Erlangen 2026 – scientific programme

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P: Fachverband Plasmaphysik

P 11: Magnetic Confinement IV

P 11.3: Talk

Wednesday, March 18, 2026, 14:45–15:10, KH 02.016

Mode activity during high plasma beta at the Wendelstein 7-X stellarator — •Charlotte Büschel, Christian Brandt, Henning Thomsen, Ksenia Aleynikova, Kian Rahbarnia, Edith Victoria Hausten, Martin Clifton Kelly, Sara Vaz Mendes, Pedro Pons Villalonga, Kai-Jakob Brunner, Golo Fuchter, Jens Knauer, Ekkehardt Pasch, Andreas Langenberg, and W7-X Team — IPP Greifswald, Greifswald, Germany

During the last two campaigns of Wendelstein 7-X, starting in October 2024 and lasting until May 2025, high plasma β was achieved in three different plasma scenarios: injection of frozen hydrogen pellets, a combined heating scenario of NBI and ECRH, and operation at reduced magnetic field around 1.8 T. Averaged plasma β values up to ⟨ β ⟩ = 3 % and core beta values of β₀=8.5 % were reached. This contribution categorizes the different types of mode activity observed at high plasma β and focuses on the characterization of quasi-coherent modes in a frequency range of f=20−60 kHz. The mode analysis is based on the line-integrated photodiode signals from the soft X-ray multi-camera system installed in Wendelstein 7-X utilizing the high spatial and temporal resolution of 360 photodiodes arranged in one poloidal plane of the plasma. The analysis includes the determination of the poloidal mode number, the ballooning character, the radial location and the propagation direction of the mode. The mode characteristics are analyzed with respect to their correlations to general plasma parameters such as temperature, density and confinement time.

Keywords: Soft X-ray multi-camera tomographic system; Mode analysis; High plasma beta; Tomographic reconstruction; Coherent mode activity