Production of ${}^{67}$Cu by enriched ${}^{70}$Zn targets. First measurements of formation cross sections of ${}^{67}$Cu, ${}^{64}$Cu, ${}^{67}$Ga, ${}^{66}$Ga, ${}^{69m}$Zn and ${}^{65}$Zn in interactions of ${}^{70}$Zn with protons above 45 MeV

Despite its insufficient availability, Copper-67 is currently attracting much attention for its enormous potential for cancer therapy as theranostic radionuclide. This work aims to accurately measure the unexplored cross section ${}^{70}$Zn(p,x)${}^{67}$Cu in the energy range 45–70 MeV and to evaluate its potential advantages in the case of high-intensity proton beams provided by compact cyclotrons. Thin target foils of enriched ${}^{70}$Zn were manufactured by lamination at the INFN-LNL and irradiated at the ARRONAX facility using the stacked-foils method. A radiochemical procedure for the separation of Cu, Ga and Zn contaminants and the isolation of ${}^{67}$Cu from the irradiated material was developed. The efficiency of the chemical processing was determined for each foil by monitoring the activity of selected tracer radionuclides (${}^{61}$Cu, ${}^{66}$Ga and ${}^{69m}$Zn) through γ-spectrometry. Experimental data of the ${}^{70}$Zn(p,x)${}^{67}$Cu, ${}^{64}$Cu, ${}^{67}$Ga, ${}^{66}$Ga, ${}^{69m}$Zn, ${}^{65}$Zn cross sections were measured for the first time in the energy range 45–70 MeV and compared with the theoretical results obtained by using the TALYS code. The ${}^{67}$Cu production yield by using enriched ${}^{70}$Zn thick targets was compared with the results obtained by using ${}^{68}$Zn targets in the same irradiation conditions.