Performance comparison of NE213 detectors for their application in moisture measurement

The pulse shape discrimination (PSD) characteristic and neutron detection efficiency of NE213 detectors have been measured for their application in moisture measurements using 252Cf and 241Am-Be sources. In PSD studies, neutron peak to valley (Pn/V) ratio and figure of merit M were measured at four different bias values for cylindrical 50, 125 and 250 mm diameter NE213 detectors. The result of this study has shown that better PSD performance with the NE213 detector can be achieved with a smaller volume detector in conjunction with a neutron source with smaller gamma-ray/neutron ratio. The neutron detection efficiency of the 125 mm diameter NE213 detector for 241Am-Be and 252Cf source spectra was determined at 0.85, 1.25 and 1.75 MeV bias energies using the experimental neutron detection efficiency data of the same detector over 0.1-10 MeV energy range. Due to different energy spectra of the 241Am-Be and 252Cf sources, integrated efficiency of the 125 mm diameter NE213 detector for the two sources shows bias dependence. At smaller bias, 252Cf source has larger efficiency but as the bias is increased, the detector has larger efficiency for 241Am-Be source. This study has revealed that NE213 detector has better performance (such as PSD and neutron detection efficiency) in simultaneous detection of neutron and gamma-rays in moisture measurements, if it is used in conjunction with 241Am-Be source at higher detector bias.