Study of defect production in neutron irradiated Cu, Ni and Pb using positron annihilation spectroscopy (PAS)

Abstract

Abstract The study of radiation damage by neutrons is important for nuclear reactors and space programs. Doppler broadening is an important technique of Positron Annihilation Spectroscopy (PAS) for the measurement of defect production by neutrons of energy range up to 10 MeV. Doppler broadening in PAS spectra of elements Cu, Ni, and Pb has been carried out using High Purity Germanium (HPGe) detector. A 5.0 Ci Am(Be) neutron source has been used for irradiation of the samples. The available neutron flux at the irradiated position was 3.3 × 105n/cm2/sec. These samples have been irradiated for different time periods ranging from 35 days to 264 days to obtain different neutron fluence. A positron source Na22 of strength 35 mCi was used for PAS. The S and W parameters for Doppler Broadening have been calculated using SP-11 software. Scanning Electron Microscope (SEM) pictures of the samples at different irradiation state have taken for the study of surface morphology of these materials. SEM measurements of the surface of the samples show substantial changes after the irradiation. The electric resistance of these materials, for different periods of neutron irradiation, has also been measured to verify the results. This study shows that the production of defects increases with the neutron dose.