Analysis of Neutron Scattering Interactions in Plastic Scintillators

The MoNA collaboration is a group of primarily undergraduate institutions that studies neutron-unbound nuclei at FRIB. To better understand neutron scattering in our plastic scintillator detectors and to test the prediction accuracy of our Geant4-based Monte Carlo simulation, our group conducted a neutron scattering experiment using a pulsed neutron beam at the LANSCE facility. Neutrons scatter in various ways from the H and C nuclei in the scintillator detectors, some of which produce sufficient light to be detected above detector threshold (n-p charge exchange, carbon excitation, ...). In particular, n-p charge exchange scattering produces high energy protons which can travel from our target bar to the back wall of our array. We measured the energy-dependent angular distribution of these charge-exchange protons relative to the beam axis. We removed the muon background by using a scaled version of data taken during beam-off cycles. We compared our neutron scattering measurements with simulation to determine simulation's accuracy to predict neutron kinematics inside our scintillator array. Our next experiment will use a diamond detector as an active target to measure several elastic and inelastic n-C interactions with minimal background contribution. Results will be presented.