München 2019 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 7: Helmholtz Graduate School II - Magnetic Confinement I
P 7.5: Vortrag
Montag, 18. März 2019, 18:15–18:30, HS 21
Influence of magnetic islands on plasma profiles and dynamics in the Scrape-Off-Layer of Wendelstein 7-X — •Carsten Killer1, Olaf Grulke1,2, Philipp Drews3, Alexander Knieps3, Dirk Nicolai3, Guruparan Satheeswaran3, and W7-X Team1 — 1Max-Planck-Institute for Plasma Physics, Greifswald, Germany — 2Department of Physics, Technical University of Denmark, Lyngby, Denmark — 3IEK4-Plasmaphysik, Forschungszentrum Jülich, Germany
The W7-X divertor concept employs large resonant magnetic islands at the plasma edge to control the heat and particle fluxes to the divertor. Using reciprocating probe measurements, we show that the presence and particular topology of magnetic islands significantly affects the Scrape-Off Layer (SOL) profiles of electron temperature, density and electric field, as well as the fluctuation characteristics, turbulence-induced radial transport, and plasma flows. These quantities are explored in different magnetic configurations and the role of central plasma heating and fuelling is discussed.
As a key result, we report on particularly broad SOL temperature and density profiles in the presence of magnetic islands, resulting in very large effective SOL widths up to 5 cm (with a strongly non-exponential profile shape) which is favourable as it results in a broader heat flux distribution on the divertor. In these situations, the islands can feature a local minimum of the plasma potential accompanied by a direction reversal of E× B driven dynamics, indicating that the islands with connection lengths of a few 100 m can act as plasma confining regions.