Study of DIII-D tungsten erosion processes by using a carbon–tungsten mixed material model

Abstract

The tungsten erosion process for an H-mode discharge from the DIII-D Metal Rings Campaign is modeled using OEDGE and TRIM.SP. The OEDGE code is employed to calculate tungsten erosion between edge-localized modes (ELMs). Then a newly developed semi-analytical carbon–tungsten mixed material model based on TRIM.SP is used to simulate the intra-ELM tungsten gross erosion profiles. The tungsten erosion is found to be dominated by carbon, with different origin for carbon between ELMs and during ELMs. For inter-ELM, the tungsten is mainly eroded by locally redeposited low charge state carbon, while for intra-ELM, the C6+ originated from the pedestal region is found to dominate the tungsten erosion in the near separatrix region, whereas the locally redeposited low charge state C fluxes lead to a nonnegligible tungsten erosion in the outer SOL region. These results suggest that modeling of W erosion during ELMs needs to include impurity transport from the pedestal to the divertor during an ELM. In addition, for both inter- and intra-ELM simulation, a carbon coverage of 30% on the tungsten surface is needed to reproduce the measured erosion at the divertor target. Keywords: Plasma material interaction, Tungsten, Carbon, Erosion