PhD in Laser-Plasma Interaction Physics Applied to Inertial Confinement Fusion (M/F)

Job Description

Thesis Subject

This thesis focuses on the theoretical and numerical study of parametric instabilities driv-en by broadband, low-temporal-coherence laser beams, in the context of future laser fa-cilities for inertial fusion. It will be carried out within the theory group TIPS (Theory, Plas-ma Interpretation & Simulation), in close collaboration with the experimental teams of the Laboratoire pour l'Utilisation des Lasers Intenses (LULI) on the campus of École Poly-technique in Palaiseau (France).

Context - In 2022, the National Ignition Facility (NIF, United States) demonstrated net en-ergy gain in inertial fusion for the first time, marking a major scientific advancement. This breakthrough has since spurred numerous international projects aimed at developing low-carbon power-generating reactors based on laser fusion. In France, the Taranis project, selected in March 2024 as part of the France 2030 plan and led by the startup GenF, brings together a national consortium comprising Thales, the CEA, and the CNRS (through its two laboratories, LULI and CELIA).
In this context, LULI is responsible for several work packages, including the development of innovative laser sources to test advanced inertial fusion concepts, particularly in direct-drive geometries. This thesis is part of this effort, exploring the use of broadband inco-herent sources to drive the implosion. The goal is to improve the coupling between the laser beam and the target while minimizing undesirable effects: laser imprint and, at the heart of this thesis, parametric instabilities, in particular stimulated Raman scattering and two-plasmon decay, which involve Langmuir waves, as well as stimulated Brillouin scatter-ing and cross-beam energy transfer (CBET), which involve the ion acoustic response.

Scientific objectives - Advances in broadband laser technology are fueling hopes of achiev-ing inertial confinement fusion in a regime largely free of parametric instabilities, paving the way for more robust implosions [Froula et al., Phys. Plasmas 32, 052713 (2025)]. How-ever, the actual effectiveness of this suppression depends heavily on the specific nature of the broadband source, and not just on its spectral width: discrete frequency comb ver-sus continuous spectrum, and the presence or absence of spectral dispersion. Added to this are kinetic effects (electron trapping, plasma wave broadening) and geometric effects, such as 2D/3D propagation and beam speckle patterns, which remain largely unexplored because they require significant simulation capabilities.
This thesis aims to conduct a systematic kinetic analysis, based on particle-in-cell (PIC) simulations, in order to (1) compare the effect of different types of broadband sources on the growth and saturation of three-wave coupling instabilities (Raman and Brillouin); (2) to extend this analysis to an inhomogeneous geometry representative of direct drive con-ditions, in 2D or 3D geometry, and taking into account the spatial structure of the beam (speckle pattern) and spectral dispersion; (3) to assist in the conception and interpreta-tion of experiments conducted on LULI's laser facilities (LULI2000 and Apollon).

Methodology - The numerical studies will be conducted primarily using the SMILEI kinetic (PIC) code, which was co-developed by LULI and several laboratories at the Saclay Plateau. They will complement the experiments conducted on LULI's laser facilities. Close collabo-ration with partners in the Taranis consortium is planned.

Required Profile :
- Education: Master's degree or engineering degree in plasma physics or fusion phys-ics
- Technical skills:
o Knowledge of plasma physics, laser physics, laser-matter interaction
o Proficiency in scientific programming languages (Python required, C/C++ appreciated)
o Skills in data processing, physical modeling, and experimental analysis
- Personal qualities: rigor, autonomy, ability to work in a team and communicate scientifically, good command of English

Application :
Interested candidates should send:
- a cover letter,
- a detailed CV,
- the contact details of two scientific referees (professors or researchers).

Your Work Environment

CNRS is a major player in fundamental research worldwide. LULI, a reference laboratory in the field of intense lasers, is located on the École Polytechnique campus in Palaiseau, as well as at the Orme des Merisiers site (CEA) and Sorbonne University (Jussieu). It compris-es about 110 staff members (researchers, engineers, PhD students) and operates several major experimental facilities: LULI2000, Apollon, HERA, XCAN.

The PhD student will join LULI's theory team (TIPS) and will work closely with LULI's exper-imental teams involved in the Taranis project.

Constraints and risks

Collaboration with Taranis partner laboratories (CEA/DAM, CELIA, GenF) are expected, as well as participation in experimental campaigns in France and abroad.

Laser risks.

The post is in a sector covered by the Protection of Scientific and Technical Potential (PPST) scheme and therefore, in accordance with the regulations, your appointment must be authorised by the relevant authority.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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