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P: Fachverband Plasmaphysik

P 10: Poster Session I

P 10.43: Poster

Dienstag, 1. April 2025, 16:15–18:15, ZHG Foyer 1. OG

A new method to characterize instabilities in fusion plasmas using the soft x-ray multicamera system at Wendelstein 7- X — •Charlotte Büschel, Christian Brandt, Henning Thomsen, Kian Rahbarnia, Sara Vaz Mendes, Edith Victoria Hausten, and Wendelstein 7-X Team — Max Planck Institute for Plasma Physics, Greifswald, Germany

Soft x-ray tomography is widely used in fusion experiments for the reconstruction of two-dimensional density profiles. The soft x-ray multi-camera tomography system (XMCTS) installed in Wendelstein 7-X consists of 20 pinhole cameras [C. Brandt et al. 2020]. Each camera has 18 photodiodes, measuring the line-integrated soft x-ray emissivity of the plasma. As the emissivity is strongly related to the plasma density, the fluctuating part of the signal can be used to analyze instabilities propagating in the plasma. Electrostatic and electromagnetic instabilities affect the particle and energy transport within a plasma and are one of the main reasons for particle and energy losses. To control or even prevent instabilities, their characterization regarding amplitude, frequency, radial location, poloidal structure and propagation direction is important. A new method has been developed to analyze the 360 line-integrated signals of the photodiodes to determine the radial location and the poloidal structure of instabilities with poloidal mode numbers up to m=20. The workflow of the analysis is presented based on artificial data.

Keywords: Soft x-ray tomography; Wendelstein 7-X; plasma instabilities; mode analysis; estimation of poloidal mode number