Optical guide property of alternative He-3 neutron detectors using solid scintillators for nuclear safeguards

Numerical analysis of the optical guide properties of the scintillation lights in the alternative He-3 neutron detector tube using a scintillator sheet has been carried out by using a ray-tracing simulation code. The detector tube consists of a light-reflecting tube, a rectangular solid scintillator sheet, and two photo-multiplier tubes (PMTs). The scintillator sheet is built inside the tube, and the scintillation lights induced on the surface of the scintillator sheet are detected with the two PMTs mounted at both ends of the tube. Dependences of the optical guide property on arrangement of the scintillator in the tube and length of the tube are investigated. The results obtained with the simulations indicate that the optical guide property is strongly dependent on the arrangement of the scintillator sheet in the tube and the shape of the tube.