Gamma–neutron imaging system utilizing pulse shape discrimination with CLYC

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2015-06, Vol.784, p.346-351
• Main Authors: Whitney, Chad M., Soundara-Pandian, Lakshmi, Johnson, Erik B., Vogel, Sam, Vinci, Bob, Squillante, Michael, Glodo, Jarek, Christian, James F.
• Format: Article
• Language: English
• Subjects: CLYC; Gamma–neutron imaging; Pulse shape discrimination; RadCam
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2014.09.022

Recently, RMD has investigated the use of CLYC (Cs2LiYCl6:Ce), a new and emerging scintillation material, in a gamma–neutron coded aperture imaging system based on RMD׳s commercial RadCamTM instrument. CLYC offers efficient thermal neutron detection, fast neutron detection capabilities, excellent pulse shape discrimination (PSD), and gamma-ray energy resolution as good as 4% at 662keV. PSD improves the isolation of higher energy gammas from thermal neutron interactions (>3MeV electron equivalent peak), compared to conventional pulse height techniques. The scintillation emission time in CLYC provides the basis for PSD; where neutron interactions result in a slower emission rise and decay components while gamma interactions result in a faster emission components. By creating a population plot based on the ratio of the decay tail compared to the total integral amplitude (PSD ratio), discrimination of gammas, thermal neutrons, and fast neutrons is possible. Previously, we characterized the CLYC-based RadCam system for imaging gammas and neutrons using a layered W-Cd coded aperture mask and employing only pulse height discrimination. In this paper, we present the latest results which investigate gamma-neutron imaging capabilities using PSD. An FPGA system is used to acquire the CLYC–PSPMT last dynode signals, determine a PSD ratio for each event, and compare it to a calibrated PSD cutoff. Each event is assigned either a gamma (low) or neutron (high) flag signal which is then correlated with the imaging information for each event. •The latest results are presented for our CLYC RadCam-2 system which investigate gamma–neutron imaging using pulse shape discrimination.•CLYC RadCam-2 system successfully discriminates gammas, thermal neutrons, and fast neutrons by employing a fully integrated, FPGA-based PSD system.•Imaging of our 252Cf source was possible using both pulse height and pulse shape discrimination with CLYC.•Imaging with PSD demonstrates the potential for increasing the neutron contrast by discriminating gammas at higher energies.