Optimizing Cs2LiYCl6 for fast neutron spectroscopy

Cs2LiYCl6 (CLYC) has generated recent interest as a thermal neutron detector due to its excellent n/γ-ray pulse-shape discrimination and energy resolution. Here, the capabilities of CLYC as a fast neutron detector and spectrometer are reported. A 1 in.×1 in. CLYC detector was used to measure the response of mono-energetic neutrons over a range of 0.8-2.0 MeV produced via the 7Li(p,n) reaction at the University of Massachusetts Lowell 5.5 MV Van de Graaff accelerator. A broad continuum from the 6Li(n, α) reaction was observed, as well as additional peaks below the thermal capture peak. Based on possible reactions in CLYC, the additional peaks are determined to be due to the 35Cl(n,p)35S reaction, with a Q-value of +615 keV, and corroborated in simulations using MCNPX. The average resolution of 9% for these peaks makes CLYC a promising candidate for a fast neutron spectrometer.