Abstract:The pulse shape discrimination performance of a pixelated organic plastic scintillator has been investigated. The scintillator has been built using 169 plastic scintillator blocks (arranged into a 13 × 13 square array) of 2.8 × 2.8 × 15 mm3 each. The scintillator was coupled with a single-channel photomultiplier tube. The scintillator was exposed to a mixed-field environment provided by 252Cf and its pulse shape discrimination capabilities are presented in this paper. Initial results revealed t… Show more
“…Thus, the light loss might cause a lower FOM value. Nevertheless, because intrinsic particle separation of the scintillator is achieved 5 , the low sampling rate ADCs were capable of performing satisfactory PSD using the pixelated stilbene-SiPM array module. Figure 6 ( a ) The overall detector PSD plot for 1,500,000 pulses produced by the stilbene-SiPM module with a threshold of 50 keVee by measuring a 3.5 × 10 5 n/s 252 Cf spontaneous fission source at 75 cm distance and a 137 Cs source producing 30.16 μR/h at 30 cm distance.…”
Section: Resultsmentioning
confidence: 99%
“…The experiments verified that the coded aperture-based DPI can provide effective neutron-source imaging with a limited number of counts and therefore rapid imaging for relatively intense or proximate neutron sources. This can be compared with H2DPI from the University of Michigan 5 that has a quoted localization time of 30 min for the neutron image of a 1.2 × 10 7 n/s 252 Cf source at 58.4 cm from the center of system.…”
Section: Resultsmentioning
confidence: 99%
“…In 5 , the authors implemented a pixelated detector in a hand-held DPI configuration using pulse-shape discrimination (PSD). The instrument, which consisted of a plastic scintillator (EJ-299-34) 13 × 13 square array with a small pixel size (2.8 × 2.8 × 15 mm 3 ), exhibited a marked degradation of PSD performance in the pixelated crystal array when compared to a single crystal.…”
Dual particle imaging, in which both neutrons and gamma-rays in the environment can be individually characterized, is particularly attractive for monitoring mixed radiation emitters such as special nuclear materials (SNM). Effective SNM localization and detection benefits from high instrument sensitivity so that real-time imaging or imaging with a limited number of acquired events is enabled. For portable applications, one also desires a dual particle imager (DPI) that is readily deployable. We have developed a hand-held type DPI equipped with a pixelated stilbene-silicon photomultiplier (SiPM) array module and low sampling-rate analog-to-digital converters (ADCs) processed via a multiplexed readout. The stilbene-SiPM array (12 × 12 pixels) is capable of effectively performing pulse shape discrimination (PSD) between gamma-ray and neutron events and neutron/gamma-ray source localization on the imaging plane, as demonstrated with 252Cf neutron/gamma and 137Cs gamma-ray sources. The low sampling rate ADCs connected to the stilbene-SiPM array module result in a compact instrument with high sensitivity that provides a gamma-ray image of a 137Cs source, producing 6.4 μR/h at 1 m, in less than 69 s. A neutron image for a 3.5 × 105 n/s 252Cf source can also be obtained in less than 6 min at 1 m from the center of the system. The instrument images successfully with field of view of 50° and provides angular resolution of 6.8°.
“…Thus, the light loss might cause a lower FOM value. Nevertheless, because intrinsic particle separation of the scintillator is achieved 5 , the low sampling rate ADCs were capable of performing satisfactory PSD using the pixelated stilbene-SiPM array module. Figure 6 ( a ) The overall detector PSD plot for 1,500,000 pulses produced by the stilbene-SiPM module with a threshold of 50 keVee by measuring a 3.5 × 10 5 n/s 252 Cf spontaneous fission source at 75 cm distance and a 137 Cs source producing 30.16 μR/h at 30 cm distance.…”
Section: Resultsmentioning
confidence: 99%
“…The experiments verified that the coded aperture-based DPI can provide effective neutron-source imaging with a limited number of counts and therefore rapid imaging for relatively intense or proximate neutron sources. This can be compared with H2DPI from the University of Michigan 5 that has a quoted localization time of 30 min for the neutron image of a 1.2 × 10 7 n/s 252 Cf source at 58.4 cm from the center of system.…”
Section: Resultsmentioning
confidence: 99%
“…In 5 , the authors implemented a pixelated detector in a hand-held DPI configuration using pulse-shape discrimination (PSD). The instrument, which consisted of a plastic scintillator (EJ-299-34) 13 × 13 square array with a small pixel size (2.8 × 2.8 × 15 mm 3 ), exhibited a marked degradation of PSD performance in the pixelated crystal array when compared to a single crystal.…”
Dual particle imaging, in which both neutrons and gamma-rays in the environment can be individually characterized, is particularly attractive for monitoring mixed radiation emitters such as special nuclear materials (SNM). Effective SNM localization and detection benefits from high instrument sensitivity so that real-time imaging or imaging with a limited number of acquired events is enabled. For portable applications, one also desires a dual particle imager (DPI) that is readily deployable. We have developed a hand-held type DPI equipped with a pixelated stilbene-silicon photomultiplier (SiPM) array module and low sampling-rate analog-to-digital converters (ADCs) processed via a multiplexed readout. The stilbene-SiPM array (12 × 12 pixels) is capable of effectively performing pulse shape discrimination (PSD) between gamma-ray and neutron events and neutron/gamma-ray source localization on the imaging plane, as demonstrated with 252Cf neutron/gamma and 137Cs gamma-ray sources. The low sampling rate ADCs connected to the stilbene-SiPM array module result in a compact instrument with high sensitivity that provides a gamma-ray image of a 137Cs source, producing 6.4 μR/h at 1 m, in less than 69 s. A neutron image for a 3.5 × 105 n/s 252Cf source can also be obtained in less than 6 min at 1 m from the center of the system. The instrument images successfully with field of view of 50° and provides angular resolution of 6.8°.
“…This is because the stilbene scintillator pixels used here are not only smaller than those used in the reference studies, but also the pixels of SiPM used here have smaller active areas than the PMT. Nevertheless, because intrinsic particle separation of the scintillator is achieved [5], the low sampling rate ADCs were capable of performing satisfactory PSD using the pixelated stilbene-SiPM array module.…”
Section: Resultsmentioning
confidence: 99%
“…The experiments verified that the coded aperture-based DPI can provide effective neutron-source imaging with a limited number of counts and therefore rapid imaging for relatively intense or proximate neutron sources. This can be compared with H2DPI from the University of Michigan [5] that has a quoted localization time of 30 minutes for the neutron image of a 1.2 × 10 7 n/s 252 Cf source at 58.4 cm from the center of system. Similar to neutron image evaluation, we estimated the quality of gamma-ray images by measuring the 137 Cs producing 6.4 μR/h at 100 cm from the hand-held DPI.…”
Dual particle imaging, in which both neutrons and gamma-rays in the environment can be individually characterized, is particularly attractive for monitoring mixed radiation emitters such as special nuclear materials (SNM). Typical dual particle imagers (DPIs) are not readily deployable and easily portable for hand-held applications because they are implemented using bulky single-crystal scintillators and photomultiplier tubes (PMTs) implemented with a 1:1 channel readout. Effective SNM localization and detection also benefits from high instrument sensitivity so that real-time imaging or imaging with a limited number of acquired events is enabled. We have developed a hand-held type DPI equipped with a pixelated stilbene-silicon photomultiplier (SiPM) array module and low sampling-rate analog-to-digital converters (ADCs) processed via a multiplexed readout. The stilbene-SiPM array (12 × 12 pixels) is capable of effectively performing pulse shape discrimination (PSD) between gamma-ray and neutron events and neutron/gamma-ray source localization on the imaging plane, as demonstrated with 252Cf neutron/gamma and 137Cs gamma-ray sources. The low sampling rate ADCs connected to the stilbene-SiPM array module result in a compact instrument with high sensitivity that provides a gamma-ray image of a 137Cs source, producing 6.4 μR/h at 1 m, in less than 69 seconds. A neutron image for a 3.5 × 105 n/s 252Cf source can also be obtained in less than 6 minutes at 1 m from the center of the system. The instrument images successfully with field of view of 50° and provides angular resolution of 6.8°.
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.
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