Fabrication of CeCl₃/LiCl/CaCl₂ Ternary Eutectic Scintillator for Thermal Neutron Detection

To date, ³He gas has been commonly used to detect thermal neutrons because of their high chemical stability and low sensitivity to γ-rays, owing to their low density and large neutron capture cross-section. However, the depletion of ³He gas prompts the development of a new solid scintillator for thermal neutron detection to replace ³He gas detectors. Solid scintillators containing ⁶Li are commonly used to detect thermal neutrons. However, they are currently used in single crystals only, and their ⁶Li concentration is defined by their chemical composition. In this study, ⁶Li-containing eutectic scintillators were developed. CeCl₃ was selected as the scintillator phase because of its low density (3.9 g/cm³); high light yield (30,000 photons/MeV); and fast decay time with four components of 4.4 ns (6.6%), 23.2 ns (69.6%), 70 ns (7.5%) and >10 μs (16.3%), owing to the Ce³⁺ 5d-4f emission peak at approximately 360 nm. Crystals of the CeCl₃, LiCl and CaCl₂ ternary eutectic were fabricated by the vertical Bridgman technique. The grown eutectic crystals exhibited Ce³⁺ 5d-4f emission with a peak at 360 nm. The light yield was 18,000 photons/neutron, and the decay time was 10.5 ns (27.7%) and 40.1 ns (72.3%). Therefore, this work demonstrates optimization by combining a scintillator phase and Li-rich matrix phase for high Li content, fast timing, high light yield and low density.