Recent progress in understanding the L–H transition physics from ASDEX Upgrade

Le résumé fourni par la source

Kinetic edge profiles are measured with high spatial and temporal resolution and their behaviour before and after the time of the L–H transition is analysed. It is shown that at low densities electron and ion channels are strongly decoupled and that the ion kinetic profiles determine the transition to H-mode. At medium densities, where electrons and ions are coupled, the H–L back-transition occurs at the same pressure gradients as the L–H transition. The threshold power for the H–L back-transition exhibits the same increase at low densities as the L–H transition. After the L–H transition the density development depends on the available neutral gas reservoir. Modelling of particle transport indicates that the temporal development of the density profiles can be reproduced assuming only a reduction in the edge diffusion coefficient. The influence of magnetic perturbation coils on the L–H transition power threshold strongly increases with density above a Greenwald factor of about 0.6.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.