Göttingen 2025 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 5: Magnetic Confinment Fusion/HEPP III
P 5.2: Vortrag
Dienstag, 1. April 2025, 11:30–11:55, ZHG102
Characterization of low frequency electromagnetic modes in the W7-X core and scrape-off layer plasma — •Dario Cipciar1, Carsten Killer1, Jiri Adamek2, Kian Rahbarnia1, Christian Brandt1, Olaf Grulke1,3, Neha Chaudhary1, Henning Thomsen1, and W7-X Team1 — 1Max-Planck-Institut fur Plasmaphysik, Wendelsteinstr. 1, 17491 Greifswald, Deutschland — 2Institute of Plasma Physics of the CAS, U Slovanky 2525/1a, 18200 Prague 8, Czech Republic — 3Department of Physics, Technical University of Denmark, Lyngby, Denmark
Global low-frequency electromagnetic oscillations of m=1 type are often observed in the Wendelstein 7-X stellarator. These modes significantly modulate the plasma stored energy and can appear as harmonic oscillations or as intermittent bursts, depending on the magnetic configuration. The bursty mode activity occurs in scenarios with large stationary magnetic islands just inside the last closed flux surface. In this case, a particularly strong effect on the plasma confinement is observed, via the effect of bursts on the density gradient and a gradient-associated temporary suppression of cross-field losses. Further, both continuous and bursty mode activity is observed in the Scrape-Off Layer using electric probes. The fluctuations of the poloidal electric field, electron temperature and density is captured using an array of Langmuir and ball-pen probes and used to calculate the perpendicular transport parameters. A Ball-pen probe in a swept regime (20 kHz) is used to measure the fluctuations of ion temperature, crucial for the material sputtering of the first wall due to transiently high Ti.
Keywords: cross-field transport; ball-pen probe; MHD modes; magnetic islands; ILMs