Coincidence Doppler Broadening of Positron Annihilation Radiation for Detection of Helium in Irradiated Ni and Cu

A new composition analysis method, namely, coincidence Doppler broadening (CDB) of positron annihilation radiation, was employed to detect He atoms in ion irradiated Ni and neutron irradiated Cu. The results of positron lifetime and transmission electron microscopy (TEM) show that microvoids and voids were formed in ion-irradiated Ni and neutron-irradiated Cu, respectively. The results of CDB measurements indicate that He atoms were present in the microvoids and voids, even in microvoids annealed at 1273 K in ion-irradiated Ni. Coincidence Doppler broadening measurement, which is a nondestructive technique for testing materials, is effective for detecting He atoms.