Modeling the reduction of gross lithium erosion observed under high-flux deuterium bombardment

Abstract

Both thin (<1μm) and thick (∼500μm) lithium films under high-flux deuterium and neon plasma bombardment were studied in the linear plasma device Magnum-PSI at ion fluxes >1024m−2s−1 and surface temperatures <700°C. During Ne plasma exposures, Li erosion rates inferred from measurements of Li–I radiation exceed Langmuir Law evaporation, but no previous results exist to benchmark the binary collision approximation (BCA) and thermal sputtering measurements. Measured Li erosion rates during D plasma bombardment were compared to the adatom-evaporation model of thermal sputtering with an additional reduction term to account for the relative D/Li composition of the Li film. This model captures the qualitative evolution of the Li erosion yield but still overestimates the measured erosion by a factor of 5–10. This suggests that additional refinements to the mixed-material model are needed.