In situ observation of β-ray induced UV optical absorption in a-SiO2: Radiation darkening and room temperature recovery

We studied the optical absorption in the 3.0-6.2 eV range induced in bulk amorphous SiO2 by β-ray irradiation up to ∼1 MGy at room temperature. The induced absorption was measured in situ both during irradiation and in the post irradiation time. Our data evidence Eγ′ center as the main defect induced by irradiation and the partial decay of their absorption band at about 5.8 eV after irradiation. A quantitative analysis of the time evolution of the induced absorption shows that the transmission recovery observed after irradiation is compatible with the reaction of radiation-induced defects with H-related (H2, H2O) species diffusing in the amorphous matrix.