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 &nmacr;e up to 4 10[SUP20]m[SUP-3], edge radiation levels up to 90%, and partial plasma detachment at the divertor targets can be simultaneously realized. [ABSTRACT FROM AUTHOR]