Catégorie d'emplois: Physics

Associate professor (M/F) in experimental and/or theoretical physics for Magnetic Confinement Fusion

During the 2025 associate professor recruitment campaign, Aix-Marseille Université will be offering a position for an associate professor in Physics (CNU section 28 ou CNU section 30)to carry out research in the PIIM (Physics of the Interactions of Ions and Molecules) laboratory.

This position will be based in the Faculty of Sciences, which is very committed to gender diversity in its recruitment and encourages a policy of parity in this area.

The profile of this post is shown below. In addition, these duties will require a real ability to communicate and work as part of a team in an international environment.

Applications may be submitted on the Odyssée application from 4 March 2025 10:00 to 4 April 2025 16:00 (Paris time). Applications cannot be submitted directly via this site.

However, applicants who are considering submitting an application may contact the laboratory to prepare their research project (see the research section below).

Candidates whose applications are selected by the selection committee will be interviewed on  May 16th 2025.

Research section

PIIM has a strong activity in the field of Magnetic Confinement Fusion, with 5 teams involved (Hydrogen, Molecules, Materials; Atomic Physics and Transport in Plasmas; Surface Plasma; Plasma, Theory and Modelling; Plasma Turbulence) in the activities of the FR-FCM national federation and the ISFIN institute.

The person recruited will present a project closely linked to the problems of magnetic fusion, as part of the activities of one of the five teams concerned. These teams work on the experimental, theoretical and numerical study of :

  • plasmas and their dynamics
  • plasma-wall interactions
  • surface physics and fusion materials.
    The development, implementation and interpretation of diagnostics is also a key area of activity. This research is carried out with strong international links, particularly at European level as part of the EUROfusion consortium, and in close collaboration with local players (CEA Cadarache, ITER). Experience in the field of fusion by magnetic confinement will be appreciated.

The skills expected for this recruitment are theoretical and/or numerical and/or experimental, depending on the host team and the nature of the project. Candidates should clearly explain their plans for joining the target team.

Teaching section

The teaching part will take place in the Physics Department of the Faculty of Sciences.

The person recruited will teach physics and/or physical chemistry at all levels, in the three entries to L1 (AMNS, ‘L1en2ans’ and portail) and in all the physics courses managed by the department, on four teaching sites (Marseille Saint-Charles, Saint-Jérôme, Luminy and Aix-Montperrin), particularly in the Physics and Physics-Chemistry bachelor’s degrees, the Fundamental Physics and Applications master’s degree, the Instrumentation Measurement Metrology master’s degree, and the ‘Nano2’ master’s degree in Nanosciences and Nanotechnologies. An interest in active and innovative teaching practices adapted to new university audiences, and/or the ability to teach in English in the department’s internationally-oriented courses, would be particularly welcome.

Post-doctoral (M/F) researcher in characterization of innovative carbon-based nanomaterials

A fully-funded post-doctoral position (2 years), as part of the i-DEMO regionalized project (France 2030) M.A.G.I.C. (Matériaux Avancés pour l’Innovation en Graphène et Cristallographie), is available until April 1, 2025 in the “Physique des Interactions Ioniques et Moléculaires” (PIIM) laboratory of Aix-Marseille Université, CNRS (France).

As part of the M.A.G.I.C. project, we are looking for an experimental postdoctoral researcher to work on the development and characterization of innovative carbon-based nanomaterials, such as Ginestium©, multilayer rhombohedral graphene and other relevant systems. Ginestium© could be a revolutionary nanostructured carbon material developed by EffiBLUE (https://effiblue.com). Multilayer rhombohedral graphene and some multilayer twisted graphene are known to be superconductors at temperatures close to 1K. Manipulating the structural properties of carbon-based materials, such as sp2/sp3 ratio and stacking configurations, enables fine-tuning of their physical characteristics, including electronic conductivity, optical response and mechanical strength. These tunable materials have great potential for applications in the electronics, telecommunications and energy sectors.

This complete job offer is available here. Applications should be sent via the candidate space on the CNRS website.

PhD Thesis (M/F) – Physics – 2025/2028 -Experimentation – AE/2

Organism: Aix-Marseille University

Laboratory: PIIM UMR 7345

Location: Campus Saint-Jérôme

Supervisor: Alexandre Escarguel

Funding : AMIDEX Aix-Marseille University project “Table Top Accretion Disks”

e-mail: alexandre.escarguel@univ-amu.fr 

Analysis and control of ExB magnetized plasma column self-organization in the frame of astrophysical accretion mechanisms’ study

This PhD proposes an innovative way to use a laboratory experiment to study Keplerian rotating discs in astrophysics. Indeed, stellar accretion disks are complex systems whose dynamics cover a large number of research fields. They are indeed made of dust, neutral gas and plasmas orbiting around young or rising stars and seed planet formation [1]. In link with the observation capabilities of modern instruments such as James Webb space telescope [2], intense efforts are nowadays undertaken to explain accretion mechanisms and disk formation. How a Keplerian rotation can lead to matter transport toward the center is still a matter of debate, since collisional diffusion is negligible in these systems, and Keplerian discs are stable with respect to classical hydrodynamics instabilities. How instabilities and transport occur, can be elucidated by setting up dedicated experimental devices. Laboratory plasma experiments with controlled plasma rotation is an innovative way to explore such scientific questions.

Mistral is a cold magnetized plasma experiment with a constant magnetic field [3, 4, 5, 6]. It is a canonical experiment to study various kind of instabilities of weakly magnetized ExB plasmas, such as centrifugal instabilities [7]. In the presence of a magnetic field B perpendicular to an electric field E, charged particles drift in the ExB direction. Combined with plasma inhomogeneities, this drift is favorable to the apparition of instabilities that considerably increase the transport across the magnetic field B (« anomalous transport »). These cross-field configurations are exploited in numerous applications.

Rotating plasma are easily obtained in the Mistral experiment, but there is a lack of control of the azimuthal differential rotation. This can be done by a fine control of the radial electric field profile in the plasma. Indeed, the prediction of the rotation properties and the control of the flow profiles is still an open problem regarding rotating plasmas in such devices. Previous works in our SoPlasma network (https://gitlab.com/soplasma/soplasma), including the Mistral device, have shown that rotation of plasmas can be challenging to control. Recent progress however provides a path to achieve this important objective by the use of concentric cold or hot cathodes [8, 9] . Another possible way to control the plasma column rotation specific to Mistral is to control the energetic ionizing electrons in Mistral by independent concentric grids.

Investigation of the plasma self-organization and experimental control of its rotation is the main objective of this PhD proposition. First, PhD student will study the stability/turbulent areas in the parameter space (plasma pressure and boundary conditions) by experimental acquisition of plasma parameters with Langmuir probes, fast camera and optical tomography. Second, new innovative experimental configurations will be studied to better control the plasma azimuthal differential rotation: concentric grids controlling ionizing electrons injection and cold/hot cathodes placed at the end of the plasma column.

Finally, a comparison of experimental results with theory will allow a better understanding of ExB plasma rotation physics to ultimately propose an experimental setup with a Keplerian plasma rotation. The importance of this part will be modulated, according to the student’s motivation for theoretical work.

The project, being within the framework of AMIDEX (“Excellence initiative” of Aix-Marseille University) project “Table Top Accretion Disks”, is 100% funded.

References

[1] G. R. J. Lesur, J. Plasma Phys. 87 205870101 (2021) [2] Burrows et al, Astrophys. J 473, 437 (1996), https://jwst.nasa.gov

[3] N. Claire, A. Escarguel, C. Rebont, F. Doveil, Phys.Plasma 25, 061203 (2018)

[4] A. Escarguel, Eur. Phys. J. D, 56, 209-214 (2010).

[5] Th. Pierre, A. Escarguel, D. Guyomarc’h, R. Barni, C. Riccardi, Phys. Rev. Lett., 92, 065004 (2004).

[6] S. Aggarwal, Y. Camenen, A. Escarguel, and A. Poye, Journal Plasma Phys., 89(3), 905890310 (2023).

[7] R. Gueroult et al, Phys. Plasmas 082102 (2017)

[8] B. Trotabas and R. Gueroult, Plasma Sources Sci. Technol. 31, 025001 (2022)

[9] V.Désangles et al, J. Plasma Phys. 87, 905870308 (2021) and Désangles, Ph.D. thesis, Ecole Normale Supérieure de Lyon, France (2018)

 

M2 internship – 2025 – Physics – Experimentation – TP/AE/3

Organism: Aix-Marseille University

Laboratory: PIIM UMR 7345

Location: Campus Saint-Jérôme

Supervisor: Alexandre Escarguel

Funding : AMIDEX Aix-Marseille University project “Table Top Accretion Disks”

e-mail: alexandre.escarguel@univ-amu.fr

 

Analysis and control of ExB magnetized plasma column self-organization in the frame of astrophysical accretion mechanisms’ study

 

This internship is the first step of a funded PhD subject, in the frame of the “Table Top Accretion Disk” project. It proposes an innovative way to use a laboratory experiment to study Keplerian rotating discs in astrophysics. Indeed, stellar accretion disks are complex systems whose dynamics cover a large number of research fields. They are indeed made of dust, neutral gas and plasmas orbiting around young or rising stars and seed planet formation [1]. In link with the observation capabilities of modern instruments such as James Webb space telescope [2], intense efforts are nowadays undertaken to explain accretion mechanisms and disk formation. How a Keplerian rotation can lead to matter transport toward the center is still a matter of debate, since collisional diffusion is negligible in these systems, and Keplerian discs are stable with respect to classical hydrodynamics instabilities. How instabilities and transport occur, can be elucidated by setting up dedicated experimental devices. Laboratory plasma experiments with controlled plasma rotation is an innovative way to explore such scientific questions.

Mistral is a cold magnetized plasma experiment with a constant magnetic field [3, 4, 5, 6]. It is a canonical experiment to study various kind of instabilities of weakly magnetized ExB plasmas, such as centrifugal instabilities [7]. In the presence of a magnetic field B perpendicular to an electric field E, charged particles drift in the ExB direction. Combined with plasma inhomogeneities, this drift is favorable to the apparition of instabilities that considerably increase the transport across the magnetic field B (« anomalous transport »). These cross-field configurations are exploited in numerous applications.

Rotating plasma are easily obtained in the Mistral experiment, but there is a lack of control of the azimuthal differential rotation. This can be done by a fine control of the radial electric field profile in the plasma. Indeed, the prediction of the rotation properties and the control of the flow profiles is still an open problem regarding rotating plasmas in such devices. Previous works in our SoPlasma network (https://gitlab.com/soplasma/soplasma), including the Mistral device, have shown that rotation of plasmas can be challenging to control. Recent progress however provides a path to achieve this important objective by the use of concentric cold or hot cathodes [8, 9]. Another possible way to control the plasma column rotation specific to Mistral is to control the energetic ionizing electrons in Mistral by independent concentric grids.

Investigation of the plasma self-organization and experimental control of its rotation is the main objective of this work. Student will study the stability/turbulent areas in the parameter space (plasma pressure and boundary conditions) by experimental acquisition of plasma parameters with Langmuir probes and fast camera. This will allow to find the most adapted plasma regime for the control of differential plasma rotation. In parallel, theoretical approach will be started. The importance of this part will be modulated, according to the student’s motivation for theoretical work.

The project, being within the framework of AMIDEX (“Excellence initiative” of Aix-Marseille University) project “Table Top Accretion Disks”, is 100% funded.

 

References

[1] G. R. J. Lesur, J. Plasma Phys. 87 205870101 (2021) [2] Burrows et al, Astrophys. J 473, 437 (1996), https://jwst.nasa.gov

[3] N. Claire, A. Escarguel, C. Rebont, F. Doveil, Phys.Plasma 25, 061203 (2018)

[4] A. Escarguel, Eur. Phys. J. D, 56, 209-214 (2010).

[5] Th. Pierre, A. Escarguel, D. Guyomarc’h, R. Barni, C. Riccardi, Phys. Rev. Lett., 92, 065004 (2004).

[6] S. Aggarwal, Y. Camenen, A. Escarguel, and A. Poye, Journal Plasma Phys., 89(3), 905890310 (2023).

[7] R. Gueroult et al, Phys. Plasmas 082102 (2017)

[8] B. Trotabas and R. Gueroult, Plasma Sources Sci. Technol. 31, 025001 (2022)

[9] V.Désangles et al, J. Plasma Phys. 87, 905870308 (2021) and Désangles, Ph.D. thesis, Ecole Normale Supérieure de Lyon, France (2018)

 

M1 internship – 2025 – Physics – Experimentation – TP/AE/2

Organism: Aix-Marseille University

Laboratory: PIIM UMR 7345

Location: Campus Saint-Jérôme

Supervisor: Alexandre Escarguel

e-mail: alexandre.escarguel@univ-amu.fr

Analysis and control of ExB magnetized plasma column self-organization in the frame of astrophysical accretion mechanisms study 

This M1 internship will take place in the frame of A*MIDEX (“Excellence initiative” of Aix-Marseille University) project “Table Top Accretion Disks”, It proposes an innovative way to use a laboratory experiment to study Keplerian rotating discs in astrophysics. Indeed, stellar accretion disks are complex systems whose dynamics cover a large number of research fields. They are indeed made of dust, neutral gas and plasmas orbiting around young or rising stars and seed planet formation [1]. In link with the observation capabilities of modern instruments such as James Webb

space telescope [2], intense efforts are nowadays undertaken to explain accretion mechanisms and disk formation. How a Keplerian rotation can lead to matter transport toward the center is still a matter of debate, since collisional diffusion is negligible in these systems, and Keplerian discs are stable with respect to classical hydrodynamics instabilities. How instabilities and transport occur, can be elucidated by setting up dedicated experimental devices. Laboratory plasma experiments with controlled plasma rotation is an innovative way to explore such scientific questions.

Mistral is a cold magnetized plasma experiment with a constant magnetic field [3, 4, 5, 6].

It is a canonical experiment to study various kind of instabilities of weakly magnetized ExB plasmas, such as centrifugal instabilities [7]. In the presence of a magnetic field B perpendicular to an electric field E, charged particles drift in the ExB direction. Combined with plasma inhomogeneities, this drift is favorable to the apparition of instabilities that considerably increase the transport across the magnetic field B (« anomalous transport »). These cross-field configurations are exploited in numerous applications.

Rotating plasma are easily obtained in the Mistral experiment, but there is a lack of control of the azimuthal differential rotation. This can be done by a fine control of the radial electric field profile in the plasma. Indeed, the prediction of the rotation properties and the control of the flow profiles is still an open problem regarding rotating plasmas in such devices. Previous works in our SoPlasma network (https://gitlab.com/soplasma/soplasma), including the Mistral device, have shown that rotation of plasmas can be challenging to control. Recent progress however provides a path to achieve this important objective by the use of concentric cold or hot cathodes [8, 9]. Another possible way to control the plasma column rotation specific to Mistral is to control the energetic ionizing electrons in Mistral by independent concentric grids.

Investigation of the energetic ionizing electrons in Mistral is the main objective of this work. The student will study its energy distribution function with Langmuir probes and Retarding field Analysers in the parameter space of Mistral (plasma pressure and boundary conditions). This will allow to find the most adapted plasma regime for the control of differential plasma rotation.

References

[1] G. R. J. Lesur, J. Plasma Phys. 87 205870101 (2021) [2] Burrows et al, Astrophys. J 473, 437 (1996), https://jwst.nasa.gov

[3] N. Claire, A. Escarguel, C. Rebont, F. Doveil, Phys.Plasma 25, 061203 (2018)

[4] A. Escarguel, Eur. Phys. J. D, 56, 209-214 (2010).

[5] Th. Pierre, A. Escarguel, D. Guyomarc’h, R. Barni, C. Riccardi, Phys. Rev. Lett., 92, 065004 (2004).

[6] S. Aggarwal, Y. Camenen, A. Escarguel, and A. Poye, Journal Plasma Phys., 89(3), 905890310 (2023).

[7] R. Gueroult et al, Phys. Plasmas 082102 (2017)

[8] B. Trotabas and R. Gueroult, Plasma Sources Sci. Technol. 31, 025001 (2022)

[9] V.Désangles et al, J. Plasma Phys. 87, 905870308 (2021) and Désangles, Ph.D. thesis, Ecole Normale Supérieure de Lyon, France (2018)

 

 

PhD Thesis (M/F) – Physics – 2025/2028 -Experimentation – AE/1

Laboratory : PIIM/Turbulence Plasma team

Supervisors : Alexandre Escarguel and Laurence Cherigier-Kovacic

Tel: 06 42 54 87 97

Email : alexandre.escarguel@univ-amu.fr ; laurence.kovacic@univ-amu.fr

Funding : Aix-Marseilles University doctoral school of physics and matter science 352

Subject : Optical electric field diagnostic in a magnetized plasma by Lyman-alpha stimulated emission (EFILE) 

Subject description :

Project framework and experiment description:

Plasma, result from the partial or total ionization of neutral gases. Coupling between fields (electric, magnetic) and charged particles leads to collective effects and turbulence, specific to these media. Their behavior and their fields of application depend on the ion temperature: cold plasmas are used in industry for surface treatment (etching of circuits, deposits, production of reactive species, etc.); hot plasmas are produced in tokamaks (Tore-Supra, ITER…) in order to produce energy from controlled fusion. In both cases, it is essential to determine the fundamental parameters associated with the charged species present in the plasmas.

The Turbulence Plasma team has developed an optical diagnostic (EFILE) for direct measurement of an electric field in vacuum or in plasma [1, 2]. This diagnostic is based on the emission of the Lyman-α line by a hydrogen probe beam in the 2s state submitted to an electric field. As a result of the 2s-2p coupling created by the field, atoms in the 2s (metastable) level is transferred to the 2p level, which then rapidly de-excites to the ground level. The intensity of the electric field-induced Lyman-α emission is proportional to the square of the field amplitude. This diagnostic was experimentally validated in a simple cylindrical configuration, in vacuum and in a non-magnetized plasma.

Objective and description of the subject:

The objective of the thesis is to measure the electric field in a magnetized plasma. The EFILE diagnostic is being implemented on the MISTRAL machine of the Turbulence Plasma team of the PIIM laboratory. The MISTRAL machine [3, 4] produces a cold plasma column in a linear magnetic field, over a wide range of parameters. It is a fundamental research machine whose linear configuration simplifies the study of instabilities in a magnetized plasma (compared to tokamaks where the curvature of the magnetic field induces more complex phenomena). Mistral is the ideal device to validate the EFILE diagnostic which is a unique way of measurement of the electric field in a direct and non-intrusive way.

Present work is focused on the study of the influence of the magnetic field on the diagnostic and the measurement of an electric field at different points along the radius of the machine. These two aspects are studied in vacuum or in a plasma, independently of each other, in order to fully understand the capabilities of the diagnostic.

The selected PhD student will proceed to the measurement of the electric field which, together with the magnetic field, is responsible for rotating non linear instabilities of the plasma column [5, 6].

The general objective of this work is to develop a diagnostic for the absolute measurement of a static or oscillating electric field that can be transferred to different systems and applied to various current research problems in plasma physics. Within this framework, the diagnostic will be applied by the PhD student to the study of plasma sheaths, a crossdisciplinary issue involving cold plasmas, hot plasmas, applied mathematics, theories, simulations, and experiments [4].

This project is granted by the FR-FCM (Federation de Recherche sur le Fusion Contrôlée par Confinement Magnétique).

 

References

[[1] L. Chérigier-Kovacic, P. Ström, A. Lejeune and F. Doveil, Review of Scientific Instruments 86, 063504 (2015); doi: 10.1063/1.4922856

[2] L. Chérigier-Kovacic, Static and RF electric field direct measurement based on Lyman-a emissionfrom a hydrogen probe beam ; Invited talk @ XXXIV ICPIG conference, July 14-19 2019, Sapporo, Japan.

[3] A. Escarguel, ExB workshop, nov 2018, Princeton Plasma Physic Lab, USA.

[4] Atelier Gaine Plasma 4-6 novembre 2024, Marseille, https://gaine2024.sciencesconf.org/?lang=fr (consulté le 30 novembre 2024).

M2 internship – 2025 – Physics – Experimentation – TP/AE/1

Laboratory : PIIM/Turbulence Plasma team

Supervisors : Alexandre Escarguel and Laurence Cherigier-Kovacic

Tel: 06 42 54 87 97

Email : alexandre.escarguel@univ-amu.fr ; laurence.kovacic@univ-amu.fr

Subject : Optical electric field diagnostic in a magnetized plasma by Lyman-alpha stimulated emission (EFILE) 

Subject description :

Project framework and experiment description:

Plasma, result from the partial or total ionization of neutral gases. Coupling between fields (electric, magnetic) and charged particles leads to collective effects and turbulence, specific to these media. Their behavior and their fields of application depend on the ion temperature: cold plasmas are used in industry for surface treatment (etching of circuits,deposits, production of reactive species, etc.); hot plasmas are produced in tokamaks (Tore-Supra, ITER…) in order to produce energy from controlled fusion. In both cases, it is essential to determine the fundamental parameters associated with the charged species present in the plasmas.

The Turbulence Plasma team has developed an optical diagnostic (EFILE) for direct measurement of an electric field in vacuum or in plasma [1, 2]. This diagnostic is based on the emission of the Lyman-α line by a hydrogen probe beam in the 2s state submitted to an electric field. As a result of the 2s-2p coupling created by the field, atoms in the 2s (metastable) level is transferred to the 2p level, which then rapidly de-excites to the ground level. The intensity of the electric field-induced Lyman-α emission is proportional to the square of the field amplitude. This diagnostic was experimentally validated in a simple cylindrical configuration, in vacuum and in a non-magnetized plasma.

Objective and description of the subject:

The objective of the thesis is to measure the electric field in a magnetized plasma. The EFILE diagnostic is being implemented on the MISTRAL machine of the Turbulence Plasma team of the PIIM laboratory. The MISTRAL machine [3, 4] produces a cold plasma column in a linear magnetic field, over a wide range of parameters. It is a fundamental research machine whose linear configuration simplifies the study of instabilities in a magnetized plasma (compared to tokamaks where the curvature of the magnetic field induces more complex phenomena). Mistral is the ideal device to validate the EFILE diagnostic which is a unique way of measurement of the electric field in a direct and non-intrusive way.

Present work is focused on the study of the influence of the magnetic field on the diagnostic and the measurement of an electric field at different points along the radius of the machine. These two aspects are studied in vacuum or in a plasma, independently of each other, in order to fully understand the capabilities of the diagnostic.

The selected student will proceed to the measurement of the electric field which, together with the magnetic field, is responsible for rotating non linear instabilities of the plasma column [5, 6].

The general objective of this work is to develop a diagnostic for the absolute measurement of a static or oscillating electric field that can be transferred to different systems and applied to various current research problems in plasma physics. Within this framework, the diagnostic will be applied by the student to the study of plasma sheaths, a crossdisciplinary issue involving cold plasmas, hot plasmas, applied mathematics, theories, simulations, and experiments [4].

This project is granted by the FR-FCM (Federation de Recherche sur le Fusion Contrôlée par Confinement Magnétique).

 

References

[[1] L. Chérigier-Kovacic, P. Ström, A. Lejeune and F. Doveil, Review of Scientific Instruments 86, 063504(2015); doi: 10.1063/1.4922856

[2] L. Chérigier-Kovacic, Static and RF electric field direct measurement based on Lyman-a emission from a hydrogen probe beam ; Invited talk @ XXXIV ICPIG conference, July 14-19 2019, Sapporo, Japan.

[3] A. Escarguel, ExB workshop, nov 2018, Princeton Plasma Physic Lab, USA.

[4] Atelier Gaine Plasma 4-6 novembre 2024, Marseille, https://gaine2024.sciencesconf.org/?lang=fr (consulté le 30 novembre 2024).

M2 Internship – Physics – Modeling – PATP/MK/1

Length: 4-6 months

Laboratory: PIIM, UMR7345, group PATP (Atomic Physics and Transport in Plasmas)

Supervisor: Mohammed KOUBITI (mohammed.koubiti@univ-amu.fr)

 Address: Campus St Jérôme, Service 232, Av. Escadrille Normandie Niemen, Marseille

Phone : +33 (0)4 13 94 64 47 

Research type: Theory/Numerical Modeling/Comparison with Experimental data

 Subject description: Artificial intelligence (AI) is increasingly used in physics including magnetic fusion plasmas. For instance, a Machine Learning (ML) algorithm [1] was used recently to predict the plasma parameters for PISCES-B and NAGDIS linear plasma devices [2-3]. Unlike the standard line ratio technique which relies on collisional-radiative modelling [4], in [2-3] no physical model is combined with the spectroscopic measurements. More precisely, using the intensities of few neutral helium lines the electron density and temperature were predicted by the ML algorithm and compared to their values measured by independent diagnostic techniques like Langmuir probes or Thomson scattering [2-3]. In this internship proposal, we suggest applying deep-learning techniques to line spectra of hydrogen isotopes in tokamak plasmas. We will apply in particular Dense Neural Networks (DNN) and Convolutional Neural Networks (CNN) to generated spectra of hydrogen isotopes for the aim of plasma diagnostics and predictions for future experiments. Our objective of applying DL techniques to the line emission of hydrogen isotopes in tokamaks is the prediction of the hydrogen isotopic ratio (defined as D/(D+T) for a D-T mixture) whose knowledge is of great importance for safety reasons and reaction performance control [5-6]. The algorithms can be also applied to impurity spectra to predict their plasma parameters such as the electron temperature. The candidate will have the task to develop a computer program (in Python) allowing to apply DNN and CNN algorithms to Ha/Da/Ta line spectra generated by an existing code for various conditions in terms of neutral temperatures, neutral population densities, magnetic field strength and hydrogen isotopic ratio. Thanks to the involvement in the tasks of data analysis of the EUROfusion workplan Tokamak Exploitation (TE) for several tokamaks including JET, the candidate may also apply the trained deep-learning models to experimental data from devices like JET and/or WEST.

  1. F. Pedregosa et al 2011 the Journal of machine Learning research 12 2825
  2. S. Kajita et al 2020 AIP Advances 10 025225
  3. D. Nishijima et al 2021 Rev. Sci. Instrum. 92 023505
  4. S. Kajita et al 2021 Plasma Phys. Control. Fusion 63 055018
  5. M. Koubiti and M. Kerebel 2022 Appl Sci 12 9891
  6. N. Saura, M. Koubiti, S. Benkadda, Study of line spectra emitted by hydrogen isotopes in tokamaks through Deep-Learning algorithms, submitted to Journal of Nuclear Material Energy (2024).This internship can be followed by a PhD thesis with funding by doctoral school ED352

M2 INTERNSHIP – Physics – Modeling – PTM/MM/1

By nature, a plasma is composed of charged particles which, in response to electromagnetic fields they generate or which are applied to them, exhibit collective behaviors from which quasineutrality results on spatial scales larger than the Debye lengths.

This property break-down when the plasma encounters a solid frontiers where non-neutral sheath forms at Debye length scales and, potentially, deeply impact on the bulk dynamics, i.e. far from the frontiers.

Ions and electrons dynamics, due to their mass difference, evolve with different temporal scales. In particular, when approaching an external object , which can be device boundaries in experiments or bodies in astrophysical contexts, multi-scale physics phenomena emerge especially where the sheath is formed. Surfaces immersed in a plasma could emit secondary electrons which change the physics of the sheath. Even more, some numerical theories predict an “inverse sheath” [1].

The physics of plasma sheath is of major interest in the fields of, both, laboratory, astrophysics and fusion by magnetic confinement (tokamaks,…). Many studies have been devoted to the understanding of plasma sheath [2]. However, comparisons of theoretical models to experiment can sometimes show disagreements, in particular in sheath where secondary electrons are emitted [1, 3, 4].

In that context, the first goal of this internship is to improve comparison between models (already existing) and experiments of electrostatic plasma sheath. Models developed during this internship will be compared with experimental results on emissive sheath obtained by the experimental group of the PIIM laboratory. The second goal of the internship is to improve the model adding the impact of an oblique magnetic field on the sheath properties.

Here, it is expected to improve the fundamental knowledge of the physical mechanisms at play in a magnetized plasma sheath that is crucial for fusion plasmas.

The student must have master’s level knowledge in mathematics, numerical calculation and plasma physics to carry out theoretical calculations and participate in numerical code development.

He will have available fluid [5] and kinetic codes developed at the PIIM.

The master’s internship will be supervised at the PIIM laboratory by M. Muraglia.

This subject is associated to a thesis subject funded by AMIDEX which will be directed by M.Muraglia and co-directed by G. Fubiani (Lalpace laboratory at Toulouse) and supervised by N.Claire (PIIM).

 

References

[1] M. D. Campanell, Phys. Rev E 88, 033103 (2013)

[2] R. N. Franklin, J. Phys. D: Appl. Phys. 36, R309 (2003)

[3] V. Pigeon et al, Phys. Plasmas 27, 043505 (2020)

[4] D. Coulette et al, Phys. Plasmas 22, 0043505 (2015)

[5] J-H Mun et al [tPhys. Plasmas 31, 073906 (2024)]

[6] M. D. Campanell and M.V. Umansky, Physics of Plasmas 24, 057101 (2017)

PhD Thesis (M/F) – Physics – 2025/2028 – AE

This PhD proposes an innovative way to use a laboratory experiment to study Keplerian rotating discs in astrophysics. Indeed, stella@r accretion disks are complex systems whose dynamics cover a large number of research fields. They are indeed made of dust, neutral gas and plasmas orbiting around young or rising stars and seed planet formation [1]. In link with the observation capabilities of modern instruments such as James Webb space telescope [2], intense efforts are nowadays undertaken to explain accretion mechanisms and disk formation. How a Keplerian rotation can lead to matter transport toward the center is still a matter of debate, since collisional diffusion is negligible in these systems, and Keplerian discs are stable with respect to classical hydrodynamics instabilities. How instabilities and transport occur, can be elucidated by setting up dedicated experimental devices. Laboratory plasma experiments with controlled plasma rotation is an innovative way to explore such scientific questions.

Mistral is a cold magnetized plasma experiment with a constant magnetic field [3, 4 ,5, 6]. It is a canonical experiment to study various kind of instabilities of weakly magnetized ExB plasmas,such as centrifugal instabilities [7]. In the presence of a magnetic field B perpendicular to an electric field E, charged particles drift in the ExB direction. Combined with plasma inhomogeneities, this drift is favorable to the apparition of instabilities that considerably increase the transport across the magnetic field B (« anomalous transport »). These cross-field configurations are exploited in numerous applications.

Rotating plasma are easily obtained in the Mistral experiment, but there is a lack of control of the azimuthal differential rotation. This can be done by a fine control of the radial electric field profile in the plasma. Indeed, the prediction of the rotation properties and the control of the flow profiles is still an open problem regarding rotating plasmas in such devices. Previous works in our SoPlasma network (https://gitlab.com/soplasma/soplasma), including the Mistral device, have shown that rotation of plasmas can be challenging to control. Recent progress however provides a path to achieve this important objective by the use of concentric cold or hot cathodes [8, 9] . Another possible way to control the plasma column rotation specific to Mistral is to control the energetic ionizing electrons in Mistral by independent concentric grids.

Investigation of the plasma self-organization and experimental control of its rotation is the main objective of this PhD proposition. First, PhD student will study the stability/turbulent areas in the parameter space (plasma pressure and boundary conditions) by experimental acquisition of plasma parameters with Langmuir probes, fast camera and optical tomography. Second, new innovative experimental configurations will be studied to better control the plasma azimuthal differential rotation: concentric grids controlling ionizing electrons injection and cold/hot cathodes placed at the end of the plasma column.

Finally, a comparison of experimental results with theory will allow a better understanding of ExB plasma rotation physics to ultimately propose an experimental setup with a Keplerian plasma rotation. The importance of this part will be modulated, according to the student’s motivation for theoretical work.

The project, being within the framework of AMIDEX (“Excellence initiative” of Aix-Marseille University) project “Table Top Accretion Disks”, is 100% funded.

 

References

[1] G. R. J. Lesur, J. Plasma Phys. 87 205870101 (2021) [2] Burrows et al, Astrophys. J 473, 437 (1996),

https://jwst.nasa.gov

[3] N. Claire, A. Escarguel, C. Rebont, F. Doveil, Phys.Plasma 25, 061203 (2018)

[4] A. Escarguel, Eur. Phys. J. D, 56, 209-214 (2010).

[5] Th. Pierre, A. Escarguel, D. Guyomarc’h, R. Barni, C. Riccardi, Phys. Rev. Lett., 92, 065004 (2004).

[6] S. Aggarwal, Y. Camenen, A. Escarguel, and A. Poye, Journal Plasma Phys., 89(3), 905890310 (2023).

[7] R. Gueroult et al, Phys. Plasmas 082102 (2017)

[8] B. Trotabas and R. Gueroult, Plasma Sources Sci. Technol. 31, 025001 (2022)

[9] V.Désangles et al, J. Plasma Phys. 87, 905870308 (2021) and Désangles, Ph.D. thesis, Ecole Normale Supérieure de Lyon, France (2018)