Radiation effect in silica optical fiber exposed to intense mixed neutron-gamma radiation field

We measured in situ the radiation-induced absorption of pure silica core fibers exposed to a fission nuclear reactor. We observed the growth of the 1.39-/spl mu/m. OH vibration band in polymer coated fiber. Three mechanisms are responsible for this effect: recoil protons, hydrogen diffusion, and a probable compaction effect. Based on this experiment, a fiber-optic neutron monitor prototype is proposed.