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Digital n-γ pulse shape discrimination in organic scintillators with a high-speed digitizer
Chanho Kim2, Jung-Yeol Yeom2, Geehyun Kim1
1Department of Nuclear Engineering, Sejong University, Seoul, Korea
2Department of Bio-convergence Engineering, Korea University, Seoul, Korea
Correspondence  Geehyun Kim ,Tel: 82234084013, Fax: 82234083821, Email: gkim01@sejong.ac.kr
Received: October 11, 2018;  Accepted: April 9, 2019.
As neutron fields are always accompanied by gamma rays, it is essential to distinguish neutrons from gamma rays in the detection of neutrons. In scintillators, neutrons and gamma rays can be separated by pulse shape discrimination (PSD) methods. We performed characterization of a stilbene scintillator detector and a EJ-301 liquid scintillator detector with a high-speed digitizer and investigated optimized PSD variables for both detectors. This study is for providing a basis for developing fast neutron/gamma-ray dual-particle imager.
Materials and Methods:
We conducted PSD experiments using a stilbene scintillator and an EJ-301 liquid scintillator and evaluated neutron/gamma-ray discriminability of each PSD method with a 137Cs gamma source and a 252Cf neutron source. We implemented digital signal processing techniques to apply two PSD methods – the charge comparison (CC) method and the constant time discrimination (CTD) method – to distinguish neutrons from gamma rays. We tried to find optimized PSD variables giving the best discriminability in a given experimental condition.
Results and discussion:
For the stilbene scintillator detector, the charge comparison method and the constant time discrimination method both delivered the PSD FOM values of 1.7. For the EJ-301 liquid scintillator detector, both PSD methods delivered the PSD FOM values of 1.79. With the same PSD variables, PSD performance was excellent in 300±100 keVee, 500±100 keVee, and 700±100 keVee energy regions. This result shows that we can achieve an effective discrimination of neutrons from gamma rays using these scintillator detector systems.
We applied both PSD methods to a stilbene and a liquid scintillator and optimized the PSD performance represented by FOM values. We observed a good separation performance of both scintillators by digital PSD using a high-speed digitizer. These results will provide reference values for the dual-particle imager we are developing, which can image both fast neutrons and gammas simultaneously.
Keywords: Pulse shape discrimination; Stilbene; Liquid Scintillator; Digital signal processing; Dual-particle imager
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