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P: Fachverband Plasmaphysik
P 4: Magnetic Confinement II
P 4.1: Invited Talk
Tuesday, August 31, 2021, 11:00–11:30, H5
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
The presentation intends to give an overview on mode and turbulence phenomena observed in the plasma edge, island divertor and scrape-off layer (SOL) at the stellarator W7-X. This region is investigated by a suit of probe heads measuring profile properties as well as characterizing turbulence in the SOL and island region. In the shear layer those measurements are continued by poloidal correlation reflectometry. Measurements of quasi coherent modes are reported in the shear layer located in the plasma edge. Furthermore a low frequency mode in plasmas with an edge iota of ι=1 are observed which show a modulation of the plasma flow as well.
During scans of the edge iota, plasmas with an increased diamagnetic energy due to variations in the positioning of the 5/5 island chain gained large interest. In these plasmas a low frequency modulation of the plasma rotation is observed, interrupted by fast events in the plasma current. Transient high frequency events in the range of 800 kHz−1000 kHz precede the observation of spikes in the plasma current signal.