Growth of large size (≥ 38 mm diameter) KCaI3:Eu scintillator crystals

KCaI3:Eu is a scintillator composition that is promising for national security applications, with a high light yield and good energy resolution (∼70,000 ph/MeV and ∼3% E.R. at 662 keV, respectively). In addition to its high performance, we have been successful at growing KCaI3:Eu at larger sizes (38 mm diameter) without cracking. In this work we utilized a multi ampoule growth station to grow four 38 mm diameter crystals simultaneously. Three of these crystals achieved an energy resolution of ∼ 4% at 662 keV. The three crystals were hermetically packaged and a collimation study was carried out. This study revealed that light yield at a given irradiation location is dominated by photon path lengths and self-absorption, while the energy resolution dependence is affected heavily by local crystal quality. A 50 mm diameter KCaI3:Eu crystal was grown that achieved an energy resolution of 4.6% at 662 keV. GEANT4 was used to model a gap-style package that results in reduced photon path lengths, and therefore reduced self-absorption probability.