Island divertor experiments on the Wendelstein 7-AS stellarator
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چکیده
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 energyand 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 10 m , 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 Hþ and Dþ plasmas. The development of plasma energy as a function of density shows an isotopic dependence. 2003 Elsevier Science B.V. All rights reserved.
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تاریخ انتشار 2003