Inter-ELM Ion Transport in the ASDEX Upgrade Far Scrape-Off Layer



New measurements of ion transport in the scrape-off layer (SOL) during inter-ELM periods are obtained from a retarding field analyzer (RFA) in the ASDEX Upgrade tokamak. The ion current density measured in the far SOL features large-amplitude bursts associated with turbulent plasma filaments passing the RFA. These filaments convect plasma to the wall with larger density than the background plasma density. The ions in the filament also have higher impact energies than the background ion impact energies. These observations indicate that a filament-wall interaction can lead to erosion of the first wall in the burning plasma tokamaks such as ITER (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)