A prototype detector for directional measurement of the cosmogenic neutron flux

This paper describes a novel directional neutron detector. The low pressure time projection chamber uses a mix of helium and CF4 gases. The detector reconstructs the energy and angular distribution of fast neutron recoils. This paper reports results of energy calibration using an α source and angular reconstruction studies using a collimated neutron source. The best performance is obtained with a 12.5% CF4–87.5% He gas mixture. At low energies the target for fast neutrons transitions is primarily helium, while at higher energies, the fluorine contributes as a target. The reconstruction efficiency is both energy and target dependent. For neutrons with energies less than 20 MeV, the reconstruction efficiency is ∼40% for fluorine recoils and ∼60% for helium recoils.