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D.Ing. / An optimal laser pulser topology for employment in a future commercial molecular laser isotope separation (MLIS) plant is proposed by this thesis. It is pointed out in the introduction that power modulator research and development were performed without much regard to economic constraints in the past. These conditions were mainly caused by international strategic initiatives and spawned a wealth of different circuit topologies and techniques. Many more can be devised by using the various subsystems of these topologies and techniques in different combinations. However, under the paradigm of a modern day commercial application, the luxury of trying yet another new topology, merely on the merits of personal preference, does not exist. Therefore, it is proposed that a laser pulser topology be formally selected by using suitable criteria derived from the application. Formal definitions are provided for the general subsystems found in all laser excitation systems, as a foundation for the selection process. The available options for each subsystem type, as well as the options for combining them into various topologies are described. Many examples are quoted from the literature to corroborate the basic descriptions. Practical circuit issues are dealt with in an appendix. Selection criteria are determined by contemplating the theory and practical issues of pulse power technology, transversely excited atmospheric carbon dioxide lasers as well as molecular laser isotope separation. It is argued that all of these criteria can be combined into a single economic criterion, namely life cycle cost. This argument is supported by the commercial requirement of economic viability of the future plant. The author formulates a life cycle cost calculation model (LCCCM) from all the technical and economic issues previously mentioned. It includes a flexible design section that can accommodate any of the possible topology options. Cost functions, which include reliability analysis, are used to calculate capital and operating costs from the design parameters, throughout the life cycle of the plant. Probability theory is used to model parameters with indeterminate values. The use of the LCCCM and its subtleties are demonstrated by comparing two basic options in a case study. It is finally used in a reasoned process of elimination to find the best topology option for the application.

published_or_final_version / Radio Chemistry / Master / Master of Philosophy

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Jeffrey P. Chanton, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed Jan. 26, 2006). Document formatted into pages; contains xii, 145 pages. Includes bibliographical references.

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Thesis (PhD)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Radiochemical research involving ion exchange chromatography is of paramount importance to the future of radionuclide production at the Radionuclide Production Group (RPG) of iThemba LABS. It is required for the production of high-activity yields of radionuclides to effectively remove impurities and for the safety of the operators performing such productions. The radiochemical separations of some new products from their target material, as well as experiments to determine whether production is viable, are described. 67Ga is currently being produced at the RPG and makes use of zinc targets. With the production of ultra-pure 67Ga, it was necessary to remove any Fe(III) impurities from the final product, such that it may be possible to label peptides with this product. The use of Amberchrom CG161M for this purpose was found to be satisfactory. Interest was shown in 88Y by an overseas company for the manufacture of sources. While a method involving extraction of the radionuclide and the ion exchange thereof using Chelex 100 chelating resin had been published, problems with the production persisted. Three methods, using ion exchange chromatography, were devised to produce the radionuclide, with two of them being adopted for production purposes. Thick-target nuclear data have also recently been accumulated in collaboration with colleagues from ATOMKI, Debrecen, Hungary. There is a large demand for 82Sr for the manufacture of 82Sr/82Rb generators for medical use. A method was developed to manufacture this radionuclide with thicker (32 g) target material, bombarded in the Vertical Beam Target Station (VBTS), and to separate 82Sr from its target material with the use of Purolite S950 chelating resin. 68Ge/68Ga generators are becoming increasingly important in the world of radiopharmaceuticals. A project to develop a local generator was funded by the Innovation Fund and research was performed to produce 68Ge, such that the generator could be manufactured. This involved bombarding thicker Ga targets in the VBTS and performing the chemical separation using AG MP-1 anion exchange resin. The final product was loaded onto generators, although tests performed on different materials to the ones being marketed are also reported in this work. A project was initiated to study the cluster radioactive decay of 223Ac via 14C and 15N emission. To produce 223Ac for these observations, a Th target was bombarded. The 227Pa was separated from the target material using AG MP-1 macroporous anion exchange resin and used as a source, which decayed to 223Ac. The chemical separation and the drying of the final product onto a source plate were completed within approximately 70 minutes from the end of bombardment. The work was performed in collaboration with JINR, Russia, and University of Milan and INFN, Italy. 133Ba has a half-life of over 10 years and is an expensive radionuclide to produce. It has been used in medical and biological studies and there still appears to be a demand for it. A method was devised, utilizing AG50W-X4 cation exchange resin, to separate 133Ba from its CsCl target material. Agricultural specialists in the past have shown an interest in 28Mg, to determine the uptake of the element in fruit. It has long been regarded by some of the local researchers as an interesting project to investigate. It has been determined that the product can be produced in reasonable quantities using LiCl target material, with ten targets being bombarded in series using a 200 MeV proton beam delivered by the Separated Sector Cyclotron. A method, involving the use of Purolite S950 chelating resin, was devised to separate 28Mg from its target material. / AFRIKAANSE OPSOMMING: Radiochemiese navorsing, wat ioonuitruiling chromatografie behels, is van uiterste belang vir die toekoms van die produksie van radionukliede by die Radionukliedproduksiegroep (RPG) van iThemba LABS. Dit is nodig vir die hoë aktiwiteit opbrengs van radionuklied produkte om onsuiwerhede te verwyder en vir die veiligheid van die operateurs wat die produksies moet uitvoer. Die skeiding van nuwe produkte van hulle skyfmateriaal, sowel as eksperimente om vas te stel of ‘n produksie uitvoerbaar is, word in die werk beskryf. 67Ga word tans by RPG vervaardig en maak gebruik van sink as skyfmateriaal. Vir die produksie van “ultra-suiwer” 67Ga was dit belangrik om enige Fe(III) onsuiwerhede uit die finale produk te verwyder om sodoende peptiede merking te kan uitvoer. Die gebruik van Amberchrom CG161M hars was voldoende vir dié eksperiment. ‘n Oorsese maatskappy het belangstelling getoon in 88Y vir die vervaardiging van bronne. Alhoewel ‘n metode wat die ekstraksie van die radionuklied en die ioonuitruiling daarvan met die gebruik van Chelex 100 chelerende hars reeds gepubliseer was, het probleme met die produksie voortgeduur. Drie metodes is opgestel om 88Y te produseer, waarvan twee van die metodes tans gebruik word vir produksie doeleindes. Dik-skyf kerndata is ook versamel in samewerking met kollegas van ATOMKI, Debrecen, Hongarye. Daar is ‘n groot aanvraag vir 82Sr vir die vervaardiging van 82Sr/82Rb generators vir mediese doeleindes. ‘n Metode is ontwikkel om die radionuklied te vervaardig van dikker skyfmateriaal (32 g), in die Vertikale Bundelstasie gebombardeer, en om 82Sr van sy skyfmateriaal te skei met die gebruik van Purolite S950 chelerende hars. 68Ge/68Ga generators is besig om toenemend belangrik te word in die wêreld van radiofarmasie. iThemba LABS kry baie navrae om die produk te vervaardig. Die projek was ook deel van die voorlegging aan die “Innovation Fund” en ‘n manier is ondersoek om 68Ge te vervaardig, wat benodig word om so ‘n generator te laai. Dik Ga skyfmateriaal word in die Vertikale Bundelstasie gebombardeer en ‘n chemiese skeiding is uitgevoer deur gebruik te maak van AG MP-1 anioonuitruiling hars. Die finale produk is op die generators gelaai vir toetsdoeleindes. Toetse is ook op ‘n ander tipe generator uitgevoer en word in die werk beskryf. ‘n Projek is begin om “cluster” radioaktiewe verval van 223Ac, via 14C en 15N emissie, te bestudeer. ‘n Th-skyf is met protone gebombardeer om die 223Ac te produseer vir die eksperiment. 227Pa is vervaardig en geskei van die skyfmateriaal. Dit is gedoen met die gebruik van AG MP-1 makroporeuse anioonuitruiling hars en drooggemaak op ‘n bronplaat, waar dit verval het na 223Ac. Die chemiese skeiding en die droogmaak van die finale produk op ‘n bronplaat is uitgevoer binne 70 minute na Einde van Bombardering (EVB). Die werk is deel van ‘n samewerking met kollegas van JINR, Rusland, en die Universiteit van Milaan, sowel as INFN, Italië. 133Ba het ‘n halveertyd van oor die tien jaar en is ‘n duur produk om te vervaardig. Dit is al gebruik in mediese en biologiese studies en daar is deesdae ‘n redelike aanvraag daarvoor. ‘n Metode is uitgewerk om 133Ba te skei van die CsCl skyfmateriaal met die gebruik van AG50W-X4 katioonuitruiling hars. Spesialiste in landboustudies het in die verlede belangstelling getoon in 28Mg. Dit word gebruik om die absorpsie van dié element in vrugte te ondersoek. Die produk kan vervaardig word met die gebruik van LiCl skyfmateriaal: tot soveel as tien skywe (agter mekaar) word gebombardeer met ‘n 200 MeV protonbundel te iThemba LABS. ‘n Metode, wat Purolite S950 behels, is daargestel om 28Mg van die skyfmateriaal te skei.

Mass spectrometers are analytical instruments that convert neutral atoms and molecules into gaseous ions and separate those ions according to the ratio of their mass to charge, m/z. The measurement is reported as a mass spectrum: a plot of relative intensity vs. m/z that can be used to deduce the chemical structure and composition of materials and compounds. Initially, the use of mass spectrometers was restricted to the analysis of volatile compounds. Recent advances in the development of ionisation techniques to produce intact molecules directly from samples in the liquid or solid phase, has extended the powerful use of mass spectrometry to compounds of increasingly higher molecular mass. The aim of this study was twofold: develop diagnostic techniques for the in-situ measurement of isotope ratios in laser isotope separation experiments; and to correlate it with the measured isotope ratios on the collected product. The outcome is a thesis that can be divided into two distinct fields of application: Firstly; the Atomic Vapour Laser Isotope Separation (AVLIS) of lithium, and secondly the Molecular Laser Isotope Separation (MLIS) of uranium, In both AVLIS and MLIS pulsed laser systems were used to ionise and/or dissociate atomic or molecular beams. The pulsed nature of the lasers is ideally suited to in-situ time-of-flight detection of the produced ions. Different types of inter-changeable ion sources are common to the same TOF mass spectrometer. Each of these sources is selected according to its application. For instance, applications vary from photo- and multiphoton ionisation (laser ionisation) to surface analysis (laser desorption or particle bombardment) to chromatography (electron impact ionisation). Four different source configurations were considered in this study: (i) Atomic Laser Isotope Separation (AVLIS) of lithium; (ii) Multiphoton Ionisation (MPl) of UF6 gas; (iii) Non-resonant ionisation during Laser Desorption (LDI) of solids; and (iv) Matrix-Assisted Laser Desorption (MALD) of biopolymers. The design of each of these sources will be discussed in detail in chapters to follow. Bulk analysis of harvested laser-produced products needs to be in correlation with in-situ analysis. Three different characterisation methods were used in this study: (i) Laser Desorption Time-of-Flight Mass Spectrometry (LD-TOF-MS) (ii) Quadrupole-based Secondary Ion Mass Spectrometry (SIMS); and (iii) TOF-MS-based Secondary Ion Mass Spectrometry (TOF-SIMS). Chapter I describes the principles of time-of-flight mass spectrometry, design parameters, as well as the instrumentation that were designed and constructed for the purposes of this study. Chapter II describes the principles of Secondary Ion Mass Spectrometry (SIMS). In particular, research done on the establishment of tools to the non-expert user of SIMS to select analyses conditions, is described. Chapter III reports on the application of TOF-MS and SIMS during the AVLIS of lithium. Chapter IV reports on the application of the different combinations of TOF-MS, LD-TOF-MS, SIMS, and TOF-SIMS during the MLIS of uranium. / Thesis (Ph.D.)-University of Natal, Durban, 1999.

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