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 $^{3}{\rm He}\,{\rm BF}_{3}$ 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 ($7.5\pm 1.2$) \% 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.