Neutron/Gamma-ray Pulse Shape Discrimination with a CLYC Scintillator

Cs ₂ LiYCl ₆ :Ce ³⁺ (CLYC) is a promising Li-based inorganic scintillator for its dual-mode detector capability to perform neutron detection and gamma spectroscopy. Pulse Shape Discrimination (PSD) between neutron and gamma-ray signals can achieve superior results owing to the fundamentally unique scintillation mechanisms within CLYC crystal. In this work, an 1×1 inch CLYC scintillator enriched with 95% ⁶ Li was used for simultaneous neutron and gamma-ray detection. Difference on pulse rise time between neutron and gamma-ray was found and its effects on traditional charge integration method were analyzed. A pulse shape discrimination (PSD) method based on Fisher linear discriminant was used to discriminate neutron and gamma-ray signals with different parts of waveform. The results show that positive effect on neutron and gamma-ray PSD appears when the integral window is well set based on the pulse rise time. Fisher classification achieves better figure-of-merit (FOM) of 4.6±0.1 compared to charge integration method. This method also shows reliable screening ability only using the short recording waveforms whose distinctions are mainly from the rising part. When the length of waveforms is 80 ns, the FOM is 2.3±0.1. This benefits the applications of CLYC in high count rate situations with short recording waveforms.