Fast neutron radiation damage in aluminium studied by interstitial trapping at57Co Mossbauer atoms

Abstract

A description is given of Mossbauer studies of interstitial atom trapping at ⁵⁷Co impurities in Al after fast neutron irradiation at 4.6K with doses from 0.2*10¹⁸ n cm^-2. Trapping and detrapping during irradiation and during subsequent isochronal annealing was detected directly by the appearance and development of an additional Mossbauer line due to ⁵⁷Co atoms with trapped interstitials. Simultaneous electrical resistivity measurements on the Mossbauer samples allowed the novel information from the Mossbauer studies to be correlated with the well known annealing stages of the resistivity. The isomer shift of the additional Mossbauer line was +0.42 mm s^-1 relative to ⁵⁷Co on substitutional sites, its small quadrupole splitting was 0.17 mm s^-1. From irradiation dose and annealing temperature dependence it was concluded that trapping starts during irradiation at 4.6K and continues when interstitials are freely mobile (stage I_E). Detrapping occurs by vacancy migration to the trapped interstitials (stage III).