Year
2013
Abstract
One of the top priorities in the nuclear-nonproliferation field is the detection of special nuclear material and other radiation sources. In order to protect against the proliferation of nuclear material across borders, it is important to utilize fast and robust detection/identification methods. Due to the shortage of He-3, our current standard neutron-detection medium, other detection materials must be identified, characterized, and compared to the He-3 systems. Organic scintillators (sensitive to neutrons and gamma rays) have been used for decades in areas such as nuclear nonproliferation, reactor instrumentation, particle physics, material science, dosimetry, and astrophysics, and their performance has been significantly improved over time. One of the improvements is related to the advances in the field of fast-waveform digitizers; the digitizers, after carefully choosing their sampling properties, help to utilize most of the information available in the organic-scintillator signal and optimize pulse-shape discrimination (PSD) of neutrons from gamma rays. Accurate PSD is essential for accurate detection of neutrons with organic scintillators in mixed neutron/gamma-ray fields. This work compares the PSD properties of three organic-scintillator materials: stilbene, pterphenyl, and EJ-309 organic-liquid scintillators. Digital PSD analyses were performed, the PSD performance was optimized for each material individually, and the results were quantitatively compared against each other. Measurements were performed with various gammaray and neutron sources. Previously developed figures of merit were used to compare the scintillators in an unbiased way. The measurement and data-acquisition systems used were developed at the University of Michigan utilizing a CAEN V1720 digitizer and optimized PSD algorithms. In the paper, the PSD properties of the aforementioned organic scintillators are discussed in detail.