Development of novel rare earth doped fluoride and oxide scintillators for two-dimensional imaging

Two topics were focused. The first one was about the gamma-ray scintillator, Pr³⁺:Lu₃Al₅O₁₂ (LuAG). The second one was about neutron scintillator, Ce³⁺: ⁶LiCaAlF₆ and Eu²⁺:⁶LiCaAlF ₆ (⁶LiCAF). Those scintillators have been developed very recently for modern imaging applications in the medical and homeland security fields. In both cases, the rare earth ions are playing the crucial role as emission centers. Pr³⁺ in LuAG provided fast 5d→4f transition providing noticeably shorter decay time than that of Ce³⁺. Among several candidate hosts, LuAG showed the best performance. Bulk crystal growth, basic scintillation properties, two-dimensional gamma-ray imaging and positron emission mammography (PEM) application were demonstrated. Due to the international situation, the homeland security was compromized by illicit traffic of explosives, drugs, nuclear materials, etc. and the ways to its improvement became an important R&D topic. For this purpose the Ce and Eu doped LiCAF appeared competitive candidates. Especially, when substitution of ³He neutron detectors was considered, the discrimination ability of gamma-ray from alpha-ray was important. Bulk crystal growth, basic scintillation properties and two-dimensional neutron imaging were demonstrated.