Showing papers in "Journal of Synchrotron Radiation in 1998"

WinXAS: a program for X-ray absorption spectroscopy data analysis under MS-Windows.

Abstract: WinXAS is a new X-ray absorption spectroscopy (XAS) data-analysis program. It runs under the operating system MS-Windows 95/NT and offers several unique features. It has a user-friendly graphical environment and is capable of reading a variety of data formats. It contains a number of useful numerical algorithms beyond those used in conventional XAS analysis and offers a simple interface to the ab-initio theoretical code FEFF. The availability of fast macros in WinXAS makes it particularly useful for on-line data examination at synchrotron radiation facilities during XAS experiments as well as for the analysis of multiple-scan data such as those from time-resolved experiments.

A three-dimensional magnetostatics computer code for insertion devices.

Abstract: RADIA is a three-dimensional magnetostatics computer code optimized for the design of undulators and wigglers. It solves boundary magnetostatics problems with magnetized and current-carrying volumes using the boundary integral approach. The magnetized volumes can be arbitrary polyhedrons with non-linear (iron) or linear anisotropic (permanent magnet) characteristics. The current-carrying elements can be straight or curved blocks with rectangular cross sections. Boundary conditions are simulated by the technique of mirroring. Analytical formulae used for the computation of the field produced by a magnetized volume of a polyhedron shape are detailed. The RADIA code is written in object-oriented C++ and interfaced to Mathematica [Mathematica is a registered trademark of Wolfram Research, Inc.]. The code outperforms currently available finite-element packages with respect to the CPU time of the solver and accuracy of the field integral estimations. An application of the code to the case of a wedge-pole undulator is presented.

First performance assessment of the small-angle X-ray scattering beamline at ELETTRA.

Abstract: The double-focusing high-flux wiggler beamline dedicated to small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) at ELETTRA has gone into user operation recently. It has been designed specifically for time-resolved studies of non-crystalline and fibrous materials in the submillisecond time scale, and has been optimized for small-angle scattering measurements. An overview of the beamline status and of some representative results, highlighting the performance of the SAXS beamline, are given.

The Dutch-Belgian beamline at the ESRF.

Abstract: A brief description is given of the design principles and layout of the Dutch–Belgian beamline at the ESRF. This beamline optimizes the use of the available bending-magnet radiation fan by splitting the beam into two branches, each accommodating two experimental techniques.

The Gas Phase Photoemission Beamline at Elettra

Abstract: This paper reports the present stage of commissioning of the gas-phase photoemission beamline at Elettra, Trieste. The beamline is designed for atomic and molecular science experiments with high-resolution and high-flux synchrotron radiation. It consists of an undulator source, variable-angle spherical-grating monochromator and two experimental stations. The design value of the energy range is 20 to 800 eV with a specified resolving power of over 10000. The procedure adopted for calibration of this type of monochromator is discussed. At present a resolving power up to 20000 and a range up to 900 eV have been measured. Absorption spectra taken at the argon LII,III-edge and at the nitrogen, oxygen and neon K-edges are as sharp as, or sharper than, any reported in the literature. The instrumental broadening is well below the natural line-width making it difficult to quantify the resolution; this problem is discussed.

A triple-crystal diffractometer for high-energy synchrotron radiation at the HASYLAB high-field wiggler beamline BW5.

Abstract: The triple-crystal diffractometer installed at HASYLAB beamline BW5 with a high-field wiggler of critical energy 27 keV for DORIS III, operated at 4.5 GeV electron energy, is described. Samples can be mounted in large cryostats or furnaces normally used in neutron scattering experiments. The instrument has been successfully applied to measure structure factors S(Q) in liquids and amorphous materials, to collect full data sets of highly accurate structure factors for charge-density work, to measure the spin component of the ground-state magnetization in transition-metal and rare-earth compounds, to study the diffuse scattering from stacking faults and dislocation loops in Si single crystals, and for the investigation of various aspects of structural phase transitions: critical scattering in SrTiO3, oxygen order and stripe order in high-To materials. A crossed-beam technique allows for local studies of texture, internal strain and phase changes in the bulk of materials.

A plane-grating monochromator beamline for the PTB undulators at BESSY II.

Abstract: At the BESSY II storage ring, the Physikalisch–Technische Bundesanstalt (PTB) will operate insertion devices dedicated to radiometric use. One branch of the appendant beamline system will be equipped with a grazing-incidence monochromator, described here. The monochromator concept is based on a plane grating operated in parallel light; therefore exact focusing is maintained for all photon energies irrespective of the angular setting at the grating. The monochromator has been optimized for small higher-order transmittance and high power throughput, as required by radiometric applications in the wide photon energy range from 20 eV to 1900 eV.

Small-angle X-ray scattering using coherent undulator radiation at the ESRF.

Abstract: A high-coherent-flux X-ray beam for small-angle-scattering studies has been produced and analyzed at the Troika beamline of the European Synchrotron Radiation Facility. The statistics of a static speckle pattern are used to characterize the coherence properties.

Development of a two-dimensional imaging system for clinical applications of intravenous coronary angiography using intense synchrotron radiation produced by a multipole wiggler.

Abstract: A two-dimensional clinical intravenous coronary angiography system, comprising a large-size view area produced by asymmetrical reflection from a silicon crystal using intense synchrotron radiation from a multipole wiggler and a two-dimensional detector with an image intensifier, has been completed. An advantage of the imaging system is that two-dimensional dynamic imaging of the cardiovascular system can be achieved due to its two-dimensional radiation field. This world-first two-dimensional system has been successfully adapted to clinical applications. Details of the imaging system are described in this paper.

Multi-segmented piezoelectric mirrors as active/adaptive optics components

Abstract: The angular acceptance of piezoelectric (Pzt) bimorph mirrors is limited by the maximum length of commercially available Pzt ceramic plates. To overcome this limit and manufacture longer devices, several (2n + 1) 150 mm-long bimorph Pzt stacks were assembled side-to-side. Two prototype mirrors, 450 (n = 1) and 750 (n = 2) mm long, were designed, assembled, polished and optically characterized. They are fully UHV compatible and are now installed in the monochromatic section of the ESRF beamlines ID26 and ID32. Both mirrors cover the full range of required bending radii (1 km concave–3.5 km convex). Junctions between segments do not spoil the optical surface quality. The surface slope error r.m.s. can be kept well below 1 arcsec over the full bending range. Adaptive compensation for low-frequency figure errors was shown to be easy and reliable. After compensation, residual shape errors are of the order of 40 nm r.m.s. over 700 mm.

Commissioning and first results of the LNLS XAFS beamline.

Abstract: An X-ray absorption fine-structure spectroscopy beamline has been installed and commissioned at a bending-magnet source at LNLS. Three monochromators are available: a channel-cut, a double-crystal and a four-crystal set-up. They have been operated from 2500 up to 15000 eV, with a resolving power better than 5500 in the full range. Photon flux of the order of 108 photons s−1 up to 1010 photons s−1 has been attained. The experimental station is equipped with a table that can withstand a weight of 300 kg and track the vertical position of the beam with a 2.5 µm accuracy over a 120 mm stroke. The beamline has been fully characterized and the first results are presented.

Isochronous storage ring of the New SUBARU project.

Abstract: The aims of the New SUBARU project are to promote industrial applications in the VUV and soft X-ray region and to develop research and development towards new light sources The main facility of the New SUBARU project is the 15 GeV electron storage ring which is under construction at the SPring-8 site in Harima Science Garden City, Japan The storage ring is quasi-isochronous and has variable momentum dispersion for the deep study of beam dynamics in very short bunches

Optical design of the general-purpose Spanish X-ray beamline for absorption and diffraction.

Abstract: This paper describes the optical design of the general-purpose Spanish beamline for absorption and diffraction (SpLine), which will be installed on a bending-magnet port of the ESRF. This beamline is planned to cover the needs of the Spanish synchroton radiation community with broad scientific fields of interest, covering physics, chemistry, materials science and biology. By using the advantages of a wide front end (9 mrad), the Spanish beamline will be split into two branches. Both branches will be equipped with focusing optics and experimental stations. Thus, each branch can be operated simultaneously and independently from each other. One branch (A) will have two experimental stations, one for high-resolution powder diffraction (HRPD) and the other for X-ray absorption spectroscopy (XAS) and X-ray standing waves (XSW). The other branch (B) will have facilities for macromolecular crystallography and for single-crystal diffraction analysis, including that of surfaces and interfaces, as well as an X-ray diffraction/scattering camera for non-crystalline specimens.

Soft X-ray beamline specialized for actinides and radioactive materials equipped with a variably polarizing undulator.

Abstract: This report presents the design of an undulator beamline at SPring-8 to be used for soft X-ray spectroscopy focused on radioactive materials. Photoemission spectroscopy experiments are carried out in a radioisotope (RI)-controlled area where actinide compounds as well as unsealed radioactive materials are usable. Intrusion of the radioactive materials into the electron storage ring or to the outside of the evacuated beamline components can be avoided by a specially devised RI protection/ inspection mechanism. The combination of a variably polarizing undulator and a varied-line-spacing plane-grating monochromator provides linearly or circularly polarized soft X-rays with a high resolving power in the energy range 0.28-1.5 keV. The beamline will become operational in December 1997.

A novel approach to extract morphological variables in crystalline polymers from time-resolved synchrotron SAXS data.

Abstract: A novel approach to extract morphological variables in crystalline polymers from time-resolved SAXS data using the method of correlation and interface distribution functions has been devised. The principle of the calculation is based on two alternative expressions of Porod's law using the form of the interference function. The approach enables the continuous estimate of the Porod constant, and corrections for liquid scattering and finite interface between the two phases, from the time-resolved data. A model of lamellar morphology has been implemented to interpret the calculated correlation and interface distribution functions. Many detailed morphological variables such as lamellar long period, thicknesses of crystal and amorphous phases, interface thickness, and scattering invariant can be estimated. An example analysis of isothermal crystallization in PET measured by synchrotron SAXS is demonstrated.

Set-up and experimental parameters of the protein crystallography beamline at the Brazilian National Synchrotron Laboratory.

Abstract: The Brazilian National Synchrotron Light Laboratory (LNLS) has a dedicated protein crystallography beamline. The optical elements of the beamline include an elastically bent cylindrical mirror and a triangular bent-crystal monochromator, which focus synchrotron radiation at the position of the sample in the vertical and horizontal planes, respectively. The monochromatic radiation is tunable between 2.0 and 1.2 A with the optimum wavelengths from 1.3 to 1.6 A, chosen to maximize the photon flux from the bending magnets of the storage ring (1.37 GeV). Diffraction images are recorded on a 345 mm-diameter MarResearch image-plate detector system with on-line readout. The experimental parameters of the beamline, such as the integral monochromatic flux and focus size, have been measured. The size of the beam at the position of the focal point is 0.5 x 0.5 mm(2). The flux density is between 4.4 x 10(10) and 8 x 10(10) photons s(-1) mm(-2) for wavelengths from 1.28 to 1.6 A. The energy resolution is sufficient to measure absorption edges of elements between 1.28 and 2 A. The facility, intended to serve the national and international community, has been commissioned and is available for users.

Microfocusing of Hard X-rays with Cylindrically Bent Crystal Monochromators

Abstract: High-energy X-ray focusing with bent-crystal monochromators is known to be hampered by so-called depth or crystal-thickness aberrations A theoretical model of focus broadening based on the geometrical theory of X-ray diffraction in slightly deformed crystals is presented and compared with experimental data First, it is shown that depth broadening can be avoided in the Laue geometry by an appropriate choice of asymmetry angle Based on this finding, a monochromator for high-pressure diffraction experiments has been designed and a source-size-limited focal spot below 10 microns is observed As a consequence of the box-shaped rocking curve of bent Laue crystals, the focus is free of long-ranging tails Diffraction patterns of standard powder samples were recorded on imaging plates and a theoretical description of the energy-dispersion-related peak broadening is given Finally, diffraction patterns of N2 at 180 kbar demonstrate the excellent data quality achievable with this monochromator

In-vacuum undulators of SPring-8

Abstract: Most of the SPring-8 insertion devices are in-vacuum undulators except for the soft X-ray devices and one elliptical wiggler. The standard-type SPring-8 in-vacuum undulator has a period of 32 mm and a minimum gap of 8 mm. The fundamental radiation energy ranges from 5.2 to 18.5 keV. Three standard in-vacuum undulators are already installed in the ring and are operating without any problems. The magnetic field correction, the vacuum system and the commissioning of the in-vacuum undulators are described in this paper.

Phase-contrast X-ray CT image of breast tumor.

Abstract: Phase-contrast X-ray CT images generated by differences in refractive indices can be used to visualize the internal structures of soft tissues without contrast enhancement. In this study, imaging of human breast tumor was performed on formalin-fixed samples. Experiments were carried out at the synchrotron source of the Photon Factory, Tsukuba, Japan. The X-ray energy was adjusted to 17.7 keV. Phase-contrast X-ray CT images revealed various structures of human breast tumor as clearly as optical images.

X-ray imaging and microspectroscopy of plants and fungi

Abstract: X-ray fluorescence microscopy and microspectroscopy with micrometre spatial resolution and unprecedented capabilities for the study of biological and environmental samples are reported. These new capabilities are a result of both the combination of high-brilliance synchrotron radiation and high-performance X-ray microfocusing optics and the intrinsic advantages of X-rays for elemental mapping and chemical-state imaging. In this paper, these capabilities are illustrated by experimental results on hard X-ray phase-contrast imaging, X-ray fluorescence (XRF) imaging and microspectroscopy of mycorrhizal plant roots and fungi in their natural hydrated state. The XRF microprobe is demonstrated by the simultaneous mapping of the elemental distributions of P, S, K, Ca, Mn, Fe, Ni, Cu and Zn with a spatial resolution of approximately 1 × 3 µm and with an elemental sensitivity of approximately 500 p.p.b. Microspectroscopy with the same spatial resolution is demonstrated by recording near-edge X-ray absorption (XANES) spectra of Mn at a concentration of approximately 3 p.p.m.

Design of a four-crystal monochromator beamline for radiometry at BESSY II.

Abstract: 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.

Dead-time correction of a multi-element SSD for fluorescent XAFS.

Abstract: The correct evaluation of the live time of a detection system is found to be important for correcting the counting loss of a multi-element detection system for fluorescent XAFS experiments. Synchronous resetting of preamplifiers and the suspension of electronics during the reset period is an effective method. The dead time of the incoming count rate should also be corrected, since its non-linearity cannot be neglected. A 19-element solid-state detector system which can count up to 3.7 × 105 counts s−1 channel−1 with <270 eV FWHM for Mn Kα has been realized; the dead time was independent of the incoming photon energy.

High-throughput asymmetric double-crystal monochromator of the SAXS beamline at ELETTRA.

Abstract: A new high-flux wiggler beamline for fast time-resolved small-angle X-ray scattering (SAXS) based on double-focusing optics has recently commenced operation at the 2 GeV third-generation storage ring ELETTRA at Trieste, Italy. Its non-dispersive double-crystal monochromator contains three pairs of interchangeable asymmetrically cut flat Si(111)-crystal pairs, each of which is optimized for high throughput at one of the three fixed energies 5.4, 8 and 16 keV. To cope with the severe thermal power load produced by a 57-pole wiggler on the first crystal of each pair (up to 5.4 W mm−2 and 700 W under normal incidence, for 400 mA), grazing angles of 2° and optimized back-cooling have been chosen. This solution allows simultaneously a gain of 2.5–3.0 in throughput and, accordingly, in flux density. Finite-element analysis as well as commissioning tests showed that the cooling layout functions very satisfactorily, and that up to 5 × 1012 photons s−1 are available at the sample (at 8 keV and 250 mA), as predicted.

SPring-8 twin helical undulator.

Abstract: There are several ways of producing circularly polarized light, such as using asymmetric devices, crossed undulators etc. The SPring-8 helical undulator introduces a simple way of producing both horizontal and vertical fields in one undulator. All the magnet arrays are arranged above and below the plane of the electron orbit, so there is no limitation of access from the sides of the undulator. For the SPring-8 BL25SU, two helical undulators will be installed in tandem, and the helicity of the polarization can be switched at up to 10 Hz using five kicker magnets.

Instrumentation Developments for X-ray Linear and Circular Dichroism at the ESRF Beamline ID12A.

Abstract: This paper reports on the performance of the instrumentation developed for the ESRF beamline ID12A, which is dedicated to spectroscopic applications requiring full control of the polarization at energies ≥2.0 keV. Emphasis is placed on the characterization of various optical components of the beamline and on problems associated with either the control or the conversion of the polarization state. A few examples have been selected to illustrate what sort of new spectroscopic information has already been obtained at the beamline. These include the comparison of X-ray magnetic dichroism spectra recorded with linear or circular polarization and the very first detection of X-ray natural circular dichroism in single crystals known to exhibit a very large non-linear susceptibility at optical wavelengths.

Plane‐grating monochromator at BESSY II using collimated light

Abstract: At the German synchrotron radiation facility BESSY II, the VUV photon energy range between 15 and 600 eV is covered by the first, third and fifth harmonics of the U125 undulator. The beamline connected to this source is a plane-grating monochromator (PGM) with a variable deviation angle. The plane grating is illuminated by collimated radiation, allowing very flexible use of the monochromator. Depending on users' demands, it can be operated at high spectral resolution, high-order suppression or in high-flux mode, simply by software control.

Twin helical undulator beamline for soft X-ray spectroscopy at SPring-8.

Abstract: A very high resolution soft X-ray beamline, BL25SU, has been designed and is under construction at SPring-8. Completely right or left circularly polarized light is supplied on a common axis of a newly designed twin helical undulator. A helicity modulation up to 10 Hz can be performed using five kicker magnets. The fundamental radiation covers the region 0.5–3 keV. Higher-order radiation is rather weak on the axis. A monochromator with varied-line-spacing plane gratings is installed to cover the region below 1.5 keV. A very high resolution beyond 104 is expected for the whole energy region.

Phase-Contrast Tomographic Imaging Using an X-ray Interferometer.

Abstract: Apparatus for phase-contrast X-ray computed tomography using a monolithic X-ray interferometer is presented with some observational results for human breast tissues. Structures characteristic of the tissues were revealed in the phase-contrast tomograms. The procedure of image analysis consists of phase retrieval from X-ray interference patterns and tomographic image reconstruction from the retrieved phase shift. Next, feasibility of phase-contrast imaging using a two-crystal X-ray interferometer was studied aiming at in vivo observation in the future. In a preliminary study, the two-crystal X-ray interferometer was capable of generating fringes of 70% visibility using synchrotron X-rays.

Density measurements of liquid under high pressure and high temperature

Abstract: A new method for density measurements by means of X-ray absorption under high pressure and high temperature using synchrotron radiation has been developed. The method has been modified for a large-volume Paris–Edinburgh press and combined with intense high-energy X-rays at the ESRF. In order to overcome effects of deformation of sample shape under pressure, a ruby cylinder was used as a sample container. The density was determined from the intensity profile of transmitted X-rays. The densities of crystalline and liquid Bi were successfully measured up to 750 K at 1 GPa.

The Hiroshima Synchrotron Radiation Center (HSRC).

Abstract: The history of HSRC is briefly sketched, going back to the early HiSOR project. The present status of this 0.7 GeV compact storage ring is described and an outline of the future of the facility is given in the context of western Japan.