Direct Production of Ultra-High Radioisotopic Pure $^{64}$Cu from Natural Zinc Metal via D-D Fusion Narrowband Fast Neutron Source Irradiation
Copper-64 radiopharmaceuticals have seen limited clinical deployment primarily due to the high cost of the isotopically enriched $^{64}$Ni metal required for its production. In this work we demonstrate that ultra-high radioisotopic pure $^{64}$Cu can be directly produced in a no-carrier-added-form from natural zinc metal through irradiation with D-D fusion narrowband fast neutron sources. A highly controlled D-D fusion narrowband fast neutron source at the ELI-ALPS Laser Facility was deployed to irradiate encapsulated 99.995\% pure natural zinc for 1 hour. Time-resolved gamma-ray spectroscopy of the irradiated sample over 72 hours was deployed to assess copper radioisotope activity. $^{64}$Cu was the only copper radioisotope detected within the irradiated sample, with a minimum and Minimum Detection Activity (MDA) threshold-corrected $^{64}$Cu radioisotopic purity of 99.62\% and 99.97\% respectively. Our result illustrates that highly controlled D-D fusion narrowband fast neutron sources have the potential to reduce the raw material production costs for $^{64}$Cu radiopharmaceuticals on the order of 2000 times. Cheaper $^{64}$Cu radiopharmaceuticals will increase their use in clinical practice, and, in-turn, increase outcomes for cancer patients receiving radionuclide therapy.