High recycling outer divertor regimes after type-I ELMs at high density in ASDEX Upgrade

Experiments have been conducted in SNL type-I ELMy H-mode on ASDEX Upgrade. Depending on the upstream conditions in the Scrape-off-layer and core plasma, different temporal evolutions of the plasma regime in the outer divertor are identified during the recovery period following an ELM. The divertor plasma is characterized using experimental measurements such as line radiation (Dα, CIII), spatially resolved thermography (IR) and fixed Langmuir probes (LP). Whilst in one case a first clear temporal peak in line radiation (Dα, CIII) as well as power (IR) and particle fluxes (LP) onto the outer divertor plate is followed by a quiescent inter-ELM phase, in the other case this initial peak is followed by a broader temporal peak in all but the IR and CIII signals. A possible explanation based on simple analytic considerations is presented.