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

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>

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.

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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.

The second report from the Project-Group ESRF-Beamline of the Forschungszentrum Rossendorf covers the period from July 1999 until December 2000. The ROssendorf BeamLine (ROBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France performed quite well during this time. In the beamtime used by the FZR and collaborating institutes 44 scheduled experiments were performed, while in the ESRF scheduled beamtime 12 experiments. Additionally, a distinct amount of beamtime was devoted to in-house research of the FZR and methodical experiments. Since February 2000 ROBL is part of the European Commission's programme "Access to Research Infrastructure" which supports user groups from member and associated states of the EU during experiments at ROBL. In the year 2000 ROBL hosted 6 groups for experiments. The report is organised in three main parts. The first part contains extended contributions on results obtained at ROBL. The second part gives an overview about the scheduled experiments, publications, guests having visited ROBL with support of the EC, and some other information. Finally, the third part collects the experimental reports of the user groups received.

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