Home About us Contact
|
Home About us Contact | ||
|
|
||
keV
Terms modified by keV Selected AbstractsNonlinear optical properties of poly-ortho-toluidine films implantated by N+ ions with different energyPOLYMER COMPOSITES, Issue 10 2009Yan Shaolin This article reports experimental work on the effect of N+ ion implantation on third-order nonlinear optical properties of POT films. Using K2Cr2O7 as oxidizing agent, poly- ortho -toluidine (POT) was synthesized in 1 M hydrochloric. The POT films were prepared by spin-coating method and then implantated by N+ ions (15,30 KeV) at a dose 1.9 × 1016 ions/cm2. The films were characterized by FT-IR spectroscopy, visible spectroscopy and SEM, their third-order nonlinear optical susceptibility (,(3)) were also examined by a degenerate four-wave mixing (DFWM) system at 532nm. Compared to pristine POT films, the optical band gap obtained from visible spectra decreased from 3.58 to 3.48 eV when the energy was 30 KeV. Also, The ,(3) value of implantated POT films increased from 3.31 × 10,10 esu to 4.04 × 10,9 esu when the implantated energy was 25 KeV. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Chemical-Picture-Based Modeling of Thermodynamic Properties of Dense Multicharged-Ion Plasmas Using the Superconfiguration ApproachCONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2009P.A. Loboda Abstract Using the chemical-picture representation of plasmas as a mixture of various ions and free electrons, a consistent description of thermodynamics of dense multicharged-ion plasmas is being developed that involves the effects of Coulomb non-ideality and degeneracy of plasma electrons; contribution of the excited ion states (on the base of the superconfiguration approach) that may exist under an appropriate truncation of ion energy spectra due to plasma effects; hard-sphere-model representation of the finite-volume effects of plasma ions with the model parameters (effective ion sizes) corresponding to superconfigurations yielding the greatest contribution to partition functions. We present the calculated data for average ionization, Grüneisen coefficient, and specific heat of aluminum and iron plasmas at temperatures of 0.03,3 keV and densities 10,3 , 10,5 of their normal material densities. Calculated thermodynamic functions and shock Hugoniots are compared with other theoretical and experimental data (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low-energy irradiation effects of gas cluster ion beamsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 2 2008Shingo Houzumi Abstract A cluster-ion irradiation system with cluster-size selection has been developed to study the effects of the cluster size for surface processes using cluster ions. A permanent magnet with a magnetic field of 1.2 T is installed for size separation of large cluster ions. Trace formations at HOPG surface by the irradiation with size-selected Ar-cluster ions under an acceleration energy of 30 keV were investigated by scanning tunneling microscopy. Generation behavior of the craterlike traces is strongly affected by the number of constituent atoms (cluster size) of the irradiating cluster ion. When the incident cluster ion is composed of 100 to 3000 atoms, craterlike traces are observed on the irradiated surfaces. In contrast, such traces are not observed at all with the irradiation of the cluster ions composed of over 5000 atoms. Such behavior is discussed on the basis of the kinetic energy per constituent atom of the cluster ion. To study GCIB irradiation effects on macromolecules, GCIB was irradiated on DNA molecules absorbed on graphite surface. Using GCIB irradiation, many more DNA molecules were sputtered away compared with the monomer-ion irradiation. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(2): 40,45, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10031 [source] Monte Carlo Study of Quantitative Electron Probe Microanalysis of Monazite with a Coating Film: Comparison of 25 nm Carbon and 10 nm Gold at E0= 15 and 25 keVGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2007Takenori Kato simulation par la méthode de Monte Carlo; microanalyse par sonde électronique (EPMA); analyse quantitative; film de revêtement; monazite Carbon (25,30 nm in thickness) is the most common coating material used in the electron probe microanalysis (EPMA) of geological samples. A gold coating is also used in special cases to reduce the surface damage by electron bombardment. Monte Carlo simulations have been performed for monazite with a 25 nm carbon and a 10 nm gold coating to understand the effect of a coating film in quantitative EPMA at E0= 15 keV and 25 keV. Simulations showed that carbon-coated monazite gave the same depth distribution of the generated X-rays in the monazite as uncoated monazite, whilst gold-coated monazite gave a distorted depth distribution. A 10 nm gold coating was 1.06 (15 keV) and 1.05 (25 keV) times higher in k -ratio between monazite and pure thorium than a 25 nm carbon coating at an X-ray take-off angle of 40 degrees. Thus, a 10 nm gold coating is a possible factor contributing to inaccuracy in quantitative EPMA of monazite, while a 25 nm carbon coating does not have a significant effect. Le carbone, avec des épaisseurs de 25 à 30 nm, est le matériel de dépôt le plus fréquemment utilisé en microanalyse par sonde électronique (EPMA) d'échantillons géologiques. Un dépôt d'or est aussi utilisé dans des cas spécifiques, pour réduire les dommages causés à la surface par le bombardement d'électrons. Des simulations par la méthode de Monte Carlo ont été effectuées pour une monazite recouverte d'une couche de carbone de 25 nm et d'une couche d'or de 10 nm, dans le but de comprendre l'effet du dépôt dans les mesures quantitatives à l'EPMA, à E0= 15 keV et 25 keV. Les simulations ont montré que la monazite recouverte de carbone avait la même distribution en profondeur de rayons X générés qu'une monazite non recouverte, tandis que la monazite recouverte d'or avait une distribution en profondeur déformée. Le dépôt de 10 nm d'or avait un k -ratio qui était 1.06 (pour 15 keV) et 1.05 (pour 25 keV) fois plus important pour la monazite et du thorium pur que le dépôt de 25 nm de carbone dans le cas d'un angle de sortie des rayons X de 40 degrés. En conséquence un dépôt d'or de 10 nm est un facteur possible d'inexactitude lors de mesures quantitatives de monazites par EPMA, alors qu'un dépôt de carbone de 25 nm n'a pas d'effet significatif sur la mesure. [source] Self-Assembly of Ordered Semiconductor Nanoholes by Ion Beam SputteringADVANCED MATERIALS, Issue 28 2009Qiangmin Wei Periodic nanohole arrays are formed on a Ge substrate by self-assembly using focused ion beam sputtering at normal incidence with an energy of 5,keV. The figure shows an SEM image of a hexagonally ordered hole domain that has hexagonally ordered quantum dots,20,nm diameter and 3,nm height,around each hole The structured Ge has high surface area and a considerably blue-shifted energy gap. [source] Proton collisions with the water dimer at keV energiesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2009O. Quinet Abstract Proton collisions with the water dimer are studied using a nonadiabatic, direct, time-dependent approach called electron nuclear dynamics (END). Fragmentation of the water dimer in collisions with protons at energies of 5.0, 1.0 keV and 200 eV is the primary aim of this initial study of water clusters using END. We report on the initial fragmentation dynamic, that is, for times less than 200 fs. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Time-dependent density functional theory calculations of X-ray absorptionINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2003J. J. Rehr Abstract There has been dramatic progress in recent years both in calculations and in the interpretation of X-ray absorption spectra (XAS). Often an independent-electron approximation with final state potentials is adequate. However, for soft X-rays (i.e., energies less than about 1 keV) local field effects can be important. Such local fields arise from the dynamic screening of both the external X-ray field and the coupling to the core hole created in the absorption process. These effects require a theory that goes beyond the independent-electron approximation. We developed an efficient approach for treating such effects in molecules and solids based on a generalization of time-dependent density functional theory (TDDFT), with a local approximation for the screening response. The approach has been implemented in our self-consistent, real-space Green's function code FEFF8 in terms of screened dipole transition matrix elements. Typical results are discussed for the XAS of the N4,5 edges of solid Xe and for the L2,3 edges of 3d transition metals. Our approach accounts for the deviations of the L3/L2 intensity branching ratio from the 2:1 value of the independent electron approximation. For the N4,5 edges of Xe, the approach also accounts for the observed fine structure. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [source] Ultra-small-angle X-ray scattering at the Advanced Photon SourceJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2009Jan Ilavsky The design and operation of a versatile ultra-small-angle X-ray scattering (USAXS) instrument at the Advanced Photon Source (APS) at Argonne National Laboratory are presented. The instrument is optimized for the high brilliance and low emittance of an APS undulator source. It has angular and energy resolutions of the order of 10,4, accurate and repeatable X-ray energy tunability over its operational energy range from 8 to 18,keV, and a dynamic intensity range of 108 to 109, depending on the configuration. It further offers quantitative primary calibration of X-ray scattering cross sections, a scattering vector range from 0.0001 to 1,Å,1, and stability and reliability over extended running periods. Its operational configurations include one-dimensional collimated (slit-smeared) USAXS, two-dimensional collimated USAXS and USAXS imaging. A robust data reduction and data analysis package, which was developed in parallel with the instrument, is available and supported at the APS. [source] A focusing Laue diffractometer for the investigation of bulk crystalsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2008Matthias Stockmeier A focusing Laue diffractometer for high-energy X-rays of up to 300,keV in a laboratory environment is presented. The long attenuation length for X-ray energies above 50,keV allows for the non-destructive investigation of structural issues and bulk properties of single crystals. Furthermore, massive sample environments such as high-temperature furnaces can be used more easily. With an area detector, anisotropic mosaicities or crystallite structure become visible without any rocking movement of the sample. [source] A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004Yanbin Wang A new diffraction technique for combined angle- and energy-dispersive structural analysis and refinement (CAESAR), by collecting angle-dispersive data using a solid-state detector (SSD) and white synchrotron radiation, is introduced. By step scanning a well calibrated SSD over a limited 2, range, a series of one-dimensional energy-dispersive data (intensity versus energy) are obtained as a function of 2,. The entire intensity (Int) data set consists of several thousand channels covering a range of photon energies, E (up to ,150,keV), at each of the ,1000 2, steps, forming a 2,4 mega-element two-dimensional array, Int(E, 2,). These intensity data are then regrouped according to photon energies, which are defined in the multichannel SSD as individual channels, yielding a large number of intensity versus 2, (angle-dispersive) data sets, Int(E = const., 2,), each of which corresponds to a given photon energy or wavelength. The entire data set, selected subsets or composite scans can be used for multiple data set Rietveld refinement. Data collected both on ,-Al2O3 (a NIST diffraction standard) at ambient conditions and on a mixture of MgO and Au at high pressure were analyzed using the Rietveld technique, with varying schemes of data treatment. Furthermore, it is demonstrated that data within certain energy bands (,E/E = ±10%) may be binned together to improve counting statistics in a composite angle-dispersive scan, even when collected with much coarser scan steps of 0.1 or 0.2°. This technique is useful for high-pressure as well as general purpose powder diffraction studies that have limited X-ray access to the sample using synchrotron radiation. Several advantages are discussed. [source] Phase composition depth profiles using spatially resolved energy dispersive X-ray diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004Andrew C. Jupe Spatially resolved energy dispersive X-ray diffraction, using high-energy synchrotron radiation (,35,80,keV), was used nondestructively to obtain phase composition profiles along the radii of cylindrical cement paste samples to characterize the progress of the chemical changes associated with sulfate attack on the cement. Phase distributions were acquired to depths of ,4,mm below the specimen surface with sufficient spatial resolution to discern features less than 200,µm thick. The experimental and data analysis methods employed to obtain quantitative composition profiles are described. The spatial resolution that could be achieved is illustrated using data obtained from copper cylinders with a thin zinc coating. The measurements demonstrate that this approach is useful for nondestructively visualizing the sometimes complex transformations that take place during sulfate attack on cement-based materials. These transformations can be spatially related to microstructure as seen by computed microtomography. [source] Preparation and animal biodistribution of 166Ho labeled DOTA for possible use in intravascular radiation therapy (IVRT)JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2003Tapas Das Owing to its favorable decay characteristics (T1/2=27 h, E,(max)=1.85 MeV, E,=81 keV) and its availability with a specific activity of 3.7,4.4 GBq/mg from a moderate flux reactor, 166Ho can be considered as a potential radionuclide for intravascular radiation therapy (IVRT) using liquid-filled balloons. In the present work, studies on the use of 166Ho labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) as a possible agent for IVRT for the prevention of restenosis has been initiated. 166Ho was obtained by irradiating natural Ho2O3 powder and DOTA was synthesized by a multistep procedure. The optimum protocol of radiolabeling of DOTA with 166Ho was achieved by varying different reaction parameters. The complex was found to retain its stability for 7 days at room temperature. Bioevaluation studies carried out in Wistar rats showed that >95% of the injected activity was excreted within 3 h p.i. with almost no retention in any major organ. Both radiochemical and biological studies showed that 166Ho labeled DOTA can be further explored as a potential agent for IVRT. Copyright © 2002 John Wiley & Sons, Ltd. [source] X-ray magnetic circular dichroism measurements using an X-ray phase retarder on the BM25 A-SpLine beamline at the ESRFJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2010Roberto Boada Circularly polarized X-rays produced by a diamond X-ray phase retarder of thickness 0.5,mm in the Laue transmission configuration have been used for recording X-ray magnetic circular dichroism (XMCD) on the bending-magnet beamline BM25A (SpLine) at the ESRF. Field reversal and helicity reversal techniques have been used to carry out the measurements. The performance of the experimental set-up has been demonstrated by recording XMCD in the energy range from 7 to 11,keV. [source] X-ray spectromicroscopy in soil and environmental sciencesJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2010J. Thieme X-ray microscopy is capable of imaging particles in the nanometer size range directly with sub-micrometer spatial resolution and can be combined with high spectral resolution for spectromicroscopy studies. Two types of microscopes are common in X-ray microscopy: the transmission X-ray microscope and the scanning transmission X-ray microscope; their set-ups are explained in this paper. While the former takes high-resolution images from an object with exposure times of seconds or faster, the latter is very well suited as an analytical instrument for spectromicroscopy. The morphology of clusters or particles from soil and sediment samples has been visualized using a transmission X-ray microscope. Images are shown from a cryo-tomography experiment based on X-ray microscopy images to obtain information about the three-dimensional structure of clusters of humic substances. The analysis of a stack of images taken with a scanning transmission X-ray microscope to combine morphology and chemistry within a soil sample is shown. X-ray fluorescence is a method ideally applicable to the study of elemental distributions and binding states of elements even on a trace level using X-ray energies above 1,keV. [source] Linear polarization scans for resonant X-ray diffraction with a double-phase-plate configurationJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2009Valerio Scagnoli An in-vacuum double-phase-plate diffractometer for performing polarization scans combined with resonant X-ray diffraction experiments is presented. The use of two phase plates enables the correction of some of the aberration effects owing to the divergence of the beam and its energy spread. A higher rate of rotated polarization is thus obtained in comparison with a system with only a single retarder. Consequently, thinner phase plates can be used to obtain the required rotated polarization rate. These results are particularly interesting for applications at low energy (e.g. 4,keV) where the absorption owing to the phase plate(s) plays a key role in the feasibility of these experiments. Measurements by means of polarization scans at the uranium M4 edge on UO2 enable the contributions of the magnetic and quadrupole ordering in the material to be disentangled. [source] Determination of X-ray flux using silicon pin diodesJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2009Robin L. Owen Accurate measurement of photon flux from an X-ray source, a parameter required to calculate the dose absorbed by the sample, is not yet routinely available at macromolecular crystallography beamlines. The development of a model for determining the photon flux incident on pin diodes is described here, and has been tested on the macromolecular crystallography beamlines at both the Swiss Light Source, Villigen, Switzerland, and the Advanced Light Source, Berkeley, USA, at energies between 4 and 18,keV. These experiments have shown that a simple model based on energy deposition in silicon is sufficient for determining the flux incident on high-quality silicon pin diodes. The derivation and validation of this model is presented, and a web-based tool for the use of the macromolecular crystallography and wider synchrotron community is introduced. [source] A dedicated small-angle X-ray scattering beamline with a superconducting wiggler source at the NSRRCJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2009Din-Goa Liu At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5,GeV storage ring, a dedicated small-angle X-ray scattering (SAXS) beamline has been installed with an in-achromat superconducting wiggler insertion device of peak magnetic field 3.1,T. The vertical beam divergence from the X-ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (,E/E, 2 × 10,4) in the energy range 5,23,keV, or by a double Mo/B4C multilayer monochromator for 10,30 times higher flux (,1011,photons,s,1) in the 6,15,keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of ,0.9,mm × 0.3 mm (horizontal × vertical) at the focus point located 26.5,m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing-incidence SAXS (GISAXS) from liquid surfaces. Two online beam-position monitors separated by 8,m provide an efficient feedback control for an overall beam-position stability in the 10,µm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray-tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core-shell quantum dots) and GISAXS from liquid surfaces. [source] Comparison of calculated brightness and flux of radiation from a long-period wiggler and a short-period undulatorJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2008T. Shaftan In this article the calculation of brightness and flux for two insertion devices of the 2.8,GeV X-ray storage ring at the NSLS is discussed. The radiation properties from the X25 linearly polarized wiggler and the new X25 short-period undulator are compared at a fixed photon energy (11.3,keV) corresponding to emission from the fifth harmonic of the short-period undulator. For this computation, three commonly available synchrotron radiation programs are used. The capabilities of each of these codes are briefly discussed, and their range of applicability are commented on. It is concluded that special care is needed when modeling the radiation of the classes of insertion devices considered here. [source] Quantitative studies of pyrocarbon-coated materials using synchrotron radiationJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2008Poonamlata S. Yadav Phase-contrast imaging provides enhanced image contrast and is important for non-destructive evaluation of structural materials. In this paper, experimental results on in-line phase-contrast imaging using a synchrotron source (ELETTRA, Italy) for objects required in material science applications are discussed. Experiments have been carried out on two types of samples, pyrocarbon-coated zirconia and pyrocarbon-coated alumina microspheres. These have applications in both reactor and industrial fields. The phase-contrast imaging technique is found to be very useful in visualizing and determining the coating thickness of pyrocarbon on zirconia and alumina microspheres. The experiments were carried out at X-ray energies of 16, 18 and 20,keV and different object-to-detector distances. The results describe the contrast values and signal-to-noise ratio for both samples. A comprehensive study was carried out to determine the thickness of the pyrocarbon coating on zirconia and alumina microspheres of diameter 500,µm. The advantages of phase-contrast images are discussed in terms of contrast and resolution, and a comparison is made with absorption images. The results show considerable improvement in contrast with phase-contrast imaging as compared with absorption radiography. [source] ID20: a beamline for magnetic and resonant X-ray scattering investigations under extreme conditionsJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2007L. Paolasini A new experimental station at ESRF beamline ID20 is presented which allows magnetic and resonant X-ray scattering experiments in the energy range 3,25,keV to be performed under extreme conditions. High magnetic field up to 10,T, high pressure up to 30,kbar combined with low temperatures down to 1.5,K are available and experiments can be performed at the M -edges of actinide elements, L -edges of lanthanides and K -edges of transition metals. [source] Zr and Ba edge phenomena in the scintillation intensity of fluorozirconate-based glass-ceramic X-ray detectorsJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2007Bastian Henke The energy-dependent scintillation intensity of Eu-doped fluorozirconate glass-ceramic X-ray detectors has been investigated in the energy range from 10 to 40,keV. The experiments were performed at the Advanced Photon Source, Argonne National Laboratory, USA. The glass ceramics are based on Eu-doped fluorozirconate glasses, which were additionally doped with chlorine to initiate the nucleation of BaCl2 nanocrystals therein. The X-ray excited scintillation is mainly due to the 5d,4f transition of Eu2+ embedded in the BaCl2 nanocrystals; Eu2+ in the glass does not luminesce. Upon appropriate annealing the nanocrystals grow and undergo a phase transition from a hexagonal to an orthorhombic phase of BaCl2. The scintillation intensity is investigated as a function of the X-ray energy, particle size and structure of the embedded nanocrystals. The scintillation intensity versus X-ray energy dependence shows that the intensity is inversely proportional to the photoelectric absorption of the material, i.e. the more photoelectric absorption the less scintillation. At 18 and 37.4,keV a significant decrease in the scintillation intensity can be observed; this energy corresponds to the K -edge of Zr and Ba, respectively. The glass matrix as well as the structure and size of the embedded nanocrystals have an influence on the scintillation properties of the glass ceramics. [source] A monolithic Fresnel bimirror for hard X-rays and its application for coherence measurementsJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2007Ullrich Pietsch Experiments using a simple X-ray interferometer to measure the degree of spatial coherence of hard X-rays are reported. A monolithic Fresnel bimirror is used at small incidence angles to investigate synchrotron radiation in the energy interval 5,50,keV with monochromatic and white beam. The experimental set-up was equivalent to a Young's double-slit experiment for hard X-rays with slit dimensions in the micrometre range. From the high-contrast interference pattern the degree of coherence was determined. [source] Dose dependence of radiation damage for protein crystals studied at various X-ray energiesJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2007Nobutaka Shimizu Radiation damage to protein crystals is the most serious problem in obtaining accurate structures from protein crystallography. In order to examine the photon energy dependence of radiation damage, 12 to 15 data sets from each of nine tetragonal lysozyme crystals were collected at nine different X-ray energies (6.5, 7.1, 8.3, 9.9, 12.4, 16.5, 20.0, 24.8 and 33.0,keV) using beamline BL41XU at SPring-8. All results were compared on the basis of absorbed dose, expressed in Gray (Gy). Crystallographic statistics, such as the values of lattice constants, Rmerge and I/,(I), for each data set degraded at all nine energies as the exposure time for each crystal increased. In all data sets, radiation damage was observed after the absorbed dose exceeded 106,Gy. However, from the point of view of crystallographic statistics normalized to the absorbed dose, no clear dependence on photon energy was observed in these results. Structural refinement showed that the average B -factor for the last data set was larger than that for the first data set at all energies tested. However, no energy dependence of radiation damage on B -factor was found. Furthermore, disruption of disulfide bonds due to radiation damage was observed in electron density maps even at the highest photon energy (33,keV) used in this study. Therefore, these results suggest that radiation damage in the energy range investigated could be evaluated based on absorbed dose without energy dependence, and that it is important to minimize the absorbed dose in a crystal sample for obtaining an accurate protein structure. [source] The new HMI beamline MAGS: an instrument for hard X-ray diffraction at BESSYJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2006Esther Dudzik The Hahn-Meitner-Institute Berlin is operating the new hard X-ray diffraction beamline MAGS at the Berlin synchrotron radiation source BESSY. The beamline is intended to complement the existing neutron instrumentation at the Berlin Neutron Scattering Centre. The new beamline uses a 7,T multipole wiggler to produce photon fluxes in the 1011,1012,photons s,1 (100,mA),1 (0.1% bandwidth),1 range at energies from 4 to 30,keV at the experiment. It has active bendable optics to provide flexible horizontal and vertical focusing and to compensate the large heat load from the wiggler source. The experimental end-station consists of a six-circle Huber diffractometer which can be used with an additional (polarization) analyser and different sample environments. The beamline is intended for single-crystal diffraction and resonant magnetic scattering experiments for the study of ordering phenomena, phase transitions and materials science. [source] Three-dimensional visualization of the inner structure of single crystals by step-scanning white X-ray section topographyJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2006Taihei Mukaide Visualization of the three-dimensional distribution of the crystal defects of large single crystals of calcium fluoride has been demonstrated by white X-ray section topography using sheet-like X-rays (BL28B2 at SPring-8). An image of the three-dimensional distribution of the crystal defects was reconstructed by stacking section topographs, which expressed the images of cross sections of the sample. The section topographs were recorded using a CMOS flat-panel imager or a CCD detector combined with scintillator (Gd2O2S:Tb) and relay lens system. The section topographs were measured by repeating cycles of exposure and sample translation along the direction perpendicular to the top face of the sample. Using high-brilliance and high-energy white X-rays (,60,keV) efficiently, visualization of the three-dimensional structure of subgrains of a sample of up to 60,mm in diameter was achieved. Furthermore, the three-dimensional distribution of the glide plane in the crystal was visualized by reconstructing the linear contrast of the glide plane. [source] XAFS experiments at beamline I811, MAX-lab synchrotron source, SwedenJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2006Stefan Carlson A description of a new facility for X-ray absorption spectroscopy at the materials science beamline, I811, at MAX-lab synchrotron source, Lund, Sweden, is given. The beamline is based on a superconducting multipole wiggler source inserted in a straight section of the 1.5,GeV MAX-II ring. X-rays in the energy range 2.4,12,keV are extracted by a standard optical scheme consisting of a vertical collimating first mirror, double-crystal monochromator, and a second vertically focusing mirror. The second monochromator crystal provides sagittal focusing. The total flux impinging on the sample at 9,keV is 5 × 1011,photons,s,1, for a minimum beam spot of 0.5,mm × 0.5,mm. The beamline has facilities for experiments in transmission, fluorescence and total-electron-yield mode and experiments have been performed by international research groups on a wide range of materials, such as dilute systems with metal concentrations below 10,p.p.m. [source] Quantitative high-pressure pair distribution function analysisJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2005John B. Parise The collection of scattering data at high pressure and temperature is now relatively straightforward thanks to developments at high-brightness synchrotron radiation facilities. Reliable data from powders, that are suitable for structure determination and Rietveld refinement, are routinely collected up to about 30,GPa in either a large-volume high-pressure apparatus or diamond anvil cell. In those cases where the total elastic scattering is of interest, as it is in the case of nano-crystalline and glassy materials, technical developments, including the use of focused high-energy X-rays (>80,keV), are advantageous. Recently completed experiments on nano-crystalline materials at the 1-ID beamline at the Advanced Photon Source suggest that quantitative data, suitable for pair distribution function analysis, can be obtained. [source] An X-ray nanodiffraction technique for structural characterization of individual nanomaterialsJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2005Y. Xiao An X-ray micro/nanodiffraction technique that allows structural characterization of individual nanomaterials has been developed at an insertion-device beamline of the Advanced Photon Source. Using the extremely high brightness of the third-generation synchrotron radiation source and advanced high-resolution high-energy zone-plate focusing optics, X-rays of energies from 6 to 12,keV have been focused into a spot smaller than 200,nm with a photon density gain of more than 50000 so that significant photon flux can be intercepted by a nanoscale material to generate a measurable diffraction signal for structural characterization. This paper describes the instrumentation of the technique and discusses the application of the technique to studies of tin oxide nanobelts. [source] Beamline 10.3.2 at ALS: a hard X-ray microprobe for environmental and materials sciencesJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2004Matthew A. Marcus Beamline 10.3.2 at the ALS is a bend-magnet line designed mostly for work on environmental problems involving heavy-metal speciation and location. It offers a unique combination of X-ray fluorescence mapping, X-ray microspectroscopy and micro-X-ray diffraction. The optics allow the user to trade spot size for flux in a size range of 5,17,µm in an energy range of 3,17,keV. The focusing uses a Kirkpatrick,Baez mirror pair to image a variable-size virtual source onto the sample. Thus, the user can reduce the effective size of the source, thereby reducing the spot size on the sample, at the cost of flux. This decoupling from the actual source also allows for some independence from source motion. The X-ray fluorescence mapping is performed with a continuously scanning stage which avoids the time overhead incurred by step-and-repeat mapping schemes. The special features of this beamline are described, and some scientific results shown. [source] Small-gap insertion-device development at the National Synchrotron Light Source , performance of the new X13 mini-gap undulatorJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2004J. M. Ablett The National Synchrotron Light Source (NSLS) 2.8,GeV electron storage ring continues to set high standards in insertion-device research and development. The Chasman,Green NSLS lattice design provides for dispersion-free long straight sections in addition to a very small vertical , function. As the electron beam size is proportional to the square root of this function, a program to exploit this feature was undertaken more than a decade ago by implementing short-period small-gap insertion devices in the NSLS storage ring. The possibility of utilizing existing moderate-energy synchrotron radiation electron storage rings to produce high-brightness photon beams into the harder X-ray region have been realised using in-vacuum undulators. In this article the operation of a 1.25,cm-period mini-gap undulator, operating down to a gap of 3.3,mm within the NSLS X13 straight section, is reported. It is the brightest source of hard X-rays in the energy range ,3.7,16,keV at the NSLS, and replaces an in-vacuum undulator which had a more limited tunability. [source] | ||||||||||||||||||||||||||||||||||