Accumulation of stable optical centres in silica glasses under pulse beam irradiation

Stable optical centres production under 10 MeV electron irradiation were investigated in three types of commercial silica glasses with different concentrations of the OH-group in the range 10(-2)-10(-4)%. The dependencies 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 fixed dose of 0.56 MGy measurements of alpha(215) dependencies at temperature 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 (Delta tau) between electron pulses with a life time in ms range. Measured dependencies alpha(215) = f(Delta tau) at temperatures 520 and 620 K show the intensification of radiation annealing process, that leads to very low efficiency of stable defect production at high electron pulse repetition rate.