A comparison on three neutron-gamma discrimination methods used with NE213, UGLLT and UGAB scintillators

Liquid organic scintillators are widely used in radiation measurements. NE213 (or its equivalent, BC-501A) in neutron-gamma discrimination (NGD) and two new scintillators, UGLLT and UGAB, in alpha-beta discrimination are two common examples. In this paper, the NGD capabilities of these three scintillators were studied and their figure-of-merits (FoMs) were measured for comparison. The three different NGD methods used in this study were zero-cross method (ZCM), charge integration method (CIM) and filtered charge integration method (FCIM), where ZCM was analog and the two other methods were digital. A 1.1 mu Ci point Na-22 gamma ray source and 100 mCi cylindrical Am-241-Be neutron source (3.5 cm diameter by 5 cm length) were used for the energy calibration and the NGD, respectively. The FoM values for NE213, UGLLT and UGAB at 100 keVee discrimination bias (i.e., the preset threshold voltage, generally expressed in keVee unit, upon which the generated pulse-heights are recorded) using ZCM, CIM and FCIM methods were (1.060 +/- 0.037, 1.430 +/- 0.040, 1.70 +/- 0.054), (0.910 +/- 0.029, 1.270 +/- 0.018, 1.460 +/- 0.027) and (0.890 +/- 0.027, 1.200 +/- 0.020, 1.460 +/- 0.026), respectively. Although UGAB scintillator exhibits the least discrimination quality, one can choose an appropriate neutrongamma discrimination method to improve its FoM. The low-temperature flammability, toxicity and high-evaporation properties of NE213 scintillator may motivate some researchers to use UGLLT and UGAB scintillators as alternatives to NE213, however, by selecting the most efficient discrimination method.