Simulated Neutron Response Functions of Phoswich-Type Neutron Detector and Thin Organic Liquid Scintillator

Neutron response functions of a phoswich neutron detector and thin organic liquid scintillator were simulated using the multi-purpose Monte Carlo code MCNPX, incorporating functions of light outputs, energy resolutions, and uniformity of scintillation. The simulated response functions were verified by response-function measurement for high-energy neutrons produced by bombarding thin lithium targets with 10to 80-MeV protons. Our procedures can simulate the response functions of the organic liquid scintillator and the phoswich neutron detector without limits of neutron energies, materials, or geometries. Based on the evaluated neutron response functions, we obtained neutron energy spectra using an unfolding method. One is the high-energy neutron spectrum at the aviation altitude, 10.8 km, and the other is at an intense fast neutron field for biological study in the National Institute of Radiological Sciences.