Li-Based Thermal Neutron Scintillator Research; ${\hbox {Rb}}_{2}{\hbox {LiYBr}}_{6}:{\hbox {Ce}}^{3+}$ and Other Elpasolites

We investigated $\gamma$- and neutron-scintillation properties of ${\hbox {A}}_{2}{\hbox {LiLnX}}_{6}:{\hbox {Ce}}^{3+}$ ( ${\hbox {A}}={\hbox {Cs}}$, Rb, K, Na, Li; ${\hbox {Ln}}={\hbox {La}}$, Y, Lu, Sc; ${\rm X}={\hbox {Br}}$, I) with the aim to develop new scintillators with high neutron detection efficiencies. Among the investigated thermal neutron scintillators, ${\hbox {Rb}}_{2}{\hbox {LiYBr}}_{6}:{\hbox {Ce}}^{3+}$ shows an excellent neutron peak resolution of 3.6%. This is the best neutron peak resolution ever reported. Together with the large $\alpha/\beta$ ratio of 0.74, ${\hbox {Rb}}_{2}{\hbox {LiYBr}}_{6}:{\hbox {Ce}}^{3+}$ offers the possibility of excellent neutron/$\gamma$ discrimination. The highest thermal neutron scintillation light yield of 83,000 photons/neutron is also reported for ${\hbox {Rb}}_{2}{\hbox {LiYBr}}_{6}:{\hbox {Ce}}^{3+}$.