Gas release from first wall coatings under electron impact

Wall coatings produced for JET (TiC, SiC, TiO2, MgAl2O4, Al2O3, and Si on Inconel 600) and coatings produced by General Atomic for Doublet III, PDX, and TFTR (TiC and C–SiC on POCO graphite) were subjected to low energy (300 eV) electron bombardment and the release of various gas species were monitored. Virgin samples, samples baked for various periods at various temperatures, and samples exposed to air after baking are compared. Release rates for hydrogen and methane span the ranges 10−1 to 10−3 H2/e− and 10−2 to <10−4 CH4/e−, respectively. X‐ray diffraction analysis was performed on coatings of TiC and SiC on Inconel (JET) and TiC and C–SiC on POCO graphite (GA) samples. This analysis indicates that the stoichiometry of the coating material may depend on the coating process.