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arXiv · 2306.03694

Enhanced transport at high plasma pressure and sub-threshold kinetic ballooning modes in Wendelstein 7-X

P. Mulholland·K. Aleynikova·B. J. Faber·M. J. Pueschel·J. H. E. Proll·C. C. Hegna·P. W. Terry·C. Nührenberg
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Abstract

High-performance fusion plasmas, requiring high pressure $\beta$, are not well-understood in stellarator-type experiments. Here, the effect of $\beta$ on ion-temperature-gradient-driven (ITG) turbulence is studied in Wendelstein 7-X (W7-X), showing that subdominant kinetic ballooning modes (KBMs) are unstable well below the ideal MHD threshold and get strongly excited in the turbulence. By zonal-flow erosion, these sub-threshold KBMs (stKBMs) affect ITG saturation and enable higher heat fluxes. Controlling stKBMs will be essential to allow W7-X and future stellarators to achieve maximum performance.

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P. Mulholland, K. Aleynikova, B. J. Faber, M. J. Pueschel, J. H. E. Proll, C. C. Hegna, P. W. Terry, C. Nührenberg. 2023-06-06. Enhanced transport at high plasma pressure and sub-threshold kinetic ballooning modes in Wendelstein 7-X. https://arxiv.org/abs/2306.03694

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