Production of radionuclides with medium energy protons with the emphasis on targetry

[摘要] ENGLISH ABSTRACT: The facilities for radionuclide production at iThemba LABS have undergone a number of significant upgradesover the last decade in order to increase the production capacity and to diversify the productportfolio. Central to this effort is a new vertical beam target station (VBTS) and its associated targetry,designed and built to operate at higher proton beam intensities for the large-scale production of relativelylong-lived, high-value radionuclides such as 22Na, 68Ge and 82Sr. Along with the VBTS, an existing smallerhorizontal beam target station was adapted to accommodate targetry for 18F production, mainly to supply18F-FDG for use in positron emission tomography (PET). The production capacity was further enhancedby means of a beam splitter to enable bombardments in two target stations simultaneously. This requirednew developments on several systems, e.g. beam diagnostics, control, interlocking and cooling.This project brings together a number of different aspects of the upgraded facilities as well as theassociated research and development that enable the production of radionuclides in the medium energyregion, up to approximately 70 MeV. Investigations were performed on the cooling of the interfacial windowsbetween the cyclotron vacuum and the targets as well as the direct cooling of the targets themselvesduring intense proton bombardments. For this purpose, empirical as well as computational fluid dynamics(CFD) calculations were performed. In addition, the local radiation shield of the VBTS as well as thebeam transport in some of the targetry was investigated by means of Monte Carlo radiation transportcalculations.Excitation functions for the production of various radionuclides in the 66 MeV proton bombardmentof 192Os, 159Tb, natGd, 155Gd, 152Gd, 93Nb, natZr and 89Y were measured and compared with theoreticalpredictions by means of statistical nuclear model calculations as well as the TENDL-2012 library. Inparticular, the production of 186Re, selected radioterbiums (149;152;155Tb) and radiozirconiums (88;89Zr) is ofinterest in existing and emerging diagnostic and therapeutic applications in nuclear medicine. A study on28Mg production in the proton bombardment of natCl using stacked chloride targets was also performedat 200 MeV. This radionuclide is of interest as 28Mg is the only practical radiotracer of Mg. Finally, newtargetry for the production of 18F was developed, modelled and optimized for the non-standard degradedbeam employed in this particular case.

[发布机构] Stellenbosch University