Characterization of heavy oxide inorganic scintillator crystals for direct detection of fast neutrons based on inelastic scattering

Abstract

Heavy oxide inorganic scintillators may prove viable in the detection of fast neutrons based on the mechanism of inelastic neutron scattering. A candidate set of crystals incorporating constituents of heavy atomic mass, namely bismuth germinate (BGO), zinc tungstate (ZWO), cadmium tungstate (CWO), lead tungstate (PWO), lutetium-gadolinium orthosilicate activated with cerium (LGSO:Ce) and lutetium-aluminum garnet with cerium (LuAG:Ce), were characterized to reveal relevant properties for efficient fast neutron detection. The optical measurements indicated strong transmittance with minimal absorption occurring in the visible spectrum. On average, the crystals achieved approximately 80% transmittance and 3% absorption, with the remaining light reflected at the air/crystal interface. Cathodoluminescence (CL) measurements with electron excitation energy of 5 keV provided information on the peak wavelength emission and light intensity. Results show that BGO and LGSO:Ce produced the highest scintillation light output and sharpest peak formation. Uncertain Ce3+ concentration and the presence of Eu3+ admixture caused LuAG:Ce to red shift and produce a false-positive bright emission. The gamma induced scintillation measurement yielded preliminary results showing stratification in light output based on incident energy in the range of 0.081–1.275 MeV. CWO and LGSO:Ce, crystals with similar structure, appeared less susceptible to this phenomenon.