Amorphization and siliconization of silicon carbide as a first wall material*

Crystalline SiC gets amorphized in contact with L-mode plasma due to accumulation of displacement damages under ion irradiation. Simulations indicate that a time-varying amorphous/crystalline sputtering yield ratio of around 0.2 is needed to explain experimentally measured Si gross erosion rates in the DIII-D divertor. Excellent thermo-mechanical properties, neutron irradiation resistance make SiC a promising first wall material. Although crystalline SiC is preferable, this work cautions that amorphization leads to higher sputtering and 1.5x increase in Si gross erosion. This is of interest with the anticipated DIII-D wall change. We use coupled simulations of the SOL plasma impurity transport code GITR and a mixed-material surface model, which shows that gross erosion is primarily influenced by background plasma and prompt re-deposition affects local impurity migration. Preferential sputtering of C from SiC leads to Si enrichment of about 10% at the end of a 4s high-density L-mode shot, which has implications for core performance. This work is important for understanding SiC behavior when put in contact with fusion plasmas.