Digital techniques for n/γ pulse shape discrimination and capture-gated neutron spectroscopy using liquid scintillators

We have investigated the use of digital pulse processing techniques for n/γ pulse shape discrimination (PSD) in liquid scintillators, and the application of these techniques to a capture-gated fast neutron monitor developed using the enriched 10B-loaded liquid scintillator BC523A. The motivation for this study has been to develop computationally fast digital PSD algorithms that can be implemented in a compact portable fast neutron monitor. The PSD separation achieved with a digital pulse risetime algorithm has a Figure of Merit comparable with previously reported analogue techniques, and provides extremely sensitive fast neutron detection in the presence of a strong gamma background. The capture-gated performance of a 685 cm3 BC523A liquid scintillator cell was investigated using fast neutrons from an Am–Be source, and the application of digital pulse processing techniques to the capture-gated detection mode is discussed. The measured mean neutron capture time in BC523A was 470±80 ns which is a factor of five shorter than that reported for liquid scintillators loaded with natural boron.