Image fiber reduced in irradiation-induced loss by photobleaching

Protection of an image fiber against irradiation-induced loss by utilizing photobleaching (increase-suppressing effect of light energy on light absorption) has been demonstrated for the first time. Photobleaching effects on the silica glass image fiber were investigated in detail. I evaluated photobleaching characteristics of the fiber by using He–Cd laser, a xenon lamp, and a D2 lamp as photobleaching light sources. Fibers were irradiated at two levels of dosage: 300 and 104 R/h. The thermal effect on photobleaching was also evaluated by comparing the effect at 28 and 70 °C. A comparison of light sources for photobleaching have been shown a xenon lamp is the most effective and a wavelength range 0.3–0.36 μm contributes to photobleaching. Based on these evaluation results, through the xenon lamp bleaching, I have succeeded in elongating the useful life time of an image fiber in a 300 R/h gamma-ray environment to more than five times that of an unbleached fiber for the first time.