Abstract
Copper samples have been irradiated with protons in the energy range 4.5 to 25 MeV. The resulting damage effects in the copper have been studied with the positron-lifetime measurement. Evidence that the surviving defects are vacancylike is presented. The dependence of the defect production rate on proton energy and on irradiation temperature suggest that the defect production depends on more than one mechanism, one of which occurs only when the copper recoil energy is above a threshold of about 55 keV.