Digital Pulse Processing and Pile-up Correction in NaI(Tl) for Neutron Active Interrogation

Neutron active interrogation (NAI) is a valuable technique for detecting specific elements in materials to monitor hazardous or potentially threatening substances. This study proposes a pulsed fast neutron analysis (PFNA) method using a NaI(Tl) detector with digital processing and pile-up correction. By measuring the event time distribution during the operation of a deuterium-tritium (DT) neutron generator, time gating is applied, while modified phase-only correlation (MPOC) and maximum likelihood estimation (MLE) methods are used for pile-up correction. The pile-up corrected spectrum is compared with a conventional pulse-integrated spectrum. Application of time gating and pile-up correction techniques to gamma-ray spectroscopy in PFNA leads to an increased signal-to-background ratio in detecting specific gamma-ray lines. Different target materials are tested to distinguish the amount of carbon and observe the evidence of nitrogen presence.