Mechanism of chemical sputtering of graphite under high flux deuterium bombardment

Chemical sputtering of graphite materials (isotropic graphite and carbon fiber composite) was studied by irradiation of 5 keV D3+ beam with a flux up to 4×1021 m−2 s−1, which is more than one order magnitude higher than previous low flux beam experiments (<1020 m−2 s−1). The chemical sputtering yield was obtained from measurements of the released methane signal with a quadrupole mass analyser. It was found that the methane yield at peak temperatures is almost independent of flux from 5×1020 to 4×1021 m−2 s−1. Peak temperatures range between 900 and 1000 K, which is higher than those of the previous low flux experiments (<900 K, <1020 m−2 s−1). By comparing our experimental results with calculation results based on Rothʹs model, the annealing effect of radiation damage to prevent methyl group formation appears to be unimportant.