The accumulation of vacancy-type defects, produced by ion irradiation at room temperature, was investigated by using positron beam Doppler broadening techniques. Various ions (He, C, O, Fe) were used to investigate the effect of the primary knock-on energy upon vacancy-type defect production. The accumulation of vacancy-type defects led to sharpening of the Doppler broadening spectra (increase in S-parameter). The latter was measured as a function of the ion fluence, for various ion species, at a fixed positron energy of 15keV. In the early stages of irradiation, the S parameter increased with increasing fluence and reached a saturated S-parameter value that varied with the ion species. The saturated S-parameter values tended to be higher for heavier-ion irradiation. When compared with the incremental change in S-parameter, at the same low dpa level, heavier ions also led to a greater change.

Vacancy-Type Defect Production in Iron under Ion Beam Irradiation Investigated with Positron Beam Doppler Broadening Technique. T.Iwai, Y.Ito, M.Koshimizu: Journal of Nuclear Materials, 2004, 329-333[2], 963-6