Measurement of fast neutron fluences by the nuclear track technique

Abstract

The properties of solid state nuclear track detectors (SSNTDs) for fast neutron measurements in the presence of high gamma radiation fields have been investigated. A comparative study of two different modes of fast neutron measurements based on SSNTDs is presented. In the internal radiator mode (IRM), the neutrons are detected due to the alpha particles and recoil nuclei created in materials, e.g. C and O present in the SSNTD itself by neutron interactions. In the external radiator mode (ERM), the SSNTD is covered by a front radiator consisting of 0.5 mm polyethylene, and the tracks are produced by recoil protons of the (n, p) converter reaction, and recoil particles and (n, α) reactions created in the detector itself by neutron interactions. In this work, we have used CSR (China Shanghai Resin) which is a polymeric track detector (Allyl diglycol carbonate) for measuring fast neutron fluences ranging from 10 6 to 10 11 n cm 2 . Results show that the CSR plastic detector can be used successfully for detecting 14 MeV neutron fluences in the range from 5 × 10 7 to 6 × 10 10 n cm 2 , and the detection efficiency of the CSR with polyethylene radiator is on the average 3.32×10 −5 tracks per neutron.