XANES and EXAFS of dilute solutions of transition metals at XFELs
This work has demonstrated that X-ray absorption spectroscopy (XAS), both Mn XANES and EXAFS, of solutions with millimolar concentrations of metal is possible using the femtosecond X-ray pulses from XFELs. Mn XAS data were collected using two different sample delivery methods, a Rayleigh jet and a drop-on-demand setup, with varying concentrations of Mn. Here, a new method for normalization of XAS spectra based on solvent scattering that is compatible with data collection from a highly variable pulsed source is described. The measured XANES and EXAFS spectra of such dilute solution samples are in good agreement with data co...
Source: Journal of Synchrotron Radiation - August 7, 2019 Category: Physics Authors: Chatterjee, R. Weninger, C. Loukianov, A. Gul, S. Fuller, F.D. Cheah, M.H. Fransson, T. Pham, C.C. Nelson, S. Song, S. Britz, A. Messinger, J. Bergmann, U. Alonso-Mori, R. Yachandra, V.K. Kern, J. Yano, J. Tags: X-ray free electron lasers X-ray near-edge spectroscopy extended X-ray absorption fine structure X-ray absorption spectroscopy research papers Source Type: research

Device for source position stabilization and beam parameter monitoring at inverse Compton X-ray sources
Compact X-ray sources based on inverse Compton scattering provide brilliant and partially coherent X-rays in a laboratory environment. The cross section for inverse Compton scattering is very small, requiring high-power laser systems as well as small laser and electron beam sizes at the interaction point to generate sufficient flux. Therefore, these systems are very sensitive to distortions which change the overlap between the two beams. In order to monitor X-ray source position, size and flux in parallel to experiments, the beam-position monitor proposed here comprises a small knife edge whose image is acquired with an X-...
Source: Journal of Synchrotron Radiation - August 7, 2019 Category: Physics Authors: G ü nther, B. Dierolf, M. Achterhold, K. Pfeiffer, F. Tags: inverse Compton X-ray sources beam-position monitor active source position stabilization research papers Source Type: research

Intense sub-micrometre focusing of soft X-ray free-electron laser beyond 1016 W   cm − 2 with an ellipsoidal mirror
Intense sub-micrometre focusing of a soft X-ray free-electron laser (FEL) was achieved by using an ellipsoidal mirror with a high numerical aperture. A hybrid focusing system in combination with a Kirkpatrick – Baez mirror was applied for compensation of a small spatial acceptance of the ellipsoidal mirror. With this system, the soft X-ray FEL pulses were focused down to 480   nm × 680   nm with an extremely high intensity of 8.8 × 1016   W   cm − 2 at a photon energy of 120   eV, which yielded saturable absorption at the L-edge of Si (99.8   eV) with a drastic increase of transmittance ...
Source: Journal of Synchrotron Radiation - August 5, 2019 Category: Physics Authors: Motoyama, H. Owada, S. Yamaguchi, G. Kume, T. Egawa, S. Tono, K. Inubushi, Y. Koyama, T. Yabashi, M. Ohashi, H. Mimura, H. Tags: ellipsoidal mirror soft X-ray free-electron laser saturable absorption optical design research papers Source Type: research

Dead-time correction for spectroscopic photon-counting pixel detectors
Modern photon-counting pixel detectors have enabled a revolution in applications at synchrotron light sources and beyond in the last decade. One of the limitations of the current detectors is their reduced counting linearity or even paralysis at high counting rates, due to dead-time which results in photon pile-up. Existing dead-time and pile-up models fail to reproduce the complexity of dead-time effects on photon-counting, resulting in empirical calibrations for particular detectors at best, imprecise linearization methods, or no linearization. This problem will increase in the future as many synchrotron light sources pl...
Source: Journal of Synchrotron Radiation - August 5, 2019 Category: Physics Authors: Blaj, G. Tags: photon-counting hybrid pixel detectors detector dead-time photon pile-up high photon flux linearization research papers Source Type: research

X-ray photon diagnostics at the European XFEL
This article describes the as-built realization of photon diagnostics for this facility, the diagnostics commissioning and their application for commissioning of the facility, and results from the first year of operation, focusing on the SASE1 beamline, which was the first to be commissioned. The commissioning consisted of pre-beam checkout, first light from the bending magnets, X-rays from single undulator segments, SASE tuning with many undulator segments, first lasing, optics alignment for FEL beam transport through the tunnel up to the experiment hutches, and finally beam delivery to first users. The beam properties as...
Source: Journal of Synchrotron Radiation - August 2, 2019 Category: Physics Authors: Gr ü nert, J. Carbonell, M.P. Dietrich, F. Falk, T. Freund, W. Koch, A. Kujala, N. Laksman, J. Liu J. Maltezopoulos, T. Tiedtke, K. Jastrow, U.F. Sorokin, A. Syresin, E. Grebentsov, A. Brovko, O. Tags: XFEL physics free-electron lasers photon diagnostics hard X-rays soft X-rays instrumentation research papers Source Type: research

Method of calculating the aberrations of soft X-ray and vacuum ultraviolet optical systems
Based on the the third-order aberration theory of plane-symmetric optical systems, this paper studies the effect on aberrations of the second-order accuracy of aperture-ray coordinates and the extrinsic aberrations of this kind of optical system; their calculation expressions are derived. The resultant aberration expressions are then applied to calculate the aberrations of two design examples of soft X-ray and vacuum ultraviolet (XUV) optical systems; images are compared with ray-tracing results using SHADOW software to validate the aberration expressions. The study shows that the accuracy of the aberration expressions is ...
Source: Journal of Synchrotron Radiation - August 1, 2019 Category: Physics Authors: Cao, Y. Shen, Z. Zheng, Z. Tags: soft X-ray and vacuum ultraviolet intrinsic aberrations extrinsic aberrations synchrotron optics optical design research papers Source Type: research

Revealing phase boundaries by weighted parametric structural refinement
In this study, a weighted parametric method is   demonstrated whereby the scale factor is restrained via an inverse tan function, making the phase boundary composition a refinable parameter. This is demonstrated using compositionally graded samples within the lead-free piezoelectric (BiFeO3)x(Bi0.5K0.5TiO3)y(Bi0.5Na0.5TiO3)1 – x – y and (Bi0.5Na0.5TiO3)x(BaTiO3)1 – x systems. This has proven to be an effective method for diffraction experiments with relatively low resolution, weak peak splitting or compositionally complex multiphase samples. (Source: Journal of Synchrotron Radiation)
Source: Journal of Synchrotron Radiation - August 1, 2019 Category: Physics Authors: Marlton, F. Checchia, S. Daniels, J. Tags: parametrics powder diffraction ferroelectrics Rietveld refinement research papers Source Type: research

Diamond nanofocusing refractive X-ray lenses made by planar etching technology
The manufacturing steps and first tests of a refractive lens made of polycrystalline diamond are described. A fabrication process based on electron-beam lithography and deep reactive ion etching is introduced. Experimental tests on beamline ID13 at the ESRF have been performed. A spot size of 360   nm (FWHM) at an energy E = 24.3   keV is observed. (Source: Journal of Synchrotron Radiation)
Source: Journal of Synchrotron Radiation - August 1, 2019 Category: Physics Authors: Lyubomirskiy, M. Boye, P. Feldkamp, J.M. Patommel, J. Schoeder, S. Schropp, A. Burghammer, M. Wild, C. Schroer, C.G. Tags: diamond X-ray lenses compound refractive lens (CRL) focusing research papers Source Type: research

Resolving dynamic fragmentation of liquids at the nanoscale with ultrafast small-angle X-ray scattering
High-brightness coherent ultrashort X-ray free-electron lasers (XFELs) are promising in resolving nanoscale structures at the highest temporal resolution ( ∼ 10   fs). The feasibility is explored of resolving ultrafast fragmentation of liquids at the nanoscale with single-shot small-angle X-ray scattering (SAXS) on the basis of large-scale molecular dynamics simulations. Fragmentation of liquid sheets under adiabatic expansion is investigated. From the simulated SAXS patterns, particle-volume size distributions are obtained with the regularization method and average particle sizes with the weighted Guinier method, at...
Source: Journal of Synchrotron Radiation - August 1, 2019 Category: Physics Authors: Chen, S. Chai, H.-W. He, A.-M. Tschentscher, T. Cai, Y. Luo, S.-N. Tags: XFELs small-angle X-ray scattering nanoscale fragmentation liquids research papers Source Type: research

Energy-dispersive Laue diffraction by means of a pnCCD detector coupled to a CsI(Tl) scintillator using ultra-hard X-ray synchrotron radiation
The lattice parameters and unit-cell orientation of an SrLaAlO4 crystal have been determined by means of energy-dispersive X-ray Laue diffraction (EDLD) using a pnCCD detector coupled to a columnar structure CsI(Tl) scintillator in the energy range between 40 and 130   keV. By exploiting the high quantum efficiency (QE) achieved by this combined detection system for hard X-rays, a large number of Bragg reflections could be recorded by the relatively small detector area, allowing accurate and fast determination of the lattice parameters and the moduli of the structure factors. The experiment was performed on the energy-di...
Source: Journal of Synchrotron Radiation - July 25, 2019 Category: Physics Authors: Shokr, M. Tosson, A. Abboud, A. Algashi, A. Schlosser, D. Hartmann, R. Klaus, M. Genzel, C. Str ü der, L. Pietsch, U. Tags: PnCCD detector CsI(Tl) scintillator X-ray Laue diffraction energy-dispersive X-ray detectors ultra-hard X-ray synchrotron radiation research papers Source Type: research

Corvus: a framework for interfacing scientific software for spectroscopic and materials science applications
Corvus, a Python-based package designed for managing workflows of physical simulations that utilize multiple scientific software packages, is presented. Corvus can be run as an executable script with an input file and automatically generated or custom workflows, or interactively, in order to build custom workflows with a set of Corvus-specific tools. Several prototypical examples are presented that link density functional, vibrational and X-ray spectroscopy software packages and are of interest to the synchrotron community. These examples highlight the simplification of complex spectroscopy calculations that were previousl...
Source: Journal of Synchrotron Radiation - July 24, 2019 Category: Physics Authors: Story, S.M. Vila, F.D. Kas, J.J. Raniga, K.B. Pemmaraju, C.D. Rehr, J.J. Tags: Corvus workflow manager spectroscopy materials science property-driven research papers Source Type: research

A micro-focusing and high-flux-throughput beamline design using a bending magnet for microscopic XAFS at the High Energy Photon Source
An optical design study of a bending-magnet beamline, based on multi-bend achromat storage ring lattices, at the High Energy Photon Source, to be built in Beijing, China, is described. The main purpose of the beamline design is to produce a micro-scale beam from a bending-magnet source with little flux loss through apertures. To maximize the flux of the focal spot, the synchrotron source will be 1:1 imaged to a virtual source by a toroidal mirror; a mirror pair will be used to collimate the virtual source into quasi-parallel light which will be refocused by a Kirkpatrick – Baez mirror pair. In the case presented here...
Source: Journal of Synchrotron Radiation - July 23, 2019 Category: Physics Authors: Tang, K. Zheng, L. Zhao, Y.D. Liu, S.H. Ma, C.Y. Dong, Y. Tags: bending-magnet beamline micro-XAFS full-field nano-XAFS full-field transmission X-ray microscopy quick-XAFS HEPS beamlines Source Type: research

Implications of disturbed photon-counting statistics of Eiger detectors for X-ray speckle visibility experiments
This paper reports on coherent scattering experiments in the low-count regime with less than one photon per pixel per acquisition on average, conducted with two detectors based on the Eiger single-photon-counting chip. The obtained photon-count distributions show systematic deviations from the expected Poisson – gamma distribution, which result in a strong overestimation of the measured speckle contrast. It is shown that these deviations originate from an artificial increase of double-photon events, which is proportional to the detected intensity and inversely proportional to the exposure time. The observed miscounti...
Source: Journal of Synchrotron Radiation - July 23, 2019 Category: Physics Authors: M ö ller, J. Reiser, M. Hallmann, J. Boesenberg, U. Zozulya, A. Rahmann, H. Becker, A.-L. Westermeier, F. Zinn, T. Zontone, F. Gutt, C. Madsen, A. Tags: X-ray speckle visibility spectroscopy (XSVS) X-ray photon correlation spectroscopy (XPCS) X-ray coherence dynamics photon-counting detectors photon-counting statistics research papers Source Type: research

Fast identification of mineral inclusions in diamond   at GSECARS using synchrotron X-ray microtomography, radiography and diffraction
Mineral inclusions in natural diamond are widely studied for the insight that they provide into the geochemistry and dynamics of the Earth's interior. A major challenge in achieving thorough yet high rates of analysis of mineral inclusions in diamond derives from the micrometre-scale of most inclusions, often requiring synchrotron radiation sources for diffraction. Centering microinclusions for diffraction with a highly focused synchrotron beam cannot be achieved optically because of the very high index of refraction of diamond. A fast, high-throughput method for identification of micromineral inclusions in diamond has bee...
Source: Journal of Synchrotron Radiation - July 19, 2019 Category: Physics Authors: Wenz, M. D. Jacobsen, S. D. Zhang, D. Regier, M. Bausch, H. J. Dera, P. K. Rivers, M. Eng, P. Shirey, S. B. Pearson, D. G. Tags: diamond minerals microinclusions computed microtomography microdiffraction radiography research papers Source Type: research

High-efficiency X-ray multilayer-coated blazed gratings with shifted boundaries
A new design for a high-efficiency multilayer-coated blazed X-ray grating with horizontal-shifted (non-conformal) boundary profiles is proposed. The investigation of the grating design is carried out using an integrated approach based on rigorous numerical calculations of light diffraction by gratings with realistic boundary profiles obtained from simulations of multilayer grating growth. By varying the incidence angle of the deposition flux, one can set the direction and magnitude of the boundary profile shifts over a wide range of values. It is shown that the diffraction efficiency of the blazed gratings with shifted bou...
Source: Journal of Synchrotron Radiation - July 19, 2019 Category: Physics Authors: Lubov, M. Goray, L. Tags: multilayer-coated diffraction grating soft X-ray range grating efficiency growth modeling multilayer-coated blazed X-ray grating thin-film growth simulations diffraction efficiency electromagnetic diffraction theory research papers Source Type: research

Asymmetric response of electrical conductivity and V valence state to strain in cation-deficient Sr1 – yVO3 ultrathin films based on absorption measurements at the V L2- and L3-edges
The correlation between electronic properties and epitaxial strain in a cation-deficient system has rarely been investigated. Cation-deficient SrVO3 films are taken as a model system to investigate the strain-dependent electrical and electronic properties. Using element- and charge-sensitive soft X-ray absorption, V L-edge absorption measurements have been performed for Sr1 – yVO3 films of different thicknesses capped with 4   u.c. (unit cell) SrTiO3 layers, showing the coexistence of V4+ and V5+ in thick films. A different correlation between V valence state and epitaxial strain is observed for Sr1 – yVO3 ul...
Source: Journal of Synchrotron Radiation - July 12, 2019 Category: Physics Authors: Wu, M. Huang, S.-Z. Zeng, H. Koster, G. Huang, Y.-Y. Zheng, J.-C. Wang, H.-Q. Tags: soft X-ray absorption measurements 3d transition metal oxides thin-film engineering thickness-dependent properties research papers Source Type: research

Overcoming the challenges of high-energy X-ray ptychography
X-ray ptychography is a coherent diffraction imaging technique with a high resolving power and excellent quantitative capabilities. Although very popular in synchrotron facilities nowadays, its implementation with X-ray energies above 15   keV is very rare due to the challenges imposed by the high energies. Here, the implementation of high-energy X-ray ptychography at 17 and 33.6   keV is demonstrated and solutions to overcome the important challenges are provided. Among the particular aspects addressed are the use of an efficient high-energy detector, a long synchrotron beamline for the high degree of spatial coherenc...
Source: Journal of Synchrotron Radiation - July 12, 2019 Category: Physics Authors: da Silva, J.C. Guilloud, C. Hignette, O. Jarnias, C. Ponchut, C. Ruat, M. Labiche, J.-C. Pacureanu, A. Yang, Y. Salome, M. Bohic, S. Cloetens, P. Tags: X-ray ptychography coherent X-ray diffraction high-energy X-rays nano-imaging coherence KB mirrors research papers Source Type: research

Eyeing the past: synchrotron µ -XANES and XRF imaging of tarnish distribution on 19th century daguerreotypes
Louis-Jacques-Mand é Daguerre introduced the first successful photographic process, the daguerreotype, in 1839. Tarnished regions on daguerreotypes supplied by the National Gallery of Canada were examined using scanning electron microscopy energy-dispersive X-ray spectroscopy and synchrotron-radiation analysis. Synchrotron X-ray fluorescence imaging visualized the distribution of sulfur and chlorine, two primary tarnish contributors, and showed that they were associated with the distribution of image particles on the surface. X-ray absorption near-edge structure spectroscopy determined the tarnish to be primarily co...
Source: Journal of Synchrotron Radiation - July 12, 2019 Category: Physics Authors: Kozachuk, M.S. Sham, T.K. Martin, R.R. Nelson, A.J. Coulthard, I. Tags: synchrotron X-ray fluorescence imaging daguerreotypes absorption spectroscopy scanning electron microscopy surface analysis tarnish degradation compounds research papers Source Type: research

3D digital anatomic angioarchitecture of the mouse brain using synchrotron-radiation-based propagation phase-contrast imaging
In this study, a systematic analysis is developed to visualize the 3D angioarchitecture of mouse brain at ultrahigh resolution using synchrotron-radiation-based propagation phase-contrast imaging. This method provides detailed restoration of the intricate brain microvascular network in a precise 3D manner. In addition to depicting the delicate 3D arrangements of the vascular network, 3D virtual micro-endoscopy is also innovatively performed to visualize randomly a selected vessel within the brain for both external 3D micro-imaging and endoscopic visualization of any targeted microvessels, which improves the understanding o...
Source: Journal of Synchrotron Radiation - July 12, 2019 Category: Physics Authors: Shi, S. Zhang, H. Yin, X. Wang, Z. Tang, B. Luo, Y. Ding, H. Chen, Z. Cao, Y. Wang, T. Xiao, B. Zhang, M. Tags: high resolution mouse brain angioarchitecture propagation phase-contrast imaging research papers Source Type: research

MCP-based detectors: calibration and first photon radiation measurements
Detectors based on microchannel plates (MCPs) are used to detect radiation from free-electron lasers. Three MCP detectors have been developed by JINR for the European XFEL (SASE1, SASE2 and SASE3 lines). These detectors are designed to operate in a wide dynamic range from the level of spontaneous emission to the SASE saturation level (between a few nJ up to 25   mJ), in a wide wavelength range from 0.05   nm to 0.4   nm for SASE1 and SASE2, and from 0.4   nm to 4.43   nm for SASE3. The detectors measure photon pulse energies with an anode and a photodiode. The photon beam image is observed with an MCP imager with...
Source: Journal of Synchrotron Radiation - July 12, 2019 Category: Physics Authors: Syresin, E. Grebentsov, A. Brovko, O. Yurkov, M. Freund, W. Gr ü nert, J. Tags: XFEL physics photon beam diagnostics microchannel plate detectors research papers Source Type: research

X-ray radiation damage to biological samples: recent progress
With the continuing development of beamlines for macromolecular crystallography (MX) over the last few years providing ever higher X-ray flux densities, it has become even more important to be aware of the effects of radiation damage on the resulting structures. Nine papers in this issue cover a range of aspects related to the physics and chemistry of the manifestations of this damage, as observed in both MX and small-angle X-ray scattering (SAXS) on crystals, solutions and tissue samples. The reports include measurements of the heating caused by X-ray irradiation in ruby microcrystals, low-dose experiments examining damag...
Source: Journal of Synchrotron Radiation - July 1, 2019 Category: Physics Authors: Garman, E.F. Weik, M. Tags: X-ray radiation damage macromolecular crystallography dose X-ray imaging SAXS DNA temperature effects metalloproteins editorial Source Type: research

Structural knowledge or X-ray damage? A case study on xylose isomerase illustrating both
In this study, consecutive high-resolution data sets from a single XI crystal from the same wedge were collected at 100   K and the progression of radiation damage was tracked over increasing dose (0.13 – 3.88   MGy). The catalytic metal and its surrounding amino acid environment experience a build-up of free radicals, and the results show radiation-damage-induced structural perturbations ranging from an absolute metal positional shift to specific residue motions in the active site. The apparent metal movement is an artefact of global damage and the resulting unit-cell expansion, but residue motion appears to be ...
Source: Journal of Synchrotron Radiation - June 24, 2019 Category: Physics Authors: Taberman, H. Bury, C.S. van der Woerd, M.J. Snell, E.H. Garman, E.F. Tags: metalloprotein enzyme radiation damage specific structural damage xylose isomerase dose structural pertubation research papers Source Type: research

Zinc K-edge XANES spectroscopy of mineral and organic standards
Zinc K-edge X-ray absorption near-edge (XANES) spectroscopy was conducted on 40 zinc mineral samples and organic compounds. The K-edge position varied from 9660.5 to 9666.0   eV and a variety of distinctive peaks at higher post-edge energies were exhibited by the materials. Zinc is in the +2 oxidation state in all analyzed materials, thus the variations in edge position and post-edge features reflect changes in zinc coordination. For some minerals, multiple specimens from different localities as well as pure forms from chemical supply companies were examined. These specimens had nearly identical K-edge and post-edge peak...
Source: Journal of Synchrotron Radiation - June 21, 2019 Category: Physics Authors: Castorina, E. Ingall, E.D. Morton, P.L. Tavakoli, D.A. Lai, B. Tags: zinc standards Zn K-edge XANES spectroscopy research papers Source Type: research

The SwissFEL soft X-ray free-electron laser beamline: Athos
The SwissFEL soft X-ray free-electron laser (FEL) beamline Athos will be ready for user operation in 2021. Its design includes a novel layout of alternating magnetic chicanes and short undulator segments. Together with the APPLE X architecture of undulators, the Athos branch can be operated in different modes producing FEL beams with unique characteristics ranging from attosecond pulse length to high-power modes. Further space has been reserved for upgrades including modulators and an external seeding laser for better timing control. All of these schemes rely on state-of-the-art technologies described in this overview. The...
Source: Journal of Synchrotron Radiation - June 21, 2019 Category: Physics Authors: Abela, R. Alarcon, A. Alex, J. Arrell, C. Arsov, V. Bettoni, S. Bopp, M. Bostedt, C. Braun, H.-H. Calvi, M. Celcer, T. Craievich, P. Dax, A. Dijkstal, P. Dordevic, S. Ferrari, E. Flechsig, U. Follath, R. Frei, F. Gaiffi, N. Geng, Z. Gough, C. Hiller, N. H Tags: FEL superradiance APPLE undulator chicane research papers Source Type: research

Radiation-damage investigation of a DNA 16-mer
In macromolecular crystallography, a great deal of effort has been invested in understanding radiation-damage progression. While the sensitivity of protein crystals has been well characterized, crystals of DNA and of DNA – protein complexes have not thus far been studied as thoroughly. Here, a systematic investigation of radiation damage to a crystal of a DNA 16-mer diffracting to 1.8   Å resolution and held at 100   K, up to an absorbed dose of 45   MGy, is reported. The RIDL (Radiation-Induced Density Loss) automated computational tool was used for electron-density analysis. Both the global and specific...
Source: Journal of Synchrotron Radiation - June 21, 2019 Category: Physics Authors: Bugris, V. Harmat, V. Ferenc, G. Brockhauser, S. Carmichael, I. Garman, E.F. Tags: DNA radiation damage global damage specific damage research papers Source Type: research

Three-dimensional visualization of fibrous tissues in cirrhotic rats via X-ray phase-contrast computed tomography with iodine staining
In this study, cirrhotic livers induced by carbon tetrachloride (CCl4) in rats were imaged via PCCT and then histopathologically processed. Characteristics of the cirrhosis, i.e. abnormal nodules surrounded by annular fibrosis, were established and a 3D reconstruction of these structures was also performed via PCCT. Fibrosis area, septal width and nodular size were measured and the correlation for these quantitative measurements between PCCT and histopathologic findings was analyzed. The results showed that fibrous bands, small nodules and angio-architecture in cirrhosis were clearly presented in the PCCT images, with hist...
Source: Journal of Synchrotron Radiation - June 20, 2019 Category: Physics Authors: Jian, J. Zhao, X. Qin, L. Zhao, Y. Sun, M. Lv, W. Hu, C. Tags: X-ray phase-contrast computed tomography cirrhosis fibrous tissues iodine staining three-dimensional imaging research papers Source Type: research

Polarization control with an X-ray phase retarder for high-time-resolution pump – probe experiments at SACLA
Control of the polarization of an X-ray free-electron laser (XFEL) has been performed using an X-ray phase retarder (XPR) in combination with an arrival timing diagnostic on BL3 of the SPring-8 Angstrom Compact free-electron LAser (SACLA). To combine with the timing diagnostic, a pink beam was incident on the XPR crystal and then monochromated in the vicinity of samples. A high degree of circular polarization of ∼ 97% was obtained experimentally at 11.567   keV, which agreed with calculations based on the dynamical theory of X-ray diffraction. This system enables pump – probe experiments to be operated using ci...
Source: Journal of Synchrotron Radiation - June 20, 2019 Category: Physics Authors: Kubota, Y. Suzuki, M. Katayama, T. Yamamoto, K. Tono, K. Inubushi, Y. Seki, T. Takanashi, K. Wadati, H. Yabashi, M. Tags: X-ray free-electron lasers polarization dynamical theory of diffraction research papers Source Type: research

FEL performance achieved at PAL-XFEL using a three-chicane bunch compression scheme
PAL-XFEL utilizes a three-chicane bunch compression (3-BC) scheme (the very first of its kind in operation) for free-electron laser (FEL) operation. The addition of a third bunch compressor allows for more effective mitigation of coherent synchrotron radiation during bunch compression and an increased flexibility of system configuration. Start-to-end simulations of the effects of radiofrequency jitter on the electron beam performance show that using the 3-BC scheme leads to better performance compared with the two-chicane bunch compression scheme. Together with the high performance of the linac radiofrequency system, it en...
Source: Journal of Synchrotron Radiation - June 19, 2019 Category: Physics Authors: Kang, H.-S. Yang, H. Kim, G. Heo, H. Nam, I. Min, C.-K. Kim, C. Baek, S.Y. Choi, H.-J. Mun, G. Park, B.R. Suh, Y.J. Shin, D.C. Hu, J. Hong, J. Jung, S. Kim, S.-H. Kim, K. Na, D. Park, S.S. Park, Y.J. Han, J.-H. Jung, Y.G. Jeong, S.H. Kim, M.J. Lee, H.G. L Tags: free-electron laser hard X-rays bunch compression coherent synchrotron radiation stability arrival timing jitter research papers Source Type: research

Wavefront sensing at X-ray free-electron lasers
Here a direct comparison is made between various X-ray wavefront sensing methods with application to optics alignment and focus characterization at X-ray free-electron lasers (XFELs). Focus optimization at XFEL beamlines presents unique challenges due to high peak powers as well as beam pointing instability, meaning that techniques capable of single-shot measurement and that probe the wavefront at an out-of-focus location are desirable. The techniques chosen for the comparison include single-phase-grating Talbot interferometry (shearing interferometry), dual-grating Talbot interferometry (moir é deflectometry) and s...
Source: Journal of Synchrotron Radiation - June 19, 2019 Category: Physics Authors: Seaberg, M. Cojocaru, R. Berujon, S. Ziegler, E. Jaggi, A. Krempasky, J. Seiboth, F. Aquila, A. Liu, Y. Sakdinawat, A. Lee, H.J. Flechsig, U. Patthey, L. Koch, F. Seniutinas, G. David, C. Zhu, D. Mike š , L. Makita, M. Koyama, T. Mancuso, A.P. Chapman, H Tags: X-ray free-electron lasers wavefront sensing grating interferometry speckle tracking research papers Source Type: research

Doping site identification in 112 iron pnictides through a first-principles core-electron spectroscopic study
Density functional theory based first-principles core-electron spectroscopic studies on iron-based superconducting 112 materials are presented. The existence of an extra As zigzag chain structure along with Fe – As planes in 112 materials is emphasised. Doping on an As site belonging to a chain by Sb is found to enhance the superconducting transition temperature. This is also shown from calculations with enhanced density of states when doped on chain-As. Therefore, As site identification in 112 is crucial. Theoretically computed As K-edge absorption spectra of two different types of As atoms for Ca0.85La0.15FeAs2 sho...
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Ghosh, H. Ghosh, S. Ghosh, A. Tags: Fe-based 112 superconducting materials core-electron spectroscopy core-hole effect electronic structure calculations short communications Source Type: research

Metrology characterization of ultraprecise bendable mirrors for the European XFEL: from offsite calibration to installation and commissioning
The European XFEL requires long and ultraflat X-ray mirrors of high precision for the beam offset and distribution system [Altarelli et al. (2006), XFEL Technical Design Report, DESY 2006-097. DESY, Hamburg, Germany]. A general specification of the beam transport mirrors is a length of up to 950   mm and an optical surface with a deviation from a perfectly flat surface of (Source: Journal of Synchrotron Radiation)
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Vannoni, M. Freijo Mart í n, I. Smidtchen, S. Baumann, T.M. Meyer, M. Music, V. Tags: X-ray optics metrology bender mirror research papers Source Type: research

Hard X-ray self-seeding commissioning at PAL-XFEL
A wake monochromator based on a large-area diamond single crystal for hard X-ray self-seeding has been successfully installed and commissioned in the hard X-ray free-electron laser (FEL) at the Pohang Accelerator Laboratory with international collaboration. For this commissioning, the self-seeding was demonstrated with a low bunch charge (40   pC) and the nominal bunch charge (180   pC) of self-amplified spontaneous emission (SASE) operation. The FEL pulse lengths were estimated as 7   fs and 29.5   fs, respectively. In both cases, the average spectral brightness increased by more than three times compared with the...
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Min, C.-K. Nam, I. Yang, H. Kim, G. Shim, C.H. Ko, J.H. Cho, M.-H. Heo, H. Oh, B. Suh, Y.J. Kim, M.J. Na, D. Kim, C. Kim, Y. Chun, S.H. Lee, J.H. Kim, J. Kim, S. Eom, I. Kim, S.N. Koo, T.-Y. Rah, S. Shvyd'ko, Y. Shu, D. Kim, K.-J. Terentyev, S. Blank, V. Tags: free-electron lasers hard X-rays self-seeding electron-energy jitter diamond monochromators self-amplified spontaneous emission research papers Source Type: research

Demonstration of high-performance pole pieces made of monocrystalline dysprosium for short-period undulators
Reported here are the results of experiments carried out to demonstrate the magnetic performance of dysprosium (Dy) to enhance the capability of undulators. Tiny pieces of monocrystalline Dy surrounded by permanent magnets (PMs) work as pole pieces (PPs) to concentrate the magnetic flux, when cooled down below the Curie temperature of 85   K. A PP made of Dy is much more attractive than one made of a conventional material, because its saturation magnetization is much higher. Furthermore, it also allows for a more flexible selection of PM material, potentially leading to further enhancement of the performance of short-per...
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Tanaka, T. Kagamihata, A. Tags: short-period undulators high-performance pole pieces monocrystalline dysprosium research papers Source Type: research

A real-time phase-space beam emittance monitoring system
An electron beam position and angle monitoring system, ps-BPM, has been shown to be able to measure the electron source position and angle at a single location in a beamline at a synchrotron source. This system uses a monochromator to prepare a photon beam whose energy is at that of the K-edge of an absorber filter. The divergence of the beam from the source gives an energy range that will encompass the K-edge of the filter. A measurement of the centre of the monochromatic beam and the K-edge location through the absorber filter gives the position and angle of the electron source. Here, it is shown that this system is also...
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Samadi, N. Shi, X. Dallin, L. Chapman, D. Tags: beam emittance monitor X-ray diffraction phase space diagnostics and feedback research papers Source Type: research

CRL-based ultra-compact transfocator for X-ray focusing and microscopy
A new ultra-compact transfocator (UCTF) based on X-ray compound refractive lenses (CRLs) is presented. The device can be used to change the number of one- and two-dimensional focusing CRLs by moving the individual parabolic lenses one-by-one independently, thus providing permanent energy and focal-length tunability for scanning and full-field X-ray microscopy applications. The small overall size and light weight of the device allow it to be integrated in any synchrotron beamline, while even simplifying the experimental layout. The UCTF was tested at the Excillium MetalJet microfocus X-ray source and at the   P14 EMBL ...
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Narikovich, A. Polikarpov, M. Barannikov, A. Klimova, N. Lushnikov, A. Lyatun, I. Bourenkov, G. Zverev, D. Panormov, I. Sinitsyn, A. Snigireva, I. Snigirev, A. Tags: compound refractive lenses X-ray microscopy synchrotron radiation research papers Source Type: research

Development of low-energy X-ray detectors using LGAD sensors
Recent advances in segmented low-gain avalanche detectors (LGADs) make them promising for the position-sensitive detection of low-energy X-ray photons thanks to their internal gain. LGAD microstrip sensors fabricated by Fondazione Bruno Kessler have been investigated using X-rays with both charge-integrating and single-photon-counting readout chips developed at the Paul Scherrer Institut. In this work it is shown that the charge multiplication occurring in the sensor allows the detection of X-rays with improved signal-to-noise ratio in comparison with standard silicon sensors. The application in the tender X-ray energy ran...
Source: Journal of Synchrotron Radiation - June 18, 2019 Category: Physics Authors: Andr ä , M. Zhang, J. Bergamaschi, A. Barten, R. Borca, C. Borghi, G. Boscardin, M. Busca, P. Br ü ckner, M. Cartiglia, N. Chiriotti, S. Dalla Betta, G.-F. Dinapoli, R. Fajardo, P. Ferrero, M. Ficorella, F. Fr ö jdh, E. Greiffenberg, D. Huthwelker, T. Tags: hybrid detectors silicon detectors low gain avalanche detectors single photon counting research papers Source Type: research

Advancements towards the implementation of clinical phase-contrast breast computed tomography at Elettra
Breast computed tomography (BCT) is an emerging application of X-ray tomography in radiological practice. A few clinical prototypes are under evaluation in hospitals and new systems are under development aiming at improving spatial and contrast resolution and reducing delivered dose. At the same time, synchrotron-radiation phase-contrast mammography has been demonstrated to offer substantial advantages when compared with conventional mammography. At Elettra, the Italian synchrotron radiation facility, a clinical program of phase-contrast BCT based on the free-space propagation approach is under development. In this paper, ...
Source: Journal of Synchrotron Radiation - June 14, 2019 Category: Physics Authors: Longo, R. Arfelli, F. Bonazza, D. Bottigli, U. Brombal, L. Contillo, A. Cova, M.A. Delogu, P. Di Lillo, F. Di Trapani, V. Donato, S. Dreossi, D. Fanti, V. Fedon, C. Golosio, B. Mettivier, G. Oliva, P. Pacil è , S. Sarno, A. Rigon, L. Russo, P. Taibi, A. Tags: breast CT phase contrast free space propagation single photon counting research papers Source Type: research

In-plane wavevector distribution in partially coherent X-ray propagation
The MOI (Mutual Optical Intensity) code for propagating partially coherent radiation through beamline optics is updated by including the in-plane wavevector in the wavefield calculation. The in-plane wavevector is a local function and accurately describes the average phase distribution in a partially coherent wavefield. The improved MOI code is demonstrated by beam propagation through free space and non-ideal mirrors. The improved MOI code can provide more accurate results with lower numbers of elements, and thus has a higher calculation efficiency. Knowledge of the in-plane wavevector also enables detailed studies of wave...
Source: Journal of Synchrotron Radiation - June 14, 2019 Category: Physics Authors: Ren, J. Wang, Y. Meng, X. Shi, X. Assoufid, L. Tai, R. Tags: mutual optical intensity partially coherent light wavevectors synchrotron beamlines software research papers Source Type: research

Low-dose X-ray structure analysis of cytochrome c oxidase utilizing high-energy X-rays
To investigate the effect of high-energy X-rays on site-specific radiation-damage, low-dose diffraction data were collected from radiation-sensitive crystals of the metal enzyme cytochrome c oxidase. Data were collected at the Structural Biology I beamline (BL41XU) at SPring-8, using 30   keV X-rays and a highly sensitive pixel array detector equipped with a cadmium telluride sensor. The experimental setup of continuous sample translation using multiple crystals allowed the average diffraction weighted dose per data set to be reduced to 58   kGy, and the resulting data revealed a ligand structure featuring an identical...
Source: Journal of Synchrotron Radiation - June 14, 2019 Category: Physics Authors: Ueno, G. Shimada, A. Yamashita, E. Hasegawa, K. Kumasaka, T. Shinzawa-Itoh, K. Yoshikawa, S. Tsukihara, T. Yamamoto, M. Tags: radiation damage high-energy X-ray macromolecular crystallography research papers Source Type: research

Radiation damage studies in cardiac muscle cells and tissue using microfocused X-ray beams: experiment and simulation
Soft materials are easily affected by radiation damage from intense, focused synchrotron beams, often limiting the use of scanning diffraction experiments to radiation-resistant samples. To minimize radiation damage in experiments on soft tissue and thus to improve data quality, radiation damage needs to be studied as a function of the experimental parameters. Here, the impact of radiation damage in scanning X-ray diffraction experiments on hydrated cardiac muscle cells and tissue is investigated. It is shown how the small-angle diffraction signal is affected by radiation damage upon variation of scan parameters and dose. ...
Source: Journal of Synchrotron Radiation - June 14, 2019 Category: Physics Authors: Nicolas, J.-D. Aeffner, S. Salditt, T. Tags: radiation damage scanning X-ray diffraction microdiffraction Monte Carlo simulation EGSnrc research papers Source Type: research

Shining light on cysteine modification: connecting protein conformational dynamics to catalysis and regulation
Cysteine is a rare but functionally important amino acid that is often subject to covalent modification. Cysteine oxidation plays an important role in many human disease processes, and basal levels of cysteine oxidation are required for proper cellular function. Because reactive cysteine residues are typically ionized to the thiolate anion (Cys-S − ), their formation of a covalent bond alters the electrostatic and steric environment of the active site. X-ray-induced photo-oxidation to sulfenic acids (Cys-SOH) can recapitulate some aspects of the changes that occur under physiological conditions. Here we propose how s...
Source: Journal of Synchrotron Radiation - June 13, 2019 Category: Physics Authors: van den Bedem, H. Wilson, M.A. Tags: cysteine modification radiation-controlled photo-oxidation serial X-ray crystallography enzyme conformational dynamics molecular dynamics simulations research papers Source Type: research

The potential benefits of using higher X-ray energies for macromolecular crystallography
Using X-ray energies higher than those normally used (5 – 15   keV) for macromolecular X-ray crystallography (MX) at synchrotron sources can theoretically increase the achievable signal as a function of dose and reduce the rate of radiation damage. In practice, a major stumbling block to the use of higher X-ray energy has been the reduced quantum efficiency of silicon detectors as the X-ray energy increases, but hybrid photon-counting CdTe detectors are optimized for higher X-ray energies, and their performance has been steadily improving. Here the potential advantages of using higher incident beam energy together ...
Source: Journal of Synchrotron Radiation - June 13, 2019 Category: Physics Authors: Dickerson, J.L. Garman, E.F. Tags: radiation damage incident X-ray energies dose photoelectron escape research papers Source Type: research

Structural consequences of transforming growth factor beta-1 activation from near-therapeutic X-ray doses
Dissociation of transforming growth factor beta-1 (TGF β -1) from the inhibitory protein latency-associated peptide (LAP) can occur from low doses of X-ray irradiation of the LAP – TGF β -1 complex, resulting in the activation of TGF β -1, and can have health-related consequences. Using the tools and knowledge developed in the study of radiation damage in the crystallographic setting, small-angle X-ray scattering (SAXS) and complementary techniques suggest an activation process that is initiated but not driven by the initial X-ray exposure. LAP is revealed to be extended when not bound to TGF β -1...
Source: Journal of Synchrotron Radiation - June 13, 2019 Category: Physics Authors: Stachowski, T. Grant, T.D. Snell, E.H. Tags: latency-associated peptide transforming growth factor beta-1 SAXS radiation damage research papers Source Type: research

Identification of spatial magnetic inhomogeneities by nuclear forward scattering of synchrotron radiation
Spatially confined magnetic inhomogeneities were revealed by measuring nuclear forward scattering time spectra on the same sample in two different geometric arrangements. They differ by 180 ° rotation of the sample around one of the polarization axes. A basic theoretical description of this phenomenon and its relation to a spatial distribution of nuclei featuring different magnetic moments is provided. From an experimental point of view, the violation of rotational invariance was observed for an inhomogeneous Fe81Mo8Cu1B10 metallic glass. The development of magnetic inhomogeneities and their relation to the evolution o...
Source: Journal of Synchrotron Radiation - June 12, 2019 Category: Physics Authors: Vrba, V. Proch á zka, V. Miglierini, M. Tags: nuclear forward scattering magnetic inhomogeneities rotational invariance ö ssbauer spectroscopy metallic glasses research papers Source Type: research

Demonstration of a picosecond Bragg switch for hard X-rays in a synchrotron-based pump – probe experiment
A benchmark experiment is reported that demonstrates the shortening of hard X-ray pulses in a synchrotron-based optical pump – X-ray probe measurement. The pulse-shortening device is a photoacoustic Bragg switch that reduces the temporal resolution of an incident X-ray pulse to approximately 7.5   ps. The Bragg switch is employed to monitor propagating sound waves in nanometer thin epitaxial films. From the experimental data, the pulse duration, diffraction efficiency and switching contrast of the device can be inferred. A detailed efficiency analysis shows that the switch can deliver up to 109   photons   s &m...
Source: Journal of Synchrotron Radiation - June 12, 2019 Category: Physics Authors: Sander, M. Bauer, R. Kabanova, V. Levantino, M. Wulff, M. Pfuetzenreuter, D. Schwarzkopf, J. Gaal, P. Tags: ultrafast X-ray diffraction photoacoustics synchrotrons pump – probe experiments active X-ray optics research papers Source Type: research

An X-ray gas monitor for free-electron lasers
A novel X-ray gas monitor (XGM) has been developed which allows the measurement of absolute photon pulse energy and photon beam position at all existing and upcoming free-electron lasers (FELs) over a broad spectral range covering vacuum ultraviolet (VUV), extreme ultraviolet (EUV) and soft and hard X-rays. The XGM covers a wide dynamic range from spontaneous undulator radiation to FEL radiation and provides a temporal resolution of better than 200   ns. The XGM consists of two X-ray gas-monitor detectors (XGMDs) and two huge-aperture open electron multipliers (HAMPs). The HAMP enhances the detection efficiency of the XG...
Source: Journal of Synchrotron Radiation - June 12, 2019 Category: Physics Authors: Sorokin, A.A. Bican, Y. Bonfigt, S. Brachmanski, M. Braune, M. Jastrow, U.F. Gottwald, A. Kaser, H. Richter, M. Tiedtke, K. Tags: free-electron lasers vacuum ultraviolet soft X-rays hard X-rays photon diagnostics research papers Source Type: research

A simple and compact scheme to enhance the brightness of self-amplified spontaneous emission free-electron-lasers
A simple and compact scheme that enhances the brightness of self-amplified spontaneous-emission (SASE) free-electron lasers is presented. The method combines the high-brightness SASE scheme and the optical klystron concept to increase the temporal coherence of the produced radiation and to reduce the required length of the undulator beamline at the same time. The scheme is very simple and only requires compact chicanes between the modules of the undulator beamline. Simulations show that, in comparison with SASE, the brightness can be improved by up to a factor of ten and the required length to achieve saturation can be red...
Source: Journal of Synchrotron Radiation - June 11, 2019 Category: Physics Authors: Prat, E. Reiche, S. Tags: free-electron-laser coherence brightness compact undulator beamline simulations research papers Source Type: research

Reversible rearrangement of magnetic nanoparticles in solution studied using time-resolved SAXS method
Superparamagnetic nanoparticles have broad applications in biology and medicines. Quantitative measurements of magnetic beads in solution are essential in gaining comprehensive understanding of their dynamics and developing applications. Here, using synchrotron X-ray sources combined with well controlled magnetic fields, the results from small-angle X-ray scattering (SAXS) experiments on superparamagnetic particles in solution under the influence of external magnetic fields are reported. The particles mostly remain in monodispersed states and the linear aggregates tend to be aligned with the external magnetic field. After ...
Source: Journal of Synchrotron Radiation - June 11, 2019 Category: Physics Authors: Huang, L. Mai, J. Zhu, Q. Guo, Z. Qin, S. Yang, P. Li, X. Shi, Y. Wang, X. Wang, Q. Li, N. Xie, C. Liu, H. Tags: superparamagnetic nanoparticles small-angle X-ray scattering magnetic fields dynamic assembly monodispersed states time-resolved dynamics research papers Source Type: research

A new in-line X-ray phase-contrast computed tomography reconstruction algorithm based on adaptive-weighted anisotropic TpV regularization for insufficient data
In-line X-ray phase-contrast computed tomography (IL-PCCT) is a valuable tool for revealing the internal detailed structures in weakly absorbing objects (e.g. biological soft tissues), and has a great potential to become clinically applicable. However, the long scanning time for IL-PCCT will result in a high radiation dose to biological samples, and thus impede the wider use of IL-PCCT in clinical and biomedical imaging. To alleviate this problem, a new iterative CT reconstruction algorithm is presented that aims to decrease the radiation dose by reducing the projection views, while maintaining the high quality of reconstr...
Source: Journal of Synchrotron Radiation - June 11, 2019 Category: Physics Authors: Zhao, Y. Ji, D. Chen, Y. Jian, J. Zhao, X. Zhao, Q. Lv, W. Xin, X. Yang, T. Hu, C. Tags: in-line X-ray phase-contrast computed tomography adaptive-weighted anisotropic total p-variation regularization projection onto convex sets radiation dose research papers Source Type: research

Water-mediated photo-induced reduction of platinum films
Platinum thin films activated ex situ by oxygen plasma become reduced by the combined effect of an intense soft X-ray photon beam and condensed water. The evolution of the electronic structure of the surface has been characterized by near-ambient-pressure photoemission and mimics the inverse two-step sequence observed in the electro-oxidation of platinum, i.e. the surface-oxidized platinum species are reduced first and then the adsorbed species desorb in a second step leading to a surface dominated by metallic platinum. The comparison with measurements performed under high-vacuum conditions suggests that the reduction proc...
Source: Journal of Synchrotron Radiation - June 6, 2019 Category: Physics Authors: Fraxedas, J. Zhang, K. Sep ú lveda, B. Esplandiu, M.J. Garc í a de Andr é s, X. Llorca, J. P é rez-Dieste, V. Escudero, C. Tags: beam damage water near-ambient-pressure photoemission platinum oxides research papers Source Type: research