Hannover 2020 – scientific programme
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P: Fachverband Plasmaphysik
P 21: Helmholtz Graduate School 5
P 21.1: Invited Talk
Thursday, March 12, 2020, 14:00–14:30, b305
Overview on turbulence in the shear- and scrape-off layer at W7-X — •Andreas Krämer-Flecken1, Olaf Grulke2, Xiang Han1, Carsten Killer2, Elisee Trier3, Thomas Windisch2, and Haoming Xiang1 — 1Institut für Energie- und Klimaforschung, Forschungszentrum Jülich, 52425 Jülich — 2MPI für Plasmaphysik, Teilinstitut Greifswald, 17491 Greifswald — 3MPI für Plasmaphysik, Teilinstitut Garching, 85748 Garching
For the investigation of turbulence activity in the shear- and scrape-off layer (SOL) of W7-X different diagnostics are used. Probe heads yield information on density- and temperature profiles and on turbulence rotation and radial electric field. Deeply in the SOL and the plasma edge correlation reflectometry measures turbulence spectra and the poloidal correlation length of dominant low k-turbulence.
The presentation intends to give an overview on turbulence phenomena at W7-X as there are e.g. quasi coherent modes which are observed close to the shear layer in the plasma edge. A decomposition of the coherence spectra allows to characterize them by a few turbulence components, only. Broad band turbulence extracted from those spectra is strongly suppressed in the vicinity of the shear layer supporting that low k-turbulence is torn apart in the shear region.
Furthermore, transient high frequency events in the range of 800 kHz - 1000 kHz are observed for certain magnetic configurations in the coherence spectra. They correlate with the observation of spikes in the diamagnetic energy and the plasma current.