Thermal stability of neutron irradiation effects on KU1 fused silica

Optical absorption spectra of neutron irradiated (1021 n/m2 and 1022 n/m2) KU1 quartz glass samples have been measured. The effects of post-irradiation isochronal thermal annealing, up to 850 °C, have been investigated. The general effect of the isochronal annealing is a decrease in the optical absorption bands as the temperature increases. Optical absorption bands have been identified with known defects from the literature, and their concentration temperature dependence has been analyzed. While the annealing curves of the E′ and non-bridging oxygen hole centres (NBOHC) are similar, that corresponding to oxygen deficiency centres (ODC(II)) is quite different suggesting that the recombination of E′ and NBOHC is part of the same process whereas the recombination of ODC is controlled by the presence of another undetected defect.