POINT-DEFECTS IN HIGH-PURITY SILICA-INDUCED BY HIGH-DOSE GAMMA-IRRADIATION

The defects induced by high-dose (10 MGy) gamma irradiation (Co-60) are studied in various types of high-purity silica glasses [including synthetic crystal (alpha-quartz)]. While the defects induced by gamma irradiation of up to 1 MGy have been reported to be generated through the bond breaking of manufacturing-method-dependent point defect sites (precursors), such precursor dependency disappears or at least weakens in the defects induced by 10 MGy gamma irradiation. Electron spin resonance, optical absorption, and luminescence investigations suggest that at high-dose irradiation the defects are created mainly by radiolysis or bond breaking, and associated oxygen diffusion occurred at silicon-oxygen bonds other than at point defect sites. Crystalline alpha-quartz shows much higher radiation resistivity than amorphous silica glasses, suggesting that strained silicon-oxygen bonds are the breaking sites.