The simulated and measured angular distributions of the neutron background from 0.5 to 6 MeV in deposited energy. The angle is defined relative to vertical as described in the text. The “ideal simulated collimator” is a simulation using collimators with zero transmission through them, while the “real simulated collimator” matches the polyethylene collimator used in the experiment. Error bars shown are the standard deviation from statistical fluctuations.