Continuous observation of filaments from the confined region to the far scrape-off layer. (December 2020)

• Record Type: Journal Article
• Authors: Griener, M.; Wolfrum, E.; Birkenmeier, G.; Faitsch, M.; Fischer, R.; Fuchert, G.; Gil, L.; Harrer, G.F.; Manz, P.; Wendler, D.; Stroth, U.
• Is Part Of: Nuclear materials and energy. Volume 25(2020)
• Publication Date: 2020-12
• Subjects: Plasma filaments -- Scrape-off layer -- Convective transport -- Quasi-coherent modes -- Confinement regimes -- ELM free regimes -- Helium beam diagnostic; Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2020.100854
• Languages: English
• ISSNs: 2352-1791

Abstract

Abstract: The thermal helium beam diagnostic at ASDEX Upgrade can access the whole plasma edge region simultaneously with a high spatiotemporal resolution. Manifold dynamics of plasma edge transport is observed for different plasma confinement regimes, comprising L- and H-mode scenarios with type-I and small ELMs as well as ELM free EDA regimes. The measurements show that the plasma dynamics in the confined region close to the separatrix is often dominated by regular high frequency modes (10–100 kHz), whereas filaments with an intermittent occurrence rate of 0.1–2 kHz dominate in particular the far scrape-off layer (SOL). The comparison among different regimes shows a similar filamentary activity between L-mode and inter-ELM H-mode phases. An increased filamentary activity in H-mode, however, is found for rising densities n ∕ n GW . This is the case for the regime of quasi continuous exhaust (QCE) with three times higher filament velocities compared to a clean inter-ELM H-mode. Highlights: Manifold dynamics are observed at the plasma edge region of ASDEX Upgrade. The thermal helium beam can access the whole plasma edge region simultaneously with a 3 mm and 900 kHz resolution. Modes are found in the confined region with 10–100 kHz frequency. The scrape-off layer is dominated by intermittent filaments. Comparison of L-mode, H-mode, type-I and small ELMs as well as ELM free EDA regimes.