This study addresses five aspects in the field of radionuclide production, four of which are relevant to a new generation of high-current, 70 MeV H− cyclotrons. A related aspect has also been investigated in the proton energy region 100–200 MeV. All the experimental work of this study was performed at the cyclotron facility of the iThemba Laboratory for Accelerator-Based Sciences (iThemba LABS) near Cape Town, South Africa, with external proton beams delivered by the k = 200 MeV separated-sector cyclotron (SSC) of the laboratory. The feasibility to produce 225Ac/213Bi and 230U/226Th generators at a 70 MeV H− facility by employing proton-induced reactions on thorium (Th+p) has been investigated. This is of relevance to iThemba LABS as a new commercial 70 MeV H− cyclotron is currently being installed at the laboratory, expected to become operational in 2023, i.e. the near future. Since the SSC regularly produces 66 MeV proton beams for the routine radionuclide production programme, such beams were available to perform experimental work at an energy close to 70 MeV. New excitation-function measurements were performed for Th+p reactions by means of the stacked-foil technique, utilizing primary proton beams of 40 and 66 MeV. Both 213Bi and 226Th are alpha-particle emitters with importance in targeted alpha-particle therapy (TAT). A separate study involving Th+p reactions focused on the potential production of 225Ra/225Ac generators, in the proton energy region 100-200 MeV, at iThemba LABS. New excitation- function measurements were performed utilizing a primary proton beam of 200 MeV. The alpha-emitter 225Ac has been used directly in TAT in recent years. Interest in the 225Ra/225Ac generator stems from its ability to provide 225Ac with a very high radionuclidic purity, which is not achievable with any of the direct production routes. A possible stacked-target concept for routine production purposes is presented and discussed. The 70 MeV commercial cyclotron will enable the transfer of most of the routine radionuclide production programme, based on 66 MeV protons from the SSC, to the new machine. This will free the SSC to focus on other research objectives. A subtopic of this study was to investigate the targetry required for the new 70 MeV cyclotron, based on similar targetry used for many years on the SSC but upgraded to accommodate higher beam intensities. The inclusion of Th in various tandem target configurations was also explicitly considered. Also of importance for this study was the secondary neutron fluxes that would be generated by proton beams on these production targets, which was investigated using Monte Carlo simulations. This work also presents data obtained from secondary-neutron activations of samples be-hind a radionuclide production target during routine bombardments with 66 MeV protons. Radioactive residues from 121 neutron-induced reactions were identified on activated samples covering a wide mass region (Be to Bi). Based on the measured yields and neutron spectra ob-tained from Monte Carlo simulations, average cross sections were calculated. These values are compared with corresponding predictions as published in the TENDL nuclear data libraries.1 The last subtopic of this study focused on producing the therapeutic radionuclide 67Cu in the secondary-neutron flux behind a primary tandem target under bombardment with a 70 MeV proton beam. Metallic Zn and ZnO were considered as targets. Yield estimates were made for enriched 67Zn and 68Zn targets as well as for natZn targets. It was necessary to identify which of 67Zn or 68Zn would be the best target nucleus for 67Cu production in this case.

Thesis (MSc of Physics and Astronomy sciences)---Botswana International University of Science and Technology, 2023