The Production of ³⁸Ar and ³⁹Ar by 14-MeV Neutrons on ³⁹K

We have determined the cross sections for the production of ³⁸Ar and ³⁹Ar from the (n, n’p) and (n,p) reactions by neutrons of ∼14 MeV incident on ³⁹K. Three potassium-bearing specimens were irradiated with fluences of ∼10¹⁷ neutrons, and the argon isotopes were measured by mass spectrometry. Previously reported measurements are in substantial disagreement with our results. Values from the three new measurements are consistent with each other and our computational modeling. Nevertheless, there remains an unexplained increase in the cross sections for both reactions as the neutron energy increases from ≈14.5 to 14.8 MeV.