Characterization of a Boron-Loaded Liquid Scintillator EJ-309:B5 for Neutron Energies Between 0.5 and 10 MeV

Various neutron and gamma-ray detector types have been investigated for applications in fields such as nuclear nonproliferation, nuclear safeguards, reactor instrumentation, and dosimetry. Recently, various capture-gated organic scintillation detectors have been studied with a focus on their neutron-spectroscopy capabilities. When compared to standard organic scintillators, the capture-gated detectors contain an additional material with a high absorption cross section for thermal neutrons (B-10, Li-6, etc.). Therefore, fast neutrons can be thermalized and captured within the detector, generating two separate pulses (scatter pulse followed by capture pulse) with a characteristic time delay. The data analysis is then used to ‘confirm’ the detection of a neutron and infer the incident neutron spectrum. One example of the capture-gated detector is EJ-309:B5 (also known as EJ-339), which is a boron-loaded liquid scintillator manufactured by Eljen Technology, containing ~ 5wt% of natural boron. This detector was used in conjunction with a Cf-252 source (neutron energies up to 10 MeV) to acquire its response. An optimized digital pulse-shape discrimination method was used to separate captured neutrons from scatter neutrons and gamma rays, and to obtain the resulting pulse-height and time-to-capture distributions. The knowledge of the detector response is especially important if the original neutron spectrum of the material under investigation needs to be acquired to identify/characterize the investigated material. The average pulse height of captured neutrons was estimated to be 98 keVee which is in a good agreement with the expected value. Approximately 0.25% of the measured pulses were identified as capture pulses and the ratio of capture and scatter neutron pulses was approximately 0.62%.