Progress in understanding the physics of the H-mode pedestal and ELM dynamics

摘要

The recent progress in the experimental characterization of pedestal and ELM dynamics as well as in the insight into pedestal width scaling is reviewed. Various width scaling experiments from many devices indicate that the pedestal width scales weakly with the normalized ion Larmor radius and with the square root of the pedestal poloidal beta. The ELM onset in type I ELMy H-modes is consistently understood as an MHD stability limit on the maximum achievable edge pressure gradient. These results provide a prediction for the pedestal height in ITER. Time resolved measurements of pedestal parameters during the ELM cycle from various machines present a consistent picture of the pedestal dynamics, providing strong tests for pedestal models. Despite growing efforts in pedestal transport modelling, there is no consensus to date on what transport mechanism may explain the residual electron heat transport in the pedestal. As far as particle transport is concerned, a strong particle pinch may offset strong particle diffusion in the edge pedestal. Recent experiments have expanded the operational domains of the grassy ELM and QH-mode regimes and are consistent with predictions of the peeling-ballooning model.