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P: Fachverband Plasmaphysik

P 19: Poster II

P 19.23: Poster

Thursday, March 31, 2022, 16:00–17:30, P

Characterization and driving mechanisms of dominant Alfvén eigenmodes at the Wendelstein 7-X Stellarator — •S. Vaz Mendes, K. Rahbarnia, C. Slaby, H. Thomsen, J. Schilling, C. Brandt, M. Borchardt, R. Kleiber, A. Könies, and Wendelstein 7-X Team — Max-Planck-Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany

Alfvén waves are often present in different scenarios of the Wendelstein 7-X stellarator plasmas. Magnetic fluctuations were observed during 727 discharges with different magnetic configurations, heating scenarios and variations of further plasma parameters. The measurements were performed using a system of 41 Mirnov coils, located in half-module 11 of W7-X. The correlation of the observed Alfvénic activity with different plasma parameters is investigated. With increasing heating power the fluctuation bands in the frequency spectra (between 100-450kHz) and associated mode spectra become broader with poloidal mode numbers ||m|| ≤ 5. In addition, the overall amplitudes of the different Alfvénic fluctuations in this range increases with higher plasma energy. To better understand the conditions for enhanced Alfvénic activity at W7-X possible driving mechanisms are discussed. A possible candidate is plasma turbulence. Magnetic fluctuation levels are compared to turbulent activity, observed for e.g. in density fluctuations.