Effects of high gamma doses on the bulk etch rate of two grade CR-39 materials

In this study, the effect of gamma pre-treatment on etching rates has been investigated on CR-39 detectors manufactured by Pershore Mouldings (PM) as standard grade and (PM355) as dosimetry grade. The detectors have been exposed to 60Co gamma rays at absorbed dose ranging from 0 to 105Gy. The chemical etching was carried out in four PEW solutions (potassium ethanol in water) with various concentrations (KOH 6.25 N with 0%, 20%, 40% and 60% of ethanol). The results show that the effect of gamma rays on CR-39 etching characteristics is more pronounced when the ethanol concentration increases in the etching solution especially in the region ranging from 103103 to 104Gy. In this range, VBVB etching rate decreases till values less than those observed for virgin material. The structural alterations (cross linking or main chain scissions) produced by gamma rays in this plastic detector have been determined using UV–visible and FTIR spectroscopy and compared to those induced by proton irradiation.