Neutron-sensitive ZnS/~(10)B_2O_3 ceramic scintillator detector as an alternative to a ~3He-gas-based detector for a plutonium canister assay system

摘要

A neutron-sensitive ZnS/~(10)B_2O_3 ceramic scintillator detector was developed as an alternative to a ~3He-gas-based detector for use in a plutonium canister assay system. The detector has a modular structure, with a flat ZnS/~(10)B_2O_3 ceramic scintillator strip that is installed diagonally inside a light-reflecting aluminium case with a square cross-section, and where the scintillation light is detected using two photomultiplier tubes attached at both ends of the case. The prototype detectors, which have a neutron-sensitive area of 30 mm × 250 mm, exhibited a sensitivity of 21.7-23.4 ± 0.1 cpsv (mean ± SD) for thermal neutrons, a ~(137)Cs gamma-ray sensitivity of 1.1-1.9 ± 0.2 × 10~(-7) and a count variation of less than 6% over the detector length. A trial experiment revealed a temperature coefficient of less than -0.24±0.05%/℃ over the temperature range of 20-50 ℃. The detector design and the experimental results are presented.