Neutron spectroscopy by thermalization light yield measurement in a composite heterogeneous scintillator

Abstract

An exothermic neutron capture reaction can be used to uniquely identify neutrons in particle detectors. With the use of a capture-gated coincidence technique, the sequence of scatter events that lead to neutron thermalization prior to the neutron capture can also be used to measure neutron energy. We report on the measurement of thermalization light yield via a time-of-flight technique in a polyvinyl toluene-based scintillator EJ-290 within a heterogeneous composite detector that also includes 6 Li-doped glass scintillator. The thermalization light output exhibits a strong correlation with neutron energy because of the preference for near-complete energy deposition prior to the 6 Li(n,t) 4 He neutron capture reaction. The nonproportionality of the light yield from nuclear recoils contributes to the observed broadening of the distribution of thermalization light output. The nonproportional dependence of the scintillation light output in the EJ-290 scintillator as a function of proton recoil energy has been characterized in the range of 0.3-14.1 MeV via the Birks parametrization through a combination of time-of-flight measurement and previously conducted measurements with monoenergetic neutron sources.

Discriminating Uranium Isotopes Based on Fission Signatures Induced by Delayed Neutrons

“…The PVT matrix surrounding the lithium glass rods serves a dual purpose. Not only does it increase the capture efficiency of the detector by moderating the incident neutrons, but the scintillation response of the PVT to proton recoils in the neutron thermalization process provides a signal whose magnitude is correlated to the incident neutron energy [30]. By exploiting the time coincidence between a capture pulse and the preceding thermalization pulse, spectroscopic neutron energy analysis can be performed [31].…”