Monte Carlo simulation of a Cs26LiYCl6:Ce-based composite scintillator for neutron and gamma detection

We report on the development of a Geant4 Monte Carlo model of composite scintillators based on cerium-doped, 6Li-enriched Cs2LiYCl6 (CLYC) embedded in a plastic matrix. Simulated pulse height spectra of detectors with CLYC pillars in an EJ-290 polyvinyltoluene (PVT) matrix reproduced measured spectra. Simulated pulse shape discrimination (PSD) by a composite detector irradiated by 239PuBe also reproduced experimental results. The features of the PSD histogram were interpreted by tracking relevant particles in the simulation. Then, the model was used to characterize various CLYC–PVT geometric designs for neutron detection and gamma spectroscopy. Optimizing the design for neutron detection (5.99–7.05 cm high-density polyethylene moderation and >6.3 cm CLYC pillar spacing) came with a tradeoff in photopeak efficiency. Calculated neutron detection and photopeak efficiencies of 1”, 1.5”, 2”, 3”, and 4”-diameter CLYC crystals were comparable to those of equivalent amounts of smaller CLYC pillars in EJ-290. These results encourage the development of large-area CLYC–PVT arrays, to achieve detection efficiencies exceeding those of the largest CLYC crystals grown to date.