No description available.

No description available.

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.

No description available.

This thesis addresses one of the major outstanding problems in the study of self-assembled InAs quantum dots (QDs): their physical profile after deposition of a capping layer and post-growth processing. The optical properties of QDs depend critically on the shape, composition and strain profile, yet these parameters are inaccessible to most experimental techniques once the dots are buried. Data from various x-ray scattering experiments are presented here, along with a novel approach to simulating diffuse scattering using an atomistic model based on Keating energy minimisation. The size and position of the diffuse scattering on the low-Q side of the Bragg peak, which are strongly influenced by the shape and composition of the QDs, has been used to determine that the QDs are truncated pyramids with a diagonal base length of 28 nm, with their edges aligned along the [100] and [010] directions. The composition profile varies from pure InAs at the top to 40-60% InAs at the base. These properties all agree with recent cross-sectional scanning tunnelling microscopy (X-STM) measurements by Bruls et al. It was shown that post-growth annealing causes a reduction in the In content of the QDs, primarily by diffusion from the base of the dot into the wetting layer. Grazing incidence small angle x-ray scattering (GISAXS) measurements have been made from samples of QDs produced with varying growth interruptions (GI) before deposition of the capping layer. The QDs were found to be highly diffuse. After a GI, the dots have been shown to change shape anisotropically, with two facets becoming sharper. An investigation of the use of resonant scattering to study buried QDs has shown that the method of contrast variation is of limited use for enhancing the measurement of diffuse features away from the Bragg peak. It is unsuitable for the study of buried nanostructures.

Thesis (Ph. D.)--University of Hong Kong, 1990.

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.

The Rossendorf Beamline (ROBL) - located at BM20 of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France - is in operation since 1998. This 6th report covers the period from January 2007 to December 2008. In these two years, 50 peerreviewed papers have been published based on experiments done at the beamline. The average citation index, which increased constantly over the years, has now reached 3.5 (RCH) and 3.0 (MRH), indicating that papers are predominately published in journals with high impact factors. Six exemplary highlight reports on the following pages should demonstrate the scientific strength and diversity of the experiments performed on the two end-stations of the beamline, dedicated to Radiochemistry (RCH) and Materials Research (MRH). Demand for beamtime remains very high as in the previous years, with an average oversubscription rate of 1.8 for ESRF experiments. The attractiveness of our beamline is based upon the high specialization of its two end-stations. RCH is one of only two stations in Europe dedicated to x-ray absorption spectroscopy of actinides and other radionuclides. The INE beamline at ANKA provides superior experimental flexibility and extends to lower energies, including important elements like P and S. In contrast, ROBL-RCH provides a much higher photon flux, hence lower detection limits crucial for environmental samples, and a higher energy range extending to elements like Sb and I. Therefore, both beamlines are highly complementary, covering different aspects of radiochemistry research. Once the MARS beamline at SOLEIL is ready to run radionuclides (>2010), it will cover a third niche (Materials Science of actinides, including irradiated fuel) not accessible for the two other beamlines. The Materials Research Hutch MRH has realized an increasing number of in-situ investigations in the last years. On the one hand thin film systems were characterized during magnetron sputtering. On the other hand diffraction experiments under controlled atmosphere were performed. A high variety of experimental parameters was covered by varying pressure, temperature and atmospheric compositions including highly reactive gases. Furthermore structural investigations were combined with electrical conductivity measurements. These kind of in-situ experiments are the key to monitor and understand reaction mechanism or the influence of process parameters, which are again the basis to tailor materials properties on demand. The core competences of MRH are these experimental possibilities, which make it unique among other diffraction beamlines. In fall 2007, ROBL was reviewed by an international panel on behalf of the ESRF. The very positive panel report recommended a renewal of the contract between ESRF and FZD for the next five years, and a major upgrade of critical optical components of the beamline to keep ROBL competitive for the next decade. The FZD will provide 2 Mio € from 2009 to 2011 for this upgrade, which will be performed in parallel to the major upgrade of the ESRF to minimize the downtime. According to the current plans of the ESRF, our users have to expect that ROBL will have only limited or no operation for several months from August 2011 on. Since July 2004 the beamline is a member of the pooled facilities of ACTINET – European Network of Excellence. In the reported period, RCH has provided 27 % of its inhouse beamtime to perform 11 ACTINET experiments. The success of ACTINET within FP-6 has now led to a renewal of ACTINET within FP-7, running until end of 2011.