Digital discrimination of neutrons and [formula omitted]-rays in liquid scintillation detectors by using low sampling frequency ADCs

Abstract

It is well known that the digital pulse-shape discrimination (PSD) of fast neutrons and γ-rays in liquid scintillation detectors can be adversely affected by the low sampling frequency of the analog-to-digital converter (ADC). Previous studies have recommended that using an ADC with a sampling frequency of above 250 MHz is necessary to achieve a PSD performance comparable to that of the analog PSD systems. In the present study, we show that, in principle, a sampling frequency of above 32 MHz is sufficient to fully preserve the pulse-shape information of liquid scintillation detectors, though at such sampling frequencies a significant degradation of the PSD performance may arise from the used PSD algorithm. To avoid this problem, a new PSD algorithm in the frequency domain is presented and its excellent performance at low sampling frequencies is experimentally demonstrated. At the sampling frequency of 32 MHz, a Figure-of-Merit (FOM) of 1.31 ± 0.04 in the light output range of 200–1400 keVee (electron equivalent energy) is achieved with an ADC of 10-bit resolution.