Göttingen 2025 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
P: Fachverband Plasmaphysik
P 5: Magnetic Confinment Fusion/HEPP III
P 5.1: Hauptvortrag
Dienstag, 1. April 2025, 11:00–11:30, ZHG102
Mode activity at the Wendelstein 7-X stellarator - Turbulence driven Alfvén modes — •S. Vaz Mendes1, K. Rahbarnia1, H. Thomsen1, C. Büschel1, J. Riemann1, C. Slaby1, R. Kleiber1, A. Könies1, M. Borchardt1, J.P. Bähner2, A. von Stechow1, and Wendelstein 7-X Team1 — 1Max-Planck-Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany — 2MIT Plasma Science and Fusion Center, MA 02139, USA
In the optimized stellarator Wendelstein 7-X, magnetic fluctuation measurements reveal the excitation of Alfvén eigenmodes (AEs) in electron cyclotron resonance heated plasmas, despite the absence of a normal fast-particle driving source. This work presents an explanation for AE excitation via ion-temperature-gradient (ITG) turbulence. The detected AEs (Mirnov-measurements) in the range 50 < f < 450 kHz are consistent with ellipticity, toroidicity, and non-circularity induced AEs. Density fluctuations (Phase Contrast Imaging measurements) indicated dominant ITG turbulence in these plasmas. The amplitudes of AEs and density fluctuations show a correlation for different magnetic field configurations. Moreover, in turbulence-reduced regimes, caused by peaking of the density profile via pellet injection, a reduction in the AE amplitude is found. Non-linear gyrokinetic simulations using the EUTERPE code revealed simultaneous excitation of zonal flow activity and generation of AEs driven by ITG turbulence. They also show that ITG modes are necessary to excite AEs above their initial low level.
Keywords: Plasma Physics; Magnetohydrodynamics; Electromagnetic fluctuations; Alfvén waves; Turbulence driven waves