Neutron-Gamma Pulse Shape Discrimination Using Organic Scintillators With Silicon Photomultiplier Readout

Abstract

Neutron/Gamma pulse shape discrimination (PSD) was measured using stilbene and EJ-299-34 plastic scintillators with readout by silicon photomultipliers (SiPMs). The SiPM pulses were digitized and processed for energy and pulse shape information using a digital technique performing numerical weighted integrations on each pulse. A genetic algorithm (GA) was developed to optimize the weighting vectors used for the pulse shape discrimination. Efficient PSD was obtained down to an electron-equivalent energy of 127 keV with stilbene and 391 keV with the EJ-299-34 PSD plastic. Separation at lower energies was possible at reduced detection efficiency, down to 78 keV and 186 keV at 50% efficiency. The detectors were used to measure separated gamma and neutron spectra from an Americium-Beryllium neutron source and from a Na-22 gamma source. The GA-optimized weighted integration was compared with digital charge comparison (DCC). The GA exhibited slightly improved performance with a 400 MSps digitization rate and showed a significant advantage at sample rates below 100 MSps.

Pulse shape discrimination performance of stilbene coupled to low-noise silicon photomultipliers

“…When coupled to a scintillating medium, these devices have been used in a variety of radiation detection and spectroscopy applications including dosimetry [3,4], medical imaging [5][6][7][8], high-energy physics [9][10][11], and homeland security [12][13][14]. Additionally, organic crystals with pulse shape discrimination (PSD) capabilities coupled to SiPMs have been shown to be capable of fast-neutron detection [15][16][17]. Previous approaches used complex PSD algorithms and exhibited poorer PSD performance with SiPMs when compared to PMTs.…”

Comparative Study of SiPM Arrays Performances for Neutron Detectors

“…Dark pulses arise from thermally generated electrons initiating avalanches in high-field regions, while after-pulsing is triggered by the release of trapped charges within the silicon crystal, leading to a secondary avalanche within the same micro-cell. The occurrence of these phenomena is influenced by pixel recovery times, as discussed in [8], [9]. Another challenge encountered in SiPMs arises when covering extensive areas, leading to high capacitance, and consequently, the need for pre-amplification stages.…”

“…Importantly, it must be recognized that the conversion of light into charge in a SiPM does not follow the same principles as in a PMT. Several authors have demonstrated the possibility to perform neutron/gamma-ray using millimeter scale scintillators coupled to single SiPMs, obtaining good results [8], [16], [17]. However, when large area SiPMs (array of single SiPMs) are coupled to medium-sized scintillators, achieve n/γ discrimination performance comparable with the one obtained with the PMTs is still a significant challenge, as reported in [18]- [20].…”

Impact of the Detected Scintillation Light Intensity on Neutron-Gamma Discrimination

“…In the last decade, SiPMs have been used in a variety of fields, such as particle and nuclear physics, medical imaging and homeland security [1]- [3]. It has been shown that SiPMs, coupled to specifically engineered scintillators with sensitivity to both fast and slow neutrons, represent a viable solution for the discrimination of light pulses originated by gamma rays against neutrons [4]. The enabling feature of this class of scintillators is the different light emission time in response to interactions of neutrons or gamma rays.…”