POSITRON-ANNIHILATION STUDIES OF HEAVY-ION-INDUCED RADIATION DAMAGES IN STAINLESS-STEELS

Variable-energy (0-30 keV) positrons were used to study the depth dist ribution of heavy-ion induced vacancy type defects in the following sp ecimens, SUS304 and SUS316 austenitic stainless steels, a SUS444 ferri tic stainless steel and nickel metal, which were irradiated by 0.5 MeV He+, 2.0 MeV C+, 3.5 MeV Si2+ and 4.0 MeV Ni2+ ions up to 0.01 dpa at peak. Vacancy type effective residual defects (ERD) were evaluated fr om the line shape parameter S of Doppler broadened positron annihilati on photon spectra. With increasing primary knock-on atom (PKA) energy, a decrease of the vacancy type ERD was observed. The ERD differences among the specimens are discussed in comparison with theoretical predi ctions.