Compact MPPC-based coded aperture imaging camera for dual-particle detection

Abstract

Purpose Fast neutrons and gamma-ray imaging detection is an effective way to detect and identify radioactive material in the field of nuclear security. A compact coded aperture imaging (CAI) camera was designed to be sensitive to both gamma and neutron radiation based on plastic scintillators and multi-pixel photon counters (MPPC). Methods MPPCs coupling with the 13 × 13 pixelated plastic scintillators one-to-one were utilized to reduce the scale of the CAI system while maintaining good positional performance. The symmetric charge division (SCD) circuit was adopted to reduce the 169 signals output from the MPPC array to 26. Each waveform was collected and processed with four Domino Ring Sampler 4 (DRS4) chips and two 16-channel analog-to-digital converter (ADC) modules. As the pulse shapes of fast neutrons would be broadened after elastic scattering multiple times in the scintillators, the Anger-Logic method was applied to eliminate multiple elastic scattering events so that good pulse shape discrimination (PSD) performance can be achieved. Results The imaging and detection ability of the camera was evaluated using the 241 Am-Be (5.9 × 10 5 n/s) neutron source and 137 Cs (370 MBq) gamma source. The camera can be used to detect fast neutrons (0.5-10 MeV) and gamma rays (0.2-2.5 MeV). Furthermore, it can implement efficient neutron/gamma PSD capabilities in the mixed-field environment. The figure of merit (FOM) of the camera calculated at 400keVee energy cut is 0.93. Conclusion A compact MPPC-based CAI camera was designed to detect and discriminate fast neutrons and gamma rays. Its good PSD performance was well suited to distinguish fast neutrons from gamma rays in a dual-particle environment. The portable design makes it promising for complex monitoring scenarios in nuclear security. Keywords Coded aperture imaging • Fast neutron imaging • Gamma imaging • n-γ discrimination Projects of Chinese Academy of Sciences (Grant Number ZDRW-CN-2018-1-01) and the Research Equipment Development Project of Chinese Academy of Sciences (Grant Number YZ201415).The authors would also like to acknowledge Division of Nuclear Technology and Applications, IHEP staff for their valuable technical support.

Evaluation of a Positron-Emission-Tomography-based SiPM readout for Compact Segmented Neutron Imagers

“…Worldwide, there are now multiple efforts to develop a "single-volume" directional neutron detectors [1][2][3][4][5][6][7][8][9], motivated primarily by a desire to reduce size and complexity of neutron imagers. An effective way to achieve the detection and characterization of multiple neutron scatters is to use an array of independent detector segments.…”