Seminar by Dominique ESCANDE – Laboratoire PIIM

will take place on

Tuesday, December 19th at 15:00

in the Salle du Conseil, service 322 of the PIIM laboratory (Campus St. Jerome)

Abstract: Increasing the density limit in tokamaks would make easier ITER operation and would enable smaller reactors than presently considered. This sounds possible on the basis of a theory of plasma-wall self-organization published in 2022, and of its first experimental confirmation published in 2023. These results were presented in a poster at the 2023 IAEA Fusion Energy Conference. The basic theoretical idea is the existence of a time delay in the feedback loop relating radiation and impurity production on divertor targets. A way to increase the density limit in tokamaks is suggested by the plasma breakdown in the W7-X stellarator at high density of neutrals and high power electron cyclotron resonance heating: it yields an initial density an order of magnitude higher than in tokamak breakdown. Better performance is expected from plasma-wall self-organization with tungsten walls where physical sputtering dominates, than with carbon ones. Therefore, the first experimental confirmation in the J-TEXT tokamak despite its carbon walls is very encouraging. A proposal is made for the 2024 EUROfusion program of parallel experiments in the TCV, ASDEX Upgrade, and WEST tokamaks, the last two ones with tungsten walls.