Avis de Soutenance
Monsieur Patrick TAMAIN
Soutiendra publiquement son Habilitation à Diriger des Recherches intitulée:
Self-consistent numerical modelling of exhaust issues in tokamaks
Soutenance prévue le jeudi 16 janvier 2025 à 14h00
Lieu : salle René Gravier, bâtiment 506, CEA Cadarache
Et par Skype
Composition du jury :
- Fulvio MILITELLO : UKAEA – Culham, Royaume-Uni (Rapporteur)
- Volker NAULIN : DTU – Lyngby, Danemark (Rapporteur)
- Paolo Ricci : EPFL – Lausanne, Suisse (Rapporteur)
- Yanick SARAZIN : CEA / IRFM – Cadarache (Examinateur)
- Philippe CHOMAZ : CEA / DIR – Saclay (Examinateur)
- Eric SERRE : M2P2 / AMU – Marseille (Tuteur)
- Emmanuelle TSITRONE : CEA / IRFM – Cadarache (Invitée)
Abstract :
Heat and particle exhaust issues are some of the main challenges faced by magnetic fusion energy research. The constrains imposed by the management of power fluxes to the wall as well as the pumping of ashes largely determine the design and operational space of the machines and therefore the achievable performances. Understanding the underlying physics and eventually achieving predictive capabilities is necessary to reduce uncertainties both in the design of future machines and in the preparation of operational scenarios. The physics at play in the Scrape-Off Layer (SOL) and in the rest of the edge plasma covers a wide variety of complex and non-linear phenomena, ranging from magnetized plasma turbulence to atomic and molecular physics through plasma-solid interaction. The complexity is further amplified by the sensitivity of the system to the geometry of the plasma or of the plasma-facing components, limiting the applicability of simple analytical models and posing technical challenges for the numerical discretization of equations. This largely explains why, to this date, no model nor numerical tool has been developed that offers a self-consistent view of the edge plasma without requiring ad-hoc parametrization of some significant part of the physics. Historically, this led to the parallel development of 2 classes of edge modelling tools. On the one hand, turbulence codes were entirely dedicated to the study of transverse turbulent transport most often in reduced idealized geometries and with little consideration for the other aspect of edge plasma physics, especially neutrals recycling. On the other hand, mean-field codes integrate most of the relevant physics in realistic plasma and wall geometries, at the cost of an ad-hoc description of turbulent transport.
This presentation reports work performed in the last 15 years aiming at bridging the gap between these 2 approaches. The strategy chosen to do so has consisted in progressively adding relevant physics and geometrical capabilities in edge fluid turbulence codes. It has taken shape in the development and exploitation of a suit of 3D edge fluid turbulence codes, namely TOKAM3D, TOKAM3X and SOLEDGE3X. We will first reviews the key features of these numerical tools, both in terms of physics and numerical implementation. The main focus will be given to the TOKAM3X code with which most of the results presented in the manuscript have been obtained. We will then review some of the main scientific findings achieved in the last decade through the exploitation of the TOKAM3X code, addressing 3 main topics:
- the multi-scale self-organization of the edge plasma, from turbulence scales to equilibrium scales
- the effect of the magnetic geometry on edge plasma turbulence and transport, highlighting specifically the similarities and differences between the limited and diverted magnetic configuration
- the impact of neutrals recycling and plasma-neutrals interactions on edge plasma turbulence
These results will finally lead us to a discussion on the current status of some of the main remaining open questions to be solved on the path to the self-consistent modelling and understanding of exhaust issues. The questions are both of physical and technical order. We analyse the associated challenges, the state of the art and put forward possible solutions.