Optimization of the <i>n</i> / <i>γ</i> Pulse Shape Discrimination Performance of Plastic Scintillator Coupled With SiPM Arrays

This paper studies the influence of bias voltage on pulse waveform, energy resolution, and particle discrimination performance to optimize the performance of n / γ pulse shape discrimination (PSD) for plastic scintillator coupled with SiPM arrays. Experiments were carried out with the EJ‐276 plastic scintillator detection system based on 2 × 2 SiPM arrays in gamma sources ( 22 Na, 60 Co, 137 Cs) and neutron source ( 252 Cf). And the pulse amplitude, shape, and the dispersion degree of the pulse waveform with bias voltage in the range of 25.8–28.8 V were analyzed. Gauss expansion method and PSD method based on the charge integration were used to obtain accurate energy resolution and PSD parameter, respectively. The results showed that energy resolution and PSD performance improved firstly and then deteriorated as bias voltage increases, and the optimum bias voltage for both energy resolution and PSD performance was 27.6 V. Within the bias voltage range of 25.8–28.8 V, the energy resolutions at the optimal bias voltage were improved by 25.17% (0.341 MeV for 22 Na source) and 22.24% (1.062 MeV for 22 Na source). Additionally, the PSD performance for n / γ discrimination was improved by 19.6%.