en Radiation Biology Radiation Biology تحقيق بديع Original Research <span style="font-weight: bold">Background:</span> 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. <span style="font-weight: bold">Material and Methods: </span>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. <span style="font-weight: bold">Results:</span> 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. <span style="font-weight: bold">Conclusion: </span>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 Neutron dosemetry, electrochemical etching, MCNPX, simulation 95 102 http://ijrr.com/browse.php?a_code=A-10-1-389&slc_lang=en&sid=1 M.R. Deevband 790031947532846002263 790031947532846002263 No P. Abdolmaleki parviz@modares.ac.ir 790031947532846002264 790031947532846002264 Yes M.R. Kardan 790031947532846002265 790031947532846002265 No H.R. Khosravi 790031947532846002266 790031947532846002266 No M. Taheri 790031947532846002267 790031947532846002267 No F. Nazeri 790031947532846002268 790031947532846002268 No N. Ahmadi 790031947532846002269 790031947532846002269 No