Comparison of deuterated and normal liquid scintillators for fast-neutron detection

Liquid organic scintillators have long been used for fast-neutron detection due to their fast response and the ability to use pulse-shape discrimination (PSD) to distinguish between neutron and γ-ray interactions. Deuterated liquid organic scintillators have, in addition to the aforementioned properties, structure on their pulse-height spectra due to the different characteristics of n-d vs. n-p scattering. We report on the direct comparison of two small-volume liquid scintillator detectors with exactly the same geometries (11.43 cm diameter and 2.54 cm thickness); the first based on NE213 produced by Nuclear Enterprise, and the second based on EJ-315 produced by Eljen Technologies, the latter being a deuterated scintillator. A variety of photomultiplier tubes (PMTs) were used, but the quality of the data was determined to be independent of the PMT type. It is shown that, while the light output of the deuterated detector is lower than for the conventional non-deuterated detector, it is possible to detect 60 keV neutrons. The PSD capabilities of the deuterated detector match and surpass those of the NE213 detector. Its efficiency is comparable to that of the NE213 detector at neutron energies above 2 MeV; below that energy its relative efficiency suffers from the significantly lower n-d scattering cross-section. For very low neutron energies (<200keV), the relative efficiency of the deuterated detector increases again, due to the lower noise level for our particular detectors, showing the importance of low photomultiplier tube noise for the detection of low-energy neutrons.