Study of plastic scintillators for fast neutron measurements and the potential application to neutron cameras

In this research, we measured pulse spectra of fast neutrons in an energy range from 1 to 7 MeV by using plastic scintillators. The fast neutrons emitted by spontaneous fission decays of a 5-μCi ²⁵²Cf isotope, whose mean energy was ∼2.1 MeV, were used for the measurements of the energy-dependent pulse spectra of the fast neutrons. The neutron energies were determined by using a time-of-flight method. The gamma rays, emitted together with fission neutrons, were eliminated by applying a proper cut in the time-of-flight spectrum. Monte-Carlo simulations based on a GEANT4 program were performed to predict the neutron sensitivities and the deposit energies in the scintillators. Furthermore, we performed a feasibility study on the potential application of the plastic scintillators to the measurement of neutron tracks for searching for special nuclear materials (SNM).