Characterizing Emerging Detectors for Neutron and Gamma-ray Spectroscopy*

Cs₂LiYCl₆ (CLYC) detectors are novel scintillators capable of detecting both gamma rays and neutrons at room temperature. Four ⁷Li-enriched CLYCs of 1” x 1” square cross-sections and 3” length (the first of their kind in non-cylindrical shapes) were tested in different setups for their use in gamma and neutron spectroscopy. The first tests focused on the energy-dependent attenuation of gammas in stacked CLYC crystals, using a Eu-152 calibration source and a high-resolution Ge detector operated at liquid nitrogen temperatures. Subsequent tests used proton beams from the UML 5.5-MV Van de Graaff accelerator to produce mono-energetic neutrons by bombarding a thin Li target. The ability of CLYCs to discriminate between neutrons and gammas from their pulse shapes was quantified. The final tests had the CLYCs in a compact 2” x 2” x 3” geometry. Photopeaks in the individual detectors and the Compton scatters between the detectors were analyzed with radioactive Na-22, Cs-137, and Pu-Be sources. Energy typically lost as noise in the Compton continuum for a single detector could be tagged through coincident events between detectors and added back event-by-event to improve photopeak efficiency of the detector assembly. These tests provide an upgrade path to design CLYC arrays that overcome current crystal-growing size limitations.