Effects of High Dose Rate Ionizing Radiation on Fused Silica and Sapphire Films

The effects of high dose rate electron beam exposures on the electrical conductivity of fused silica and sapphire films are investigated via modern experimental techniques. Transient measurements have been obtained for dose rates ranging from 3×10 ⁵ rad(Si)/s to 1×10 ¹⁰ rad(Si)/s and for pulse widths ranging from 50 ns to 500 ns. The data indicate that the radiation-induced conductivity (RIC) has a varying power-law relationship with dose rate (i.e., the power-law relationship for low dose rates is different than for high dose rates) and that the RIC coefficient (k c) increases at lower dose rates, peaks, and then decreases at higher dose rates. It is also shown that the RIC response of each film increases several orders of magnitude during a high-intensity ionizing radiation exposure and is linearly dependent on applied bias. Two-dimensional (2-D) numerical simulations are used to qualitatively capture the observed RIC response and provide insight into the physics of the induced current transients.