Ytterbium-based compounds as fast and dense inorganic scintillators

The recent observation of UV scintillation in mixed yttrium/ytterbium aluminium garnets opened the field of investigation to a new class of scintillating crystals. Their interesting luminescence properties make them very attractive not only for solar neutrino spectroscopy as ytterbium containing detector material, but also for radiation detection in general, as dense, fast and efficient scintillators. Studies of charge transfer luminescence and quenching mechanisms in single crystals of the garnet system (Y-Yb)₃Al₃O₅ are reported. Fluorescence intensity and decay time under X-ray and VUV excitations decrease at low temperatures (T∼100 K) and demonstrate the important role played by the traps. The fluorescence intensity and decay time are also dependent on Yb³⁺ concentration and the presence of Yb²⁺. The results trace major directions to get optimized scintillators in terms of their efficiency and lifetime. X-ray luminescence has also been found in gallium garnets (Y-Yb)₃Ga₃O₅ and the perovskites (Y-Yb)AlO₃ and LaYbO₃ in the form of single crystals and/or powders. More specific properties required by neutrino spectroscopy, such as radioactive background, pulse shape, false signatures, alpha/gamma discrimination, are also addressed.