by Leung Chu Wah. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 181-182). / Acknowledgements --- p.vi / Abstract --- p.vii / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Evaluation of Far Field by Lai and Char's Method --- p.6 / Chapter 2.1 --- Far Field Expression --- p.6 / Chapter 2.2 --- Radiation Power --- p.12 / Chapter 2.3 --- Gaussian Curvature and Point of Stationary Phase of Cylindrically Symmetry DWS --- p.16 / Figures for Chapter2 --- p.19 / Chapter 3. --- Synchrotron Radiation in Vacuum Using Lai and Char's Method --- p.20 / Chapter 3.1 --- The Far Field --- p.20 / Chapter 3.2 --- Current Density for a Gyrating Charge --- p.22 / Chapter 3.3 --- Radiation Power --- p.25 / Chapter 3.4 --- Some Angular Properties of Synchrotron Radiation --- p.29 / Chapter 3.5 --- Total Power Emitted in N-th Harmonic --- p.32 / Chapter 3.6 --- Total Power Emitted in All Harmonics --- p.33 / Figures for Chapter3 --- p.36 / Chapter 4. --- Synchrotron Radiation in a Cold Magnetoplasma --- p.42 / Chapter 4.1 --- DWS for a Cold Magnetoplasma --- p.42 / Chapter 4.2 --- Derivatives of kp and Gaussian Curvature of DWS --- p.45 / Chapter 4.3 --- Group Velocity --- p.46 / Chapter 4.4 --- Current Density --- p.47 / Chapter 4.5 --- Point of Stationary Phase --- p.48 / Chapter 4.6 --- Identification of Different Wave Modes --- p.48 / Chapter 4.7 --- Radiation Power --- p.49 / Chapter 4.8 --- Relation with Vacuum Case --- p.53 / Figures for Chapter4 --- p.56 / Chapter 5. --- Incoherent Radiation from an Assembly of Charges --- p.79 / Chapter 5.1 --- Total Incoherent Energy Flux from N Particles --- p.79 / Chapter 5.2 --- Synchrotron Radiation from Particles with Momentum Distribution --- p.80 / Chapter 5.3 --- Mono-Energetic Particles with Distributed Parallel Momentum --- p.82 / Chapter 5.4 --- "Angular Distribution, Frequency Distribution and Total Radiation Power" --- p.87 / Figures for Chapter5 --- p.88 / Chapter 6. --- Coherent Radiation from an Assembly of Charges --- p.94 / Chapter 6.1 --- Bunching Factor --- p.94 / Chapter 6.2 --- Some Arrangements of Particles --- p.96 / Chapter 6.2.1 --- Charges Distributed Uniformly over an Arc of Angular Width --- p.96 / Chapter 6.2.2 --- Charges Distributed Along a Straight Line --- p.100 / Chapter 6.2.3 --- Charges Distributed Uniformly on a Helical Path --- p.101 / Chapter 6.2.4 --- Charges Distributed Randomly on an Arc --- p.102 / Chapter 6.3 --- Effect of Bunching in a Cold Magnetoplasma --- p.104 / Figures for Chapter6 --- p.105 / Chapter 7. --- Correction to Radiation Power Formula for Degenerate DWS --- p.113 / Chapter 7.1 --- Far Field Expression for Degenerate DWS --- p.113 / Chapter 7.2 --- Radiation Power for Degenerate DWS --- p.115 / Chapter 7.3 --- Alternate Proof for the Extra Factorin (7.2.11) --- p.118 / Chapter 7.4 --- Example of Degenerate DWS - Vacuum --- p.120 / Chapter 8. --- "Ratio of Emitted Power to Received Power, f" --- p.122 / Chapter 8.1 --- Group Velocity in terms of Derivatives of DWS --- p.122 / Chapter 8.2 --- Calculation of Derivatives --- p.124 / Chapter 8.3 --- Expression for f --- p.126 / Chapter 8.4 --- Alternate Form of f --- p.127 / Chapter 8.5 --- Examples of Calculating f Using (8.4.1) --- p.129 / Chapter 8.5.1 --- Isotropic Cold Plasma --- p.129 / Chapter 8.5.2 --- Cold Magnetoplasma --- p.130 / Figures for Chapter8 --- p.132 / Chapter 9. --- Comparison of Far Field by Lai and Chan with that by Others --- p.135 / Chapter 9.1 --- Expressing the Far Field Ratio in terms of Derivatives of DWS and WS --- p.135 / Chapter 9.2 --- Far Field Ratio for an Uniaxial Non-Dispersive Medium --- p.137 / Chapter 9.3 --- Far Field Ratio for an Isotropic Cold Plasma --- p.138 / Chapter 10. --- Minimum Far Field Distance to a Moving Radiating Source in an Anisotropic and Dispersive Medium --- p.140 / Chapter 10.1 --- Sub-Dominant Terms of the Far Field --- p.141 / Chapter 10.2 --- Minimum Far Field Distance --- p.147 / Chapter 10.3 --- Minimum Far Field Distance in an Isotropic Non-Dispersive Medium --- p.152 / Chapter 10.4 --- Minimum Far Field Distance in an Isotropic Dispersive Cold Plasma --- p.156 / Chapter 10.5 --- Minimum Far Field Distance for Alfven Waves in a Cold Magnetoplasma --- p.159 / Chapter 10.6 --- Comparison of Results by Other Authors --- p.162 / Figures for Chapter 10 --- p.165 / Chapter 11. --- Conclusions / Chapter Appendix 1. --- Calculation of the Total Power Emitted in Synchrotron Radiation in Vacuum --- p.170 / Chapter Appendix 2. --- "Derivatives of stix's Parameters and a1,a2 of Equation (4.1.22)-(4.1.23 )" --- p.176 / Chapter Appendix 3. --- Dispersion Relation for Alfven Wavesin a Cold Magnetoplasma --- p.179 / References --- p.181

La spectroscopie par transformée de Fourier est l’outil multiplexe de mesure de spectres à haute résolution le plus utilisé dans l’infrarouge. Son extension au domaine Térahertz se révèle de grand intérêt pour la spectroscopie de molécules présentes dans le milieu interstellaire, mais se heurte à différents obstacles : en particulier, aucune source large bande n'est suffisamment intense et stable pour ces applications. Cette thèse présente des développements instrumentaux basés sur l’exploitation du rayonnement synchrotron cohérent (CSR) sur la ligne AILES du synchrotron SOLEIL, optimisée pour l'infrarouge lointain. Les conditions de production du CSR sont étudiées pour les besoins des analyses spectroscopiques à haute résolution ; les performances de cette source sont caractérisées et comparées à celles du rayonnement incohérent. La mise en place d'un système de double détection permet une correction de l'effet des instabilités de la source et une augmentation conséquente du rapport signal-sur-bruit. Ces développements sont appliqués à la mesure de spectres de rotation pure ; une modélisation améliorée du spectre dans l'état fondamental de la molécule de propynal a ainsi pu être faite, prouvant la complémentarité de la source étudiée vis-à-vis des sources micro-onde ou infrarouge classiques. / Fourier Transform spectroscopy is the most used multiplex tool for high-resolution measurements in the infrared range. Its extension to the Terahertz domain is of great interest for spectroscopic studies of interstellar molecules. This application is however hampered by the lack of dedicated, broadband sources with a sufficient intensity and stability. In this work, Coherent Synchrotron Radiation (CSR) was used as a source for molecular spectroscopy at high resolution on the AILES infrared and Terahertz beamline of SOLEIL synchrotron. The beamline being optimized for far-infrared, we could characterize the properties of CSR and compare them to the incoherent synchrotron radiation. A double detection system allowed to correct the effect of the source-related instabilities, hence to significantly increase the signal-to-noise ratio. Pure rotational spectra were measured using these developments. The case of the propynal molecule, for which a refined set of rotational and centrifugal distortion constants was calculated, proves the complementarity between CSR and the classical microwave or infrared sources.

No description available.

Mon projet porte sur l'elaboration d'un microscope optique en champ proche (SNOM) sans ouverture fonctionnant dans le domaine de l'infrarouge et utilisant le rayonnement synchrotron de l'ESRF comme source de lumiere infrarouge. Ce rayonnement a deux particularites bien adaptees aux etudes spectroscopiques: c'est une source de lumiere blanche couvrant la bande du proche infrarouge de 5 a 15 microns alors que les sources lasers accordables sont encore en developpement. Il est tres brillant et stable, a la fois dans le temps et dans l'espace. Une fois elaboree, le microscope sera appliquee a la spectroscopie infrarouge - essentiellement vibrationelle - et le diagnostic des materiaux et des nanostructures qui sont d'inter^et actuel pour l'industrie micro et nanoelectronique [RCB+02]. Comme mon projet est tres instrumental, le debut a ete consacre a la conception de tout un systeme de microscopie, a partir du zero et avec tout le materiel necessaire disponible a la n de la premiere annee. La seconde annee a ete consacree a l'integration et la mise en oeuvre du dispositif experimental, a la comprehension de ses fonctionnalites et a des essais de validation du nouveau outil. Apres nous nous sommes pleinement engages dans la recherche et la comprehension de cet outil unique. Nous avons commence par quelques resultats preliminaires, puis cela a ete essentiellement une question de temps experimental alloue pour obtenir les resultats que nous avions vises. Notre conguration est unique et donc les travaux que nous avons pour reference sont ceux de groupes utilisant les m^emes techniques d'exploitation dans des conditions tres dierentes. Notre principale diculte est de detecter un signal faible. Je montrerai plus loin quelques calculs qui nous y ont fait croire. Notre groupe de reference a reussi a le faire dans des conditions plus simples que les notres, mais il est utile de rappeler que cela leur a pris 3 ans pour adapter leur sensibilite a l'installation, ce qui conrme que ce sont des techniques tres dur. Notre idee de depart etait d'utiliser le rayonnement synchrotron comme source de lumiere dans l'infrarouge en raison de ses caracteristiques. Il s'agit d'une source de lumiere blanche, avec toutes les longueurs d'onde presentes en meme temps, nous permettant d'eectuer une spectroscopie, ce qui signie que nous obtiendrons une information chimique sur l'echantillon [Hil04; MGCS04]. Telle est la grande nouveaute en comparison avec les autres travaux. Il s'est avere que la lumiere est assez faible ce qui rend la recherche du signal dicile. Notre installation doit alors etre testee avec un laser, qui est de plusieurs ordres de grandeur plus puissant que le rayonnement synchrotron, et qui pourrait etre un bon outil de debogage. Cela semble une bonne alternative pour mieux comprendre les points essentiels qui doivent etre ameliores dans notre systeme. Les lasers a utiliser pourraient etre visible, infrarouge (CO2), ou accordable. Pour la spectroscopie, les lasers accordables sont non seulement moins stables mais ils sont aussi plus limites dans la gamme spectrale sur la partie infrarouge proche du spectre, que le rayonnement synchrotron. Le synchrotron de l'ESRF est mon laboratoire d'accueil, et j'ai travaille en collaboration avec le CEA-LETI pour le developpement de cet outil.

This dissertation addresses two critical issues in the deformation of nc metals and alloys: (1) A stress-induced genuine grain growth after the plastic deformation rather than just a change of the grain shape; (2) A systematically quantitative study of micrsostructural evolution during the plastic deformation. These two critical issues point to the deformation of nc materials with the average-grain sizes within the range of 10 to 50 nm, which is the most interesting and controversial region in the current time. The current study provides a systematic and detailed microstructural evolution for this region, which is definitely beneficial for the investigation of the deformation mechanism in this region, especially for the simulation. The main experimental and data-analysis methods employed in this research are synchrotron high-energy X-ray diffraction, X-ray line profile analysis, and texture analysis. The combination of these methods is beneficial to the accurate microstructural interpretation of the bulk materials.

This thesis describes a new type of refractive lens for hardx-rays. It is shown that a linear array of prisms, slightlyinclined with respect to the optical axis, will form a linefocus at a certain distance from the lens. Hence, the namemulti-prism lens. These lenses are free from sphericalaberration and are similar to planar parabolic compoundrefractive lenses in terms of performance. However, theydistinguish themselves in that only planar surfaces need to befabricated. A special feature is that the focal length can beeasily varied by adjusting the inclination angle. Theoretical calculations, based on geometrical and physicaloptics, are used to characterize the lenses. Aberrations arediscussed, as well as the sensitivity to fabricationimperfections, and insufficient flatness is identified as apotential problem. Ray-tracing is used to test theapproximations and assumptions used in the theory. Applicationsin x-ray microscopy and mammography are discussed. Lenses have been made of beryllium, silicon, epoxy anddiamond using different methods. Results from measurements ofsurface roughness and figure error show that the imperfectionsof the silicon and epoxy lenses should have a small impact,while the beryllium lenses should suffer from strongscattering. Experiments were performed at the EuropeanSynchrotron Radiation Facility and sub-µm focal linewidths, close to theoretical expectations, were measured forsilicon and epoxy lenses at 30 keV and 14 keV, respectively.Insertion gains up to 40 were reached. Two crossed lenses wereused to obtain focusing in two dimensions and a point focus.The smallest measured focal spot size was 1.0 µm by 5 .4µm, and an insertion gain exceeding 100 was achieved usingepoxy lenses. The diamond lenses suffered from voids in the materialformed in the chemical vapor deposition process, butnevertheless provided focal lines less than 2 µm in width,albeit at at relatively low insertion gain of 13. Due to theirexcellent thermal properties, these lenses are put forward ascandidates for optics at the next generationultra-high-intensity synchrotron beams and x-ray free electronlasers. Keywords:x-ray, optics, refractive, lens, mammography,synchrotron. / QC 20100524

This thesis is based on studies of multiple ionization of atoms and molecules induced by the absorption of a single photon. For the experimental investigations a time-of-flight magnetic bottle spectrometer has been used to detect the emitted electrons in coincidence. The method of coincidence time-of-flight spectroscopy and the experimental setup used is described. Experimental and theoretical results on molecular double core holes (DCHs) and multiple ionization of atoms are presented. Molecular DCHs are of considerable interest, as their chemical shifts are predicted to be more sensitive than their single core hole counterparts. Using CH4 and NH3 as examples, it is shown that molecules with two vacancies in the innermost shell can be studied using synchrotron light in combination with our coincidence technique. The chemical shifts of S 2p DCHs are investigated for the molecules CS2, H2S and SO2 and the influence of relaxation effects on the shifts are estimated. In the studies of atoms, the main focus is on the processes leading to double and higher degrees of ionization, and the final state populations. In cadmium double photoionization in the photon energy region 40-200 eV occurs mainly by indirect ionization via valence ionized satellite states and through Coster-Kronig decay of inner shell hole states. In valence-valence ionization of krypton by 88 eV photons both direct and indirect ionization processes are found to be important. For the indirect pathways strong final state selectivity in the autoionization decays of the intermediate states is observed. Triple ionization of krypton via intermediate core-valence doubly ionized states is investigated. The intermediate states are observed in the energy region 120-125 eV, and their decay to states of the triply charged ion is mapped. Experimental and theoretical results on the formation of 2p double hole states in argon are presented. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

In this thesis, two aspects of research in soft X-ray absorption spectroscopy chemistry are explored. The first objective was to measure the natural circular dichroism of small chiral organic molecules at soft X-ray wavelengths. The second objective was to characterize the electronic structure and spectra of a series of organometallic polymers. <p>The goal of the first part of this thesis was to enhance the sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to the intrinsic handedness of chiral organic molecules. The phenomenon of X-ray natural circular dichroism (XNCD) has been well described by theoreticians; however, there have been few successful measurements reported, mainly due to the weakness of the effect and the difficulty of preparing suitable samples. The fourth chapter of this thesis outlines the requirements for XNCD experiments and the efforts made to prepare appropriate samples. <p>The goal of the second part was to use NEXAFS spectroscopy as an analytical technique for the elemental and chemical characterization of innovative materials based on organoiron compounds. The interpretation of transition metal compounds by NEXAFS spectroscopy is difficult due to complex interactions between the metal and its surroundings. Two approaches are commonly used; an atomic multiplet model and a covalent bonding model, which lead to conflicting spectral assignments. Earlier NEXAFS studies of metallocene complexes were found to be lacking as these two models were not adequately rationalized. Owing in part to greatly improved instrumental sensitivity and to efficient theoretical calculations, the interpretation of NEXAFS spectra for a series of metallocene and metal arene complexes was refined. Enhanced understanding of the spectroscopy of these compounds eventually contributed to the characterization of a series of organometallic polymeric materials.<p>Underlining these studies is the remarkable complementarity of NEXAFS spectroscopy and chemistry. A comprehensive understanding of the chemistry of the samples examined in the measurement of XNCD is shown to be crucial for a successful advancement of this spectroscopy. In return, optimization of soft X-ray spectroscopy of metallocenes is demonstrated to remarkably benefit the understanding of the organometallic polymers.

The development of X-ray Beam Position Monitors (XBPM) used on the Canadian Light Source front ends is described in this thesis, from the design concepts to the practical implementation and commissioning. Surveyed into position to provide a fiducialized point of origin for incoming synchrotron radiation, the primary purpose of the XBPM is to provide a measure of synchrotron beam motion. Currently XBPMs have been installed on three beamlines at the Canadian Light Source, a 2.9 GeV third generation synchrotron radiation source. Two of the XBPMs are comprised of chemical vapour deposition synthetic diamond blades coated with gold and installed on insertion device beamlines, while the third makes use of molybdenum blades for a dipole beamline. By incrementally scanning the blades of the XBPM through the synchrotron beam it is possible to determine the monitors� spatial resolution to beam motion. For the commissioned XBPM a typical spatial resolution of +/- 1 micron of beam motion was achieved; and the thermal power loading capacity has been tested to the 2/5 of maximum value. An independent white beam profiler, comprised of a converter crystal and image acquisition software, was constructed to corroborate the functionality of the XBPM.

Alginate is a popular biomaterial in tissue engineering. When crosslinked with calcium ions (Ca2+), alginate forms a hydrogel which provides necessary mechanical support as a scaffold. The material properties as well as the biological properties of alginate scaffold are of great importance. In this thesis, the aim is to use traditional methods, such as scanning electron microscopy (SEM) and light microscopy, and emerging X-ray imaging techniques, such as micro-computed tomography (micro-CT) and synchrotron radiation (SR) X-ray imaging, to characterize the alginate scaffolds. Firstly, the material properties of freeze-dried alginate scaffolds were evaluated using micro-CT, as it is a non-destructive and non-invasive imaging method, and can provide three-dimensional information. Alginate scaffolds made with different sodium alginate concentrations and frozen to different temperatures were scanned and analyzed in micro-CT. Results indicated that lower freezing temperature and higher sodium alginate concentration lead to smaller pore size and porosity. Secondly, cell culture experiments were carried out to study the biological properties and the interactions of alginate hydrogel with cells. A Schwann cell line was either blended with alginate solution before crosslinking with calcium chloride (CaCl2) or put around alginate gel in the culture dish. Light microscopy of sectioned slices showed that cells surrounding the alginate gel could not grow into the gel, while cells blended with alginate solution before crosslinking could proliferate inside the hydrogel. Cells grown inside a thin slice of alginate gels appeared to be in better condition and were larger in size and also grew in clusters. Thirdly, in order to image soft tissue buried inside alginate gels, such as brain slices, novel imaging methods based on synchrotron radiation (SR) were applied, such as absorption and phase contrast imaging, diffraction-enhanced imaging (DEI) and also combined with computed tomography (CT). Synchrotron-based monochromatic X-ray imaging proved to be good at distinguish objects of similar density, especially biological soft tissue samples, even without any staining material, such as osmium tetroxide (OsO4). These three pieces of research work show the potential in applying the emerging X-ray imaging in soft tissue engineering.