Gamma-Ray Irradiation-Induced Optical Attenuation in Co/Fe Co-Doped Alumino-Silicate Optical Fiber for Dosimeter Application

Dose dependence of radiation-induced optical attenuation (RIA) at 1310 nm of the Co/Fe co-doped alumino-silicate optical fiber was investigated under gamma-ray irradiation at dose rates from 6.7 to 78.3 Gy/min. From the measured RIA, radiation dose sensitivity (ΔRIA/ΔDose) and rate of RIA change with irradiation time (ΔRIA/ΔTime) at the different dose rates were estimated. RIAs at various wavelengths (800 to 1600 nm) of the optical fiber were also measured and the RIA characteristics at 800 and 1310 nm under discrete gamma-ray irradiation were investigated. The measured RIA of the Co/Fe co-doped fiber showed very high dose sensitivity regardless of the dose rates and the ΔRIA/ΔTime was found to show linear response with respect to the dose rate. The significantly large RIA was attributed to Co, Fe, and Al-related defects in the fiber core which were formed by the irradiation, and it became larger at shorter wavelength. The high radiation dose sensitivity, linear response of the ΔRIA/ΔTime with respect to dose rate, and the high reproducibility of the dose dependence of RIA under the discrete irradiation clearly indicate that the Co/Fe co-doped fiber is able to provide highly accurate information of not only total accumulated dose but also dose rate of the radiation with irradiation time.