A new ceramic scintillator for neutron detection: CaF/sub 2/:Eu/sup 2+///sup 6/LiF

A CaF₂:Eu²⁺/⁶LiF translucent composite ceramic is a new scintillator for neutron detection. In this material, as in ZnS:Ag/⁶LiF phosphor, neutrons are absorbed by ⁶LiF grains, and the scintillation is provided by the complementary grains of CaF₂:Eu²⁺. However unlike phosphors, ceramics have higher packing density and are more translucent. This allows the use of thicker layers with improved detection efficiency (or thinner layers showing better spatial resolution). Better translucency also provides a well-defined neutron photopeak in the energy spectrum. The light output of samples fabricated so far reaches about 25,000 photons per neutron at the neutron photopeak, with a possible maximum up to about 45,000 photons/neutron. The emission (at 425 nm) under neutron excitation decays with a time constant of 590 ns, and there are no significant slower components. Faster decay permits higher count rates and better timing resolution, that is important for spallation neutron sources, where the neutron energy needs to be determined by the time-of-flight techniques. In addition, this material is characterized by a low effective atomic number (16.6) and low refractive indices (1.44/1.39)