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15th International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI 15), Gifu, 2002-05-26 to 2002-05-31
Abstract:
A promising new operational regime on the Wendelstein stellarator W7-AS has been discovered,
fulfilling the conditions of optimal core behavior in combination with edge parameters suitable for
successful divertor scenarios. This regime, the high density H-mode (HDH), displays no
systematically evident mode activity, and is edge localized mode (ELM)-free. It is extant above a
power-dependent 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-stationary discharges with line-averaged densities ne to
4×10²⁰ m⁻³, radiation levels to 90%, and partial plasma detachment at the divertor target plates can
be simultaneously realized. Energy confinement is up to twice that predicted by a conventional
scaling. HDH has been attained for both H⁺ and D⁺ plasmas. The development of plasma energy as
a function of density shows an isotopic dependence.
