An approach to measure low LET radiation at high dose using CR-39 track detector

CR-39 track detectors are commonly used for measuring high LET (linear energy transfer) radiation with LET values above 10 keV/μm. This study proposes a method for using CR-39 to measure low LET radiation, such as photons and electrons, at high doses in the order of kilogray (kGy). CR-39 detectors were irradiated with bremsstrahlung photons generated from 10 MeV electrons striking a tantalum target, resulting in absorbed doses ranging from 6.5 kGy to 261.4 kGy. FLUKA Monte Carlo simulation was performed to estimate the dose deposition in CR-39 due to bremsstrahlung photons and to estimate the primary and secondary electron fluences incident on CR-39. The simulations revealed that the secondary electrons produced by the interactions of primary electron beam were of two orders less magnitude than that of bremsstrahlung photons. The results showed no significant changes in the absorbance values of different functional group vibrations of unetched CR-39 even they were exposed to high dose up to 261.4 kGy. However, after chemical etching, the intensities of two prominent peaks at 1230 cm^-1 (aliphatic ester C-O-C stretching) and 1735 cm^-1 (ester C=O stretching) significantly decreased at doses above 65.3 kGy. The study demonstrates the feasibility of using CR-39 track detectors for measuring low LET radiation at high doses in the range from 46 to 197 kGy by combining FTIR spectroscopy with chemical etching.