Measurements of the ${}^{27}\mathrm{Al}(\hat{I}\pm ,n)$ Thick Target Yield Near Threshold

Abstract

We present results from direct measurements of the ${}^{27}\mathrm{Al}(\hat{I}\pm ,n)$ thick target yield from laboratory incident energies $E_{\hat{I}}\pm \approx$ 3$-$5~MeV, performed with the ${}^3$HeBF${}_3$ 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 $E_{\hat{I}}\pm \approx 4-5$~MeV. However, for $E_{\hat{I}}\pm <3.5$~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 ${}^{27}\mathrm{Al}(\hat{I}\pm ,n)$ contribution to neutrino and dark matter detector backgrounds and result in increased viability of ${}^{27}\mathrm{Al}(\hat{I}\pm ,n)$ as a plasma diagnostic tool at fusion facilities such as the National Ignition Facility.

Accepted to Nuclear Science and Engineering