ACCUMULATION OF STABLE OPTICAL-CENTERS IN SILICA GLASSES UNDER PULSE BEAM IRRADIATION

Stable optical centres production under 10 MeV electron irradiation we re investigated in three types of commercial silica glasses with diffe rent concentrations of the OH-group in the range 10(-2)-10(-4)%. The d ependencies of absorption coefficient at wavelength 215 nm (alpha(215) ) on absorbed dose show the saturation at doses greater than or equal to 2 MGy for glasses with high concentrations of the OH-group. At a fi xed dose of 0.56 MGy measurements of alpha(215) dependencies at temper ature 310 K on electron pulse repetition rate (f) gives a substantial increase of efficiency of defects production at high value of f, that indicates the existence of transition effects in the time interval (De lta tau) between electron pulses with a life time in ms range. Measure d dependencies alpha(215) = f(Delta tau) at temperatures 520 and 620 K show the intensification of radiation annealing process, that leads t o very low efficiency of stable defect production at high electron pul se repetition rate.