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

Abstract

We present results from direct measurements of the ${ }^{27}Al(\alpha ,n)$ thick-target yield from laboratory incident energies $E_{\alpha }\approx$ 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 $E_{\alpha }\approx 4to5$ MeV. However, for $E_{\alpha }<3.5$ 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 ${ }^{27}Al(\alpha ,n)$ contribution to neutrino and dark matter detector backgrounds and result in increased viability of ${ }^{27}Al(\alpha ,n)$ as a plasma diagnostic tool at fusion facilities such as the National Ignition Facility.

Keywords:

• Thick target yield
• neutron background
• National Ignition Facility diagnostic

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

Thick-target yields reported in this work are available as a text file in the Supplemental Material. See the Supplemental Material for a table of our measured yield.

Supplemental Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00295639.2022.2118483

Additional information

Funding

This work was supported in part by the U.S. Department of Energy Office of Science under grant numbers DE-FG02-88ER40387 and DE-SC0019042 and the U.S. National Nuclear Security Administration through grant numbers DE-NA0003883 and DE-NA0003909. The helium ion source was provided by grant number PHY-1827893 from the U.S. National Science Foundation. We also benefited from support by the U.S. National Science Foundation under grant number PHY-1430152 (Joint Institute for Nuclear Astrophysics, Center for the Evolution of the Elements).