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November 2016 issue
Cover illustration: Overlay of the elemental maps of Fe and P X-ray fluorescence detected from a Human Cell Nucleus while scanning a nanometer-sized X-ray beam across it at beamline ID-16A of the ESRF. The Fe signal is a marker of certain proteins, while P mostly indicates the concentration of DNA. Yellow color would indicate colocalization of the two elements, but there is relatively little of this, suggesting that Fe and DNA are mostly located in separate nuclear compartments. By contrast, Fe and S, reported in the article in this issue (see Robinson, Yang, Zhang, Lynch, Yusuf and Cloetens, pages 1490-1497), are found to have significant overlap. Figure prepared by Yang Yang, ESRF.
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research papers
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A method is proposed to generate an isolated attosecond X-ray free-electron laser pulse with the peak power beyond 1 TW.
The head-on collision of a relativistic dense electron beam with a laser wiggler is studied in a free-electron laser. Laser gain and stability analysis of electron motions are presented in the presence of electron beam self-fields.
A newly designed system of slits for depth-resolved X-ray powder diffraction has been developed and tested at the National Synchrotron Light Source.
A new equation for simulating the propagation of X-rays through a system of many focusing elements and a method of computation of X-ray waves with control reliability and accuracy are presented.
An analysis of basic parameters of promising and commonly used materials for X-ray refractive optics has been performed in the extended energy range 8–100 keV.
An automatic crystal centring procedure is reported, which is extremely effective under fluctuating light states as well as for poorly frozen and opaque samples at macromolecular crystallography beamlines.
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A piezo bimorph mirror is deformed into three distinct re-entrant surface modifications as well as being simply defocused. A re-entrant modification with seven segments (the maximum possible for this mirror) produces an expanded beam with less striation than a simply defocused beam.
A practical scheme is proposed to control and inspect X-ray deformable mirrors using a feedback mechanism with residual curvature estimated from shape metrology data.
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ShadowOui is introduced, a new computer environment for X-ray optics, beamline simulations and virtual experiments using the ray-tracing code SHADOW.
A new sample cell assembly for the Paris-Edinburgh type large-volume press to measure Seebeck coefficients and the relative changes in the thermal conductivity and dimensionless figure of merit has been developed and its feasibility demonstrated. The measurements are performed on Bi and PbTe over a temperature range 300–450 K and pressures up to 5.5 GPa.
A unique high-temperature cell combined with in situ wide-angle X-ray diffraction was used to follow the formation of graphitic structure in carbon fibre produced from a polyacrylonitrile precursor.
A new design of an operando soft X-ray transmission and fluorescence cell with capability of fast membrane replacement and easy operation compared to the previous designs is presented. The cell is suitable for studying solids, liquids and solid/liquid interfaces and manipulating the sample with electrochemical techniques and visible light.
A mapping technique has been developed where a sub-micrometer focused polychromatic X-ray beam is scanned across a stationary sample instead of scanning the sample in front of the X-ray microbeam. For setups where motion is forbidden, e.g. due to the sample environment, standard methods are restricted to one singular position in the sample, whereas the new technique gives access to the complete specimen as demonstrated on an in situ mechanically deformed gold nanowire.
Combining microfluidics with coherent X-ray scattering experiments enables the flow characterization of collodial suspensions in microflow of different geometries. Here, evaluation of the flow geometries, main flow directions, advective flow velocities and diffusive dynamics are presented.
A time-resolved X-ray absorption spectroscopy setup has been developed and tested, comprising a synchronized MHz fiber amplifier laser system with a multi-MHz data acquisition scheme capable of detecting multi-photon events in a single X-ray photon pulse. This system permits recording time-resolved X-ray absorption spectra with quasi-static signal quality.
Gamma irradiation was found to change the elemental concentration of the atoms in Nd-doped phosphate glass The intensity of the white line in the XANES spectrum correlated with the ratio O/Nd in the glass matrix. The ratio of non-bridging oxygen to total oxygen in the glass after gamma radiation correlated with the concentration of defects in the glass samples. Glasses having a higher concentration of oxygen were found to be soft to gamma irradiation.
A technically simple method to include vibrations in X-ray absorption near-edge structure (XANES) calculations is used to demonstrate that vibrations have a significant effect on the polarized Cu K-edge spectrum of creatinium tetrachlorocuprate, (creat)2CuCl4, even in the XANES region.
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Synchrotron radiation nanotomography has been used to quantify the packing fraction in a photonic glass sample.
An analytical formula for two-dimensional ring artefact suppression based on processing of projections rather than sinograms is proposed. A modified flat field can be found as a convolution of an averaged projection and the given filter.
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The MÖNCH 25 µm-pitch hybrid pixel detector is described in detail and characterized. The interpolation algorithm developed to achieve micrometer-level resolution is applied to grating interferometry measurements.
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A compact design for a miniature tensile stress rig, compatible with the space and weight constraints imposed by near-field diffraction imaging techniques, is presented. The device can carry tensile loads up to 500 N and is driven by a piezoelectric actuator which can work in a static and dynamic regime up to frequencies of 100 Hz.
The combination of X-ray analyzer-based phase-contrast imaging and computed laminography opens up new possibilities for imaging regions of interest in laterally extended flat specimens of weak absorption contrast.
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Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei at the new ID16 beamline. Estimates of P, S and mass signals for the chromosomal matter agree with quantitative X-ray phase contrast projection microscopy images of the same samples, while fluorescence shows Fe incorporation.
short communications
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The effect of minor mismatch between the geometric and single-ray foci for a cylindrically bent Laue double-crystal monochromator is examined and found to be less detrimental than previously believed. Even without exact matching, the transverse coherence of the X-ray beam is not deteriorated by the system, enabling the phase-based imaging techniques critical to modern biomedical imaging experiments.
beamlines
X-ray powder diffraction at the upgraded and comissioned XRD1 beamline is reported. The beamline operates in the 5.5–14 keV range with a photon flux of 3.4 × 1010 photons s−1 at 8 keV.
BOREAS is a beamline operating at the ALBA Synchrotron Light Source, dedicated to resonant X-ray absorption and scattering experiments using soft X-rays, in an unusually extended photon energy range from 80 to >4000 eV, with full polarization control. Here its optical scheme and the first commissioning results are described.
An innovative scheme to carry out continuous X-ray absorption spectroscopy measurements similar to quick-EXAFS mode at the step-by-step Energy-Scanning EXAFS beamline BL-09 at the INDUS-2 synchrotron source is presented.
A detailed description of the TwinMic beamline installed at Elettra, Italy, is presented. The beamline hosts a unique soft X-ray microscope supporting both transmission and scanning X-ray microscopy (TXM and STXM, respectively) within the one instrument. The beamline presently fosters the following techniques: STXM, TXM and ptychography, that can be combined with low-energy X-ray fluorescence and X-ray absorption near-edge structure spectroscopies. A detailed update of the design, operational modes and future upgrades of the TwinMic beamline is presented.
A new multi-purpose materials science beamline at the Brazilian Synchrotron (LNLS) is described, which operates in the energy range 5–30 keV. A few examples of new experimental possibilities, including total X-ray scattering, X-ray diffraction under high pressures and resonant X-ray emission spectroscopy, are presented.
The integration of a Maia detector in the Microprobe setup of beamline P06 at the storage ring PETRA III at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany, is described. The Maia detector is an advanced imaging scheme for energy-dispersive detection and the analytical performance at the beamline is characterized and examples from key applications are provided.
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