Reduction of radiation-enhanced sublimation of graphite under high flux beam irradiation

Abstract

Radiation-enhanced sublimation (RES) of isotropic graphite was studied under high flux beam irradiation. Irradiation was performed with a 5 keV Ar beam with a maximum flux of 1.5 × 10 21 m −2 s −1, about two orders of magnitude higher than that of previous beam experiments. It is found that the total erosion yield of isotropic graphite at 1980 K under high flux conditions of 1 × 10 21 m −2 s −1 is reduced to a value of about 3 in comparison with a yield of 5.9 under low flux conditions of 3.5 × 10 19 m −2 s −1. The dependence of the RES yield (total yield subtracted by physical sputtering yield) on the flux φ ( φ > 1 × 10 20 m −2 s −1) is as φ −0.26, which is much stronger than that obtained in the low flux region ( φ −0.07, φ < 1 × 10 19 m −2 s −1). The RES model based on diffusion and annihilation of C self-interstitials including stable defects for the sinks of interstitials is discussed in terms of the flux dependence of RES yield.