Modeling of dissipative regimes in next generation high-field compact tokamaks: development of con-trol methods for detached plasma.

High-temperature superconducting (HTS) magnets represent a major breakthrough for nuclear fusion, enabling the development of compact, economically viable reactors with high power density. However, their design still faces significant physical and technological challenges, making advanced numerical modeling essential for progress. As for ITER, one of the key challenges remains power exhaust, as steady-state heat fluxes could exceed the technological limits of plasma-facing components (PFCs). Various strategies allow tokamaks to operate in dissipative regimes, such as impurity injection (Neon, Argon), which dissipates energy at the edge but dilutes the plasma. Among these, the detached plasma regime is particularly promising, as it dramatically reduces plasma temperature at the wall, leading to recombination into a protective neutral layer that shields PFCs from the hot core plasma.

While achieving this regime is relatively straightforward, controlling it in high-power machines remains a major challenge. Power fluctuations across the separatrix can trigger transients where the neutral layer reionizes, reattaching the plasma and risking PFC damage. Developing reactive control methods—capable of acting within appropriate timeframes—is therefore critical to protect PFCs continuously. This response time depends on the "burn-through" time—the duration required for plasma to ionize neutrals near the wall during a power transient.

This thesis aims to study these regimes through numerical modeling, particularly to predict transient power timescales and optimize steady-state detached plasma operation to maximize burn-through time. The ultimate goal is to achieve a state where neutrals never fully ionize during transients, enabling passive absorption of disturbances.

To accomplish this, two modeling approaches will be used:

• First-principles simulations with SOLEDGE3X-EIRENE (co-developed by the collaborating teams) for realistic simulations.
• Reduced-order models for parametric studies and extrapolating results to different machines.

Profil du candidat / Candidate profile :

Master ou diplôme d'ingénieur en physique des plasmas, mathématiques appliquées ou mécanique des fluides / Master's degree or engineering diploma in plasma physics, applied mathematics or fluid mechanics,

Related publications :

• H. Bufferand, et al. “Progress in edge plasma turbulence modelling—hierarchy of models from 2D transport application to 3D fluid simulations in realistic tokamak geometry”. In: Nuclear Fusion 61.11 (2021), p. 116052.
• J. Bucalossi, et al. “Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation”. In: Nuclear Fusion 62.4 (2022), p. 042007.

Unité de recherche en Sciences pour l'Ingénieur, le laboratoire a un spectre large et continu de recherches allant de la recherche à caractère fondamental motivée par la volonté d’accroître les connaissances à la recherche à caractère finalisé liée à des problèmes économiques et sociétaux, en lien étroit avec des partenaires privés. L'originalité du M2P2 réside dans ses thématiques de recherche dans le domaine de la Mécanique des Fluides Numérique

Master ou diplôme d'ingénieur en physique des plasmas, mathématiques appliquées ou mécanique des fluides / Master's degree or engineering diploma in plasma physics, applied mathematics or fluid mechanics,