Results 1 - 10 of 662
Results 1 - 10 of 662. Search took: 0.02 seconds
|Sort by: date | relevance|
[en] The developed curved image plate (CIP) is a one-dimensional detector which simultaneously records high-resolution X-ray diffraction (XRD) patterns over a 38.7 2θ range. In addition, an on-site reader enables rapid extraction, transfer and storage of X-ray intensity information in (le)30 s, and further qualifies this detector to study kinetic processes in materials science. The CIP detector can detect and store X-ray intensity information linearly proportional to the incident photon flux over a dynamical range of about five orders of magnitude. The linearity and uniformity of the CIP detector response is not compromised in the unsaturated regions of the image plate, regardless of saturation in another region. The speed of XRD data acquisition together with excellent resolution afforded by the CIP detector is unique and opens up wide possibilities in materials research accessible through X-ray diffraction. This article presents details of the basic features, operation and performance of the CIP detector along with some examples of applications, including high-temperature XRD.
[en] A four-crystal monochromator beamline will be part of the radiometry laboratory that the Physikalisch-Technische Bundesanstalt will install at the new storage ring BESSY II. The most important design criteria for the beamline are the tunability of the photon energy in a wide spectral range from 1.75 to 10 keV, the high spectral purity of the radiation, as well as the good reproducibility of the absolute photon flux. (au)
[en] Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continuum XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet
[en] This very first report of a X-ray absorption spectroscopy experiment on Soleil is part of a more large long term study dedicated to ectopic calcifications. Such biological entities composed of various inorganic and/or organic compounds contain also trace elements. In the case of urinary calculi, different papers already published point out that these oligo elements may promote or inhibit crystal nucleation or growth of mineral or organic species involved. By using such tool specific to synchrotron radiation i.e. determine the local environment of oligoelements and thus their occupation site, we contribute to our understanding of the role of trace elements in ectopic calcifications
[en] A new powder diffractometer for synchrotron radiation with six detector arms has been constructed. Five detector arms are attached radially at intervals of 25 deg. to the 2θ axis and form a multiple-detector system. Five scintillation counters coupled with flat Ge(111) crystal analyzers on the respective arms can simultaneously record the whole powder pattern divided into five segments, each with an equal 2θ span. The optics design is based on flat-specimen reflection geometry using a parallel beam. The intensity data are collected using a 2θ step-scan technique in asymmetric diffraction at a fixed incident angle. A sixth multi-purpose detector arm can be used in the conventional single-arm scan mode. It can be equipped with various kinds of analyzers such as long horizontal parallel slits, a flat or channel-cut crystal analyzer, a receiving slit and a solid-state detector. Test operations of the multiple-detector system, conducted at the Photon Factory in Tsukuba, recorded a full width at half maximum of 0.022 deg. and a peak maximum intensity of more than 40,000 counts s-1 for the (111) reflection from Si powder. The whole powder pattern of Mg2sIo4 over a 2θ range of 130 deg. could be step-scanned at a step interval of 0.004 deg. (2θ) in just 4 h. Results of whole-powder-pattern decomposition and Rietveld refinement of the Mg2SiO4 pattern are given. (au) 31 refs
[en] Surface-sensitive X-ray absorption fine structure (XAFS) with sub-monolayer sensitivity based on grazing-incidence fluorescence detection is reported. The efficiency of fluorescence detection increased by more than two orders of magnitude by combining a multipole wiggler with a multielement Si(Li) solid-state detector. The capability of the present technique for structure studies of surfaces and buried interfaces in the hard X-ray region was demonstrated by As K-edge XAFS studies of the InP(001) surface exposed to AsH3 flow. The results indicated that ∼0.1 monolayer As atoms are incorporated into the surface replacing the P atoms. (au) (24 refs.)
[en] With the opening of the first real 'third-generation' synchrotron source in Grenoble, in fall 1994, X-ray sources of unprecedented brilliances and qualities became available to the scientific community. Different X-ray analytical techniques could now be applied on a level that was unimaginable only a decade ago. Here are some preliminary results from an experiment where different analytical techniques have been applied on a micrometer level carried out at the most powerful synchrotron microbeam currently available in the world, the microfocus beamline (BL1) at ESRF. This beamline can now provide micrometer-sized X-ray beams with a flux density up to 1010 photons μm-2 at an energy of 13keV and with a bandwidth of 10-4. In this experiment, X-ray diffraction and X-ray fluorescence have been combined in order to obtain a precise and comprehensive micro-analytical description of micrometer-sized fly-ash particles. These types of particles are heavily inhomogeneous with a very irregular shape that makes them inaccessible to conventional micro-analysis. The experiment was performed in a scanning mode and two-dimensional images of different analytical information were reconstructed from the data recorded during the scan. The major features and limitations of this micro-analytical technique will be outlined and different examples on how the analytical information can be used for generating two-dimensional images of the sample will be demonstrated and discussed. (au) 15 refs
[en] The high-brilliance X-ray beams from undulator sources at third-generation synchrotron facilities are excellent tools for solving crystal structures of important and challenging biological macromolecules and complexes. However, many of the most important structural targets yield crystals that are too small or too inhomogeneous for a 'standard' beam from an undulator source, 25-50 (micro)m (FWHM) in the vertical and 50-100 (micro)m in the horizontal direction. Although many synchrotron facilities have microfocus beamlines for other applications, this capability for macromolecular crystallography was pioneered at ID-13 of the ESRF. The National Institute of General Medical Sciences and National Cancer Institute Collaborative Access Team (GM/CA-CAT) dual canted undulator beamlines at the APS deliver high-intensity focused beams with a minimum focal size of 20 (micro)m x 65 (micro)m at the sample position. To meet growing user demand for beams to study samples of 10 (micro)m or less, a 'mini-beam' apparatus was developed that conditions the focused beam to either 5 (micro)m or 10 (micro)m (FWHM) diameter with high intensity. The mini-beam has a symmetric Gaussian shape in both the horizontal and vertical directions, and reduces the vertical divergence of the focused beam by 25%. Significant reduction in background was achieved by implementation of both forward- and back-scatter guards. A unique triple-collimator apparatus, which has been in routine use on both undulator beamlines since February 2008, allows users to rapidly interchange the focused beam and conditioned mini-beams of two sizes with a single mouse click. The device and the beam are stable over many hours of routine operation. The rapid-exchange capability has greatly facilitated sample screening and resulted in several structures that could not have been obtained with the larger focused beam.
[en] Structural mapping of proteins and nucleic acids with high resolution in solution is of critical importance for understanding their biological function. A wide range of footprinting technologies have been developed over the last ten years to address this need. Beamline X28C, a white-beam X-ray source at the National Synchrotron Light Source of Brookhaven National Laboratory, functions as a platform for synchrotron footprinting research and further technology development in this growing field. An expanding set of user groups utilize this national resource funded by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health. The facility is operated by the Center for Synchrotron Biosciences and the Center for Proteomics of Case Western Reserve University. The facility includes instrumentation suitable for conducting both steady-state and millisecond time-resolved footprinting experiments based on the production of hydroxyl radicals by X-rays. Footprinting studies of nucleic acids are routinely conducted with X-ray exposures of tens of milliseconds, which include studies of nucleic acid folding and their interactions with proteins. This technology can also be used to study protein structure and dynamics in solution as well as protein-protein interactions in large macromolecular complexes. This article provides an overview of the X28C beamline technology and defines protocols for its adoption at other synchrotron facilities. Lastly, several examples of published results provide illustrations of the kinds of experiments likely to be successful using these approaches