Effects of background gas impurities during D+ irradiation on D trapping in single crystal tungsten

The level of impurities in the background gas during 500 eV D+ irradiation was found to influence D trapping in single crystal tungsten. Reduced D retention levels were observed for lower partial pressures of impurity gases during irradiation. D+ irradiations created near-surface peaks in the C and O depth distributions; the peak magnitudes depended on the background gas impurity levels. It is proposed that the recoil implantation of carbon and oxygen impurities arriving at the surface created vacancies in tungsten, thereby increasing D trapping.