Effects of the New Island Divertor on the Plasma Performance in the W7‐AS Stellarator

The island divertor in the W7-AS stellarator enables access to a new NBI-heated, high density operating regime with promising confinement properties. This regime - the High Density H-Mode - displays no evident mode activity,, is extant above a threshold density and characterized by flat density profiles, high energy- and low impurity-confinement times and edge localized radiation. Impurity accumulation, normally associated with ELM-free H-modes, is avoided. Quasi steady-state discharges with (n) over bar (e) up to 4 10(20) m(-3), edge radiation levels up to 90%, and partial plasma detachment at the divertor targets can be simultaneously realized.