Irradiation Behavior of developed radiaiton resistance optical-fibers and observed optical radiation from their SiO_2 cores under reactor irradiation

Two kinds of optical fibers were irradiated in a fission reactor, JMTR(Japan Materials Testing Reactor), up to a 1.55x10^n/cm^2 fast neutron fluence and a 3.3x10^9Gy ionizing dose at 370K. Optical transmission spectra were measured in the wavelength range of 450-1750nm, in-situ. Growth of strong optical absorption bands were observed in the range of wavelength shorter than 750nm. In the meantime, the fibers showed good radiation-resistance in the range of wavelength longer than 750nm. Optical radiations were observed from SiO_2 optical fibers under irradiation. A major part of the observed optical radiations is thought to be composed of broad optical radiation in the whole wavelength range studied in the present experiment. This broad optical radiation will be generated by the process of so-called Cerenkov radiation. Also, a sharp optical radiation peak was found at 1270nm on a F-doped fiber. This peak is thought to relate with doped Fluorine ions and ionizing gamma-ray irradiation

Neutron Irradiation Effects on Optical Fibers

Irradiation effects on optical fibers were observed with 14 MeV fusion neutron and fission neutron. As a result, the following characteristics have become clear. Permanent absorption loss after fission and fusion neutron irradiation, were greater than that of gamma ray irradiation. In case of fission neutron, large absorption loss appeared at wavelength of shorter than 700 nm and loss peak of 600 nm, and absorption loss increased exponentialy to the fluence of 10^ n/cm^2. During irradiation, the light emission was observed in the wavelength of 400 to 1700 nm and peak of light at about 1200 nm was appeared. Two kinds of the SiO_2 fibers were survived irradiated up to 3 x 10^ n/cm^2