Production of point defects in 14.8 MeV neutron-irradiated MgO

High-purity MgO crystals grown at ORNL have been irradiated in the LLL 14.8 MeV Rotating Target Neutron Source (RTNS) to doses varying from 1.8 x 1015 to 5.7 x 1017 n/cm2. The optical absorption spectra of these crystals resembled those irradiated in fission reactors and exhibited bands principally at 4.95, 3.5, 2.2 and 1.3 eV. The band with the largest absorption coefficient, that at 4.95 eV, is due to anion vacancies. The bands at 3.5 and 1.3 eV, attended by zero-phonon lines at 3.430 and 1.187 eV respectively, have been attributed to different optical transitions of anion divacancies. Investigation results indicate that the net production rates of the point defects resulting from irradiations with 14.8 MeV neutrons are about twice those resulting from fission neutrons in the Oak Ridge Reactor (ORR). This ratio is in reasonable accord with theoretical estimates based on damage energy calculations