Photonuclear Production of ⁶⁷Cu From Gallium

Copper-67 is a radioisotope of interest for medical imaging and therapy as well as for understanding stellar and interstellar evolution pertaining to the formation of proton-rich nuclei. Since ⁶⁷Cu decays 100% to ⁶⁷Zn, understanding this reaction can shed light on the abundance of this and other p-nuclei elements in the universe. Here, the photonuclear production of ⁶⁷Cu from ⁷¹Ga and natural gallium is examined as an alternative to its photoproduction from zinc. Two research and development production runs were performed at Thomas Jefferson National Accelerator Facility using an electron linac. During the first run, an 805-W, 30.9-MeV beam was used to irradiate a 1-mm tungsten radiator to create a bremsstrahlung flux. The resulting gamma photons irradiated 50.9 g of natural gallium encased in a graphite crucible for 24.2 h; 7.02 Bq/W∙s∙kg of ⁶⁷Cu activity was produced. During the second run, a 4380-W, 31.5-MeV beam was used for 12.0 h on the same target containing 60 g of natural gallium; 6.41 Bq/W∙s∙kg of ⁶⁷Cu activity was produced. Because of the difficulties in spectroscopically differentiating ⁶⁷Cu from ⁶⁷Ga, prior to each run, an isotopically pure ⁷¹Ga disk was irradiated using a 100-W beam for 1 h, at the same respective energies. These baseline irradiations allowed for separation of ⁶⁷Cu from ⁶⁷Ga in the spectroscopic measurements of the natural gallium targets.