Angular Distributions of High Energy Neutrons Scattered off a Plastic Scintillator

The Modular Neutron Array Collaboration ran an experiment at the Los Alamos Neutron Science Center to test the performance of neutron detectors and simulations used in experiments studying neutron-rich nuclei. The experiment consisted of a beam of 20-800 MeV neutrons colliding with a plastic scintillator target. An array of detectors was set downstream in a staircase pattern. The angles of the scattered neutrons were measured, with particular interest in neutrons that were not detected by the target detector but seen in the array. These neutrons were not detected by the target because the interaction of a neutron with a carbon nucleus in the scintillator did not produce enough light to be detected, but the products of the collision scattered into the array. Interaction with carbon is more likely than hydrogen in the scintillator, so a large amount of counts are from this interaction, but difficult to record. This is problematic in studying the decays by neutron emission as it records the wrong initial position vector for the neutron. To measure "dark scattering," scattering angles were composed from runs with the target in and out. These scattering angles were then compared with simulations using two different neutron interaction packages. Preliminary results will be presented.