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arXiv · 2512.15588

Impact of magnetic islands on plasma flow and turbulence in W7-X

T. Estrada·E. Maragkoudakis·D. Carralero·T. Windisch·J. L Velasco·C. Killer·T. Andreeva·J. Geiger·A. Dinklage·A. Krämer-Flecken·G. A. Wurden·M. Beurskens·S. Bozhenkov·H. Damm·G. Fuchert·E. Pasch
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Abstract

The effect of magnetic islands on plasma flow and turbulence has been experimentally investigated in the stellarator W7-X. Magnetic configurations with the 5/5 magnetic island positioned at the plasma edge, inside the last closed flux surface, are studied. The main diagnostic used in the present work is a V-band Doppler reflectometer that allows the measurement of the perpendicular plasma flow and density fluctuations with good spatial resolution. A characteristic signature of the 5/5 magnetic island is clearly detected in the perpendicular flow profile. The comparison of the experimental flow and the neoclassically driven $E\times B$ flow indicates that the island contribution to the flow is maximum at the island boundaries and close to zero at the island O-point. Besides, a reduction in the density fluctuation level is found nearby the island O-point. The similarities between these observations and those found in other devices and in gyrokinetic simulations are discussed.

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T. Estrada, E. Maragkoudakis, D. Carralero, T. Windisch, J. L Velasco, C. Killer, T. Andreeva, J. Geiger, A. Dinklage, A. Krämer-Flecken, G. A. Wurden, M. Beurskens, S. Bozhenkov, H. Damm, G. Fuchert, E. Pasch. 2025-12-17. Impact of magnetic islands on plasma flow and turbulence in W7-X. https://doi.org/10.1088/1741-4326%2Fac146f

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