Single crystals were bombarded with triple (0.25MeV H+, 0.6MeV He+, 2.4MeV O2+) ion beams, dual (0.25MeV H+, 1.3MeV O+) ion beams or single ion beams (1.3MeV O+ bombardment followed by 0.25MeV H+ bombardment) at 650C. In specimens which had been bombarded with a triple beam to a peak dose of 3.7dpa, dislocation loops were found to be distributed, from regions very close to the surface, down to a depth of 1.8. Cavities formed at depths ranging from 1.2 to 1.75. Dislocation loops and cavities were not observed in specimens which had been bombarded using dual beams. However, optical absorption spectroscopic studies of such specimens revealed a significant increase in the intensity of the absorption bands that were due to F and F+ centers. This indicated the production of O vacancies by the bombardment. In the case of specimens which had been subjected to O+ bombardment followed by H+ bombardment, no increase occurred in the intensity of absorption bands, although dense dislocation loops formed at depths that were close to the projected ranges of each of incident ion beams.

Y.Katano, T.Nakazawa, D.Yamaki, T.Aruga, K.Hojou, K.Noda: Nuclear Instruments and Methods in Physics Research B, 1996, 116[1-4], 230-4