POSITRON ANNIHILATION IN A NEUTRON IRRADIATED α-Al_2O_3 SINGLE CRYSTAL

摘要

The positron lifetime spectra and the angular correlation of annihilation radiation (ACAR) in neutron-irradiated α-Al_2O_3 single crystal were measured after isochronal annealing at temperatures ranging between 540K and 1560K (lifetime) and between 900K and 1825K (ACAR). The annealing behavior of the positronium component in the ACAR was studied by applying static magnetic fields. The width of the positronium momentum distribution shows the growth of the voids. The void radius calculated from the width was compared with the value estimated by using high resolution transmission electron microscopy.