Reference-pulses neutron/gamma-ray pulse shape discrimination in liquid scintillators for deposited neutron energies from 200 keV

A hybrid pulse shape discrimination (PSD) method is presented that combines a charge-integration PSD method with a reference-pulses PSD method. The reference-pulses PSD method uses detailed knowledge of the average, energy-dependent detector response to radiation. To obtain the reference pulses, a large number of neutron and gamma-ray pulses were averaged in several pulse height regions. The reference neutron and gamma-ray pulses were then used in the new PSD method for the classification of `known´ measured pulses. The reference-pulses PSD method was applied below 70 keVee (keV electron equivalent), whereas the standard charge-integration PSD method was used above 70 keVee. This new hybrid PSD method proves to be more accurate than the standard charge-integration PSD method for classification of neutrons and gamma rays. Specifically, the improvement is approximately 30% for neutrons between 20 and 30 keVee (corresponding to approximately 50 and 225 keV neutron energy deposited). For this pulse height bin, approximately 72% of the neutrons were correctly classified by the hybrid PSD method. The average number of correctly classified neutrons is approximately 88% for the hybrid PSD method between 20 and 100 keVee (150 and 670 keV neutron energy deposited) as opposed to 83% for the charge-integration PSD method.