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P: Fachverband Plasmaphysik

P 16: Poster Session Plasma Physics

P 16.119: Poster

Donnerstag, 19. März 2026, 13:45–15:45, Redoutensaal

Toward the identification of quasi-coherent modes in the Wendelstein 7-X stellarator — •M. C. Kelly, H. Thomsen, C. Brandt, S. V. Mendes, C. Büschel, E. V. Hausten, K. Rahbarnia, and P. Pons-Villalonga for the w7-x team collaboration — Max-Planck-Institut für Plasmaphysik, Wendelsteinstr. 1, 17491 Greifswald, Germany

In many plasmas on Wendelstein 7-X (W7-X), a persistent, low-frequency mode, typically in the 10-20 kHz range, can be observed in soft X-ray diagnostic signals. Due to their broad spectral features and longevity, these fluctuations are being investigated as quasi-coherent modes (QCMs), which are non-monochromatic yet structured modes, which are also routinely observed in tokamaks. This work aims to characterize such modes on W7-X in different magnetic configurations and plasma scenarios. Analysis techniques include Fourier transform spectrograms from individual signals, tomographic reconstruction methods such as minimum Fisher and Gauss Process tomography from all usable diode signals, as well as correlation with plasma parameters and data from other plasma diagnostics (Electron Cyclotron Resonance Heating power, Neutral Beam Injection power, and Thomson scattering measurements of electron temperature and density) are employed. The goal is to identify the driving mechanism of the QCMs by analyzing their spatial structure and dynamical behavior and assess their role in transport and plasma stability.

Keywords: Stellarator; Wendelstein 7-X; MHD stability; Quasi-coherent modes; Soft x-ray tomography