Description du sujet de thèse

In a nuclear fusion power reactor, the divertor is a critical subsystem responsible for extracting heat and removing impurities generated by the plasma. It is composed of several plasma-facing components (PFCs) that must withstand extreme thermal and particle loads. In the most advanced designs, solid tungsten monoblocks are actively cooled to manage the intense heat flux originating from the plasma core.
The national PEPR SupraFusion program (France 2030, CEA & CNRS) supports the development of high-temperature superconducting (HTS) cables and magnets capable of operating at magnetic fields of 20–30 T in steady-state conditions. These technological breakthroughs pave the way for compact tokamak designs, which, however, result in significantly increased heat loads on the divertor compared to larger machines. This challenge calls for the development of alternative PFC technologies to ensure the reliability and longevity of future fusion power plants.
Liquid metal-based divertors (LMDs) offer a promising solution by addressing lifetime limitations through continuous liquid replenishment. One prominent approach involves Capillary Porous Systems (CPS) actively cooled structures infiltrated with low-melting-point metals such as tin. These systems rely on capillary forces to retain the liquid metal within a porous matrix, mitigating splashing during plasma exposure and offering self-healing capabilities.
However, conventional CPS technologies face limitations in terms of pore geometry control and manufacturability. These challenges can potentially be overcome through Laser Powder Bed Fusion (LPBF) additive manufacturing, which allows precise tuning of pore size and distribution via 3D lattice architectures. Our innovative approach aims to exploit such architected structures to optimize liquid tin infiltration, enhance heat removal, and mitigate surface degradation in harsh plasma environments.
The PhD project is structured into three main phases:
- Design and Optimization of Lattice Structures:
The first phase will focus on the design, fabrication, and optimization of tungsten lattice structures with controlled porosity suitable for efficient infiltration of liquid tin. This includes optimization of LPBF process parameters, detailed characterization of the resulting materials (microstructure, thermal conductivity, wettability), and validation of the infiltration process.
- Plasma–Material Interaction Studies:
The second phase will investigate the interaction between the CPS structures and plasma in the SPEKTRE linear plasma device (Institut Jean Lamour). Special attention will be paid to contamination mechanisms such as sputtering, evaporation, and the formation of tin droplets. The study will quantify droplet size distributions, emission frequencies, and assess gas retention phenomena within the infiltrated lattice.
- High Heat Flux Qualification:
The final phase will involve high heat flux testing at the HADES facility (CEA/IRFM, Cadarache), under conditions representative of fusion reactors. This includes steady-state and cyclic thermal loading to evaluate thermal fatigue resistance and the overall performance of the structures under extreme conditions.
This multidisciplinary project combines advanced manufacturing, plasma-material interaction studies, and high-temperature testing, contributing directly to the development of next-generation plasma- facing components for future fusion reactors.

Contexte de travail

The Institute Jean Lamour (IJL) is a joint research unit of CNRS and Université de Lorraine.
Focused on materials and processes science and engineering, it covers: materials, metallurgy, plasmas, surfaces, nanomaterials and electronics.
By 2025, IJL has 259 permanent staff (34 researchers, 133 teacher-researchers, 92 IT-BIATSS) and 374 non-permanent staff (136 doctoral students, 48 post-doctoral students / contractual researchers and more than 190 trainees), from some sixty different nationalities.
Partnerships exist with 150 companies and our research groups collaborate with more than 60 countries throughout the world.
Its exceptional instrumental platforms are spread over 4 sites ; the main one is located on Artem campus in Nancy.
The PhD student will work within the “Fusion Plasmas” and “Materials and Additive Processes” research groups based in Nancy, under the supervision of Jérôme Moritz and Paul Lohmuller, in strong collaboration with the Institute for Magnetic Fusion Research (IRFM) in CEA Cadarache (the supervisor in IRFM-CEA is Alan Durif). The PhD program will very likely include several stays in CEA Cadarache.
This PhD thesis is part of the PEPR SupraFusion project.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.