Radiation-induced absorption and luminescence in specially hardened large-core silica optical fibers

Radiation-induced absorption and luminescence are measured in the visible spectral region in H₂-loaded and as-drawn fibers with KU and KS-4V silicas in the core in the process of γ-irradiation ( ⁶⁰Co-source). The induced absorption in H₂-loaded fibers is shown to be much lower than in as-drawn fibers, at least up to 1.2 MG.y A `blue´ band prevails in the luminescence spectra of all the fibers. Its intensity is greater in a KS-4V fiber than in a KU fiber. It is also somewhat greater in H<sub>2</sub>-loaded fibers than in unloaded ones. The luminescence lifetime in a KU fiber has been measured under excitation with a pulsed reactor to be 100 μs at λ=88 nm and 60 μs at λ=633 nm. It is concluded that the `blue´ radioluminescence cannot be attributed either to relaxation of the oxygen-deficient center or to Cerenkov emission. A fabrication technology of radiation-hardened H₂-containing fibers with a hermetic aluminum coating is reported. Such fibers appear to be the best candidates for various applications in radiation environments