Dose dependence of F-centre production by fast neutrons in magnesium oxide

Abstract

Parallel electron spin resonance and optical absorption studies of magnesium oxide irradiated to six different doses in the range 10¹⁷ to10¹⁹ nvt> 1 mev have made possible a detailed correlation of the F-centre with the optical band centred at 2500 Å. Thermal bleaching experiments at 320°c for periods between 5 min and two days confirm this correlation in addition to the less detailed experiments of Wertz et al. (1964). The results are consistent with an oscillator strength of 0.8 for the F-band in magnesium oxide. In samples irradiated to high dose a maximum F-centre concentration of 6 × 10¹⁸ F/cm³ is observed at 5×10¹⁹nvt. This effect may be associated with the clustering of defects caused by irradiation-induced diffusion at the ambient pile temperature of 150°c.