Self-consistent, integrated erosion and redeposition modeling of tungsten carbide and silicon carbide walls in DIII-D

We simulated the response of WC and SiC walls to DIII-D plasma discharges and calculated fluxes of generated impurities depending on plasma properties and electric fields. Time-dependent, multi-species modeling predicted the effects of redeposition, preferential sputtering, and intrinsic impurities on surface enrichment in W or in Si and on erosion or buildup of deposited material layers. Our calculations for the conditions of graphite-free walls showed that fast enrichment of W in WC compound results in near full suppression of W erosion and three orders of magnitude reduction of C impurity from the divertor in comparison with a graphite wall environment where C and W erosion does not decrease with time. This is different from the response of SiC where surface enrichment in Si leads to reduction in C erosion, however Si erosion increases in strongly attached plasma conditions. These detailed 3D models of particle interactions and transport in materials subsurface and in plasma above the surface were recently developed and integrated into a single package, ITMC+, for the first time. These models enable self-consistent analysis of time- and space- dependent changes in material surfaces and their effect on material erosion/redeposition and potential plasma contamination in fusion devices.