Sensitization of Solid State Nuclear Track Detector in Carbon Dioxide for Improved Fast Neutron Dosimeter

Monte Carlo Simulation and Experimental Results for Energy Response of Neutron Dosimeter and Quantitative Estimation of Sensitization by CO₂ Pre-etching

Abstract

A pre-etching step is applied with carbon dioxide (hereafter, CO₂ pre-etching) of a solid state nuclear track detector (SSNTD) to improve the sensitivity for protons detection. In this study, we quantitatively estimated the sensitization of SSNTD with CO₂ pre-etching to improve the sensitivity of a personal neutron dosimeter. We measured the etch pit size and the critical angle using a 1.7 MV tandem accelerator at the University of Tokyo to evaluate the proton sensitivity. In addition, we calculated the neutron energy response of SSNTD with a polyethylene radiator with the particle and heavy ion transport system multipurpose three-dimensional Monte Carlo code. To evaluate the accuracy of these calculations, neutron energy responses of SSNTD with and without CO₂ pre-etching were measured at the Facility of Radiation Standards of the Japan Atomic Energy Agency. The neutron energy responses calculated by the above Monte Carlo code agreed with the experimental results to within 35%. The results obtained in this research indicate that CO₂ pre-etching at a pressure of 0.6 MPa for 3 days increases the radiator effect by up to 250% for the 5 and 14.8 MeV neutrons.