A Systematic Study of the Quasi-Coherent Mode in the High Density H-Mode Regime of Wendelstein 7-AS

The High Density H-mode (HDH) is a highly promising ELM-free H-mode on the Wendelstein 7-AS (W7-AS) stellarator exhibiting no impurity accumulation. As future fusion-oriented stellarator devices need to run at high densities, a regime often susceptible to impurity accumulation in the standard H-mode...

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Bibliographic Details
Main Authors: Belonohy, E, Pokol, G, McCormick, K, Papp, G, Zoletnik, S
Format: Conference Proceeding
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
DIVERTORS
EDGE LOCALIZED MODES
FREQUENCY MODULATION
H-MODE PLASMA CONFINEMENT
PLASMA DENSITY
PLASMA IMPURITIES
TOKAMAK DEVICES
WENDELSTEIN-7 STELLARATOR
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Summary:The High Density H-mode (HDH) is a highly promising ELM-free H-mode on the Wendelstein 7-AS (W7-AS) stellarator exhibiting no impurity accumulation. As future fusion-oriented stellarator devices need to run at high densities, a regime often susceptible to impurity accumulation in the standard H-modes of W7-AS, the HDH is of particular interest. The mechanism responsible for the reduced impurity concentration is still undetected and remains a central question in understanding this H-mode. Preliminary results are presented on a possible candidate, a Quasi-Coherent (QC) mode sometimes observed in the HDH regime. The properties of this mode, such as its frequency modulation, frequency and amplitude dependences are discussed as well as its universality with a viewpoint to its possible role in the HDH physics.
ISSN:0094-243X
1551-7616
DOI:10.1063/1.2909159