Performance of a phoswich detector composed of an inner NaI(Tl) crystal and surrounding NE102A plastic scintillator for neutron spectrometry

We have developed a phoswich detector for neutron spectrometry, which adopts a reversed configuration of slow- and fast-decay-time scintillators in its inner and surrounding outer regions, respectively, in the detection of recoil protons from a hydrogenous radiator. The phoswich detector consists of an inner slow, NaI(Tl) scintillator, and an outer fast, plastic scintillator. This configuration allows us to discriminate protons of full kinetic-energy deposition only in the NaI(Tl) scintillator and those not stopping in the inner scintillator. The response functions of the phoswich detector were measured for neutron energies ranging from 100 to 350 MeV. The experiment used the recoil-proton method and pulse-shape discrimination with the two-gate integration technique using a spallation neutron source at the WNR facility of the Los Alamos Neutron Science Center (LANSCE). The experimental results were consistent with calculations by the Particle and Heavy Ion Transport code System (PHITS). To evaluate the effectiveness of the phoswich configuration, full energy-deposition fraction was calculated. This fraction is defined as the ratio of the integration around the full-energy peak to that of the entire energy region. The calculation confirmed that the phoswich detector with a reversed configuration is useful for neutron measurements.