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

Abstract

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.

Keywords

• scintillator
• melt growth
• vertical Bridgman technique
• thermal neutron detection
• eutectic system