Relative efficiencies of different ions for producing freely migrating defects

In situ experimental measurements of radiation-induced segregation rates in a Ni--12.7 at. % Si alloy during irradiation at temperatures from 350 to 650 0C with several different ions are reported. A simple analytical model is used to extract the relative efficiency of each ion for producing freely migrating defects, i.e., those defects which are free to induce microstructural changes. A strong decrease in efficiency is observed with increasing ion mass. Irradiations producing average recoil energies of 1.8, 2.7, 51, and 74 keV are only 48%, 37%, 8%, and <2% as efficient, respectively, at introducing defects which are free to migrate long distances as an irradiation with a weighted average recoil energy of 730 eV. The results are compared to measurements of defect production efficiencies obtained by other techniques