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P: Fachverband Plasmaphysik
P 14: Magnetic Confinement IV/HEPP VI
P 14.4: Talk
Thursday, March 23, 2023, 12:20–12:45, CHE/0091
Investigation of driving mechanisms of dominant Alfvén eigenmodes at the Wendelstein 7-X stellarator — •Sara Vaz Mendes1, Kian Rahbarnia1, Henning Thomsen1, Christoph Slaby1, Charlotte Bueschel1, Matthias Borchardt1, Ralf Kleiber1, Axel Könies1, Jan-Peter Bähner2, and Adrian von Stechow1 — 1Max-Planck-Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany — 2MIT Plasma Science and Fusion Center, Cambridge, MA 02139, USA
The basis for characterizing dominant Alfvén mode activity in the Wendelstein 7-X (W7-X) stellarator plasmas is presented with the investigation of possible driving mechanisms. In previous W7-X operational phases, Alfvén mode activity was frequently observed during plasmas operated solely with electron cyclotron resonance heating. A broad range of frequencies is observed in measurements of the fluctuating poloidal magnetic field, Ḃθ. An essential analysis was developed to track the dominant frequency bands (DFBs) from the spectrograms of Ḃθ between f=100−450 kHz. The DFBs studies allowed us to draw novel and integral analyses of the dynamics of Alfvén modes through the entire length of W7-X plasmas. Correlations between the modes dynamics with general plasma parameters are determined, and we present in which plasma conditions the spectral properties of the Alfvén DFBs show relevant changes. The amplitude of the DFBs shows a strong correlation to turbulent density fluctuations measured with the Phase contrast Imaging (PCI) diagnostic in most W7-X regimes.