Measurements of the ²⁷Al(α,n) Thick Target Yield near Threshold

We present results from direct measurements of the (Formula presented.) thick-target yield from laboratory incident energies (Formula presented.) 3 to 5 MeV, performed with the ³HeBF₃ Giant Barrel (HeBGB) neutron detector at the Edwards Accelerator Laboratory. Our measurements have a small energy cadence in order to address discrepancies and sparseness of thick-target-yield data sets existing for this energy region. We find general agreement with existing data sets, including yields derived from cross-section data, while resolving a discrepancy between existing thick-target-yield data sets for (Formula presented.)  MeV. However, for (Formula presented.)  MeV, our results are substantially lower than previous thick-target-yield data and somewhat larger than yields calculated from existing cross-section data. Our data complete the energy range needed for estimates of the (Formula presented.) contribution to neutrino and dark matter detector backgrounds and result in increased viability of (Formula presented.) as a plasma diagnostic tool at fusion facilities such as the National Ignition Facility.