${\hbox{Cs}}_{2}{\hbox{LiLa}}({\hbox{Br}},{\hbox{Cl}})_{6}$ Crystals for Nuclear Security Applications

Properties of dual-mode scintillation detectors based on CLLBC crystals are reported. Energy resolution and light yield are measured at 2.9% (FWHM) at 662 keV and 45000 photons/MeV, respectively, for a 1-in-diameter and 1-in-long crystal. With less than 2% variation in light yield as a function of energy, CLLBC has better proportionality than ${\hbox{LaBr}}_{3}$ and NaI:Tl. Neutron peak resulting from reactions with neutrons emitted by $^{252}{\hbox{Cf}}$ (moderated) is measured at a gamma energy equivalent of 3.1 MeVee (electron energy equivalent), making pulse height discrimination between gamma-rays and neutrons easy. The material is also of effective pulse shape discrimination. The figure-of-merit for discrimination of gamma rays and thermal neutrons in CLLBC can be as high as 3.2, which is comparable to that of CLYC.