  $(\alpha,n)$ 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.
