasma-wall transition with collisions and an oblique magnetic field: reversal of potential drops at grazing incidences, J. Moritz, M. Lesur, E. Faudot et al., Phys. Plasmas 26, 013507 (2019).

Dynamics of magnetic fields in collision-free plasmas

One of the outstanding characteristics of the plasma state is the coupling between the dynamics of charged particles and electromagnetic (EM) fields. This is the basis of magnetic confinement for laboratory plasmas (e.g. tokamaks) and there are a variety of conversion phenomena between EM and kinetic energies. The conversion phenomena are sometimes spectacular, such as solar flares, intense EM emissions in astrophysical systems, or particle acceleration in laser-plasma interactions. The group conducts modelling work to study 3 classes of fundamental and complementary processes: magnetic reconnection, pressure anisotropy instabilities, and dynamo-type mechanisms. Theoretical and numerical models of the fluid (MHD) and kinetic (Vlasov) types are necessary for the description of these multi-scale processes where the geometry of the system often plays a fundamental role.

Project:

AAP FR-FCM 2019, “Evolution of current sheets in low-collision plasmas”

Thesis:

Homam BETAR, “Kinetic processes in magnetic reconnection”

Articles:

Vlasov models for kinetic Weibel-type instabilities, A. Ghizzo, M. Sarrat, D. Del Sarto, J. Plasma Phys., 83, S0022377816001215 (2017)
Secondary fast reconnecting instability in the sawtooth crash, D. Del Sarto and M. Ottaviani, Phys. Plasmas 24, 012102 (2017)

Vlasov-Maxwell models for relativistic plasmas

The central theme is numerical modelling and experimentation in plasma physics, where kinetic and relativistic effects are dominant. This topic is mainly based on two aspects: the development of semi-Lagrangian techniques for the resolution of the Vlasov equation and high-performance computing, and hamiltonian reduction techniques (a multi-beam model based on the exact invariance of canonical moments). Applications concern both a very high flux laser-plasma interaction and its instabilities (Raman, Weibel, Filamentation, etc.) and astrophysics. In the long-term, simulations with adaptive meshes are envisaged in 3D as well as in particulate systems (PIC SMILEI code).

Vlasov-Maxwell models for relativistic plasmas
The central theme is numerical modelling and experimentation in plasma physics, where kinetic and relativistic effects are dominant. This topic is mainly based on two aspects: the development of semi-Lagrangian techniques for the resolution of the Vlasov equation and high-performance computing, and hamiltonian reduction techniques (a multi-beam model based on the exact invariance of canonical moments). Applications concern both a very high flux laser-plasma interaction and its instabilities (Raman, Weibel, Filamentation, etc.) and astrophysics. In the long-term, simulations with adaptive meshes are envisaged in 3D as well as in particulate systems (PIC SMILEI code).

Article:

Parallel implementation of a relativistic semi-Lagrangian Vlasov-Maxwell solver, M. Sarrat, A. Ghizzo, D. Del Sarto, L. Serrat, Euro. Phys. J. D, 71, 11 (2017)

Numerical methods for modelling codes

A relativistic version of the VLEM code now includes a load conservation method, and a parallel 6D version is being developed on GENCI's Jean Zay supercomputer. In addition to semi-Lagrangian methods, a significant effort is being made to develop adaptive mesh refinement methods (RMA) with the development of a functional 6D simulation code of the Vlasov-Gravitational Poisson equations and a code associating RMA and discontinuous Galerkin methods. The development of a high order Poisson solver in RMA has also led to the development of original compact schemes in dimensions 2, 3 and above. New on-board conditions are also studied for the simulation of magnetized plasmas in the presence of RF, for heating fusion plasmas.

Project:

Application of the RMA 6D scheme to the Vlasov-Maxwell relativist case (application underway).

Articles :

Six-Dimensional Adaptive Simulation of the Vlasov Equations Using a Hierarchical Basis, E. Deriaz, S. Peirani, Multiscale Model. Sim. 16(2) 583-614, (2018).
Compact finite difference schemes of arbitrary order for the Poisson equation in arbitrary dimensions, Deriaz, E. Bit, Numer Math (2019).
Perfectly Matched Layers for time-harmonic transverse electric wave propagation in cylindrical and toroidal gyrotropic media, L. Colas, J. Jacquot, J. Hillairet et al., Journal of Computational Physics 389, 94, 2019

Plasma diagnostics

The group is studying the physics of diagnostics used in plasmas. For example, this may involve interpreting probe measurements in a magnetized laboratory radiofrequency plasma, or reflectometry turbulence measurements in nuclear fusion reactors. This is achieved by combining theoretical and experimental approaches, and modelling with synthetic diagnostics. The group also develops methods for the analysis of experimental data in image analysis, artificial intelligence, and data mining. These can be applied to other fields of research and to industry.

Project:

Several projects are underway using Artificial Intelligence to simplify data exploitation, including a CIFRE thesis with the APREX Solutions company

Thesis:

S. Chouchene, Securing and operating large facilities with Artificial Intelligence - applications to 4.0 nuclear fusion reactors and industry, 2020-2023

Articles:

Tomographic reconstruction of tokamak edge turbulence from single visible camera data and automatic turbulence structure tracking, J. Cavalier, N. Lemoine, F. Brochard et al., Nuclear Fusion 59, 056025 (2019).
On trends of the turbulence properties emerging from systematic studies of Tore Supra reflectometry database, Y. Sun, R. Sabot, S. Heuraux et al., Phys. Plasmas 26, 032307 (2019).
The reconstruction of hollow areas in density profiles from frequency swept reflectometry, R. Morales, S. Heuraux, R. Sabot, S. Hacquin, F. Clairet, Tore Supra Team, Plasma Science & Technology (2020).

Fundamental aspects of plasma physics

Numerical experimentation and modelling based on Vlasov codes allows us to address fundamental problems (filamentation and entropy cascade, wave-particle interaction), related to the use of Hamiltonian reduction techniques (multi-beam model for magnetic reconnection, a waterbag model or with adiabatic invariants) and information theory and plasma thermodynamics. In particular, we are working on the description of mean field theory (classical, relativistic, quantum) and the study of energy transfer mechanisms between fields and matter (e.g. kinetic heating and turbulence in collisionless plasmas).

Articles:

On the multistream approach of relativistic Weibel instability. I. Linear analysis and specific illustrations, A. Ghizzo and P. Bertrand, Phys. Plasmas 20, 082019 (2013)
Pressure anisotropy and small spatial scales induced by velocity shear, D. Del Sarto, F. Pegoraro, F. Califano, Phys. Rev. E 93, 053203 (2016)

Know-how

Numerical Simulations and Methods

High Performance Computing (HPC), development and use of gyrokinetic codes
Development of a 3D code solving Maxwell's equations coupled with a solver for current density, for a magnetized plasma usable for any polarization. It describes any diagnostics using electromagnetic waves to extract the characteristics of the plasma and its fluctuations, and creates synthetic diagnostics
Expertise in modelling of the Vlasov equation (Eulerian and semi-Lagrangian methods), which led to the development of the GYSELA4D, GYSELA5D and TERESA codes for gyrokinetic modelling and the VLEM code for electromagnetic and relativistic plasmas
“Extended fluid" models with inclusion of non-ideal MHD and/or kinetic (pressure tensor) effects
Mastery of a wide range of numerical methods: waterbag schemes, mesh refinement schemes, multigrids, wavelets, PIC methods, compact schemes, discontinuous Galerkin, hollow bases and hamiltonian reduction methods (multi-beam based on the conservation of canonical moments) or in action-angle variables for gyrokinetic modelling (adiabatic invariants)

Instrumental development

Development of a diagnostic-type microwave interferometer to study the edge plasma of tokamaks, in the ASDEX-Upgrade tokamak
Elaboration of non-linear analytical interpretive models tested using wave codes for new microwave diagnostics (wave scattering in the vicinity of upper hybrid resonance, radial Doppler correlation reflectometry, collective scattering for ITER, etc.)
Development of a large-scale research tool, SPEKTRE, to conduct research on plasma turbulence and turbulent transport, plasma heating, plasma-surface interactions, in a large volume of magnetized plasma

Plasma diagnostics and data analysis

Methods of interpreting Langmuir probe data in radio frequency plasma
Tomographic inversion methods for the study of turbulence using ultrafast imaging data from tokamaks

Technological transfer

Technological transfer and development of know-how concerning data analysis in the APREX Solutions, company co-founded in 2017 by one of the members of the group