Reduction of background in CR-39 SSNTD using chemical pre-etching methods

Presently, CR-39 Solid State Nuclear Track Detectors (SSNTD) is being used for Fast Neutron Personnel Monitoring in India. Individual detectors are cut manually from CR-39 sheets. Laser-cutting of the sheets will ensure precision and also save on the laborious efforts involved in sheet cutting. It was observed that there is a slight increase in background tracks due to laser-cutting. Studies were carried out on the effect of chemical pre-etching at higher temperatures in properties of CR-39 such as the background, sensitivity and minimum measurable dose. For this purpose a pre-etch step was included in the normal processing of the CR-39 foils in an elevated temperature electrochemical cell (ETECE cell) and the duration for pre-etch step at elevated temperature was optimized. Samples of CR-39 exposed to dose equivalents ranging from 1 mSv to 10 mSv using Am-Be neutron source were processed by both the methods, under normal processing using ECE cell and in the optimized chemical pre-etch followed by normal processing. The dose responses of CR-39 processed by both methods are compared in this paper.