A Digital Method for the Discrimination of Neutrons and $\gamma$ Rays With Organic Scintillation Detectors Using Frequency Gradient Analysis

A digital method for the discrimination of neutron and γ-ray events from an organic scintillator has been investigated by using frequency gradient analysis (FGA) based on the Fourier transform. Since the scintillation process and the photomultiplier tube (PMT) anode signal are often very noisy, most pulse-shape discrimination methods in a scintillation detection system (e.g., the charge comparison (CC) method or pulse gradient analysis (PGA)) using time-domain features of the signal depend greatly on the associated de-noising algorithm. In this research, the performance of the new FGA method and the PGA method have been studied and compared on a theoretical basis and then verified by time-of-flight (TOF). The frequency-domain features extracted by the FGA method exhibit a strong insensitivity to the variation in pulse response of the photomultiplier tube (PMT) and can be used to discriminate neutron and γ-ray events in a mixed radiation field. It is shown that the FGA method results in an increased figure of merit (FOM) which corresponds to a reduction in the area of overlap between neutron and γ-ray events. The FGA method has the potential to be implemented in current embedded electronic systems to provide real-time discrimination in standalone instruments.