Optical Absorption of Quartz Fibers at Pulsed Irradiation With High-Energy $\gamma $ -Quanta

This paper presents the investigation results on light absorption of silica optical fibers under effect of $\gamma $ -quanta with the energy of 2.5 MeV. Exposure radiation doses were 100–300 R, $\gamma $ -quanta had the energy of ~13.5 MeV with the exposure radiation dose of 20–40 kR. Influence of the electron beam having the energy of 2.5 MeV at absorbed dose up to ~200 krad at rise time up to $\sim 10^{13}$ rad/s, and pulselength $\tau _{1/2}$ –20 ns in the wavelength range from 0.53 to 1.30 $\mu \text{m}$ was also studied. This paper describes investigation of the fibers with pure silica cores and the silica cores with different dopants. One could observe difference in behavior of the fibers absorption at exposure dose of 40 kR and absorbed dose of 200 krad. Increasing the light wavelength from 0.53 to 1.3 $\mu \text{m}$ , we observed the decrease of the optical absorption that was caused by radiation exposure for all studied fiber samples. We also studied optical characteristics of a single-mode fiber (pure SiO 2 core and F doped cladding) fabricated using low-birefringence technology. One can also see that radiation exposure did not cause depolarization of the linearly polarized light and did not result to polarization plane angle change for the specified fiber. This allows using of the specified fiber as the fiber-optical probe for current (tens of megamperes) and magnetic field (tens of megagauss) measurements in the conditions of high-power radiation exposure. The presented results allow selecting of the optimum light wavelength and composition of the dopants for the fibers in order to minimize the optical losses.