低エネルギーカーボンスパッタリングに関するXe蓄積効果 (イオン加速グリッド耐久認定用数値解析 JIEDI(JAXA Ion Engine Development Initiatives) ツールの研究開発ワークショップ論文集)

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The sputtering yields of carbon have been measured during xenon ion bombardment under the threshold energy predicted by the theory at normal incidence. The theoretical threshold energy is 160.84 eV for the xenon.carbon combination. These experimental results are different from the semi-empirical formula proposed by Yamamura and Tawara. We have calculated the sputtering yields of carbon under the xenon ion bombardment with a Monte Carlo code ACAT which is based on the binary collision approximation. The yields of carbon calculated with ACAT are in good agreement with the semi-empirical formula, but differ from the experiments under low-energy xenon bombardment. This discrepancy is believed to be due to the accumulation of xenon onto graphite. The semi-empirical formula and the above ACAT results do not consider this accumulation. In order to quantify this effect, we have calculated with ACAT for the carbon.xenon composite material as a function of xenon concentration. The results of ACAT with 14% xenon atoms in graphite are in good agreement with the experimental data.