CLLBC High Temperature Scintillation Characterization and Detector Integration

High-temperature detectors are required for nuclear material accounting measurements for some advanced reactor designs including molten salt reactors. The Cs
₂
LiLa (Br,Cl)
₆
:Ce (CLLBC) scintillator is a dual-mode scintillator that shows excellent gamma detection along with the capability to discriminate gamma rays from neutrons and is available as a commercial product from Radiation Monitoring Devices Inc. (RMD). The energy resolution at room temperature (RT) is ~3.0% at 662 keV with a light yield of ~45 000 ph/MeV. The gamma-neutron pulse shape discrimination (PSD) figure of merit (FOM) is ~3.5 at RT. We investigated the gamma and neutron detection performance of CLLBC scintillators from 25 °C to 200 °C. The results showed a good light yield response for gamma events as a function of temperature while the light yield for neutron-capture events monotonically decreased from 100% to 76% at 200 °C. When integrated with a high-temperature photomultiplier, at 175 °C we obtained energy resolutions of 7.8% for 662 keV gammas and 4.2% for neutron-capture events, together with a PSD FOM of 0.74.