Multi-energy neutron detector for counting thermal neutrons, high-energy neutrons, and gamma photons separately

A scintillation detector composed of two scintillators optically coupled and mounted on a single photomultiplier tube is described. The first scintillator is a ⁶Li-loaded glass that has high efficiency for thermal neutrons, and the second is a liquid scintillator (BC 501) that has fairly high efficiency for higher-energy neutrons. The ⁶Li glass scintillator emits light with a characteristic time constant of ~60 ns, whereas light emitted in the liquid scintillator by proton recoil from energetic neurons has a time constant of ~30 ns; the time constant for scintillations occurring from gamma-scattered Compton electrons in the liquid scintillator is ~3.7 ns. These differences in light decay time constants make this detector conducive to electronic separation of pulses generated by the three different radiations. Thermal neutrons, high-energy neutrons, and gamma radiation can be counted separately by operating this detector with a recently developed pulse-shape discriminator. Experimental data proves the principle of this dual scintillator detector for many applications