Experimental and Monte Carlo studies on the response of CR-39 detectors to Am-Be neutron spectrum

Background: The Poly-Allyl Diglycol Carbonate (PADC) detector is of particular interest for development of a fast neutron dosimeter. Fast neutrons interact with the constituents of the CR-39 detector and produce H, C and O recoils, as well as (n, α) reaction. These neutron- induced charged particles contribute towards the response of CR-39 detectors. Material and Methods: Electrochemical etching was used to enlarge track diameter which was made by low energy recoil protons. Before electrochemical etching, a chemical etching was performed for 1 hour. The responses were also calculated by Monte Carlo simulations, using MCNPX code in different energy bins considering H, C and O recoils. The total registered efficiency and partial contributions of the efficiency, due to interactions with each constituent of CR-39, were calculated. Results: The optimized condition of etchant was obtained to be 6N KOH 15kV.cm-1, and 6 hours etching time. The obtained results show that track efficiency of CR-39 was a function of incident neutron energy. The tracks caused by O and C recoil nuclei were negligible for neutron energies lower than 1 MeV. At neutron energies lower than 1 MeV, only recoil protons would have sufficient energy to leave visible tracks. But, O and C recoils had important contributions in overall response of PADC at neutron energies of few MeV. Conclusion: The efficiency of a CR-39 based dosemeter could be calculated by MCNPX code and the results were in a good agreement with experimental results in energy range of 241Am – Be bare source and 241Am-Be was softened with a spherical polyethylene moderator of radius of 20 cm. Iran. J. Radiat. Res., 2011 9(2): 95-102