Hannover, Universiẗat, Diss., 1999.

Hannover, University, Diss., 1999.

Mainz, Universiẗat, Diss., 2000.

Mainz, Universiẗat, Diss., 2001.

This thesis is concerned with the study of the spin-dependence of low-energy deuteron stripping on light and heavy target nuclei. In the case of a heavy target, the relative importance of the folding model spin-orbit interaction and (d,p) channel coupling effects upon the elastic vector analyzing power for deuteron scattering from [90]Zr at 5.5 MeV is studied. Coupled channels calculations areperformed in which the elastic channel and neutron transfer to thestrongly populated states of [91]Zr are treated explicitly. The resultsof these calculations indicate significant corrections to the elastic iT[11] and (d,p) reaction observables and provide a consistentqualitative description of the data. In case of a light target nucleus, it has been suggested that the spin degree of freedom in plasma fusion reactions could be utilised toenhance or suppress fusion reaction rates. For example if the d(d,n)3He reaction were suppressed then a 'neutron-free' d-3He fusion reactor is likely to work. This suppression is thought to occur at lowenergies when the deuterons are polarized with spin parallel. Calculations by Hofmann and Fick showed that the d-d reaction initiatedby low energy polarized deuterons is not suppressed and hence neitheris the neutron production. These results were contradicted by Zhang etal. In order to throw further light on the question an approximate RGM3calculation has been formulated in which the role of D-states of 3He and the deuteron were studied. In these calculations the initial state is described by distorted wave generated by i) non-local separable potentials, and ii) the orthogonality condition model (OCM). In each case the d-d phase shifts from the RGM were fitted. Nuclear wave functions consistent with a realistic nucleon-nucleon interaction wereused throughout. The distorted wave in the exit channel has been generated by a local neutron optical potential which fits the n-3He scattering data. In marked contrast with the previously reported DWBA calculations,which claim to reproduce the data, it is found that the data isoverestimated by a factor of 150 at a centre of mass energy at 55 KeV.Repeating the calculations using another neutron optical potential,which also fits the n-3He scattering data, yields a good agreement with the data.

Introduction Rhenium-186 (t1/2 = 3.72 d) is very attractive for use as a theranostic agent in targeted radionuclide therapy (Eβ max = 1.072 MeV (> 76.6 %); Eγ = 137.2 keV)1. Previously published investigations of high specific activity 186Re production have utilized the 186W(p,n)186Re or 186W(d,2n)186Re reactions2-5. Our group is interested in the refinement and scale-up of the production of high specific activity 186Re by cyclotron irradiations of 186W with deuterons; including investigations of the most suitable target material. WO3 has been successfully used as a target material in proton irradiations by two other groups4,5. Further, the physical properties of WO3, such as the reported monoclinic with Pc space group, body centered cubic crystal structure6 and melting point of 1473 °C, made for an attractive target material as sintered and other more structurally robust pressed pellet target preparations could be explored. Thus, this study reports on the characterization and suitability of WO3 as a full-thickness target material for the deuteron production of 186Re. Materials and Methods Assessments of WO3 for target material suitability and structural integrity were made on thick targets (~1 g) prepared using both commercially available and converted WO3 by either uniaxially pressing (13.8 MPa) of powdered WO3 into an aluminum target support or by placing sintered WO3 pellets (1105 °C for 12 hours) into an aluminum target support. In some experiments, WO3 pellets were prepared by dissolution of Wmetal with H2O2, then treatment with 1.5 M HCl. The recovered hydrated WO3 was calcinated at 800 °C for 4 hours, allowed to cool to ambient temperature, pulverized with a mortar and pestle, uniaxially pressed at 13.8 MPa into pellets with a 13 mm die, and subsequently sintered in a tube furnace under flowing Ar at 1105 °C for 3, 6, and 12 hours. Material characterization and product composition analyses were conducted with SEM, EDS, XRD, Raman spectroscopy, and visible photoluminescence spectroscopy. Thick WO3 targets were irradiated for 10 min at 10 µA with nominal extracted deuteron energies of 17 MeV. Gamma-ray spectroscopy was per-formed to assess production yields and radionuclidic byproducts at least 24 hours post EOB. Results While the color of the commercially available WO3 is slightly different (dull, pale green) than the brighter more yellow color of the chemically processed WO3, X-ray diffraction spectrometry (XRD) indicated the two samples were virtually identical. Attempts to determine how the duration of the sintering process (at 1105 °C) affects the chemical/physical nature of the pellet yielded surprising results. In contrast to the characteristic annealed appearance of sintered material, grains of the WO3 sample appeared more densely packed, but not sintered to one another as had been seen during higher temperature (1550 °C) reductions of WO3 irrespective of the time interval used. Full-thickness pressed or sintered pellets of WO3 were found to disintegrate upon irradiation with the deuteron beam, allowing for the direct irradiation of the aluminum target body producing 24Na as a contaminant. Upon retrieval of the target support it was observed that the WO3 had vaporized, discoloring the surface of the well in the target support and coating the walls of ~61 cm (24 inches) of the terminal portion of the beamline, which then required decontamination. We believe that these observations are the result of outgassing oxygen species that subsequently reacted with the aluminum target support. While these findings are in sharp contrast with the successful production yields and isolations previously reported by both Shigeta et al. and Fassbender et al., we believe that these differences are attributable to differences in target design (previous studies utilized an en-closed target with cooling in front of and behind the target) necessitated by the configuration of our target station. Conclusions. The physical properties of powdered WO3, including its lower melting point and more suitable compressibility than powdered Wmetal, seemed to enhance the structural integrity of a WO3 pellet (whether pressed or sintered). However, when compared to our recent successes with the use of Wmetal based targets, the disappointing degradation of our WO3 targets when irradiated with the incident deuteron beam has led us to believe that Wmetal is the more viable target material for 186Re production in our facility.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [93]-96).

Universiẗat, Diss., 2001--Mainz.

This thesis presents the results of the first application of a novel solid state nuclear magnetic resonance technique (K. P. Pauls et. al., Eur. Biophys. J. 11:1) to a naturally occuring membrane polypeptide. Deuterium NMR was used to study the structure and dynamics of hydrogen-exchanged gramicidin A', an ion channel, in model membranes. The technique exploits recently developed procedures for solvent-signal suppression (P. T. Callaghan et. al., J. Magn. Reson. 56:101), and "depakeing" powder spectra (E. Sternin, M.Sc. Thesis,U.B.C.). The spectra of gramicidin A' in crystalline form, and in the gel phase of the lipid bilayer are similar and indicate little molecular motion on the NMR timescale. In the liquid crystalline phase, however, the spectra suggest rapid uniaxial rotation of the gramicidin about the bilayer director. The frequencies of the liquid crystalline phase spectra were found to be independent of bilayer thickness, temperature, and the presence of sodium chloride, in the ranges investigated. The results are discussed in the context of the conduction properties of the gramicidin ion channel, other spectroscopic studies, and thecretical models of the structure and action of gramicidin. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The TOF-spectrometer located at the proton accelerator COSY (Juelich) stands out for experimental versatility. This is due to its modular setup: about ten subdetectors can be be arranged to satisfy the individual requirements of specific experiments. However, this flexibility hampers the calibration and the data analysis, since for each new detector setup the software has to be adjusted as well. Therefore, a new analysis framework (TofRoot) has been developed. A set of concepts is used that enables teamwork and leads to an efficient data-analysis, even for different beamtimes. Using TofRoot, three reactions are analyzed - each for two different beam momenta (2950 MeV/c, 3200 MeV/c): Firstly, the elastic proton-proton scattering. It is used to determine the luminosity and to extract benchmark results for the detector performance. Secondly, the reaction pp->deutoron-piplus is studied. Total as well as differential cross sections are presented, which nicely fit into the word data set. Finally, the vector-meson production (omega) is investigated which is the scientific focus of this work. Here, the theoretical and experimental knowledge is presently rather scarce. However, the elementary reaction dynamics is needed as an inevitable prerequisite in many fields of physics; e.g. the short range part of the nucleon-nucleon force, the description of extremely dense matter, the strangeness content of nucleons. After a detailed description of the analysis strategies, total cross sections, angular distributions, and invariant-mass spectra are presented. Some of the findings are completely new, and all provide smaller experimental uncertainties with respect to the available word data set. Finally, the results are embedded into the existing body of data and their implication on the theoretical models is discussed. / Das TOF-Spektrometer am Protonen-Beschleunigerring COSY (Juelich) besticht durch seine experimentelle Vielseitigkeit, da der modulare Aufbau aus ca.~zehn Subdetektoren eine individuelle Anpassung an spezifische experimentelle Erfordernisse ermoeglicht. Diese Flexibilitaet erschwert jedoch die Kalibrierung und die Datenauswertung, da die Software nach jedem Umbau angepasst werden muss. Daher wurde das Analyseframework TofRoot entwickelt, welches durch einen Satz von Strategien eine effiziente und teamorientierte Auswertung ermoeglicht, sogar fuer verschiedene Strahlzeiten. Mit Hilfe von TofRoot wurden drei Reaktionskanaele analysiert, jeweils fuer zwei Strahlimpulse (2950 MeV/c, 3200 MeV/c): Zuerst die elastische Proton-Proton Streuung, welche der Luminositaetsbestimmung dient und an Hand derer die Guete des Detektorsystems und der Kalibration veranschaulicht wird. Anschliessend folgt die Reaktion pp->deuteron-piplus, bei der die extrahierten Winkelverteilungen und totalen Wirkungsquerschnitte sich widerspruchsfrei in die vorhandene Datenbasis einordnen. Schliesslich wird die Vektormesonenproduktion (omega) untersucht, die den wissenschaftlichen Fokus dieser Arbeit darstellt. In diesem Kanal ist die experimentelle Datenbasis duenn und die theoretische Beschreibung bislang unvollstaendig. Ein gutes Verstaendnis der omega-Produktionsdynamik ist aber unabdingbar fuer die theoretische Beschreibung vieler Felder moderner Physik, z.B. des kurzreichweitigen Teils der Nukleon-Nukleon-Wechselwirkung, extrem dichter Materie und des Strangenessanteils im Nukleon. Nach einer detailierten Beschreibung der Analysestrategien werden totale Wirkungsquerschnitte, Winkelverteilungen und Spektren invarianter Massen vorgestellt. Verglichen mit vorhandenen Daten sind alle Angaben mit kleineren experimentellen Unsicherheiten behaftet, und zum Teil erschliessen sie zuvor nicht zugaengliche Groessen. Abschliessend werden die Ergebnisse in die vorhandene experimentelle Datenbasis eingeordnet, und ihre Auswirkung auf theoretische Modelle wird diskutiert.