EMC3-Eirene simulations of the spatial dependence of the tungsten divertor retention in ASDEX Upgrade

Abstract

The Edge Monte Carlo 3D (EMC3)-Eirene code package is applied to simulate the deuterium plasma and neutral particle as well as the tungsten impurity transport in ASDEX Upgrade. Good agreement is found for the deuterium bulk plasma for an L-mode discharge both in the upstream and downstream profiles. The tungsten concentration in the core is computed for a point source placed at different positions around the outer strike point. Comparing the mean impurity residence time for divertor and main chamber sources yields the divertor retention factor R, which shows a very strong dependence on the location of the source relative to the strike point and also on the discharge parameters. While the tungsten transport is strongly suppressed directly at the strike point, it becomes much more efficient in the region 20-100mm away from it in the far scrape-off layer.