Effects of gamma-rays on polymethylmethacrylate plastic optical fiber under low dose-rate irradiation

An irradiation test was performed for polymethylmethacrylate (PMMA) plastic optical fibers (POFs) under low dose-rate gamma-ray irradiation in order to use the fiber in low-level radiation environments. Radiation-induced loss that has peaks in the ultraviolet and near infrared wavelength range and improvement in the optical transmission over an entire wavelength range were observed under the irradiation. The peak intensity of the induced loss increases with the absorbed dose, and the intensity saturate at some absorbed doses. The absorbed dose at which the intensity becomes saturated depends on the gamma-ray dose rate. Therefore, it is necessary to take into account the dose rate when the PMMA POF used as a dosimeter in low level gamma-ray irradiation. The improvement in the optical transmission is dependent on the radiation dose rate and become large in lower gamma-ray dose rate.