The ³He BF₃ Giant Barrel (HeBGB) neutron detector

(alpha, n) reactions play an important role in nuclear astrophysics and applications and are an important background source in neutrino and dark matter detectors. Measurements of total (alpha, n) cross sections employing direct neutron detection often have a considerable systematic uncertainty associated with the energy-dependent neutron detection efficiency and the unknown initial neutron energy distribution. The He-3 BF3 Giant Barrel (HeBGB) neutron detector was built at the Edwards Accelerator Laboratory at Ohio University to overcome this challenge. HeBGB offers a near-constant neutron detection efficiency of (7.5 +/- 1.2)% over the neutron energy range 0.01 MeV-9.00 MeV, removing a significant source of systematic uncertainty present in earlier (alpha, n) cross section measurements.