Thick-target yield of 65Cu(α,n)68Ga near threshold and implications for nuclear medicine, deep underground detector backgrounds, and nucleosynthesis

We report thick target yields of 65 Cu ( α , n ) 68 Ga from α energies E α = 6.5–8 MeV measured via neutron-counting at the Edwards Accelerator Laboratory at Ohio University. Our results agree with prior results based on single-foil irradiations, while disagreeing with thick-target yields inferred from stacked-foil irradiations by up to an order of magnitude. Based on comparisons of our and prior measurements to Hauser–Feshbach calculations, we estimate the thick-target yield for 68 Ga from E α = 14 MeV impinging on 100%-enriched copper ( 65 Cu ) is 161 − 24 + 5 MBq/ μ Ah (for He + + ), which is in agreement with the current IAEA estimate of 156 MBq/ μ Ah. At E α = 8 MeV, where radioimpurity-free production of 68 Ga could be realized with a natural copper target, our yield estimate is nearly 4 × lower than the IAEA estimate. We find that the 65 Cu ( α , n ) cross section estimates presently employed for neutrino and dark matter detector backgrounds and the 65 Cu ( α , n ) astrophysical reaction rate recently recommended for nucleosynthesis calculations are in agreement with our measurement results.