Turbulence in the near scrape-off layer towards the L-mode density limit in ASDEX-Upgrade. (October 2022)

• Record Type: Journal Article
• Authors: Grenfell, G.; Manz, P.; Conway, G.D.; Eich, T.; Adamek, J.; Brida, D.; Komm, M.; Nishizawa, T.; Griener, M.; Tal, B.; Stroth, U.
• Is Part Of: Nuclear materials and energy. Volume 33(2022)
• Publication Date: 2022-10
• Subjects: Turbulence -- Scrape-off layer -- Electrostatic probes -- Tokamaks -- Density limit -- Detachment; Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2022.101277
• Languages: English
• ISSNs: 2352-1791

Abstract

Abstract: The L-mode density limit in ASDEX Upgrade is investigated with focus on the scrape-off layer. We observe a chain of events that involves the collapse of the E × B outer shear layer (just outside the separatrix), widening of the electron pressure fall-off length, outer divertor detachment, density shoulder formation, reduction and flattening of the parallel Mach number, and enhanced turbulent cross-field transport. The latter effect was associated with higher amplitude density fluctuations at low frequencies, where the turbulent cross-phase between density and velocity fluctuations pointing radially outward was favourable.