Effects of neutrons and gamma-rays on polymethylmethacrylate plastic optical fiber

The effects of neutron and gamma-ray irradiation on a polymethylmethacrylate (PMMA) plastic optical fiber (POF) were investigated. An improvement in the optical transmission was observed at the beginning of irradiation, but radiation damage (radiation-induced transmission loss in the visible wavelength range) increased as the irradiation continued. To determine the effects of neutrons and gamma-rays, the amount of energy absorbed in the PMMA POF was calculated using the PHITS codes. Energy deposition in the fiber was calculated considering nuclear reactions listed in the nuclear data file used for the Monte Carlo N-particle transport code. The effects of neutron and gamma radiation were observed to be similar with absorbed energy less than 1.2 kGy. However, the transmission loss induced by neutrons was larger than that induced by gamma-rays when higher energy was deposited.