Evaluation of light transport property in alternative He-3 neutron detectors using ceramic scintillators by a ray-tracing simulation

We have developed a He-3 alternative neutron detector using ceramic scintillator sheets for nuclear safeguards. The alternative detector tube consists of four components: an aluminum regular square envelop tube, a light reflecting tube put on the inner surface of the square tube, a rectangular scintillator sheet sintered on a glass plate, and two PMTs provided at both ends of the tube. It permits neutron counting by detecting scintillator light with the PMTs. The light transport property of scintillator light inside the tube strongly depends on the inner structure of the detector tube. The light output of the scintillator light from the surface of the scintillator and the glass plate to the end in several arrangements of the scintillator in the tubes was investigated by a ray-tracing simulation. The simulation results on the influence of the glass plate on the properties are discussed.