Journal of Synchrotron Radiation via MedWorm.com

Solutions for the storage and handling of SPINE standard pucks

Journal of Synchrotron Radiation — Sat, 28 Jan 2012 05:00:00 +0100

Currently there is no rack system for the long-term storage of SPINE pucks in spite of their commercial availability and heavy usage at the ESRF. The only way to store pucks is in transport dewar canisters which presents a number of limitations and drawbacks. Here a simple affordable rack for storing SPINE pucks is described, which we believe is accessible to not only synchrotrons but also both academic and industrial research laboratories. (Source: Journal of Synchrotron Radiation)

Operando QEXAFS studies of Ni2P during thiophene hydrodesulfurization: direct observation of Ni—S bond formation under reaction conditions

Journal of Synchrotron Radiation — Fri, 27 Jan 2012 05:00:00 +0100

Structural changes in Ni2P/MCM-41 were followed by quick extended X-ray absorption fine structure (QEXAFS) and were directly related to changes in X-ray absorption near-edge structure (XANES) which had been used earlier for the study of the active catalyst phase. An equation is proposed to correct the transient QEXAFS spectra up to second-order in time to remove spectral distortions induced by structural changes occurring during measurements. A good correlation between the corrected QEXAFS and the XANES spectral changes was found, giving support to the conclusions derived from the XANES in the previous work, namely that the formation of a Ni—S bond in a surface NiPS phase is involved in the active site for the hydrodesulfurization reaction. (Source: Journal of Synchrotron Radiation)

MxDC and MxLIVE: software for data acquisition, information management and remote access to macromolecular crystallography beamlines

Journal of Synchrotron Radiation — Thu, 26 Jan 2012 05:00:00 +0100

An integrated computer software system for on-site and remote collection of macromolecular crystallography (MX) data at the Canadian Light Source (CLS) is described. The system consists of an integrated graphical user interface for data collection and beamline control [MX Data Collector (MxDC)] which provides experiment-focused control of beamline devices, and a laboratory information management system [MX Laboratory Information Virtual Environment (MxLIVE)] for managing sample and experiment information through a web browser. The system allows remote planning and transmission of sample and experiment parameters to the beamline through MxLIVE, on-site or remote data collection through MxDC guided by information from MxLIVE, and remote monitoring and download of experimental results through...

A miniature X-ray emission spectrometer (miniXES) for high-pressure studies in a diamond anvil cell

Journal of Synchrotron Radiation — Thu, 19 Jan 2012 05:00:00 +0100

Core–shell X-ray emission spectroscopy (XES) is a valuable complement to X-ray absorption spectroscopy (XAS) techniques. However, XES in the hard X-ray regime is much less frequently employed than XAS, often as a consequence of the relative scarcity of XES instrumentation having energy resolutions comparable with the relevant core-hole lifetimes. To address this, a family of inexpensive and easily operated short-working-distance X-ray emission spectrometers has been developed. The use of computer-aided design and rapid prototype machining of plastics allows customization for various emission lines having energies from ∼3 keV to ∼10 keV. The specific instrument described here, based on a coarsely diced approximant of the Johansson optic, is intended to study volume collapse in Pr ...

In vivo physiological saline-infused hepatic vessel imaging using a two-crystal-interferometer-based phase-contrast X-ray technique

Journal of Synchrotron Radiation — Wed, 18 Jan 2012 05:00:00 +0100

Using a two-crystal-interferometer-based phase-contrast X-ray imaging system, the portal vein, capillary vessel area and hepatic vein of live rats were revealed sequentially by injecting physiological saline via the portal vein. Vessels greater than 0.06 mm in diameter were clearly shown with low levels of X-rays (552 µGy). This suggests that in vivo vessel imaging of small animals can be performed as conventional angiography without the side effects of the presently used iodine contrast agents. (Source: Journal of Synchrotron Radiation)

The kinetic dose limit in room-temperature time-resolved macromolecular crystallography

Journal of Synchrotron Radiation — Wed, 18 Jan 2012 05:00:00 +0100

Protein X-ray structures are determined with ionizing radiation that damages the protein at high X-ray doses. As a result, diffraction patterns deteriorate with the increased absorbed dose. Several strategies such as sample freezing or scavenging of X-ray-generated free radicals are currently employed to minimize this damage. However, little is known about how the absorbed X-ray dose affects time-resolved Laue data collected at physiological temperatures where the protein is fully functional in the crystal, and how the kinetic analysis of such data depends on the absorbed dose. Here, direct evidence for the impact of radiation damage on the function of a protein is presented using time-resolved macromolecular crystallography. The effect of radiation damage on the kinetic analysis of time-r...

A desktop X-ray monochromator for synchrotron radiation based on refraction in mosaic prism lenses

Journal of Synchrotron Radiation — Sat, 07 Jan 2012 07:47:38 +0100

Focusing planar refractive mosaic lenses based on triangular prism microstructures have been used as an alternative approach for wide-bandpass monochromatization of high-energy X-rays. The strong energy dependence of the refractive index of the lens material leads to an analogous energy dependence of the focal length of the lens. The refractive mosaic lens, in comparison with the refractive lens of continuous parabolic profile, is characterized by a higher aperture because of reduced passive material. In combination with a well defined pinhole aperture in the focal plane, the transmittance of photons of an appropriate energy can be relatively high and photons of deviating energy can be efficiently suppressed. The photon energy can be tuned by translating the pinhole along the optical axis,...

Soller slit design and characteristics

Journal of Synchrotron Radiation — Sat, 07 Jan 2012 05:00:00 +0100

For X-ray absorption spectroscopy, either in transmission mode with concentrated samples or for dilute samples in fluorescence mode, it is advantageous to improve the signal-to-noise ratio by implementing a slit apparatus. Several investigations into the improvement of measurements when slits and filters are employed have been reported; however, these have always been for a particular design and are not transferable between dissimilar systems. A generalized approach to Soller slit design will be presented which enables a target level of noise rejection to be achieved by varying the number, size and placement of the filter and Soller slit assembly. A procedure for determining the reduction in efficiency of the Soller slits with respect to misalignment with the sample will also be discussed....

Assessment of deviatoric lattice strain uncertainty for polychromatic X-ray microdiffraction experiments

Journal of Synchrotron Radiation — Sat, 07 Jan 2012 05:00:00 +0100

X-ray microdiffraction is a powerful technique for conducting high-spatial-resolution lattice strain measurements. However, there has been limited validation of the technique to date. An experiment was conducted at the Advanced Light Source to assess the uncertainty of deviatoric lattice strains measured using polychromatic X-ray microdiffraction. It is shown that the measurement uncertainty is different for each component of the deviatoric lattice strain tensor. Monte Carlo simulations of the experiment are used to explain the differences in uncertainty. The simulations point to the existence of spurious deformation modes that arise erroneously in the strain calculation owing to measurement noise and limited pole figure coverage. Methods for reducing measurement uncertainty are proposed. ...

In situ characterization of undulator magnetic fields

Journal of Synchrotron Radiation — Fri, 06 Jan 2012 05:00:00 +0100

A new in situ method is proposed to characterize the peak magnetic fields of undulator sources. The X-ray beam emitted by the HU52 Apple-2 undulator of the DEIMOS beamline of the SOLEIL synchrotron is analyzed using the Bragg diffraction of a Si(111) crystal. Measurements over the undulator gap range in linear horizontal polarization are compared with simulations in order to rebuild the Halbach function linking the undulator gaps to their peak magnetic fields. The method presented also allows information about the electron beam to be obtained. (Source: Journal of Synchrotron Radiation)

Modular deposition chamber for in situ X-ray experiments during RF and DC magnetron sputtering

Journal of Synchrotron Radiation — Fri, 06 Jan 2012 05:00:00 +0100

A new sputtering system for in situ X-ray experiments during DC and RF magnetron sputtering is described. The outstanding features of the system are the modular design of the vacuum chamber, the adjustable deposition angle, the option for plasma diagnostics, and the UHV sample transfer in order to access complementary surface analysis methods. First in situ diffraction and reflectivity measurements during RF and DC deposition of vanadium carbide demonstrate the performance of the set-up. (Source: Journal of Synchrotron Radiation)

Sub-10 nm beam confinement by X-ray waveguides: design, fabrication and characterization of optical properties

Journal of Synchrotron Radiation — Fri, 06 Jan 2012 05:00:00 +0100

The propagation of hard X-ray synchrotron beams in waveguides with guiding layer diameters in the 9–35 nm thickness range has been studied. The planar waveguide structures consist of an optimized two-component cladding. The presented fabrication method is suitable for short and leak-proof waveguide slices with lengths (along the optical axis) in the sub-500 µm range, adapted for optimized transmission at photon energies of 11.5–18 keV. A detailed comparison between finite-difference simulations of waveguide optics and the experimental results is presented, concerning transmission, divergence of the waveguide exit beam, as well as the angular acceptance. In a second step, two crossed waveguides have been used to create a quasi-point source for propagation-based X-ray imaging at t...

TXM-Wizard: a program for advanced data collection and evaluation in full-field transmission X-ray microscopy

Journal of Synchrotron Radiation — Thu, 05 Jan 2012 05:00:00 +0100

Transmission X-ray microscopy (TXM) has been well recognized as a powerful tool for non-destructive investigation of the three-dimensional inner structure of a sample with spatial resolution down to a few tens of nanometers, especially when combined with synchrotron radiation sources. Recent developments of this technique have presented a need for new tools for both system control and data analysis. Here a software package developed in MATLAB for script command generation and analysis of TXM data is presented. The first toolkit, the script generator, allows automating complex experimental tasks which involve up to several thousand motor movements. The second package was designed to accomplish computationally intense tasks such as data processing of mosaic and mosaic tomography datasets; du...

Grazing-incidence synchrotron-radiation 57Fe-Mössbauer spectroscopy using a nuclear Bragg monochromator and its application to the study of magnetic thin films

Journal of Synchrotron Radiation — Thu, 05 Jan 2012 05:00:00 +0100

Energy-domain grazing-incidence 57Fe-Mössbauer spectroscopy (E-GIMS) with synchrotron radiation (SR) has been developed to study surface and interface structures of thin films. Highly brilliant 57Fe-Mössbauer radiation, filtered from SR by a 57FeBO3 single-crystal nuclear Bragg monochromator, allows conventional Mössbauer spectroscopy to be performed for dilute 57Fe in a mirror-like film in any bunch-mode operation of SR. A theoretical and experimental study of the specular reflections from isotope-enriched (57Fe: 95%) and natural-abundance (57Fe: ∼2%) iron thin films has been carried out to clarify the basic features of the coherent interference between electronic and nuclear resonant scattering of 57Fe-Mössbauer radiation in thin films. Moreover, a new surface- and interface-sensit...

Fast and accurate X-ray fluorescence computed tomography imaging with the ordered-subsets expectation maximization algorithm

Journal of Synchrotron Radiation — Thu, 05 Jan 2012 05:00:00 +0100

The ordered-subsets expectation maximization algorithm (OSEM) is introduced to X-ray fluorescence computed tomography (XFCT) and studied; here, simulations and experimental results are presented. The simulation results indicate that OSEM is more accurate than the filtered back-projection algorithm, and it can efficiently suppress the deterioration of image quality within a large range of angular sampling intervals. Experimental results of both an artificial phantom and cirrhotic liver show that with a satisfying image quality the angular sampling interval could be improved to save on the data-acquisition time when OSEM is employed. In addition, with an optimum number of subsets, the image reconstruction time of OSEM could be reduced to about half of the time required for one subset. Accord...

Notes for authors 2012

Journal of Synchrotron Radiation — Tue, 20 Dec 2011 05:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Current events

Journal of Synchrotron Radiation — Tue, 20 Dec 2011 05:00:00 +0100

(Source: Journal of Synchrotron Radiation)

On the calculation of the gauge volume size for energy-dispersive X-ray diffraction. Erratum

Journal of Synchrotron Radiation — Tue, 20 Dec 2011 05:00:00 +0100

An equation in the paper by Rowles [(2011), J. Synchrotron Rad. 18, 938–941] is corrected. (Source: Journal of Synchrotron Radiation)

The high-resolution diffraction beamline P08 at PETRA III

Journal of Synchrotron Radiation — Wed, 30 Nov 2011 05:00:00 +0100

The new third-generation synchrotron radiation source PETRA III located at the Deutsches Elektronen-Synchrotron DESY in Hamburg, Germany, has been operational since the second half of 2009. PETRA III is designed to deliver hard X-ray beams with very high brilliance. As one of the first beamlines of PETRA III the high-resolution diffraction beamline P08 is fully operational. P08 is specialized in X-ray scattering and diffraction experiments on solids and liquids where extreme high resolution in reciprocal space is required. The resolving power results in the high-quality PETRA III beam and unique optical elements such as a large-offset monochromator and beryllium lens changers. A high-precision six-circle diffractometer for solid samples and a specially designed liquid diffractometer are in...

Challenges of sulfur SAD phasing as a routine method in macromolecular crystallography

Journal of Synchrotron Radiation — Tue, 29 Nov 2011 05:00:00 +0100

The sulfur SAD phasing method allows the determination of protein structures de novo without reference to derivatives such as Se-methionine. The feasibility for routine automated sulfur SAD phasing using a number of current protein crystallography beamlines at several synchrotrons was examined using crystals of trimeric Achromobacter cycloclastes nitrite reductase (AcNiR), which contains a near average proportion of sulfur-containing residues and two Cu atoms per subunit. Experiments using X-ray wavelengths in the range 1.9–2.4 Å show that we are not yet at the level where sulfur SAD is routinely successful for automated structure solution and model building using existing beamlines and current software tools. On the other hand, experiments using the shortest X-ray wavelengths availab...

Assessing noise sources at synchrotron infrared ports

Journal of Synchrotron Radiation — Fri, 25 Nov 2011 05:00:00 +0100

Today, the vast majority of electron storage rings delivering synchrotron radiation for general user operation offer a dedicated infrared port. There is growing interest expressed by various scientific communities to exploit the mid-IR emission in microspectroscopy, as well as the far infrared (also called THz) range for spectroscopy. Compared with a thermal (laboratory-based source), IR synchrotron radiation sources offer enhanced brilliance of about two to three orders of magnitude in the mid-IR energy range, and enhanced flux and brilliance in the far-IR energy range. Synchrotron radiation also has a unique combination of a broad wavelength band together with a well defined time structure. Thermal sources (globar, mercury filament) have excellent stability. Because the sampling rate of ...

Moiré pattern from a multiple Bragg–Laue interferometer

Journal of Synchrotron Radiation — Fri, 25 Nov 2011 05:00:00 +0100

In X-ray section topography of Si 220 diffraction in a multiple Bragg–Laue mode, a moiré pattern is observed when the incident beam is divided into two parts by inserting a platinum wire in the middle of the beam. The moiré pattern can be explained by the summation of two interference fringes corresponding to the two incident beams. The coherency of the X-rays from the bending-magnet beamline is estimated using the moiré pattern. (Source: Journal of Synchrotron Radiation)

Increase of lifespan for glioma-bearing rats by using minibeam radiation therapy

Journal of Synchrotron Radiation — Fri, 25 Nov 2011 05:00:00 +0100

This feasibility work assesses the therapeutic effectiveness of minibeam radiation therapy, a new synchrotron radiotherapy technique. In this new approach the irradiation is performed on 9L gliosarcoma-bearing rats with arrays of parallel beams of width 500–700 µm. Two irradiation configurations were compared: a lateral unidirectional irradiation and two orthogonal arrays interlacing at the target. A dose escalation study was performed. A factor of three gain in the mean survival time obtained for some animals paves the way for further exploration of the different possibilities of this technique and its further optimization. (Source: Journal of Synchrotron Radiation)

A scanning Kelvin probe for synchrotron investigations: the in situ detection of radiation-induced potential changes

Journal of Synchrotron Radiation — Fri, 25 Nov 2011 05:00:00 +0100

A wide range of high-performance X-ray surface/interface characterization techniques are implemented nowadays at every synchrotron radiation source. However, these techniques are not always `non-destructive' because possible beam-induced electronic or structural changes may occur during X-ray irradiation. As these changes may be at least partially reversible, an in situ technique is required for assessing their extent. Here the integration of a scanning Kelvin probe (SKP) set-up with a synchrotron hard X-ray interface scattering instrument for the in situ detection of work function variations resulting from X-ray irradiation is reported. First results, obtained on bare sapphire and sapphire covered by a room-temperature ionic liquid, are presented. In both cases a potential change was dete...

X-ray-Raman-scattering-based EXAFS beyond the dipole limit

Journal of Synchrotron Radiation — Fri, 25 Nov 2011 05:00:00 +0100

X-ray Raman scattering (XRS) provides a bulk-sensitive method of measuring the extended X-ray absorption fine structure (EXAFS) of soft X-ray absorption edges. Accurate measurements and data analysis procedures for the determination of XRS-EXAFS of polycrystalline diamond are described. The contributions of various angular-momentum components beyond the dipole limit to the atomic background and the EXAFS oscillations are incorporated using self-consistent real-space multiple-scattering calculations. The properly extracted XRS-EXAFS oscillations are in good agreement with calculations and earlier soft X-ray EXAFS results. It is shown, however, that under certain conditions multiple-scattering contributions to XRS-EXAFS deviate from those in standard EXAFS, leading to noticeable changes in t...

Circular dichroism beamline B23 at the Diamond Light Source

Journal of Synchrotron Radiation — Fri, 18 Nov 2011 04:18:18 +0100

Synchrotron radiation circular dichroism (SRCD) is a well established technique in structural biology. The first UV-VIS beamline, dedicated to circular dichroism, at Diamond Light Source Ltd, a third-generation synchrotron facility in south Oxfordshire, UK, has recently become operational and it is now available for the user community. Herein the main characteristics of the B23 SRCD beamline, the ancillary facilities available for users, and some of the recent advances achieved are summarized. (Source: Journal of Synchrotron Radiation)

Global and local hard X-ray tomography of a centimeter-size tumor vessel tree

Journal of Synchrotron Radiation — Fri, 18 Nov 2011 04:18:18 +0100

The visualization of the vascular network in tumors down to the smallest vessels requires high spatial resolution and reasonable contrast. Stained corrosion casts of the microvasculature network guarantee superior X-ray absorption contrast and highest reproduction fidelity. Tomography of a centimeter-size tumor, however, is unfeasible at the spatial resolution needed to reveal the smallest vessels. Therefore, local tomography has been performed to visualize the smallest capillaries within the region of interest. These three-dimensional data show the detailed morphology, but the reconstructed absorption coefficients obtained in local tomography differ substantially from the absorption coefficients retrieved from the less detailed global tomography data. This paper deals with the adaptation ...

A furnace and environmental cell for the in situ investigation of molten salt electrolysis using high-energy X-ray diffraction

Journal of Synchrotron Radiation — Fri, 18 Nov 2011 04:18:18 +0100

This paper describes the design, construction and implementation of a relatively large controlled-atmosphere cell and furnace arrangement. The purpose of this equipment is to facilitate the in situ characterization of materials used in molten salt electrowinning cells, using high-energy X-ray scattering techniques such as synchrotron-based energy-dispersive X-ray diffraction. The applicability of this equipment is demonstrated by quantitative measurements of the phase composition of a model inert anode material, which were taken during an in situ study of an operational Fray–Farthing–Chen Cambridge electrowinning cell, featuring molten CaCl2 as the electrolyte. The feasibility of adapting the cell design to investigate materials in other high-temperature environments is also discussed...

Synchrotron-based spectroscopy of X-ray channeling through hollow capillary microchannels inside glass plates

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

Here, soft X-ray synchrotron radiation transmitted through microchannel plates is studied experimentally. Fine structures of reflection and XANES Si L-edge spectra detected on the exit of silicon glass microcapillary structures under conditions of total X-ray reflection are presented and analyzed. The phenomenon of the interaction of channeling radiation with unoccupied electronic states and propagation of X-ray fluorescence excited in the microchannels is revealed. Investigations of the interaction of monochromatic radiation with the inner-shell capillary surface and propagation of fluorescence radiation through hollow glass capillary waveguides contribute to the development of novel X-ray focusing devices in the future. (Source: Journal of Synchrotron Radiation)

X-ray absorption measurements on an ultrasonic spray aerosol

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

The objective of the presented experiments was to investigate whether X-ray absorption measurements on solutes carried by aerosols are possible, and what count rates can be achieved depending on solution flow through and the resulting mass density in the interrogation volume. The investigated prototypical spray aerosol was InCl3 dissolved in water or ethanol dispersed via an ultrasonic nebulizer. InCl3 spray is essential for the ion layer gas reaction process used for the deposition of In2S3 buffer layers for highly efficient chalcopyrite solar cells. The discussed experiments demonstrate that measurements are possible, but that the achievement of good signal-to-noise ratios requires extended sampling times and concentrated solutions. (Source: Journal of Synchrotron Radiation)

Focusing femtosecond X-ray free-electron laser pulses by refractive lenses

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

The possibility of using a parabolic refractive lens with initial X-ray free-electron laser (XFEL) pulses, i.e. without a monochromator, is analysed. It is assumed that the measurement time is longer than 0.3 fs, which is the time duration of a coherent pulse (spike). In this case one has to calculate the propagation of a monochromatic wave and then perform an integration of the intensity over the radiation spectrum. Here a general algorithm for calculating the propagation of time-dependent radiation in free space and through various objects is presented. Analytical formulae are derived describing the properties of the monochromatic beam focused by a system of one and two lenses. Computer simulations show that the European XFEL pulses can be focused with maximal efficiency, i.e. as for a...

X-ray photon correlation spectroscopy in systems without long-range order: existence of an intermediate-field regime

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

Successful X-ray photon correlation spectroscopy studies often require that signals be optimized while minimizing power density in the sample to decrease radiation damage and, at free-electron laser sources, thermal impact. This suggests exploration of scattering outside the Fraunhofer far-field diffraction limit d2/λ \ll R, where d is the incident beam size, λ is the photon wavelength and R is the sample-to-detector distance. Here it is shown that, in an intermediate regime d2/λ > R \gg dξ/λ, where ξ is the structural correlation length in the material, the ensemble averages of the scattered intensity and of the structure factor are equal. Similarly, in the regime d2/λ > R \gg dξ(τ)/λ, where ξ(τ) is a time-dependent dynamics length scale of interest, the ensemble-averaged corr...

Automatic XAFS measurement system developed at BL14B2 in SPring-8

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

A novel XAFS measurement system has been developed in which XAFS measurements can be performed including sample-loading and detector adjustments. With this system, XAFS measurements of up to 80 samples in both transmission and fluorescence modes can be carried out. The adjustment of the optical components has also been automated. It not only saves manpower and measurement time, but also improves the accuracy and reliability of sample alignments. (Source: Journal of Synchrotron Radiation)

Mechanism for enhancing dispersion of Co3O4 nanoparticles in Co/SiO2 Fischer–Tropsch synthesis catalyst by adding glycol to impregnating solution: a quick-XAFS study

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

In situ Co K-edge quick-EXAFS (QEXAFS) coupled with temperature-programmed oxidation as well as ex situ XAFS was applied to investigating the mechanism for enhancing the dispersion of Co3O4 nanoparticles in a calcined Co/SiO2 Fischer–Tropsch synthesis catalyst prepared by adding triethylene glycol (TEG) to a Co(NO3)2.6H2O impregnating solution. Ex situ Co K-edge XAFS indicated that, regardless of whether the catalysts were prepared with or without using TEG, the hexaaqua Co (II) complex was formed in impregnated samples which then underwent the dehydration process to some extent during the subsequent drying step at 393 K. In situ QEXAFS and ex situ EXAFS results also indicated that small oxide clusters were formed in the TEG-modified catalyst calcined at ∼400–470 K which interact...

Status of the hard X-ray microprobe beamline ID22 of the European Synchrotron Radiation Facility

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

The ESRF synchrotron beamline ID22, dedicated to hard X-ray microanalysis and consisting of the combination of X-ray fluorescence, X-ray absorption spectroscopy, diffraction and 2D/3D X-ray imaging techniques, is one of the most versatile instruments in hard X-ray microscopy science. This paper describes the present beamline characteristics, recent technical developments, as well as a few scientific examples from recent years of the beamline operation. The upgrade plans to adapt the beamline to the growing needs of the user community are briefly discussed. (Source: Journal of Synchrotron Radiation)

A flow-through reaction cell for in situ X-ray diffraction and absorption studies of heterogeneous powder–liquid reactions and phase transformations

Journal of Synchrotron Radiation — Tue, 15 Nov 2011 05:00:00 +0100

A portable powder–liquid high-corrosion-resistant reaction cell has been designed to follow in situ reactions by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine-BM25 beamline at the European Synchrotron Radiation Facility. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X-ray pathway by a porous membrane, under forced liquid reflux circulation. Owing to the short pathway of the X-ray beam through the cell, XRD and XAS measurements can be carried out in transmission configuration/mode. In the case of the diffraction technique, data can be collected with either a point detector or a two...

Current events

Journal of Synchrotron Radiation — Fri, 14 Oct 2011 04:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Two-dimensional approach to fluorescence yield XANES measurement using a silicon drift detector. Erratum

Journal of Synchrotron Radiation — Fri, 14 Oct 2011 04:00:00 +0100

An error in the paper by Tamenori et al. [(2011), J. Synchrotron Rad. 18, 747–752] is corrected. (Source: Journal of Synchrotron Radiation)

Boris W. Batterman (1930–2010)

Journal of Synchrotron Radiation — Fri, 07 Oct 2011 04:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Capabilities of through-the-substrate microdiffraction: application of Patterson-function direct methods to synchrotron data from polished thin sections

Journal of Synchrotron Radiation — Thu, 06 Oct 2011 04:00:00 +0100

Some theoretical and practical aspects of the application of transmission microdiffraction (µXRD) to thin sections (≤30 µm thickness) of samples fixed or deposited on substrates are discussed. The principal characteristic of this technique is that the analysed micro-sized region of the thin section is illuminated through the substrate (tts-µXRD). Fields that can benefit from this are mineralogy, petrology and materials sciences since they often require in situ lateral studies to follow the evolution of crystalline phases or to determine new crystal structures in the case of phase transitions. The capability of tts-µXRD for performing structural studies with synchrotron radiation is shown by two examples. The first example is a test case in which tts-µXRD intensity data of pure aer...

Probing Ag nanoparticle surface oxidation in contact with (in)organics: an X-ray scattering and fluorescence yield approach

Journal of Synchrotron Radiation — Thu, 06 Oct 2011 04:00:00 +0100

Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag-Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag-Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag+ from oxidation/dissolution of Ag-Nps may strongly impact ecosystems. In this context, Ag-Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) a...

X-ray near-field speckle: implementation and critical analysis

Journal of Synchrotron Radiation — Wed, 05 Oct 2011 04:00:00 +0100

This study reveals certain limitations of the XNFS technique, especially in the characterization of static structures, which is discussed. (Source: Journal of Synchrotron Radiation)

Titanium local structure in tektite probed by X-ray absorption fine structure spectroscopy

Journal of Synchrotron Radiation — Tue, 04 Oct 2011 04:00:00 +0100

This study indicated that the local structure of Ti might change in impact events and the following stages. (Source: Journal of Synchrotron Radiation)

The inverse problem of bimorph mirror tuning on a beamline

Journal of Synchrotron Radiation — Fri, 30 Sep 2011 04:00:00 +0100

One of the challenges of tuning bimorph mirrors with many electrodes is that the calculated focusing voltages can be different by more than the safety limit (such as 500 V for the mirrors used at 17-ID at the Advanced Photon Source) between adjacent electrodes. A study of this problem at 17-ID revealed that the inverse problem of the tuning in situ, using X-rays, became ill-conditioned when the number of electrodes was large and the calculated focusing voltages were contaminated with measurement errors. Increasing the number of beamlets during the tuning could reduce the matrix condition number in the problem, but obtaining voltages with variation below the safety limit was still not always guaranteed and multiple iterations of tuning were often required. Applying Tikhonov regularization...

Design and construction of multicrystal analyser detectors using Rowland circles: application to MAD26 at ALBA

Journal of Synchrotron Radiation — Thu, 22 Sep 2011 04:00:00 +0100

A concept is given for describing multicrystal analyser detectors (MADs), as they are in use for synchrotron powder diffraction, on the basis of the Rowland circle construction. The Rowland circle is typically used to describe focusing geometries and can be adapted for the case of MADs working at a single energy as well as in a limited energy range. With this construction it is also possible to quantify and optimize the walk of the beam along non-central crystals which is inevitable in certain detector designs. The results of this geometrical inspection are correlated with a real detector design that is implemented at the ALBA synchrotron facility in Spain. An error budget is given to estimate the influence and amount of tolerance of the manufacturing process. (Source: Journal of Synchrotr...

Time-over-threshold readout to enhance the high flux capabilities of single-photon-counting detectors

Journal of Synchrotron Radiation — Thu, 22 Sep 2011 04:00:00 +0100

The MYTHEN single-photon-counting (SPC) detector has been characterized using the time-over-threshold (ToT) readout method, i.e. measuring the time that the signal produced by the detected X-rays remains above the comparator threshold. In the following it is shown that the ToT readout preserves the sensitivity, dynamic range and capability of background suppression of the SPC mode, while enhancing the count-rate capability, which is the main limitation of state-of-the-art SPC systems. (Source: Journal of Synchrotron Radiation)

Development of a soft X-ray angle-resolved photoemission system applicable to 100 µm crystals

Journal of Synchrotron Radiation — Wed, 21 Sep 2011 04:00:00 +0100

A system for angle-resolved photoemission spectroscopy (ARPES) of small single crystals with sizes down to 100 µm has been developed. Soft X-ray synchrotron radiation with a spot size of ∼40 µm × 65 µm at the sample position is used for the excitation. Using this system an ARPES measurement has been performed on a Si crystal of size 120 µm × 100 µm × 80 µm. The crystal was properly oriented on a sample stage by measuring the Laue spots. The crystal was cleaved in situ with a microcleaver at 100 K. The cleaved surface was adjusted to the beam spot using an optical microscope. Consequently, clear band dispersions along the Γ–X direction reflecting the bulk electronic states were observed with a photon energy of 879 eV. (Source: Journal of Synchrotron Radiation)

Synchrotron X-ray tests of an L-shaped laterally graded multilayer mirror for the analyzer system of the ultra-high-resolution IXS spectrometer at NSLS-II

Journal of Synchrotron Radiation — Fri, 16 Sep 2011 04:00:00 +0100

Characterization and testing of an L-shaped laterally graded multilayer mirror are presented. This mirror is designed as a two-dimensional collimating optics for the analyzer system of the ultra-high-resolution inelastic X-ray scattering (IXS) spectrometer at National Synchrotron Light Source II (NSLS-II). The characterization includes point-to-point reflectivity measurements, lattice parameter determination and mirror metrology (figure, slope error and roughness). The synchrotron X-ray test of the mirror was carried out reversely as a focusing device. The results show that the L-shaped laterally graded multilayer mirror is suitable to be used, with high efficiency, for the analyzer system of the IXS spectrometer at NSLS-II. (Source: Journal of Synchrotron Radiation)

In situ two-dimensional imaging quick-scanning XAFS with pixel array detector

Journal of Synchrotron Radiation — Fri, 16 Sep 2011 04:00:00 +0100

Quick-scanning X-ray absorption fine structure (XAFS) measurements were performed in transmission mode using a PILATUS 100K pixel array detector (PAD). The method can display a two-dimensional image for a large area of the order of a centimetre with a spatial resolution of 0.2 mm at each energy point in the XAFS spectrum. The time resolution of the quick-scanning method ranged from 10 s to 1 min per spectrum depending on the energy range. The PAD has a wide dynamic range and low noise, so the obtained spectra have a good signal-to-noise ratio. (Source: Journal of Synchrotron Radiation)

The status of strontium in biological apatites: an XANES investigation

Journal of Synchrotron Radiation — Fri, 16 Sep 2011 04:00:00 +0100

Osteoporosis represents a major public health problem and increases patient morbidity through its association with fragility fractures. Among the different treatments proposed, strontium-based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk. While the localization of Sr2+ cations in the bone matrix has been extensively studied, little is known regarding the status of Sr2+ cations in natural biological apatite. In this investigation the local environment of Sr2+ cations has been investigated through XANES (X-ray absorption near-edge structure) spectroscopy in a set of pathological and physiological apatites. To assess the localization of Sr2+ cations in these biological apatites, numerical simulations using the ab initio FEFF9 ...

Fluorescence detection of white-beam X-ray absorption anisotropy: towards element-sensitive projections of local atomic structure

Journal of Synchrotron Radiation — Thu, 15 Sep 2011 04:00:00 +0100

Projections of the atomic structure around Nb atoms in a LiNbO3 single crystal were obtained from a white-beam X-ray absorption anisotropy (XAA) pattern detected using Nb K fluorescence. This kind of anisotropy results from the interference of X-rays inside a sample and, owing to the short coherence length of a white beam, is visible only at small angles around interatomic directions. Consequently, the main features of the recorded XAA corresponded to distorted real-space projections of dense-packed atomic planes and atomic rows. A quantitative analysis of XAA was carried out using a wavelet transform and allowed well resolved projections of Nb atoms to be obtained up to distances of 10 Å. The signal of nearest O atoms was detected indirectly by a comparison with model calculations. The...

Increased strontium uptake in trabecular bone of ovariectomized calcium-deficient rats treated with strontium ranelate or strontium chloride

Journal of Synchrotron Radiation — Thu, 15 Sep 2011 04:00:00 +0100

Based on clinical trials showing the efficacy to reduce vertebral and non-vertebral fractures, strontium ranelate (SrR) has been approved in several countries for the treatment of postmenopausal osteoporosis. Hence, it is of special clinical interest to elucidate how the Sr uptake is influenced by dietary Ca deficiency as well as by the formula of Sr administration, SrR versus strontium chloride (SrCl2). Three-month-old ovariectomized rats were treated for 90 days with doses of 25 mg kg−1 d−1 and 150 mg kg−1 d−1 of SrR or SrCl2 at low (0.1% Ca) or normal (1.19% Ca) Ca diet. Vertebral bone tissue was analysed by confocal synchrotron-radiation-induced micro X-ray fluorescence and by backscattered electron imaging. Principal component analysis and k-means clustering of the acquire...

An alternative scheme of angular-dispersion analyzers for high-resolution medium-energy inelastic X-ray scattering

Journal of Synchrotron Radiation — Wed, 14 Sep 2011 10:44:10 +0100

The development of medium-energy inelastic X-ray scattering optics with meV and sub-meV resolution has attracted considerable efforts in recent years. Meanwhile, there are also concerns or debates about the fundamental and feasibility of the involved schemes. Here the central optical component, the back-reflection angular-dispersion monochromator or analyzer, is analyzed. The results show that the multiple-beam diffraction effect together with transmission-induced absorption can noticeably reduce the diffraction efficiency, although it may not be a fatal threat. In order to improve the efficiency, a simple four-bounce analyzer is proposed that completely avoids these two adverse effects. The new scheme is illustrated to be a feasible alternative approach for developing meV- to sub-meV-reso...

On the calculation of the gauge volume size for energy-dispersive X-ray diffraction

Journal of Synchrotron Radiation — Wed, 14 Sep 2011 04:00:00 +0100

Equations for the calculation of the dimensions of a gauge volume, also known as the active volume or diffraction lozenge, in an energy-dispersive diffraction experiment where the detector is collimated by two ideal slits have been developed. Equations are given for equatorially divergent and parallel incident X-ray beams, assuming negligible axial divergence. (Source: Journal of Synchrotron Radiation)

In situ multi-axial loading frame to probe elastomers using X-ray scattering

Journal of Synchrotron Radiation — Wed, 14 Sep 2011 04:00:00 +0100

An in situ tensile–shear loading device has been designed to study elastomer crystallization using synchrotron X-ray scattering at the Synchrotron Soleil on the DiffAbs beamline. Elastomer tape specimens of thickness 2 mm can be elongated by up to 500% in the longitudinal direction and sheared by up to 200% in the transverse direction. The device is fully automated and plugged into the TANGO control system of the beamline allowing synchronization between acquisition and loading sequences. Experimental results revealing the evolution of crystallization peaks under load are presented for several tension/shear loading sequences. (Source: Journal of Synchrotron Radiation)

Current events

Journal of Synchrotron Radiation — Thu, 04 Aug 2011 23:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Microprobing the molecular spatial distribution and structural architecture of feed-type sorghum seed tissue (Sorghum Bicolor L.) using the synchrotron radiation infrared microspectroscopy technique

Journal of Synchrotron Radiation — Thu, 04 Aug 2011 23:00:00 +0100

The objective of this study was to use the SR-IMS imaging technique to microprobe molecular spatial distribution and cell architecture of the sorghum seed tissue comprehensively. High-density mapping was carried out using SR-IMS on beamline U2B at the National Synchrotron Light Source (Brookhaven National Laboratory, NY, USA). Molecular images were systematically recorded from the outside to the inside of the seed tissue under various chemical functional groups and their ratios [peaks at ∼1725 (carbonyl C=O ester), 1650 (amide I), 1657 (protein secondary structure α-helix), 1628 (protein secondary structure β-sheet), 1550 (amide II), 1515 (aromatic compounds of lignin), 1428, 1371, 1245 (cellulosic compounds in plant seed tissue), 1025 (non-structural CHO, starch granules), 1246 (cellu...

Effects of alkyl side chains on properties of aliphatic amino acids probed using quantum chemical calculations

Journal of Synchrotron Radiation — Thu, 28 Jul 2011 23:00:00 +0100

Effects of alkyl side chains (R-) on the electronic structural properties of aliphatic amino acids are investigated using quantum mechanical approaches. The carbon (C 1s) binding energy spectra of the aliphatic amino acids are derived from the C 1s spectrum of glycine (the parent spectrum) by the addition of spectral peaks, depending on the alkyl side chains, appearing in the lower energy region IP < 290 eV (where IP is the ionization potential). The two glycyl parent spectral peaks of the amide 291.0 eV [C(2)] and carboxylic 293.5 eV [C(1)] C atoms are shifted in the aliphatic amino acids owing to perturbations depending on the size and structure of the alkyl chains. The pattern of the N 1s and O 1s spectra in glycine is retained in the spectra of the other amino acids with small sh...

Automated sample-scanning methods for radiation damage mitigation and diffraction-based centering of macromolecular crystals

Journal of Synchrotron Radiation — Thu, 28 Jul 2011 23:00:00 +0100

Automated scanning capabilities have been added to the data acquisition software, JBluIce-EPICS, at the National Institute of General Medical Sciences and the National Cancer Institute Collaborative Access Team (GM/CA CAT) at the Advanced Photon Source. A `raster' feature enables sample centering via diffraction scanning over two-dimensional grids of simple rectangular or complex polygonal shape. The feature is used to locate crystals that are optically invisible owing to their small size or are visually obfuscated owing to properties of the sample mount. The raster feature is also used to identify the best-diffracting regions of large inhomogeneous crystals. Low-dose diffraction images taken at grid positions are automatically processed in real time to provide a quick quality ranking of p...

In-line Bragg magnifier based on V-shaped germanium crystals

Journal of Synchrotron Radiation — Tue, 26 Jul 2011 23:00:00 +0100

In this work an X-ray imaging system based on a recently developed in-line two-dimensional Bragg magnifier composed of two monolithic V-shaped crystals made of dislocation-free germanium is presented. The channel-cut crystals were used in one-dimensional and in two-dimensional (crossed) configurations in imaging applications and allowed measurement of phase-contrast radiograms both in the edge-enhanced and in the holographic regimes. The measurement of the phase gradient in two orthogonal directions is demonstrated. The effective pixel size attained was 0.17 µm in the one-dimensional configuration and 0.5 µm in the two-dimensional setting, offering a twofold improvement in spatial resolution over devices based on silicon. These results show the potential for applying Bragg magnifiers...

Radiation damage reveals promising interaction position

Journal of Synchrotron Radiation — Tue, 26 Jul 2011 23:00:00 +0100

In this study a human aldose reductase mutant complexed with a bromine-substituted inhibitor was determined to atomic resolution [Protein Data Bank (PDB) code 3onc]. Though the radiation dose was moderate, a selective disruption of a bromine–inhibitor bond during the experiment was observed while the protein appears unaffected. A covalent bond to bromine is cleaved and the displaced atom is not scattered throughout the crystal but can most likely be assigned as a bromide to an additional difference electron density peak observed in the structure. The bromide relocates to an adjacent unoccupied site where promising interactions to protein residues stabilize its position. These findings were verified by a second similar structure determined with considerably higher radiation dose (PDB code...

Comparison of in vitro breast cancer visibility in analyser-based computed tomography with histopathology, mammography, computed tomography and magnetic resonance imaging

Journal of Synchrotron Radiation — Mon, 25 Jul 2011 23:00:00 +0100

High-resolution analyser-based X-ray imaging computed tomography (HR ABI-CT) findings on in vitro human breast cancer are compared with histopathology, mammography, computed tomography (CT) and magnetic resonance imaging. The HR ABI-CT images provided significantly better low-contrast visibility compared with the standard radiological images. Fine cancer structures indistinguishable and superimposed in mammograms were seen, and could be matched with the histopathological results. The mean glandular dose was less than 1 mGy in mammography and 12–13 mGy in CT and ABI-CT. The excellent visibility of in vitro breast cancer suggests that HR ABI-CT may have a valuable role in the future as an adjunct or even alternative to current breast diagnostics, when radiation dose is further decrease...

Introduction to XAFS. A Practical Guide to X-ray Absorption Fine Structure Spectroscopy. By Grant Bunker. Pp. viii + 260. Cambridge University Press, 2010. Price (hardback) GBP 40. ISBN-13: 978-0-521-76775-0.

Journal of Synchrotron Radiation — Wed, 20 Jul 2011 23:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Design of an anaerobic sample chamber for fluorescence measurements compatible with the Lytle detector

Journal of Synchrotron Radiation — Wed, 20 Jul 2011 23:00:00 +0100

A sample chamber has been developed that is compatible with the commercially available Lytle ion chamber with soller slits. The key features are (i) the sample position can be shifted vertically without changing the geometry with respect to the soller slits and ion chamber, (ii) the gas-tight structure makes it possible for experiments to work with samples that require anaerobic conditions. (Source: Journal of Synchrotron Radiation)

Milli-electronvolt monochromatization of hard X-rays with a sapphire backscattering monochromator

Journal of Synchrotron Radiation — Tue, 19 Jul 2011 23:00:00 +0100

A sapphire backscattering monochromator with 1.1 (1) meV bandwidth for hard X-rays (20–40 keV) is reported. The optical quality of several sapphire crystals has been studied and the best crystal was chosen to work as the monochromator. The small energy bandwidth has been obtained by decreasing the crystal volume impinged upon by the beam and by choosing the crystal part with the best quality. The monochromator was tested at the energies of the nuclear resonances of 121Sb at 37.13 keV, 125Te at 35.49 keV, 119Sn at 23.88 keV, 149Sm at 22.50 keV and 151Eu at 21.54 keV. For each energy, specific reflections with sapphire temperatures in the 150–300 K region were chosen. Applications to nuclear inelastic scattering with these isotopes are demonstrated. (Source: Journal of ...

SHADOW3: a new version of the synchrotron X-ray optics modelling package

Journal of Synchrotron Radiation — Tue, 19 Jul 2011 23:00:00 +0100

A new version of the popular X-ray tracing code SHADOW is presented. An important step has been made in restructuring the code following new computer engineering standards, ending with a modular Fortran 2003 structure and an application programming interface (API). The new code has been designed to be compatible with the original file-oriented SHADOW philosophy, but simplifying the compilation, installation and use. In addition, users can now become programmers using the newly designed SHADOW3 API for creating scripts, macros and programs; being able to deal with optical system optimization, image simulation, and also low transmission calculations requiring a large number of rays (>106). Plans for future development and questions on how to accomplish them are also discussed. (Source: Journ...

Two-dimensional approach to fluorescence yield XANES measurement using a silicon drift detector

Journal of Synchrotron Radiation — Tue, 19 Jul 2011 23:00:00 +0100

The objective of this article is to describe the capability of a two-dimensional (2D) approach to X-ray absorption near-edge structure (XANES) measurement by means of a partial fluorescence yield (PFY) method. 2D-XANES measurements were achieved by using a silicon drift detector as an energy-dispersive fluorescence detector. The advantage of this technique is that it allows full surveys of X-ray fluorescence data that are lost in conventional PFY measurements. The availability of a map approach was demonstrated by applying it to XANES measurements in both a diluted (Mn-doped nano-diamond) and a concentrated (MnO crystal) manganese sample. The 2D approach clearly distinguished between the PFY spectra of Mn and O atoms, where absorption edges of both elements are close to each other. Further...

Measurement of angular distribution of soft X-ray radiation from thin targets in the tabletop storage ring MIRRORCLE-20SX

Journal of Synchrotron Radiation — Fri, 15 Jul 2011 23:00:00 +0100

The only available tabletop electron storage rings are the machines from the MIRRORCLE series. The electrons are accelerated in a microtron and injected into the storage ring. During its circulation, each electron passes through a tiny target many times, emitting a photon beam. Both the spectrum and the angular distribution of the radiation depend on the material, the thickness and the shape of the target. In this paper measured angular distributions of the radiation from several different targets in the magnetic field of the 20 MeV storage ring MIRRORCLE-20SX are presented. The detector comprises a 3 mm × 3 mm × 8.5 µm plastic scintillator (PS) coupled to a photomultiplier by a bundle of optical fibers. The output of the photomultiplier is digitized by an IF converter. This det...

The measurement of differential EXAFS modulated by high pressure

Journal of Synchrotron Radiation — Fri, 15 Jul 2011 23:00:00 +0100

Differential EXAFS (DiffEXAFS) is able to detect subtle atomic perturbations in the local area of the absorbing atom. Here a new method of performing DiffEXAFS experiments under the modulation of high pressure has been developed. Periodic pressure was achieved in the gasket with the help of a dynamic diamond anvil cell, and the measurements were conducted in common energy-scanning mode. This technique has been utilized on ZnSe at 4.8 GPa. The present results have demonstrated a good agreement with the equation of state of ZnSe, and revealed sensitivity to atomic displacements of one order higher in magnitude than that of conventional EXAFS. (Source: Journal of Synchrotron Radiation)

Quantum critical point in SmO1−xFxFeAs and oxygen vacancy induced by high fluorine dopant

Journal of Synchrotron Radiation — Fri, 15 Jul 2011 23:00:00 +0100

The local lattice and electronic structure of the high-Tc superconductor SmO1–xFxFeAs as a function of F-doping have been investigated by Sm L3-edge X-ray absorption near-edge structure and multiple-scattering calculations. Experiments performed at the L3-edge show that the white line (WL) is very sensitive to F-doping. In the under-doped region (x ≤ 0.12) the WL intensity increases with doping and then it suddenly starts decreasing at x = 0.15. Meanwhile, the trend of the WL linewidth versus F-doping levels is just contrary to that of the intensity. The phenomenon is almost coincident with the quantum critical point occurring in SmO1–xFxFeAs at x ≃ 0.14. In the under-doped region the increase of the intensity is related to the localization of Sm-5d states, while theoretical calcul...

Application of X-ray fluorescence to turbulent mixing

Journal of Synchrotron Radiation — Tue, 12 Jul 2011 23:00:00 +0100

Combined measurements of X-ray absorption and fluorescence have been performed in jets of pure and diluted argon gas to demonstrate the feasibility of using X-ray fluorescence to study turbulent mixing. Measurements show a strong correspondence between the absorption and fluorescence measurements for high argon concentration. For lower argon concentration, fluorescence provides a much more robust measurement than absorption. The measurements agree well with the accepted behavior of turbulent jets. (Source: Journal of Synchrotron Radiation)

X-ray tomography of morphological changes after freeze/thaw in gas diffusion layers

Journal of Synchrotron Radiation — Fri, 08 Jul 2011 14:08:07 +0100

Liquid water produced in a polymer electrolyte membrane fuel cell experiences a freeze/thaw cycle when the cell is switched off and on while operating at ambient temperatures below freezing. This freeze/thaw cycle permanently deforms the polymer electrolyte membrane fuel cell capillary structures and reduces both the cell life and its ability to generate electric power. The X-ray tomography facility at the Pohang Accelerator Laboratory was used to observe the freeze/thaw effects on the gas diffusion layer (GDL), which is the thickest capillary layer in the cell. Morphological changes in the GDL under a water freeze/thaw cycle were observed. A scenario in which freeze/thaw cycles affect fuel cell performance is suggested based on images from X-ray tomography. (Source: Journal of Synchrotron...

Nanocomposite characterization on multiple length scales using µSAXS

Journal of Synchrotron Radiation — Thu, 07 Jul 2011 23:00:00 +0100

Nanocomposites have great potential for the rational synthesis of tailored materials. However, the templating process that transfers the self-organized nanostructure of a block copolymer or other mesophase onto the functional material is by no means trivial, and often involves multiple steps, each of which presents its own chemical and physical challenges. As a result the nanocomposite may not be homogeneous, but can be phase-separated into various components which may feature their own specific microstructure. Here it is shown how scanning microbeam small-angle X-ray scattering (µSAXS) can be used to characterize a thermoset resol/poly(isoprene-block-ethylene oxide) nanocomposite on multiple length scales with respect to homogeneity and microphase separation. (Source: Journal of Synchrot...

European research platform IPANEMA at the SOLEIL synchrotron for ancient and historical materials

Journal of Synchrotron Radiation — Thu, 07 Jul 2011 23:00:00 +0100

IPANEMA, a research platform devoted to ancient and historical materials (archaeology, cultural heritage, palaeontology and past environments), is currently being set up at the synchrotron facility SOLEIL (Saint-Aubin, France; SOLEIL opened to users in January 2008). The new platform is open to French, European and international users. The activities of the platform are centred on two main fields: increased support to synchrotron projects on ancient materials and methodological research. The IPANEMA team currently occupies temporary premises at SOLEIL, but the platform comprises construction of a new building that will comply with conservation and environmental standards and of a hard X-ray imaging beamline today in its conceptual design phase, named PUMA. Since 2008, the team has supporte...

Carbon contamination of soft X-ray beamlines: dramatic anti-reflection coating effects observed in the 1 keV photon energy region

Journal of Synchrotron Radiation — Thu, 07 Jul 2011 23:00:00 +0100

Carbon contamination is a general problem of under-vacuum optics submitted to high fluence. In soft X-ray beamlines carbon deposit on optics is known to absorb and scatter radiation close to the C K-edge (280 eV), forbidding effective measurements in this spectral region. Here the observation of strong reflectivity losses is reported related to carbon deposition at much higher energies around 1000 eV, where carbon absorptivity is small. It is shown that the observed effect can be modelled as a destructive interference from a homogeneous carbon thin film. (Source: Journal of Synchrotron Radiation)

Three-dimensional imaging of chemical phase transformations at the nanoscale with full-field transmission X-ray microscopy

Journal of Synchrotron Radiation — Thu, 07 Jul 2011 23:00:00 +0100

The ability to probe morphology and phase distribution in complex systems at multiple length scales unravels the interplay of nano- and micrometer-scale factors at the origin of macroscopic behavior. While different electron- and X-ray-based imaging techniques can be combined with spectroscopy at high resolutions, owing to experimental time limitations the resulting fields of view are too small to be representative of a composite sample. Here a new X-ray imaging set-up is proposed, combining full-field transmission X-ray microscopy (TXM) with X-ray absorption near-edge structure (XANES) spectroscopy to follow two-dimensional and three-dimensional morphological and chemical changes in large volumes at high resolution (tens of nanometers). TXM XANES imaging offers chemical speciation at the ...

Calcifications in human osteoarthritic articular cartilage: ex vivo assessment of calcium compounds using XANES spectroscopy. Addendum

Journal of Synchrotron Radiation — Sun, 19 Jun 2011 08:20:21 +0100

An acknowledgment is published for the paper by Nguyen et al. [(2011), J. Synchrotron Rad. 18, 475–480]. (Source: Journal of Synchrotron Radiation)

Current events

Journal of Synchrotron Radiation — Fri, 17 Jun 2011 23:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Beamline 08ID-1, the prime beamline of the Canadian Macromolecular Crystallography Facility

Journal of Synchrotron Radiation — Fri, 10 Jun 2011 23:00:00 +0100

Beamline 08ID-1 is the prime macromolecular crystallography beamline at the Canadian Light Source. Based on a small-gap in-vacuum undulator, it is designed for challenging projects like small crystals and crystals with large cell dimensions. Beamline 08ID-1, together with a second bending-magnet beamline, constitute the Canadian Macromolecular Crystallography Facility (CMCF). This paper presents an overall description of the 08ID-1 beamline, including its specifications, beamline software and recent scientific highlights. The end-station of the beamline is equipped with a CCD X-ray detector, on-axis crystal visualization system, a single-axis goniometer and a sample automounter allowing remote access to the beamline. The general user program is guaranteed up to 55% of the useful beam time ...

Radiation-induced melting in coherent X-ray diffractive imaging at the nanoscale

Journal of Synchrotron Radiation — Wed, 25 May 2011 23:00:00 +0100

Coherent X-ray diffraction techniques play an increasingly significant role in the imaging of nanoscale structures, ranging from metallic and semiconductor to biological objects. In material science, X-rays are usually considered to be of a low-destructive nature, but under certain conditions they can cause significant radiation damage and heat loading on the samples. The qualitative literature data concerning the tolerance of nanostructured samples to synchrotron radiation in coherent diffraction imaging experiments are scarce. In this work the experimental evidence of a complete destruction of polymer and gold nanosamples by the synchrotron beam is reported in the case of imaging at 1–10 nm spatial resolution. Numerical simulations based on a heat-transfer model demonstrate the high ...

Six-reflection meV-monochromator for synchrotron radiation

Journal of Synchrotron Radiation — Wed, 25 May 2011 23:00:00 +0100

This article presents the designs of two such devices along with their theoretical and measured performances. (Source: Journal of Synchrotron Radiation)

Asynchronous sampling for ultrafast experiments with low momentum compaction at the ANKA ring

Journal of Synchrotron Radiation — Tue, 24 May 2011 23:00:00 +0100

A high-repetition-rate pump–probe experiment is presented, based on the asynchronous sampling approach. The low-α mode at the synchrotron ANKA can be used for a time resolution down to the picosecond limit for the time-domain sampling of the coherent THz emission as well as for hard X-ray pump–probe experiments, which probe structural dynamics in the condensed phase. It is shown that a synchronization of better than 1 ps is achieved, and examples of phonon dynamics of semiconductors are presented. (Source: Journal of Synchrotron Radiation)

Development of an X-ray real-time stereo imaging technique using synchrotron radiation

Journal of Synchrotron Radiation — Mon, 23 May 2011 23:00:00 +0100

An X-ray stereo imaging system with synchrotron radiation was developed at BL20B2, SPring-8. A portion of a wide X-ray beam was Bragg-reflected by a silicon crystal to produce an X-ray beam which intersects with the direct X-ray beam. Samples were placed at the intersection point of the two beam paths. X-ray stereo images were recorded simultaneously by a detector with a large field of view placed close to the sample. A three-dimensional wire-frame model of a sample was created from the depth information that was obtained from the lateral positions in the stereo image. X-ray stereo angiography of a mouse femoral region was performed as a demonstration of real-time stereo imaging. Three-dimensional arrangements of the femur and blood vessels were obtained. (Source: Journal of Synchrotron Ra...

A differential pumping system to deliver windowless VUV photons at atmospheric pressure

Journal of Synchrotron Radiation — Wed, 18 May 2011 23:00:00 +0100

In order to deliver VUV (vacuum ultraviolet) photons under atmospheric pressure conditions, a differential pumping system has been built on the DISCO beamline at the SOLEIL synchrotron radiation facility. The system is made of four stages and is 840 mm long. The conductance-limiting body has been designed to allow practicable optical alignment. VUV transmission of the system was tested under air, nitrogen, argon and neon, and photons could be delivered down to 60 nm (20 eV). (Source: Journal of Synchrotron Radiation)

Fast X-ray powder diffraction on I11 at Diamond

Journal of Synchrotron Radiation — Mon, 16 May 2011 23:00:00 +0100

The commissioning and performance characterization of a position-sensitive detector designed for fast X-ray powder diffraction experiments on beamline I11 at Diamond Light Source are described. The detecting elements comprise 18 detector-readout modules of MYTHEN-II silicon strip technology tiled to provide 90° coverage in 2θ. The modules are located in a rigid housing custom designed at Diamond with control of the device fully integrated into the beamline data acquisition environment. The detector is mounted on the I11 three-circle powder diffractometer to provide an intrinsic resolution of Δ2θ ≃ 0.004°. The results of commissioning and performance measurements using reference samples (Si and AgI) are presented, along with new results from scientific experiments selected to demonst...

A narrow microbeam is more effective for tumor growth suppression than a wide microbeam: an in vivo study using implanted human glioma cells

Journal of Synchrotron Radiation — Mon, 16 May 2011 23:00:00 +0100

In this study, suppression of tumor growth in human glioma cells implanted in mice was evaluated experimentally using microbeams of two different widths: a conventional narrow beam (20 µm width, 100 µm center-to-center distance) and a wide beam (100 µm width, 500 µm center-to-center distance). The tumor growth ratio was compared and acute cell death was studied histologically. With cross-planar irradiation, tumor growth was significantly suppressed between days 4 and 28 after 20 µm microbeam irradiation, whereas tumor growth was suppressed, and not significantly so, only between days 4 and 18 after 100 µm microbeam irradiation. Immunohistochemistry using TUNEL staining showed no increase in TUNEL-positive cells with either microbeam at 24 and 72 h post-irradiation. The ...

Automatic loop centring with a high-precision goniometer head at the SLS macromolecular crystallography beamlines

Journal of Synchrotron Radiation — Fri, 13 May 2011 23:00:00 +0100

Automatic loop centring has been developed as part of the automation process in crystallographic data collection at the Swiss Light Source. The procedure described here consists of an optional set-up part, in which the background images are taken, and the actual centring part. The algorithm uses boundary and centre-of-mass detection at two different microscope image magnifications. Micromounts can be handled as well. Centring of the loops can be achieved in 15–26 s, depending on their initial position, and as fast as manual centring. The alignment of the sample is carried out by means of a new flexural-hinge-based compact goniometer head. The device features an electromagnet for robotic wet mounting of samples. The circle of confusion was measured to be smaller than 1 µm (r.m.s.); i...

DNA damage and repair kinetics after microbeam radiation therapy emulation in living cells using monoenergetic synchrotron X-ray microbeams

Journal of Synchrotron Radiation — Fri, 13 May 2011 23:00:00 +0100

A novel synchrotron-based approach, known as microbeam radiation therapy (MRT), currently shows considerable promise in increased tumour control and reduced normal tissue damage compared with conventional radiotherapy. Different microbeam widths and separations were investigated using a controlled cell culture system and monoenergetic (5.35 keV) synchrotron X-rays in order to gain further insight into the underlying cellular response to MRT. DNA damage and repair was measured using fluorescent antibodies against phosphorylated histone H2AX, which also allowed us to verify the exact location of the microbeam path. Beam dimensions that reproduced promising MRT strategies were used to identify useful methods to study the underpinnings of MRT. These studies include the investigation of diffe...

SPIO–RGD nanoparticles as a molecular targeting probe for imaging tumor angiogenesis using synchrotron radiation

Journal of Synchrotron Radiation — Thu, 12 May 2011 23:00:00 +0100

In this study a novel X-ray molecular targeting probe using superparamagnetic iron oxide (SPIO) conjugated with arginine–glycine–aspartic acid (SPIO–RGD) has been developed. Based on the extremely high sensitivity to the iron element of synchrotron radiation X-ray fluorescence and the superior spatial resolution of third-generation synchrotron radiation, the feasibility of SPIO–RGD as a promising molecular probe for imaging tumor angiogenesis has been demonstrated. (Source: Journal of Synchrotron Radiation)

Achromatic nested Kirkpatrick–Baez mirror optics for hard X-ray nanofocusing

Journal of Synchrotron Radiation — Wed, 11 May 2011 23:00:00 +0100

The first test of nanoscale-focusing Kirkpatrick–Baez (KB) mirrors in the nested (or Montel) configuration used at a hard X-ray synchrotron beamline is reported. The two mirrors are both 40 mm long and coated with Pt to produce a focal length of 60 mm at 3 mrad incident angle, and collect up to a 120 µm by 120 µm incident X-ray beam with maximum angular acceptance of 2 mrad and a broad bandwidth of energies up to 30 keV. In an initial test a focal spot of about 150 nm in both horizontal and vertical directions was achieved with either polychromatic or monochromatic beam. The nested mirror geometry, with two mirrors mounted side-by-side and perpendicular to each other, is significantly more compact and provides higher demagnification than the traditional sequential KB mi...

Calculation of anisotropic properties of dental enamel from synchrotron data

Journal of Synchrotron Radiation — Wed, 11 May 2011 23:00:00 +0100

Obtaining information about the intrinsic structure of polycrystalline materials is of prime importance owing to the anisotropic behaviour of individual crystallites. Grain orientation and its statistical distribution, i.e. the texture, have an important influence on the material properties. Crystallographic orientations play an important role in all kinds of polycrystalline materials such as metallic, geological and biological. Using synchrotron diffraction techniques the texture can be measured with high local and angular resolving power. Here methods are presented which allow the spatial orientation of the crystallites to be determined and information about the anisotropy of mechanical properties, such as elastic modulus or thermal expansion, to obtained. The methods are adapted to all ...

BioCARS: a synchrotron resource for time-resolved X-ray science

Journal of Synchrotron Radiation — Wed, 11 May 2011 23:00:00 +0100

BioCARS, a NIH-supported national user facility for macromolecular time-resolved X-ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator-based beamline optimized for single-shot laser-pump X-ray-probe measurements with time resolution as short as 100 ps. The source consists of two in-line undulators with periods of 23 and 27 mm that together provide high-flux pink-beam capability at 12 keV as well as first-harmonic coverage from 6.8 to 19 keV. A high-heat-load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick–Baez mirror system capable of focusing the X-ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high-speed chopper isola...

Atomic absorption background of Ba in EXAFS analysis of BaFe12O19 nanoparticles

Journal of Synchrotron Radiation — Tue, 10 May 2011 23:00:00 +0100

The approximate barium X-ray atomic absorption in the energy region of L-edges is reconstructed from the absorption spectrum of an aqueous solution of BaCl2. The result is corroborated by comparison with pure atomic absorption spectra of neighbour elements Xe and Cs. The application of the atomic absorption signal as a proper EXAFS background is demonstrated and discussed in the analysis of Ba hexaferrite nanoparticles with a very weak structural signal. The essential gain is found in the decrease of uncertainty intervals of structural parameters and their correlations. A simple analytical model of the absorption background for the practical EXAFS analysis is demonstrated. (Source: Journal of Synchrotron Radiation)

Measurement of persistence in YAG:Ce3+scintillator with pulsed synchrotron X-rays

Journal of Synchrotron Radiation — Tue, 10 May 2011 23:00:00 +0100

The decay time of YAG:Ce3+ phosphor was studied using a CMOS camera with a frame rate of 1302000 s−1 and pulsed X-rays from SPring-8. A high-resolution X-ray detector with YAG:Ce3+ was used with the camera to view the focused beam from the helical undulator. Mismatch between the ring circulation time and the frame time gave rise to a periodic variation of beam intensity in successive frames. Analysis of data obtained with two bunch modes showed that the decay time of YAG:Ce3+ was 60 ns. The variation of the beam positions in isolated bunches was small enough to be neglected in experiments using the focused beam. The results also show the possibility of an X-ray diffraction study at high time and space resolution. (Source: Journal of Synchrotron Radiation)

Hard X-ray Fourier transform holography from an array of oriented referenced objects

Journal of Synchrotron Radiation — Tue, 10 May 2011 23:00:00 +0100

Hard X-ray Fourier transform holography (HXFTH) is a promising method for imaging nanoscale objects, including biological molecules, with a spatial resolution of a nanometer or better. However, it suffers from low scattering intensities being available for imaging owing to smaller object size and the low scattering cross section inherent in hard X-rays. One technique to overcome the problem would be to use an array of oriented objects, each with its own reference. Here the feasibility of this approach was experimentally tested by recording diffraction patterns from nanofabricated test patterns arranged in a 5 × 5 matrix. At an X-ray energy of 8 keV (λ = 1.55 Å), the image of the original test pattern was clearly restored with 60 s exposure on an imaging plate; the image was still ...

Background subtraction for fluorescence EXAFS data of a very dilute dopant Z in Z + 1 host

Journal of Synchrotron Radiation — Fri, 06 May 2011 23:00:00 +0100

When conducting EXAFS at the Cu K-edge for ZnS:Cu with very low Cu concentration ( (Source: Journal of Synchrotron Radiation)

Macromolecular crystallography radiation damage research: what's new?

Journal of Synchrotron Radiation — Thu, 28 Apr 2011 04:27:46 +0100

Radiation damage in macromolecular crystallography has become a mainstream concern over the last ten years. The current status of research into this area is briefly assessed, and the ten new papers published in this issue are set into the context of previous work in the field. Some novel and exciting developments emerging over the last two years are also summarized. (Source: Journal of Synchrotron Radiation)

Synchrotron scanning photoemission microscopy of homogeneous and heterogeneous metal sulfide minerals

Journal of Synchrotron Radiation — Tue, 26 Apr 2011 23:00:00 +0100

Scanning photoemission microscopy (SPEM) has been applied to the investigation of homogeneous and heterogeneous metal sulfide mineral surfaces. Three mineral samples were investigated: homogeneous chalcopyrite, heterogeneous chalcopyrite with bornite, and heterogeneous chalcopyrite with pyrite. Sulfur, copper and iron SPEM images, i.e. surface-selective elemental maps with high spatial resolution acquired using the signal from the S 2p and Cu and Fe 3p photoemission peaks, were obtained for the surfaces after exposure to different oxidation conditions (either exposed to air or oxidized in pH 9 solution), in addition to high-resolution photoemission spectra from individual pixel areas of the images. Investigation of the homogeneous chalcopyrite sample allowed for the identification of step ...

Specific molecular and cellular events induced by irradiated X-ray photoactivatable drugs raise the problem of co-toxicities: particular consequences for anti-cancer synchrotron therapy

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

Synchrotrons are capable of producing intense low-energy X-rays that enable the photoactivation of high-Z elements. Photoactivation therapy (PAT) consists of loading tumors with photoactivatable drugs and thereafter irradiating them at an energy, generally close to the K-edge of the element, that enhances the photoelectric effect. To date, three major photoactivatable elements are used in PAT: platinum (cisplatin and carboplatin), iodine (iodinated contrast agents and iododeoxyuridine) and gadolinium (motexafin gadolinium). However, the molecular and cellular events specific to PAT and the radiobiological properties of these photoactivatable drugs are still misknown. Here, it is examined how standard and synchrotron X-rays combined with photoactivatable drugs impact on the cellular respons...

Calcifications in human osteoarthritic articular cartilage: ex vivo assessment of calcium compounds using XANES spectroscopy

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

Calcium (Ca2+)-containing crystals (CCs), including basic Ca2+ phosphate (BCP) and Ca2+ pyrophosphate dihydrate (CPPD) crystals, are associated with severe forms of osteoarthritis (OA). Growing evidence supports a role for abnormal articular cartilage mineralization in the pathogenesis of OA. However, the role of Ca2+ compounds in this mineralization process remains poorly understood. Six patients, who underwent total knee joint replacement for primary OA, have been considered in this study. Cartilage from femoral condyles and tibial plateaus in the medial and lateral compartments was collected as 1 mm-thick slices cut tangentially to the articular surface. First, CCs presence and biochemical composition were assessed using Fourier transform infrared spectroscopy (FT-IR). Next, Ca2+ comp...

High-resolution stress mapping of polycrystalline alumina compression using synchrotron X-ray diffraction

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

In this study high-energy X-rays were used to capture powder diffraction profiles over a half-section of a polycrystalline alumina parallelepiped sample under an increasing uniaxial compressive load. The data were converted to strain and results were used for stress mapping of the sample. Stress maps from the study quantify the higher stresses at the sample–platen contact interface and reveal the evolution of the stress distribution in these specimens with load. For the geometry of the samples used, at the center section of the specimen the overall magnitudes of the compressive stresses were found to be 20% higher compared with the average expected theoretical stress based on the applied load and cross-sectional area. The observed compressive stresses at the corners of the parallelepiped...

In situ diffuse reflectance IR spectroscopy and X-ray absorption spectroscopy for fast catalytic processes

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

A new instrument for synchronous in situ investigations of catalytic materials by IR and X-ray absorption spectroscopies was designed and built at the X18A beamline of the National Synchrotron Light Source of Brookhaven National Laboratory. It provides analytical tools for solving structural, electronic and kinetic problems in catalysis science by two complementary methods. Among the features attractive for catalysis research are the broad range of catalytically active elements that can be investigated (starting with Ni and beyond), the wide range of reaction conditions (temperatures up to 873 K, various reactive gases) and time scales (starting from tens of seconds). The results of several representative experiments that illustrate the attractive capabilities of the new set-up are discu...

Similarities and differences in radiation damage at 100 K versus 160 K in a crystal of thermolysin

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

The temperature-dependence of radiation damage in macromolecular X-ray crystallography is currently much debated. Most protein crystallographic studies are based on data collected at 100 K. Data collection at temperatures below 100 K has been proposed to reduce radiation damage and above 100 K to be useful for kinetic crystallography that is aimed at the generation and trapping of protein intermediate states. Here the global and specific synchrotron-radiation sensitivity of crystalline thermolysin at 100 and 160 K are compared. Both types of damage are higher at 160 K than at 100 K. At 160 K more residue types are affected (Lys, Asp, Gln, Pro, Thr, Met, Asn) than at 100 K (Met, Asp, Glu, Lys). The X-ray-induced relative atomic B-factor increase is shown to correlate with th...

Assessment of radiation damage behaviour in a large collection of empirically optimized datasets highlights the importance of unmeasured complicating effects

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

The radiation damage behaviour in 43 datasets of 34 different proteins collected over a year was examined, in order to gauge the reliability of decay metrics in practical situations, and to assess how these datasets, optimized only empirically for decay, would have benefited from the precise and automatic prediction of decay now possible with the programs RADDOSE [Murray, Garman & Ravelli (2004). J. Appl. Cryst. 37, 513–522] and BEST [Bourenkov & Popov (2010). Acta Cryst. D66, 409–419]. The results indicate that in routine practice the diffraction experiment is not yet characterized well enough to support such precise predictions, as these depend fundamentally on three interrelated variables which cannot yet be determined robustly and practically: the flux density distribution of the b...

Radiation damage in room-temperature data acquisition with the PILATUS 6M pixel detector

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

The first study of room-temperature macromolecular crystallography data acquisition with a silicon pixel detector is presented, where the data are collected in continuous sample rotation mode, with millisecond read-out time and no read-out noise. Several successive datasets were collected sequentially from single test crystals of thaumatin and insulin. The dose rate ranged between ∼1320 Gy s−1 and ∼8420 Gy s−1 with corresponding frame rates between 1.565 Hz and 12.5 Hz. The data were analysed for global radiation damage. A previously unreported negative dose-rate effect is observed in the indicators of global radiation damage, which showed an approximately 75% decrease in D1/2 at sixfold higher dose rate. The integrated intensity decreases in an exponential manner and t...

Radiation damage in single-particle cryo-electron microscopy: effects of dose and dose rate

Journal of Synchrotron Radiation — Fri, 08 Apr 2011 23:00:00 +0100

Radiation damage is an important resolution limiting factor both in macromolecular X-ray crystallography and cryo-electron microscopy. Systematic studies in macromolecular X-ray crystallography greatly benefited from the use of dose, expressed as energy deposited per mass unit, which is derived from parameters including incident flux, beam energy, beam size, sample composition and sample size. In here, the use of dose is reintroduced for electron microscopy, accounting for the electron energy, incident flux and measured sample thickness and composition. Knowledge of the amount of energy deposited allowed us to compare doses with experimental limits in macromolecular X-ray crystallography, to obtain an upper estimate of radical concentrations that build up in the vitreous sample, and to tra...

Current events

Journal of Synchrotron Radiation — Thu, 07 Apr 2011 23:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Suppression of ring artefacts when tomographing anisotropically attenuating samples

Journal of Synchrotron Radiation — Fri, 01 Apr 2011 23:00:00 +0100

There are many objects for which the attenuation varies significantly as they are rotated during computerized X-ray tomography, for example plate samples. This can lead to significant ring artefacts in the subsequent tomographic reconstructions. In this paper a new method is presented that can successfully suppress such ring artefacts and is applicable to both parallel and cone-beam geometries. Rapid correction is achieved via an analytical formula which involves only a matrix-vector multiplication, for which the matrix is known and depends on a regularization parameter. The efficacy of the method is demonstrated for a paleontological sample (calcified shark cartilage) and a carbon–carbon composite/Ti–SiC metal matrix composite test sample. (Source: Journal of Synchrotron Radiation)

X-ray collimation by crystals with precise parabolic holes based on diffractive–refractive optics

Journal of Synchrotron Radiation — Thu, 31 Mar 2011 23:00:00 +0100

Two crystals with precise parabolic holes were used to demonstrate sagittal beam collimation by means of a diffractive–refractive double-crystal monochromator. A new approach is introduced and beam collimation is demonstrated. Two Si(333) crystals with an asymmetry angle of α = 15° were prepared and arranged in a dispersive position (+,−,−,+). Based on theoretical calculations, this double-crystal set-up should provide tunable beam collimation within an energy range of 6.3–18.8 keV (ΘB = 71–18.4°). An experiment study was performed on BM05 at ESRF. Using 8.97 keV energy, the beam profile at various distances was measured. The experimental results are in good agreement with theoretical predictions. Owing to insufficient harmonic suppression, the collimated (333) beam was o...

Effective scavenging at cryotemperatures: further increasing the dose tolerance of protein crystals

Journal of Synchrotron Radiation — Thu, 31 Mar 2011 23:00:00 +0100

The rate of radiation damage to macromolecular crystals at both room temperature and 100 K has previously been shown to be reduced by the use of certain radical scavengers. Here the effects of sodium nitrate, an electron scavenger, are investigated at 100 K. For sodium nitrate at a concentration of 0.5 M in chicken egg-white lysozyme crystals, the dose tolerance is increased by a factor of two as judged from the global damage parameters, and no specific structural damage to the disulfide bonds is seen until the dose is greatly in excess (more than a factor of five) of the value at which damage appears in electron density maps derived from a scavenger-free crystal. In the electron density maps, ordered nitrate ions adjacent to the disulfide bonds are seen to lose an O atom, and appear...

Use of Soller slits to remove reference foil fluorescence from transmission spectra

Journal of Synchrotron Radiation — Sat, 19 Mar 2011 00:00:00 +0100

Measurement of X-ray absorption spectroscopy (XAS) in transmission is the method of choice for strong or concentrated samples. In a typical XAS experiment above 5 keV the sample is placed between the first (I0) and second (I1) ion chambers and a standard foil is placed between the second (I1) and third (I2) ion chambers for simultaneous calibration of energy during sample analysis. However, some fluorescence from the foil may be registered in I1, causing anomalies in the transmission signal of the sample, especially when the sample edge jump is relatively small. To remedy this, Soller slits were constructed and placed between the foil and I1 to minimize back-fluorescence from the foil. A comparison of blank and standard samples, measured with or without Soller slits or under a worst-case...

Geometrical layout and optics modelling of the surface science beamline station at the SESAME synchrotron radiation facility

Journal of Synchrotron Radiation — Sat, 19 Mar 2011 00:00:00 +0100

The layout and the optical performance of the SGM branch of the D09 bending-magnet beamline, under construction at SESAME, are presented. The beamline is based on the Dragon-type design and delivers photons over the spectral range 15–250 eV. One fixed entrance slit and a movable exit slit are used. The performance of the beamline has been characterized by calculating the mirror reflectivities and the grating efficiencies. The flux and resolution were calculated by ray-tracing using SHADOW. The grating diffraction efficiencies were calculated using the GRADIF code. The results and the overall shapes of the predicted curves are in reasonable agreement with those obtained using an analytical formula. (Source: Journal of Synchrotron Radiation)

Development of a hard X-ray delay line for X-ray photon correlation spectroscopy and jitter-free pump–probe experiments at X-ray free-electron laser sources

Journal of Synchrotron Radiation — Sat, 19 Mar 2011 00:00:00 +0100

A hard X-ray delay line capable of splitting and delaying single X-ray pulses has been developed with the aim of performing X-ray photon correlation spectroscopy (XPCS) and X-ray pump–probe experiments at hard X-ray free-electron laser sources. The performance of the device was tested with 8.39 keV synchrotron radiation. Time delays up to 2.95 ns have been demonstrated. The feasibility of the device for performing XPCS studies was tested by recording static speckle patterns. The achieved speckle contrast of 56% indicates the possibility of performing ultra-fast XPCS studies with the delay line. (Source: Journal of Synchrotron Radiation)

Revealing low-dose radiation damage using single-crystal spectroscopy

Journal of Synchrotron Radiation — Sat, 19 Mar 2011 00:00:00 +0100

The structural information and functional insight obtained from X-ray crystallography can be enhanced by the use of complementary spectroscopies. Here the information that can be obtained from spectroscopic methods commonly used in conjunction with X-ray crystallography and best-practice single-crystal UV-Vis absorption data collection are briefly reviewed. Using data collected with the in situ system at the Swiss Light Source, the time and dose scales of low-dose X-ray-induced radiation damage and solvated electron generation in metalloproteins at 100 K are investigated. The effect of dose rate on these scales is also discussed. (Source: Journal of Synchrotron Radiation)

Correlated single-crystal electronic absorption spectroscopy and X-ray crystallography at NSLS beamline X26-C

Journal of Synchrotron Radiation — Sat, 19 Mar 2011 00:00:00 +0100

The research philosophy and new capabilities installed at NSLS beamline X26-C to support electronic absorption and Raman spectroscopies coupled with X-ray diffraction are reviewed. This beamline is dedicated full time to multidisciplinary studies with goals that include revealing the relationship between the electronic and atomic structures in macromolecules. The beamline instrumentation has been fully integrated such that optical absorption spectra and X-ray diffraction images are interlaced. Therefore, optical changes induced by X-ray exposure can be correlated with X-ray diffraction data collection. The installation of Raman spectroscopy into the beamline is also briefly reviewed. Data are now routinely generated almost simultaneously from three complementary types of experiments from t...

ANKAphase: software for single-distance phase retrieval from inline X-ray phase-contrast radiographs

Journal of Synchrotron Radiation — Wed, 16 Mar 2011 00:00:00 +0100

A computer program named ANKAphase is presented that processes X-ray inline phase-contrast radiographs by reconstructing the projected thickness of the object(s) imaged. The program uses a single-distance non-iterative phase-retrieval algorithm described by David Paganin et al. [(2002), J. Microsc. 206, 33–40]. Allowing for non-negligible absorption in the sample, this method is strictly valid only for monochromatic illumination and single-material objects but tolerates deviations from these conditions, especially polychromaticity. ANKAphase is designed to be applied to tomography data (although it does not perform tomographic reconstruction itself). It can process series of images and perform flat-field and dark-field correction. Written in Java, ANKAphase has an intuitive graphical use...

Fast X-ray microdiffraction techniques for studying irreversible transformations in materials

Journal of Synchrotron Radiation — Wed, 16 Mar 2011 00:00:00 +0100

A pair of techniques have been developed for performing time-resolved X-ray microdiffraction on irreversible phase transformations. In one technique capillary optics are used to focus a high-flux broad-spectrum X-ray beam to a 60 µm spot size and a fast pixel array detector is used to achieve temporal resolution of 55 µs. In the second technique the X-rays are focused with Kirkpatrick–Baez mirrors to achieve a spatial resolution better than 10 µm and a fast shutter is used to provide temporal resolution better than 20 µs while recording the diffraction pattern on a (relatively slow) X-ray CCD camera. Example data from experiments are presented where these techniques are used to study self-propagating high-temperature synthesis reactions in metal laminate foils. (Source: Journ...

Three-dimensional diffraction mapping by tuning the X-ray energy

Journal of Synchrotron Radiation — Tue, 15 Mar 2011 00:00:00 +0100

Three-dimensional reciprocal-space maps of a single SiGe island around the Si(004) Bragg peak are recorded using an energy-tuning technique with a microfocused X-ray beam with compound refractive lenses as focusing optics. The map is in agreement with simulated data as well as with a map recorded by an ordinary rocking-curve scan. The energy-tuning approach circumvents both the comparatively large sphere of confusion of diffractometers compared with nanostructures and vibrations induced by motors. Thus, this method offers new possibilities for novel combinations of three-dimensional micro- and nano-focused X-ray diffraction with complex in situ sample environments such as scanning probe microscopes. (Source: Journal of Synchrotron Radiation)

In situ powder diffraction study of belite sulfoaluminate clinkering

Journal of Synchrotron Radiation — Tue, 15 Mar 2011 00:00:00 +0100

Belite sulfoaluminate (BSA) cements have been proposed as environmentally friendly building materials, as their production may release up to 35% less CO2 into the atmosphere when compared with ordinary Portland cement fabrication. However, their formation mechanism has not been studied in detail so far. Here, an in situ high-temperature high-resolution synchrotron X-ray powder diffraction study is reported. Two types of BSA clinkers have been characterized, both containing 50–60 wt% C2S and 20–30 wt% C4A3\underline{\rm S} as main phases. One type is iron-rich and a second type (with different phase assemblage) is aluminium-rich. Furthermore, the C2S phase reacts slowly with water, thus activation of this compound is desirable in order to enhance the mechanical strength development ...

Energy dependence of site-specific radiation damage in protein crystals

Journal of Synchrotron Radiation — Tue, 15 Mar 2011 00:00:00 +0100

In this study the rate of damage to specific sites in protein crystals cooled at 100 K is found to depend on the energy of the incident X-ray beam. Several lysozyme crystals were each subjected to 3–26 MGy of cumulative X-ray exposure by collecting multiple data sets from each crystal at either 9 keV or 14 keV. The integrated electron density surrounding each S atom in the structure was calculated for each data set and the change in electron density was evaluated as a function of dose at the two energies. The rate of electron density decrease per cubic Å per MGy was determined to be greater at 14 keV than at 9 keV for cysteine sulfurs involved in disulphide bridges; no statistically significant differences in the decay rates were found for methionine sulfurs. These prelimina...

Experimental procedure for the characterization of radiation damage in macromolecular crystals

Journal of Synchrotron Radiation — Fri, 11 Mar 2011 01:50:16 +0100

A reliable and reproducible method to automatically characterize the radiation sensitivity of macromolecular crystals at the ESRF beamlines has been developed. This new approach uses the slope of the linear dependence of the overall isotropic B-factor with absorbed dose as the damage metric. The method has been implemented through an automated procedure using the EDNA on-line data analysis framework and the MxCuBE data collection control interface. The outcome of the procedure can be directly used to design an optimal data collection strategy. The results of tests carried out on a number of model and real-life crystal systems are presented. (Source: Journal of Synchrotron Radiation)

Synchrotron-radiation-induced oxidation of selenite to selenate in coal-derived fly ash

Journal of Synchrotron Radiation — Fri, 11 Mar 2011 00:00:00 +0100

Systematic changes observed in consecutive XANES spectra of selenium in samples of fly ash from a power plant in Alberta, Canada, burning subbituminous coal have been interpreted as arising from synchrotron-radiation-induced oxidation of a selenite species to selenate. It was estimated that about 15–20% of the selenite was oxidized to selenate during the 2 h exposure of the fly ash to the synchrotron beam. In contrast, the XANES spectra of arsenic (and other trace elements not documented herein) showed no variation. It is believed that this is the first time that radiation-induced changes have been observed for an element in coal-derived fly ash. (Source: Journal of Synchrotron Radiation)

Reconstruction of electron beam distribution using phase-retrieval algorithm

Journal of Synchrotron Radiation — Fri, 11 Mar 2011 00:00:00 +0100

The shapes of light sources such as electron beams can be reconstructed by inverse Fourier transformation of the complex degree of spatial coherency, which can be measured using Young's interferometer. The application of the phase-retrieval algorithm to reduce phase measurement errors in the complex degree of spatial coherency is numerically studied using an electron beam with an asymmetric distribution. This application is demonstrated with experimental data measured at the diagnostic beamline at the Pohang Accelerator Laboratory. (Source: Journal of Synchrotron Radiation)

Additional phase information from UV damage of selenomethionine labelled proteins

Journal of Synchrotron Radiation — Fri, 11 Mar 2011 00:00:00 +0100

Currently, selenium is the most widely used phasing vehicle for experimental phasing, either by single anomalous scattering or multiple-wavelength anomalous dispersion (MAD) procedures. The use of the single isomorphous replacement anomalous scattering (SIRAS) phasing procedure with selenomethionine containing proteins is not so commonly used, as it requires isomorphous native data. Here it is demonstrated that isomorphous differences can be measured from intensity changes measured from a selenium labelled protein crystal before and after UV exposure. These can be coupled with the anomalous signal from the dataset collected at the selenium absorption edge to obtain SIRAS phases in a UV-RIPAS phasing experiment. The phasing procedure for two selenomethionine proteins, the feruloyl esterase ...

New developments in fabrication of high-energy-resolution analyzers for inelastic X-ray spectroscopy

Journal of Synchrotron Radiation — Thu, 10 Mar 2011 00:00:00 +0100

In this work new improvements related to the fabrication of spherical bent analyzers for 1 meV energy-resolution inelastic X-ray scattering spectroscopy are presented. The new method includes the use of a two-dimensional bender to achieve the required radius of curvature for X-ray analyzers. The advantage of this method is the ability to monitor the focus during bending, which leads to higher-efficiency analyzers. (Source: Journal of Synchrotron Radiation)

High-efficiency Fresnel zone plates for hard X-rays by 100 keV e-beam lithography and electroplating

Journal of Synchrotron Radiation — Thu, 10 Mar 2011 00:00:00 +0100

The fabrication and characterization of Fresnel zone plates (FZPs) for hard X-ray microscopy applications are reported. High-quality 500 nm- and 1 µm-thick Au FZPs with outermost zone widths down to 50 nm and 70 nm, respectively, and with diameters up to 600 µm were fabricated. The diffraction efficiencies of the fabricated FZPs were measured for a wide range of X-ray energies (2.8–13.2 keV) showing excellent values up to 65–75% of the theoretical values, reflecting the good quality of the FZPs. Spatially resolved diffraction efficiency measurements indicate the uniformity of the FZPs and a defect-free structure. (Source: Journal of Synchrotron Radiation)

Quantitative local structure determination in mica crystals: ab initio simulations of polarization XANES at the potassium K-edge

Journal of Synchrotron Radiation — Thu, 10 Mar 2011 00:00:00 +0100

An attempt to refine the local structure of a layered structure such as mica is made by combining angle-resolved XANES (AXANES) and single-crystal X-ray diffraction (SC-XRD) experiments. Ab initio calculations of AXANES spectra of several tri-octahedral micas have been used to further interpolate experimental data and to deduce physico/chemical effects. Structural distortions have been found highly correlated with the compositional disordering that arises from electronic interactions between anions and cations, and extend the interlayer entering deep into nearby tetrahedral and octahedral sheets. Multiple occupations at the same atomic site have been investigated in detail both in the parallel and perpendicular components of AXANES spectra. Finally, the best fit obtained, computed in the f...

Current events

Journal of Synchrotron Radiation — Fri, 18 Feb 2011 00:00:00 +0100

(Source: Journal of Synchrotron Radiation)

MicroGISAXS of Langmuir–Blodgett protein films: effect of temperature on long-range order. Addendum

Journal of Synchrotron Radiation — Fri, 18 Feb 2011 00:00:00 +0100

An extra acknowledgment is published for the paper by Pechkova et al. [(2009), J. Synchrotron Rad. 16, 330–335]. (Source: Journal of Synchrotron Radiation)

Time-resolved photoelectron spectroscopy using synchrotron radiation time structure

Journal of Synchrotron Radiation — Sat, 05 Feb 2011 00:00:00 +0100

Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump–probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera-based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application ha...

In situ study of nanotemplate-induced growth of lysozyme microcrystals by submicrometer GISAXS

Journal of Synchrotron Radiation — Wed, 02 Feb 2011 00:00:00 +0100

Ultrasmall lysozyme microcrystals are grown by classical hanging-drop vapor diffusion and by its modification using a homologous protein thin-film template displaying long-range order. The nucleation and growth mechanisms of lysozyme microcrystals are studied at the thin lysozyme film surface using a new in situ µGISAXS (microbeam grazing-incidence small-angle X-ray scattering) technique recently developed at the microfocus beamline of the ESRF in Grenoble, France. New insight on the nucleation and crystallization processes appear to emerge. (Source: Journal of Synchrotron Radiation)

Numerical optimization of spherical variable-line-spacing grating X-ray spectrometers

Journal of Synchrotron Radiation — Sat, 29 Jan 2011 00:00:00 +0100

Operation of an X-ray spectrometer based on a spherical variable-line-spacing (VLS) grating is analyzed using dedicated ray-tracing software allowing fast optimization of the grating parameters and spectrometer geometry. The analysis is illustrated with optical design of a model spectrometer to deliver a resolving power above 20400 at a photon energy of 930 eV (Cu L-edge). With this energy taken as reference, the VLS coefficients are optimized to cancel the lineshape asymmetry (mostly from the coma aberrations) as well as minimize the symmetric aberration broadening at large grating illuminations, dramatically increasing the aberration-limited vertical acceptance of the spectrometer. For any energy away from the reference, corrections to the entrance arm and light incidence angle on the ...

Multi-frame acquisition scheme for efficient energy-dispersive X-ray magnetic circular dichroism in pulsed high magnetic fields at the Fe K-edge

Journal of Synchrotron Radiation — Sat, 29 Jan 2011 00:00:00 +0100

Using a fast silicon strip detector, a multi-frame acquisition scheme was implemented to perform energy-dispersive X-ray magnetic circular dichroism at the iron K-edge in pulsed high magnetic fields. The acquisition scheme makes use of the entire field pulse. The quality of the signal obtained from samples of ferrimagnetic erbium iron garnet allows for quantitative evaluation of the signal amplitude. Below the compensation point, two successive field-induced phase transitions and the reversal of the net magnetization of the iron sublattices in the intermediate phase were observed. (Source: Journal of Synchrotron Radiation)

Rietveld and pair distribution function study of Hägg carbide using synchrotron X-ray diffraction

Journal of Synchrotron Radiation — Wed, 26 Jan 2011 00:00:00 +0100

Fischer–Tropsch (FT) synthesis is an important process in the manufacturing of hydrocarbons and oxygenated hydrocarbons from mixtures of carbon monoxide and hydrogen (syngas). The reduced iron catalyst reacts with carbon monoxide and hydrogen to form bulk Fe5C2 Hägg carbide (χ-HC) during FT synthesis. Arguably, χ-HC is the predominant catalyst phase present in the working iron catalyst. Deactivation of the working catalyst can be due to oxidation of χ-HC to iron oxide, a step-wise decarburization to cementite (θ-Fe3C), carbon formation or sintering with accompanying loss of catalytic performance. It is therefore critical to determine the precise crystal structure of χ-HC for the understanding of the synthesis process and for comparison with the first-principles ab initio modelling....

A large-volume gas cell for high-energy X-ray reflectivity investigations of interfaces under pressure

Journal of Synchrotron Radiation — Wed, 26 Jan 2011 00:00:00 +0100

A cell for the investigation of interfaces under pressure is presented. Given the pressure and temperature specifications of the cell, P ≤ 100 bar and 253 K ≤ T ≤ 323 K, respectively, high-energy X-rays are required to penetrate the thick Al2O3 windows. The CH4(gas)/H2O(liquid) interface has been chosen to test the performance of the new device. The measured dynamic range of the high-energy X-ray reflectivity data exceeds 10−8, thereby demonstrating the validity of the entire experimental set-up. (Source: Journal of Synchrotron Radiation)

Densification of sol–gel silica thin films induced by hard X-rays generated by synchrotron radiation

Journal of Synchrotron Radiation — Sat, 22 Jan 2011 00:00:00 +0100

In this article the effects induced by exposure of sol–gel thin films to hard X-rays have been studied. Thin films of silica and hybrid organic–inorganic silica have been prepared via dip-coating and the materials were exposed immediately after preparation to an intense source of light of several keV generated by a synchrotron source. The samples were exposed to increasing doses and the effects of the radiation have been evaluated by Fourier transform infrared spectroscopy, spectroscopic ellipsometry and atomic force microscopy. The X-ray beam induces a significant densification on the silica films without producing any degradation such as cracks, flaws or delamination at the interface. The densification is accompanied by a decrease in thickness and an increase in refractive index both...

Feasibility of in-line instruments for high-resolution inelastic X-ray scattering

Journal of Synchrotron Radiation — Fri, 21 Jan 2011 00:00:00 +0100

Inelastic X-ray scattering instruments in operation at third-generation synchrotron radiation facilities are based on backreflections from perfect silicon crystals. This concept reaches back to the very beginnings of high-energy-resolution X-ray spectroscopy and has several advantages but also some inherent drawbacks. In this paper an alternate path is investigated using a different concept, the `M4 instrument'. It consists of a combination of two in-line high-resolution monochromators, focusing mirrors and collimating mirrors. Design choices and performance estimates in comparison with existing conventional inelastic X-ray scattering instruments are presented. (Source: Journal of Synchrotron Radiation)

Coherent diffraction microscopy at SPring-8: instrumentation, data acquisition and data analysis

Journal of Synchrotron Radiation — Fri, 21 Jan 2011 00:00:00 +0100

Since the first demonstration of coherent diffraction microscopy in 1999, this lensless imaging technique has been experimentally refined by continued developments. Here, instrumentation and experimental procedures for measuring oversampled diffraction patterns from non-crystalline specimens using an undulator beamline (BL29XUL) at SPring-8 are presented. In addition, detailed post-experimental data analysis is provided that yields high-quality image reconstructions. As the acquisition of high-quality diffraction patterns is at least as important as the phase-retrieval procedure to guarantee successful image reconstructions, this work will be of interest for those who want to apply this imaging technique to materials science and biological samples. (Source: Journal of Synchrotron Radiation...

On aberrations in saw-tooth refractive X-ray lenses and on their removal

Journal of Synchrotron Radiation — Thu, 20 Jan 2011 00:00:00 +0100

This report will discuss the aberrations arising in the saw-tooth structure in its simplest form with identical prisms. It is found that the saw-tooth structures in low-Z materials with focal length below 1 m provide less flux density in the focal spot than stacks of one-dimensionally focusing refractive lenses with identical transmission function. This is due to excessive aberrations in the regular structure, which are absent in stacks of concave lenses, and which limit the focusing to spot sizes of just submicrometre dimensions, as measured experimentally for some lenses. It will be shown that this limitation can be overcome by appropriately modifying the prism shape. Then the image size could be reduced by about an order of magnitude to the diffraction limit with competitive numbers e...

Assessment of chemical species of lead accumulated in tidemarks of human articular cartilage by X-ray absorption near-edge structure analysis

Journal of Synchrotron Radiation — Thu, 20 Jan 2011 00:00:00 +0100

A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called `tidemark', is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L3-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and ...

High-throughput full-automatic synchrotron-based tomographic microscopy

Journal of Synchrotron Radiation — Thu, 20 Jan 2011 00:00:00 +0100

At the TOMCAT (TOmographic Microscopy and Coherent rAdiology experimenTs) beamline of the Swiss Light Source with an energy range of 8–45 keV and voxel size from 0.37 µm to 7.4 µm, full tomographic datasets are typically acquired in 5 to 10 min. To exploit the speed of the system and enable high-throughput studies to be performed in a fully automatic manner, a package of automation tools has been developed. The samples are automatically exchanged, aligned, moved to the correct region of interest, and scanned. This task is accomplished through the coordination of Python scripts, a robot-based sample-exchange system, sample positioning motors and a CCD camera. The tools are suited for any samples that can be mounted on a standard SEM stub, and require no specific environmental co...

A new stand-alone QEXAFS data acquisition system for in situ studies

Journal of Synchrotron Radiation — Tue, 18 Jan 2011 00:00:00 +0100

To meet the demands of the QEXAFS (quick-scanning extended X-ray absorption fine structure) technique for a fast, user-friendly and flexible data acquisition a new stand-alone system with new software exploiting a multi-functional USB board was designed. The chosen approach allows the scanning of several analogue and digital data sources with up to 500000 samples each second over hours storable in binary or ASCII format without any dead-time. At the same time it is possible to visualize the acquired data instantaneously which provides a maximum of interactivity during the running experiment and also optimal conditions to select the best suited beamline and detector settings prior to each measurement. Furthermore, the QEXAFS monochromator and typically three current amplifiers are entirely ...

Quick-EXAFS implementation on the general purpose EXAFS beamline at ESRF

Journal of Synchrotron Radiation — Tue, 18 Jan 2011 00:00:00 +0100

The new implementation of QEXAFS acquisition on the general purpose EXAFS beamline BM29 at the European Synchrotron Radiation Facility is presented. By adopting a continuous-scan mode, a high signal-to-noise ratio can be maintained, together with a fixed exit beam and full compatibility with step-by-step operation, while reducing acquisition times to a few seconds. The new equipment implemented on the beamline is described and the potential of this application is demonstrated with a few examples. (Source: Journal of Synchrotron Radiation)

In situ XAFS experiments using a microfluidic cell: application to initial growth of CdSe nanocrystals

Journal of Synchrotron Radiation — Tue, 11 Jan 2011 00:00:00 +0100

The design and performance of a compact fluorescense XAFS apparatus equipped with a microfluidic cell for in situ studies of nanoparticles are described. CdSe nanoparticles were prepared by solution reaction starting from trioctylphosphine-Se. Time-resolved experiments were performed by precisely controlling the reactor coordinates (x,y), allowing the synchrotron X-ray beam to travel along a reactor channel, covering nucleation and initial growth of nanoparticles. Detailed analysis of EXAFS data combined with UV–vis spectra allow reliable estimation of particle size and density in the initial growth that cannot be accessible by conventional optical techniques based on a long-range order. The Se K-XANES spectra are interpreted by multi-scattering calculations providing bond formation kine...

Diffractive–refractive optics: (+,−,−,+) X-ray crystal monochromator with harmonics separation

Journal of Synchrotron Radiation — Sat, 08 Jan 2011 00:00:00 +0100

A new kind of two channel-cut crystals X-ray monochromator in dispersive (+,−,−,+) position which spatially separates harmonics is proposed. The diffracting surfaces are oriented so that the diffraction is inclined. Owing to refraction the diffracted beam is sagittally deviated. The deviation depends on wavelength and is much higher for the first harmonics than for higher harmonics. This leads to spatial harmonics separation. The idea is supported by ray-tracing simulation. (Source: Journal of Synchrotron Radiation)

A simplified description of X-ray free-electron lasers

Journal of Synchrotron Radiation — Sat, 08 Jan 2011 00:00:00 +0100

It is shown that an elementary semi-quantitative approach explains essential features of the X-ray free-electron laser mechanism, in particular those of the gain and saturation lengths. Using mathematical methods and derivations simpler than complete theories, this treatment reveals the basic physics that dominates the mechanism and makes it difficult to realise free-electron lasers for short wavelengths. This approach can be specifically useful for teachers at different levels and for colleagues interested in presenting X-ray free-electron lasers to non-specialized audiences. (Source: Journal of Synchrotron Radiation)

X-ray transfocators: focusing devices based on compound refractive lenses

Journal of Synchrotron Radiation — Tue, 21 Dec 2010 00:00:00 +0100

This paper describes a tunable X-ray focusing apparatus, referred to as a transfocator, based on compound refractive lenses. By varying the number of lenses in the beam, the X-ray energy focused and the focal length can be varied continuously throughout a large range of energies and distances. The instrument can be used in both white and monochromatic beams to focus, pre-focus or collimate the beam. The transfocator can be used with other monochromators and/or other focusing elements, leading to significant increases in flux. Furthermore, the chromatic nature of the focusing means the transfocator suppresses harmonics and can also be used as an extremely high flux broad-band-pass monochromator. These devices have been installed in the first optics and second experimental hutches at the ID1...

Notes for authors 2011

Journal of Synchrotron Radiation — Thu, 16 Dec 2010 00:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Current events

Journal of Synchrotron Radiation — Thu, 16 Dec 2010 00:00:00 +0100

(Source: Journal of Synchrotron Radiation)

Small-angle solution scattering using the mixed-mode pixel array detector

Journal of Synchrotron Radiation — Wed, 08 Dec 2010 00:00:00 +0100

Solution small-angle X-ray scattering (SAXS) measurements were obtained using a 128 × 128 pixel X-ray mixed-mode pixel array detector (MMPAD) with an 860 µs readout time. The MMPAD offers advantages for SAXS experiments: a pixel full-well of >2 × 107 10 keV X-rays, a maximum flux rate of 108 X-rays pixel−1 s−1, and a sub-pixel point-spread function. Data from the MMPAD were quantitatively compared with data from a charge-coupled device (CCD) fiber-optically coupled to a phosphor screen. MMPAD solution SAXS data from lysozyme solutions were of equal or better quality than data captured by the CCD. The read-noise (normalized by pixel area) of the MMPAD was less than that of the CCD by an average factor of 3.0. Short sample-to-detector distances were required owing to the small M...