Author/Authors :
McCormick، نويسنده , , K. and Grigull، نويسنده , , P. and Burhenn، نويسنده , , R. and Brakel، نويسنده , , R. and Ehmler، نويسنده , , H. Y. Feng، نويسنده , , Y. and Fischer، نويسنده , , R. and Gadelmeier، نويسنده , , F. and Giannone، نويسنده , , L. and Hildebrandt، نويسنده , , D. and Hirsch، نويسنده , , M. and Holzhauer، نويسنده , , E. and Jaenicke، نويسنده , , R. and Kisslinger، نويسنده , , J. and Klinger، نويسنده , , T. and Klose، نويسنده ,
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 n̄e 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.
Keywords :
H-mode , Impurity control , Plasma properties , Stellarator , W7-AS , Island divertor
