The Characterization of a Compact CLLB:Ce Scintillation Detector for Mixed-Field Monitoring at a Muon Facility

Compact scintillation detectors with simultaneous gamma and neutron sensitivity are increasingly relevant for mixed-field monitoring and nuclear measurements under size and cost constraints. This work characterizes a compact Cs2LiLaBr6:Ce (CLLB:Ce) detector with integrated SiPM readout at the ISIS Muon Facility. We assess its performance as a mixed-field monitor and a complementary tool for preliminary measurements in muon-based cultural heritage applications, where reference HPGe detectors are limited by size or geometry. The detector response was investigated under three conditions: environmental background at the muon facility, revealing intrinsic alpha activity in the 3–5 MeV region; simultaneous irradiation with an AmBe neutron source and a 137Cs gamma source, producing an enhancement in the 3.1–3.5 MeV region arising from both gamma-like and charged-particle-like contributions; PSD-resolved analysis identified a localized charged-particle-like excess near 3.2–3.3 MeV compatible with a neutron-sensitive response, including a possible contribution from 6Li(n,α)3H capture; and a proof-of-concept measurement on an irradiated Ag-Cu alloy plate. Pulse-shape discrimination based on digital charge integration yielded figures of merit of 1.71 ± 0.03 for background data and 1.53 ± 0.03 for the AmBe + 137Cs configuration. Finally, the Ag-Cu alloy measurement demonstrated the feasibility of operating the detector during muon irradiation to record spectral features compatible with Ag- and Cu-related emissions. While quantitative archaeometric applications require further calibration and benchmarking against HPGe, these results support the feasibility of using compact CLLB:Ce detectors as complementary mixed-field monitoring tools at muon facilities.