Li-6 Glass Scintillator for Detecting and Discriminating Fission Neutrons in a Mixed Radiation Field Using Time-of- Flight Technique

Techniques exist for detecting neutrons in different energy regions. The energy distribution is indirectly measured by neutron interactions and characterizing the pulse height distribution of light output produced through nuclear reactions within the detectors. Cerium activated Li-6 glass scintillators have a high interaction cross section for slow neutrons which decreases with increasing neutron energy. However, by taking advantage of the pronounced resonance at En ˜ 250 keV, Li-6 glass scintillators can also be used for detecting fission neutrons. Because neutrons are also accompanied by gamma-rays in a mixed radiation field, a major limitation in the use of Li-6 glass scintillator is the discrimination of the neutron signal from the gamma-ray signal. The conventional charge-integration pulse shape discrimination technique cannot be used to discriminate neutrons from gamma-rays because of approximately similar neutron and beta excitation decay times in the scintillating medium. The purpose of this paper is to characterize spontaneous fission neutrons emitted by a 252Cf source by time-of-flight (TOF) technique. The paper additionally presents a method of discriminating fission neutrons distribution from gamma-ray distribution by selecting timing windows in TOF pulses recorded in the Li-6 glass scintillator.