Near infrared radio-luminescence of O2 loaded radiation hardened silica optical fibers: A candidate dosimeter for harsh environments

We report on an experimental investigation of the infrared Radio-Luminescence (iRL) emission of interstitial O2 molecules loaded in radiation hardened pure-silica-core and fluorine-doped silica-based optical fibers (OFs). The O2 loading treatment successfully dissolved high concentrations of oxygen molecules into the silica matrix. A sharp luminescence at 1272 nm was detected when 2.5 cm of the treated OFs were irradiated with 10 keV X-rays. This emission originates from the radiative decay of the first excited singlet state of the embedded O2 molecules. The dose, dose-rate, and temperature dependencies of the infrared emission are studied through in situ optical measurements. The results show that the iRL is quite stable in doses of up to 1 MGy(SiO2) and is linearly dependent on the dose-rate up to the maximum investigated doserate of 200 kGy(SiO2)/h. The temperature dependency of the iRL shows a decrease in efficiency above 200 C, which is attributed to the non-radiative decay of the excited O2 molecules. The results obtained and the long-term stability of the O2-loading treatment (no out-gassing effect) strongly suggest the applicability of these components to real-time remote dosimetry in environments characterized by high radiation doses and dose-rates.