Track size distributions in CR-39 neutron dosimeters treated with carbon dioxide

A parametric study was performed examining the effect on CR-39 neutron dosimeters of pre-etching treatments with carbon dioxide at different pressures and durations. The detectors were irradiated with an241Am-Be neutron source in our low-scatter laboratory, delivering a personal dose equivalent Hp(10) of 1 mSv. Prior to their chemical etching, the detectors were treated for times ranging from 1 to 5 days in carbon dioxide at pressures ranging from 0.1 to 0.5 MPa. In agreement with previous studies, track densities were found to increase following treatments of increasing duration and pressures. Our particular interest was examining the differential track size distributions produced by the treatments. In particular, we analyzed the track size distributions for untreated detectors versus detectors treated with a CO2partial pressure of 0.5 MPa for 1, 3 and 5 days. Overall, the track size distribution appears to shift to higher diameters with increasing treatment time, while the overall pattern appears largely preserved. This “signature” may be associated with the energy distribution of the neutrons. In turn, this may allow establishing “adaptive” track-to-dose conversion coefficients accounting for the energy dependence of the CR-39 dose equivalent response.