In situ luminescence measurement of silica under soft X-ray and γ-ray irradiations

Abstract

In situ luminescence measurements of silica glasses induced by γ-ray and soft X-ray irradiations have been applied to study the dynamic effects of these ionizing radiations on silica. The emission band at 3.1 eV, assigned to B 2β, an oxygen deficient center, was observed for both γ-ray and soft X-ray irradiations. The intensity of the 3.1 eV band first increased, followed by gradual decrease with the irradiation time. The first increase of the band intensity may indicate the production of the B 2β center from its precursors by γ- and soft X-ray irradiations. The following decrease indicates the transformation of the B 2β center to other types of oxygen deficiencies like E ′ centers. In spite of the large difference between γ- and soft X-ray energies, all the luminescence yields showed similar dependence on the absorbed dose, suggesting that the changes in the luminescence under the γ- and soft X-ray irradiations are mainly caused by secondary electrons and photons with low energy but not by direct excitation of primary (Compton) or high energy electrons and photons. Nevertheless, the luminescence yield induced by the soft X-rays showed very strong incident X-ray energy dependence in the energy region around Si K-edge. The excitation process of the inner-shell electrons would be also an important factor for the production of low energy secondary electrons and photons, closely relating to the changes in the luminescence yield.