Radiation resistance characteristics of quartz-fiber image guide, 2

Study was made on the increasing behavior of light transmission loss of quartzfiber prepared by the MRT method under irradiation condition. Test quartz-fiber specimen were pure or chlorine-free quartz of core material enveloped with BF-added quartz of cladding. Three kinds of test apecimens were irradiated with 60Co γ-ray source in 9 steps of radiation exposure rate from 1 x 103 R/h to 5.5 x 106 R/h and irradiated quartz-fiber lengths were 10, 20 and 30 m. As for the transmission loss of irradiated quartzfibers for the rays of 0.5 to 0.6 μm of wavelength, a DGIG/N fiber of pure quartz showed diameter dependence and a 12 μm fiber revealed more transmission loss than a 15 μm fiber. A DGIG/CF fiber of chlorine-free pure quartz core showed a superior radiation resistance characteristics of average and relatively lower transmission loss in the visible-ray wavelength region in comparison with the DGIG/N quartzfiber. For the deterioration prevention, it was experimentally clarified that a light-guide fiber in the light transmission state showed a remarkable radiation resistance that practically no transmission loss was found even in a high exposure rate of 5 x 105 R/h. It is concluded that a fiberscope of up to 10 m of length made of the abovementioned image and light guides prepared by the MRT method is employable in the radiation condition of 105 R/h or more. (Takagi, S.)