Impact of magnetic islands on plasma flow and turbulence in W7-X. (29th July 2021)

• Record Type: Journal Article
• Authors: Estrada, T.; Maragkoudakis, E.; Carralero, D.; Windisch, T.; Velasco, J.L; Killer, C.; Andreeva, T.; Geiger, J.; Dinklage, A.; Krämer-Flecken, A.; Wurden, G.A.; Beurskens, M.; Bozhenkov, S.; Damm, H.; Fuchert, G.; Pasch, E.; the W7-X Team,
• Is Part Of: Nuclear fusion. Volume 61:Number 9(2021)
• Publication Date: 2021-07-29
• Subjects: turbulence and flows -- Stellarators -- magnetic islands -- Doppler reflectometry; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ac146f
• Languages: English
• ISSNs: 0029-5515

Abstract

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 × 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.