Simultaneous Detection of Energy and Flux for Neutron and Gamma by CLYC Scintillator

A 1-in Cs2LiYCl6:Ce (CLYC) scintillator coupled with Photomultiplier tube (PMT) was used to detect neutrons and gamma rays simultaneously in this work. The pulses were captured by a high-speed digitizer with 1-Gsamples per second and 12-bit vertical resolution and further analyzed in real time to determine the pulse type, energy spectrum, and flux. The response of CLYC scintillators measured with three PMT models, R6231 and XP2020, were found to have better energy resolution, while R580 was found to have better pulse shape discrimination (PSD) performance. The energy resolution was optimized by adjusting the integration time window. Slight differences were found to be within the range of 2000-8000 ns for different PMT models. The fast neutron peaks from Cl-35(n, p)S-35 reaction were detected along with the thermal neutron peak from Li-6(n, alpha)H-3, and a quenching factor of 0.9 was obtained for protons. The energy resolution was 14.7% and the detection efficiency was about 0.15% for 1.5-MeV fast neutron. The discrimination performance between neutron and gamma pulses was studied using the charge comparison method. The figure-of-merit (FOM) value was found to be better than 1.90 within the energy range of 0.5-10 MeV, i.e., 2.0 for 1.5-MeV fast neutron and similar to 3.2 for thermal neutron. The flux of fast neutrons, thermal neutrons, and gamma rays was detected simultaneously, and the prompt gamma rays by neutron activation were also identified. It indicates that the CLYC detector can be used for multimode detection of thermal neutrons, fast neutrons, and gamma rays, and would be a suitable compact candidate for prompt gamma neutron activation (PGNAA) analysis in limited space.