Measurement of the Response of the BC-523A Capture-Gated Liquid Scintillator to Typical Neutron Sources

Capture-gated detectors are suitable for neutron spectroscopy in mixed neutron and gamma-ray fields. In addition, they are less prone to neutron misclassification due to additional measured information. This information is available in the form of measured capture pulses that sometimes follow the initial neutron scattering pulses. This time-correlated, dual signal results in accurate neutron detection, which could be beneficial in several applications. The mixed fields typically occur in nuclear safeguards, nuclear nonproliferation, and national security applications; thus, capture-gated detectors might represent a new generation of detectors for these applications. One of commercially available capture-gated detectors is a BC-523A detector. This detector is a B-10-loaded liquid scintillation detector that is sensitive to not only fast neutrons and gamma rays, but also to thermal neutrons. Thus, three different signals are measured that can be distinguished from each other. This detector has recently attracted the attention of researchers because it has shown promise for full-energy neutron spectroscopy. Several efforts have been made to accurately characterize this detector for several neutron and gamma-ray energies. In this paper, we present measurement and simulation results for typical neutron sources such as Pu-238/Be, Pu-239/Be, Am/Be, Am/Li, and Cf-252 that were used to obtain the source- dependent response of the detector. We show that the spectroscopic information obtained from the detector can be used to discriminate the (alpha, n) sources Pu-238/Be, Pu-239/Be, and Am/Be from the Cf-252 source and the Am/Li source by using measured quantities such as ratios of the number of captured neutrons to scattering neutrons. This discrimination can be performed without having to acquire complete neutron pulse height distributions. This technique has the potential of reducing measurement times needed for accurate discrimination of the sources (with fully optimized detection system and detector size) when compared to the standard organic scintillators.