PNNL

Abstract

Pulse shape discriminatioin techniques using the scintillator LiBaF3 allow very clean separation of densely ionizing radiation (protons, tritons, alphas, etc.) from less densely ionizing radiation (electrons). The pulse shape discrimination is based on the presence or absence of subnanosecond core-valence luminescence and in crystals doped with Ce+3 the presence or absence of Ce luminescence. We use a pulse discriminatin technique based on integration of the signal over a short time interval compared to integration over a long time interval. Thermal neutron capture events, fast neutron capture events, fast neutron elastic scattering events on Li, and alpha events from Ra impurities in the scintillator have distinctive loci in a two-dimensional plot of the short gate pulse heights versus long gate pulse heights. The resolution (FWHM) of the 137Cs gamma photopeak is about 16% and the resolution of the thermal neutron peak from neutron capture on 6Li is about 17%. Applications of this scintillator include measurements of fast to thermal neutron ratios, fast neutron spectroscopy, alpha contamination, etc. in the presence of significant gamma radiation.