The defect center causing the 2 eV absorption band induced in pure silica core fibers by 60Co γ-rays is discussed. The 2 eV band and non-bridging oxygen hole center (NBOHC, SI–O·) show almost the same thermal annealing characteristics. The peak wavelength of the 2 eV band in low-OH (≦6 ppm) fibers is 630 nm, but shifts to shorter wavelengths according to the amount of OH group the sample contains, and appears at 600 nm in high-OH (≧700 ppm) fibers. The peak shape is broader in high-OH fibers than in low-OH fibers. This shift and broadening is attributable to a hydrogen bond between NBOHC and a hydrogen atom. Based on the above results, the defect center responsible for the 2 eV band is considered to be NBOHC.

A pure silica core fiber with glass cladding is known to produce larger absorption in the visible wavelength region under γ-ray irradiation than a similar fiber with silicone cladding. This absorption is a serious problem, especially in image-guiding fibers used in radiation environments such as in nuclear power plants. The absorption is attributed to the formation of defect centers such as non-bridging oxygen hole centers and E' centers induced by bond scission. A new and simple method of hydrogen treatment to improve the radiation resistance of an optical fiber with a pure silica core has been proposed. Post-treatment by this method can significantly reduce existing radiation-induced absorption, while preliminary treatment can suppress the increase of the radiation-induced absorption.

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Radiation-induced optical absorption bands in pure synthetic silica-core fibers were studied. The effect of Cl contamination on the absorption change of the irradiated fibers in relation to the radiation resistance was examined, and it was deduced that low-Cl fibers have good radiation resistance even when they have a low OH content. The effect of the OH content on the radiation response in low-Cl fibers was thus investigated. The radiation-induced 630 nm band is enhanced in higher-OH-content silica-core fibers. The 660 nm and 760 nm bands were also observed in certain irradiated fibers. The former increases with dose up to 0.1∼2 kGy but decreases at higher doses. The mechanisms of the radiation-induced bands are discussed.

Rutile thin films of Au(Ti, Al)–TiO2–Pt sandwich system were prepared on a substrate glass by evaporation of Ti metal and oxidation of it by heat treatment. Through AC and DC measurements, the capacitance obtained was about 2000 pF/mm2, the dielectric constant was estimated as 60∼110, tan δ was 1∼10%, the conductivity was about 10-13Ω-1cm-1 and the electrical strength was 5∼10 V (0.3∼0.5 MV/cm), respectively. In the micro-sec- and micro-sec-pulse conduction measurement, the relation of current and time became I∝t -n , in which the value of n was 0.7∼0.8. The polarity effect on the current was considered to be due to the work functions of electrodes. The current carrier was estimated to be electronic from the measurement of photoconduction and the polarity effect in the pulse conduction.