Enhanced bulk-etch-rate of gamma irradiated PADC detector expressed by the radiation chemical yield of hydroxyl group

Enhanced bulk-etch-rate of PADC (polyallyl diglycol carbonate) detectors exposed to gamma rays has been found to be described well as an exponential function of the product of the radiation chemical yield of hydroxyl group ( G OH ) and the adsorbed dose ( D ) at different dose-rates between 0.41 and 8.14 Gy/s. The examined absorbed doses were ranging from 30 to 100 kGy, comparable with the local dose in proton tracks. By matching the bulk-etch-rates and the G OH values obtained under identical conditions on dose-rate, the following equation was derived for the relative bulk-etch-rate, V irra / V b = exp( y ･ G OH ･ D ), where, V irra and V b denote the bulk-etch-rates after and before gamma irradiations, respectively, and y is an experimentally obtained constant in a unit of kg/mol, with a value of y = 5.98. In this relation, significant dose-rate dependence is explained as the dose-rate dependence of the G OH value. This means that the radiation damage that increases the bulk-etch-rate is the hydroxyl group itself, and y appears as a constant specific to PADC which relates the damage to bulk-etch-rate. Here, y is termed the “etching coefficient ". • Dependence of the G value of hydroxyl group ( G OH ) on dose-rate was obtained. • Enhanced bulk-etch-rate depends exponentially on the product of G OH and absorbed dose. • “Etching coefficient” of y = 5.98 in kg/mol relates the damage to the bulk-etch-rate.