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P: Fachverband Plasmaphysik

P 9: Poster I

P 9.28: Poster

Dienstag, 29. März 2022, 16:00–17:30, P

Identification of multiple mode contributions in tomography data from soft X-ray diagnostics — •Henning Thomsen, Christian Brandt, Rene Bussiahn, Sara Vaz Mendes, Kian Rahbarnia, Jonathan Schilling, Thomas Wegner, and W7-X Team — MPI f. Plasmaphysics, 17491 Greifswald

External actuators like impurity injection, density or temperature modulation as well as current drive affect the stability properties of the plasma equilibrium in the Wendelstein 7-X stellarator. The dynamics on the soft X-ray radiation distribution in a poloidal plane is studied by the soft-X ray tomography system XMCTS [1], which measures in the energy range 1-12 keV. The radiation in this energy range originates mainly from Bremsstrahlung of the confined plasma and line radiation from impurity species. In different experiments with impurity injection, a dominant m=1 mode with frequencies in the range of 1-2 kHz has been observed. An analysis of dominant modes is possible with a singular value decomposition. While the dynamics associated with sucb low-frequency modes can often be reconstructed in the tomograms, higher frequency components visible in the line-integrated raw data typically do not show up in the tomographically reconstructed time series. In this contribution the possible reasons and different analysis approaches are discussed.

[1] C Brandt et al Plasma Phys. Control. Fusion 62 (2020) 035010