This talk introduces a novel and extremely simple – and therefore, easily implemented in a Field-Programmable Gate Array (FPGA) – method of neutron/gamma pulse discrimination called the Histogram-Difference Method (HDM). Crucially, this method relies on the use of a ”reference set” of γ-only pulses from Na22, Cs137 and Co60 sources and on features extracted from the pulses. The pulses from this reference set are compared to a set of an identical number of n+γ pulses from a Cf252 source. Not only can HDM determine the presence of neutrons in the Cf252 source, but it can also estimate the approximate percentage of neutron pulses from that source. The results reported in this paper are based on data from different radioactive sources and a standard scintillator for this type of research – namely, BC-501A. These results were confirmed using three other scintillators, one made in-house, and two others that are commercially available, EJ-299-33 and EJ-200. Pulses were encoded using Q-values, which are features extracted from the pulses, i.e., (Qtail, Qtotal) pairs in R2. As a control, we also encoded pulses as the Root-Mean-Square (RMS) distances from the average pulse of all known γ-only pulses and ran HDM using these pulse representations. The results are very similar to those obtained using a Q-value encoding of the pulses.
LEAD CNRS – Université Bourgogne Franche-Comté