In-reactor luminescence from silica glasses

In order to investigate detailed dynamic effects of in-reactor irradiation on silica glasses, we have carried out in situ luminescence measurements of various silica glasses in the nuclear reactor YAYOI at the University of Tokyo. In the in-reactor luminescence (IRL) spectra, the emissions peaked at 4.2 eV and ca. 3 eV (3.1 or 2.8 eV) were observed for all the silica glasses, although the emission intensity for the low-OH fused silica glass was more than orders of magnitude larger than those for the high-OH fused and synthesized silica glasses. In the IRL spectra of the low-OH fused silica glass, the intensity of the band at 4.2 eV stayed constant during the irradiation, while the 3.1 eV IRL band was inherently intense and then decreased rapidly with the irradiation time. Although the intensity of the 4.2 eV IRL band was also constant in the spectra of the high-OH silica glasses, the 2.8 eV IRL band which was very weak in the early stage of irradiation, grew slowly with the irradiation time. The variation of the 3.1 eV IRL band for the former sample would reflect that the intrinsic oxygen deficiencies were changed to another ones mainly by the electronic excitation effects during irradiation. On the other hand, the growth of the 2.8 eV IRL band for the latter samples is likely to show the formation of the oxygen vacancies mainly by the atomic displacement effects of the neutron in the reactor. Thus, the comparison of the absolute intensities of the IRL bands revealed the different nature of the oxygen deficiencies in the silica glasses