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

Vermeulen, Christiaan (2014-12)

Thesis (PhD)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: The facilities for radionuclide production at iThemba LABS have undergone a number of significant upgrades over the last decade in order to increase the production capacity and to diversify the product portfolio. 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 relatively long-lived, high-value radionuclides such as 22Na, 68Ge and 82Sr. Along with the VBTS, an existing smaller horizontal beam target station was adapted to accommodate targetry for 18F production, mainly to supply 18F-FDG for use in positron emission tomography (PET). The production capacity was further enhanced by means of a beam splitter to enable bombardments in two target stations simultaneously. This required new 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 the associated research and development that enable the production of radionuclides in the medium energy region, up to approximately 70 MeV. Investigations were performed on the cooling of the interfacial windows between the cyclotron vacuum and the targets as well as the direct cooling of the targets themselves during 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 the beam transport in some of the targetry was investigated by means of Monte Carlo radiation transport calculations. Excitation functions for the production of various radionuclides in the 66 MeV proton bombardment of 192Os, 159Tb, natGd, 155Gd, 152Gd, 93Nb, natZr and 89Y were measured and compared with theoretical predictions by means of statistical nuclear model calculations as well as the TENDL-2012 library. In particular, the production of 186Re, selected radioterbiums (149;152;155Tb) and radiozirconiums (88;89Zr) is of interest in existing and emerging diagnostic and therapeutic applications in nuclear medicine. A study on 28Mg production in the proton bombardment of natCl using stacked chloride targets was also performed at 200 MeV. This radionuclide is of interest as 28Mg is the only practical radiotracer of Mg. Finally, new targetry for the production of 18F was developed, modelled and optimized for the non-standard degraded beam employed in this particular case.

AFRIKAANSE OPSOMMING: Die fasiliteite vir die produksie van radionukliede by iThemba LABS is gedurende die afgelope dekade aansienlik opgegradeer om die produksiekapasiteit te verhoog en om die portfolio van produkte te diversifiseer. Sentraal tot hierdie poging is ’n vertikale-bundel skyfstasie (VBTS) wat gebou is om skywe met hoër intensiteit protonbundels te bombardeer ten einde relatief langlewende, hoë-waarde radionukliede op grootmaat te produseer, insluitende 22Na, 68Ge en 82Sr. Terselfdetyd is ’n bestaande, kleiner horisontale-bundel skyfstasie aangepas om skywe vir die produksie van 18F te huisves, meestal om 18FFDG vir positronemissietomografie (PET) te lewer. Die produksiekapasiteit is verder verhoog d.m.v. ’n bundeldeler sodat bundel gelyktyding aan twee skyfstasies gelewer kan word. Dit het ontwikkelingswerk vereis aan verskeie stelsels, insluitende diagnostiek, beheer, vergrendeling en verkoeling. Hierdie projek bring verskeie aspekte bymekaar t.o.v. die opgegradeerde produksiefasiliteite sowel as die geassosieerde navorsing en ontwikkeling benodig vir radionukliedproduksie in die middelenergiegebied tot ongeveer 70 MeV. Die verkoeling van die foelievensters tussen die vakuum van die siklotron en die skyfgerei is ondersoek sowel as die direkte verkoeling van skywe onder intense protonbombardement. Hierdie studie sluit beide empiriese sowel as numeriese vloeidinamika berekeninge in. Verder is die afskerming van die VBTS asook die bundeltransport in verskeie skywe ondersoek m.b.v. Monte Carlo stralingstransport berekeninge. Opwekkrommes vir die produksie van verskeie radionukliede met protongeïnduseerde reaksies tot en met 66 MeV op 192Os, 159Tb, natGd, 155Gd, 152Gd, 93Nb, natZr en 89Y is gemeet en vergelyk met statistiese kernmodel berekeninge sowel as die TENDL-2012 biblioteek. Die produksie van 186Re, verskeie radioterbiums (149;152;155Tb) en radiozirkoniums (88;89Zr) is van spesifieke belang vir bestaande en toekomstige diagnostiese en terapeutiese toepassings in die kerngeneeskunde. ’n Studie op die produksie van 28Mg in die bombardement van natCl met 200 MeV protone is ook onderneem. In hierdie ondersoek is ’n stapel chloriedskywe gebruik. Die 28Mg is van belang omdat dit die enigste Mg radioisotoop is wat geskik is as ’n radiospoorder van dié element. Laastens is nuwe skyfgerei vir die produksie van 18F ontwikkel, gemodelleer en geoptimiseer vir die nie-standaard afgeremde bundel wat benut word in hierdie geval.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/95510
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