Calibration constant of Alpha track detector-polycarbonate film, CAPFILM PC

Abstract

Research was performed to study the etching characteristics and sensitivities of commercially available polycarbonate track detectors and to compare them to cellulose nitrate film, Kodak LR-1 15 II. The polycarbonate film used was CAPFILM PC. The film was exposed first to alpha particles generated by a uranium foil to expedite the process of determining the optimal etching conditions. The initial thickness of CAPFILM PC chosen for characterization was 15 Jim. The optimal condition for this thickness required etching with 6.25 N NaOH for 3 hrs at 65 C. The chemical etching parameters for CAPFILM PC require a higher etching temperature, longer etching time, and higher concentration of etchant in comparison to LR-1 15 11. The optimal etching parameters for LR-1 15 11 were found to be with 2.5 N NaOH for 145 minutes at 60 C (Vasudevan 1991). Both LR-1 15 and CAPFILM PC were simultaneously exposed in the radon exposure chamber which was connected to a barrel containing uranium ore. The exposed film types were etched separately at their chosen conditions and the calibration constant was determined for each film. The calibration constant for CAPFILM PC was established as 0.03 tracks cm-2 kBq-1 h-1 M3 9 and, because of batch variation, the Kodak film's constant was measured to have a range from 1.03 to 2.16 tracks cm-2 kBq-1 h-1 m3. Both films responded to the typical alpha energy of radon and its daughters. The calibration constant for CAPFILM PC film was determined by using a reflected light arrangement, in which the etched tracks appeared as black holes rather than bright holes as seen with LR-1 15 11 film (using transmitted light arrangement).