A reaction cell for time‐resolved in situ XAS studies during wet chemical synthesis: the Cu2(OH)3Cl case

The use of in situ time‐resolved dispersive X‐ray absorption spectroscopy (DXAS) to monitor the formation of Cu₂(OH)₃Cl particles in an aqueous solution is reported. The measurements were performed using a dedicated reaction cell, which enabled the evolution of the Cu K‐edge X‐ray absorption near‐edge spectroscopy to be followed during mild chemical synthesis. The formed Cu₂(OH)₃Cl particles were also characterized by synchrotron‐radiation‐excited X‐ray photoelectron spectroscopy, X‐ray diffraction and scanning electron microscopy. The influence of polyvinylpyrrolidone (PVP) on the electronic and structural properties of the formed particles was investigated. The results indicate clearly the formation of Cu₂(OH)₃Cl, with or without the use of PVP, which presents very similar crystalline structures in the long‐range order. However, depending on the reaction, dramatic differences were observed by in situ DXAS in the vicinities of the Cu atoms.     

The first microbeam synchrotron X‐ray fluorescence beamline at the Siam Photon Laboratory

The first microbeam synchrotron X‐ray fluorescence (µ‐SXRF) beamline using continuous synchrotron radiation from Siam Photon Source has been constructed and commissioned as of August 2011. Utilizing an X‐ray capillary half‐lens allows synchrotron radiation from a 1.4 T bending magnet of the 1.2 GeV electron storage ring to be focused from a few millimeters‐sized beam to a micrometer‐sized beam. This beamline was originally designed for deep X‐ray lithography (DXL) and was one of the first two operational beamlines at this facility. A modification has been carried out to the beamline in order to additionally enable µ‐SXRF and synchrotron X‐ray powder diffraction (SXPD). Modifications included the installation of a new chamber housing a Si(111) crystal to extract 8 keV synchrotron radiation from the white X‐ray beam (for SXPD), a fixed aperture and three gate valves. Two end‐stations incorporating optics and detectors for µ‐SXRF and SXPD have then been installed immediately upstream of the DXL station, with the three techniques sharing available beam time. The µ‐SXRF station utilizes a polycapillary half‐lens for X‐ray focusing. This optic focuses X‐ray white beam from 5 mm × 2 mm (H × V) at the entrance of the lens down to a diameter of 100 µm FWHM measured at a sample position 22 mm (lens focal point) downstream of the lens exit. The end‐station also incorporates an XYZ motorized sample holder with 25 mm travel per axis, a 5× ZEISS microscope objective with 5 mm × 5 mm field of view coupled to a CCD camera looking to the sample, and an AMPTEK single‐element Si (PIN) solid‐state detector for fluorescence detection. A graphic user interface data acquisition program using the LabVIEW platform has also been developed in‐house to generate a series of single‐column data which are compatible with available XRF data‐processing software. Finally, to test the performance of the µ‐SXRF beamline, an elemental surface profile has been obtained for a piece of ancient pottery from the Ban Chiang archaeological site, a UNESCO heritage site. It was found that the newly constructed µ‐SXRF technique was able to clearly distinguish the distribution of different elements on the specimen.     

A portable ultrahigh‐vacuum system for advanced synchrotron radiation studies of thin films and nanostructures: EuSi2 nano‐islands

A portable ultrahigh‐vacuum system optimized for in situ variable‐temperature X‐ray scattering and spectroscopy experiments at synchrotron radiation beamlines was constructed and brought into operation at the synchrotron radiation facility ANKA of the Karlsruhe Institute of Technology, Germany. Here the main features of the new instrument are described and its capabilities demonstrated. The surface morphology, structure and stoichiometry of EuSi₂ nano‐islands are determined by in situ grazing‐incidence small‐angle X‐ray scattering and X‐ray absorption spectroscopy. A size reduction of about a factor of two of the nano‐islands due to silicide decomposition and Eu desorption is observed after sample annealing at 1270 K for 30 min.     

Investigations of mechanical vibrations for beamlines at the Canadian Light Source

Vibration is often a problem causing poor quality of photon beams at synchrotron radiation facilities, since beamlines are quite sensitive to vibrations. Therefore, vibration analysis and control at synchrotron radiation facilities is crucial. This paper presents investigations on mechanical vibrations at four beamlines and endstations at the Canadian Light Source, i.e. the Canadian Macromolecular Crystallography Facility 08ID‐1 beamline, the Hard X‐ray MicroAnalysis 06ID‐1 beamline, the Resonant Elastic and Inelastic Soft X‐ray Scattering 10ID‐2 beamline, and the Scanning Transmission X‐ray Microscope endstation at the Spectromicroscopy 10ID‐1 beamline. This study identifies vibration sources and investigates the influence of mechanical vibrations on beamline performance. The results show that vibrations caused by movable mechanical equipment significantly affect the data acquired from beamlines.     

In situ removal of carbon contamination from optics in a vacuum ultraviolet and soft X‐ray undulator beamline using oxygen activated by zeroth‐order synchrotron radiation

Carbon contamination of optics is a serious issue in all soft X‐ray beamlines because it decreases the quality of experimental data, such as near‐edge X‐ray absorption fine structure, resonant photoemission and resonant soft X‐ray emission spectra in the carbon K‐edge region. Here an in situ method involving the use of oxygen activated by zeroth‐order synchrotron radiation was used to clean the optics in a vacuum ultraviolet and soft X‐ray undulator beamline, BL‐13A at the Photon Factory in Tsukuba, Japan. The carbon contamination of the optics was removed by exposing them to oxygen at a pressure of 10^?1–10^?4 Pa for 17–20 h and simultaneously irradiating them with zeroth‐order synchrotron radiation. After the cleaning, the decrease in the photon intensity in the carbon K‐edge region reduced to 2–5%. The base pressure of the beamline recovered to 10^?7–10^?8 Pa in one day without baking. The beamline can be used without additional commissioning.     

Diamond X‐ray beam‐position monitoring using signal readout at the synchrotron radiofrequency

Single‐crystal diamond is a material with great potential for the fabrication of X‐ray photon beam‐position monitors with submicrometre spatial resolution. Low X‐ray absorption combined with radiation hardness and excellent thermal‐mechanical properties make possible beam‐transmissive diamond devices for monitoring synchrotron and free‐electron laser X‐ray beams. Tests were made using a white bending‐magnet synchrotron X‐ray beam at DESY to investigate the performance of a position‐sensitive diamond device using radiofrequency readout electronics. The device uniformity and position response were measured in a 25 µm collimated X‐ray beam with an I‐Tech Libera `Brilliance' system. This readout system was designed for position measurement and feedback control of the electron beam in the synchrotron storage ring, but, as shown here, it can also be used for accurate position readout of a quadrant‐electrode single‐crystal diamond sensor. The centre‐of‐gravity position of the F4 X‐ray beam at the DORIS III synchrotron was measured with the diamond signal output digitally sampled at a rate of 130 Msample s^?1 by the Brilliance system. Narrow‐band filtering and digital averaging of the position signals resulted in a measured position noise below 50 nm (r.m.s.) for a 10 Hz bandwidth.     

Defect engineering by synchrotron radiation X‐rays in CeO2 nanocrystals

This work reports an unconventional defect engineering approach using synchrotron‐radiation‐based X‐rays on ceria nanocrystal catalysts of particle sizes 4.4–10.6 nm. The generation of a large number of oxygen‐vacancy defects (OVDs), and therefore an effective reduction of cations, has been found in CeO₂ catalytic materials bombarded by high‐intensity synchrotron X‐ray beams of beam size 1.5 mm × 0.5 mm, photon energies of 5.5–7.8 keV and photon fluxes up to 1.53 × 10¹² photons s^?1. The experimentally observed cation reduction was theoretically explained by a first‐principles formation‐energy calculation for oxygen vacancy defects. The results clearly indicate that OVD formation is mainly a result of X‐ray‐excited core holes that give rise to valence holes through electron down conversion in the material. Thermal annealing and subvalent Y‐doping were also employed to modulate the efficiency of oxygen escape, providing extra control on the X‐ray‐induced OVD generating process. Both the core‐hole‐dominated bond breaking and oxygen escape mechanisms play pivotal roles for efficient OVD formation. This X‐ray irradiation approach, as an alternative defect engineering method, can be applied to a wide variety of nanostructured materials for physical‐property modification.     

Radiobiological features of the anti‐cancer strategies involving synchrotron X‐rays

Synchrotrons are opening new paths in innovative anti‐cancer radiotherapy strategies. Indeed, the fluence of X‐rays induced by synchrotrons is so high (10⁶ times higher than standard medical irradiators) that it enables the production of X‐ray beams tunable in energy (monochromatic beams) and in size (micrometric beams). Monochromatic synchrotron X‐ray beams theoretically permit photoactivate high‐Z elements to be introduced in or close to tumours in order to increase the yield of damage by enhanced energy photoabsorption. This is notably the case of attempts with iodinated contrast agents used in tumour imaging (the computed tomography therapy approach) and with platinated agents used in chemotherapy (the PAT‐Plat approach). Micrometric synchrotron X‐ray beams theoretically permit very high radiation doses to accumulate in tumours by using arrays of parallel microplanar beams that spare the surrounding tissues (the microbeam radiation therapy approach). These anti‐cancer applications of synchrotron radiation have been developed at the European Synchrotron Radiation Facility to be applied to glioma, one of the tumour tissues most refractory to standard treatments. In the present paper the molecular and cellular mechanisms involved in these three approaches are reviewed, in the context of recent advances in radiobiology. Furthermore, by considering the unavoidable biases, an attempt to propose a comparison of the different results obtained in preclinical trials dealing with rats bearing tumours is given.     

Soft X‐ray absorption spectroscopy and resonant inelastic X‐ray scattering spectroscopy below 100 eV: probing first‐row transition‐metal M‐edges in chemical complexes

X‐ray absorption and scattering spectroscopies involving the 3d transition‐metal K‐ and L‐edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M‐edges, which are below 100 eV. Synchrotron‐based X‐ray sources can have higher energy resolution at M‐edges. M‐edge X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS) could therefore provide complementary information to K‐ and L‐edge spectroscopies. In this study, M_2,3‐edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M_2,3‐edge RIXS on NiO, NiF₂ and two other covalent complexes have been performed and different d–d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M‐edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high‐sensitivity and high‐resolution superconducting tunnel junction X‐ray detectors below 100 eV is also illustrated and discussed.     

Distribution and speciation of lead in model plant Arabidopsis thaliana by synchrotron radiation X‐ray fluorescence and absorption near edge structure spectrometry

To obtain reliable in situ information on the distribution and speciation of Pb in plants with low Pb content, special attention needs to be paid to the synchrotron radiation based micro‐X‐ray fluorescence and micro‐X‐ray absorption near edge structure (μ‐XANES) spectrometry to avoid specious results in the chosen XRF region of interest and speciation linear combination fitting. First, an Arabidopsis thaliana shoot cultured in a Pb solution is analyzed to obtain two‐dimensional Pb distribution graphs, where an overlap of Pb, As, Se, and Br lines in synchrotron radiation based micro‐X‐ray fluorescence spectra is found. To avoid this overlap, (1)As K‐L₃ and Pb L₃‐M₅, (2)As K‐M₃, (3)Pb L₂‐M₄, (4)Se K‐L₃, and (5)Br K‐M₃ lines should be chosen in the region of interest. The Pb content in the seed coat, root, and stem are 48.2, 17.3, and 5.8 times higher, respectively, than in the leaf, while the Pb content in the seed coat, root, stem, and leaf increased 3458, 1241, 420, and 72 times, respectively, compared with the A. thaliana sample without a Pb solution soak. Second, Pb speciation of the same shoot is analyzed using μ‐XANES. It is important to define a combination fitting range because different possible Pb combinations can emerge using different ranges. Different speciations were found in the root[Pb(Ac)₂ and PbSO₄], stem[Pb(Ac)₂ and Pb₃(PO₄)₂], leaf[Pb(OH)₂ and Pb₅Cl(PO₄)₃], and seed coat[Pb₃(PO₄)₂, Pb(OH)₂, and PbCO₃] between the fitting range of E₀ ? 20eV and E₀ + 70eV. A more complete Pb XANES database with more references, especially organic Pb compounds, is needed. Copyright © 2013 John Wiley & Sons, Ltd.     

Comparative study of multilayers used in monochromators for synchrotron‐based coherent hard X‐ray imaging

A systematic study is presented in which multilayers of different composition (W/Si, Mo/Si, Pd/B₄C), periodicity (from 2.5 to 5.5 nm) and number of layers have been characterized. In particular, the intrinsic quality (roughness and reflectivity) as well as the performance (homogeneity and coherence of the outgoing beam) as a monochromator for synchrotron radiation hard X‐ray micro‐imaging are investigated. The results indicate that the material composition is the dominating factor for the performance. By helping scientists and engineers specify the design parameters of multilayer monochromators, these results can contribute to a better exploitation of the advantages of multilayer monochromators over crystal‐based devices; i.e. larger spectral bandwidth and high photon flux density, which are particularly useful for synchrotron‐based micro‐radiography and ‐tomography.     

Performance of a fuel cell optimized for in situ X‐ray absorption experiments

A commercial fuel cell has been successfully modified to carry out X‐ray absorption spectroscopy (XAS) measurements under optimized in operando conditions. The design is conceived for the performance of XAS experiments in transmission mode over a wide range of X‐ray energies above 6 keV, owing to the reduced absorption of the cell. The wide angular aperture allows the collection of XAS in fluorescence mode and of X‐ray diffraction patterns when needed. Details of the design of the cell and its performances are given. The quality of the extended X‐ray absorption fine‐structure spectra under working conditions has been verified at the ESRF and ELETTRA synchrotron radiation facilities, showing that relatively fast and low‐noise transmission measurements on electrodes over a wide range of catalyst concentrations and energies are feasible.     

Estimation of soft X‐ray and EUV transition radiation power emitted from the MIRRORCLE‐type tabletop synchrotron

The tabletop synchrotron light sources MIRRORCLE‐6X and MIRRORCLE‐20SX, operating at electron energies E_el = 6 MeV and E_el = 20 MeV, respectively, can emit powerful transition radiation (TR) in the extreme ultraviolet (EUV) and the soft X‐ray regions. To clarify the applicability of these soft X‐ray and EUV sources, the total TR power has been determined. A TR experiment was performed using a 385 nm‐thick Al foil target in MIRRORCLE‐6X. The angular distribution of the emitted power was measured using a detector assembly based on an NE102 scintillator, an optical bundle and a photomultiplier. The maximal measured total TR power for MIRRORCLE‐6X is P_max? 2.95 mW at full power operation. Introduction of an analytical expression for the lifetime of the electron beam allows calculation of the emitted TR power by a tabletop synchrotron light source. Using the above measurement result, and the theoretically determined ratio between the TR power for MIRRORCLE‐6X and MIRRORCLE‐20SX, the total TR power for MIRRORCLE‐20SX can be obtained. The one‐foil TR target thickness is optimized for the 20 MeV electron energy. P_max? 810 mW for MIRRORCLE‐20SX is obtained with a single foil of 240 nm‐thick Be target. The emitted bremsstrahlung is negligible with respect to the emitted TR for optimized TR targets. From a theoretically known TR spectrum it is concluded that MIRRORCLE‐20SX can emit 150 mW of photons with E > 500 eV, which makes it applicable as a source for performing X‐ray lithography. The average wavelength, = 13.6 nm, of the TR emission of MIRRORCLE‐20SX, with a 200 nm Al target, could provide of the order of 1 W EUV.     

Single‐cell resolution in high‐resolution synchrotron X‐ray CT imaging with gold nanoparticles

Gold nanoparticles are excellent intracellular markers in X‐ray imaging. Having shown previously the suitability of gold nanoparticles to detect small groups of cells with the synchrotron‐based computed tomography (CT) technique both ex vivo and in vivo, it is now demonstrated that even single‐cell resolution can be obtained in the brain at least ex vivo. Working in a small animal model of malignant brain tumour, the image quality obtained with different imaging modalities was compared. To generate the brain tumour, 1 × 10⁵ C6 glioma cells were loaded with gold nanoparticles and implanted in the right cerebral hemisphere of an adult rat. Raw data were acquired with absorption X‐ray CT followed by a local tomography technique based on synchrotron X‐ray absorption yielding single‐cell resolution. The reconstructed synchrotron X‐ray images were compared with images obtained by small animal magnetic resonance imaging. The presence of gold nanoparticles in the tumour tissue was verified in histological sections.     

Temperature dependence of anisotropic displacement parameters in O3‐type NaM O2 (M = Cr and Fe): Comparison with isostructural LiCoO2

O3‐type NaM O₂ (M = Cr and Fe) is a promising cathode material for sodium ion secondary batteries (SIBs). Here, we investigate the temperature dependence of anisotropic displacement parameters, U₃₃ and U₁₁, in NaM O₂ by synchrotron radiation X‐ray powder diffraction measurements. In both compounds, the displacement ratios $(r \equiv \sqrt {U_{33} /U_{11} } - 1)$ for M and O are positive, reflecting the out‐of‐plane thermal displacement of the M O₂ layer. On the other hand, the r value for Na is negative, reflecting the two‐dimensional (2D) host structure. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measurement of L subshell fluorescence yield ratios of some high Z elements by selective excitation method

The L₁, L₂ and L₃ subshells of Hf, Ta and Re atoms have been excited selectively by using microprobe XRF beam line, Indus‐2, RRCAT, India. The consequent characteristic L X‐ray photons, emitted from the targets due to creations of vacancies in L subshells, are measured using silicon drift detector (X‐123) spectrometer. As the energy of synchrotron radiation increases, the contribution of characteristic L X‐ray intensity increases. The advantage of the increase in the intensity of the characteristic L X‐ray photons with an increase in the energy of synchrotron radiation has been used to determine the L subshell fluorescence yield ratios of Hf, Ta and Re atoms by adopting the selective excitation method. The measured ratios of L subshell fluorescence yield have been compared with theoretical and other experimental values.     

Calibrating the X‐ray attenuation of liquid water and correcting sample movement artefacts during in operando synchrotron X‐ray radiographic imaging of polymer electrolyte membrane fuel cells

Synchrotron X‐ray radiography, due to its high temporal and spatial resolutions, provides a valuable means for understanding the in operando water transport behaviour in polymer electrolyte membrane fuel cells. The purpose of this study is to address the specific artefact of imaging sample movement, which poses a significant challenge to synchrotron‐based imaging for fuel cell diagnostics. Specifically, the impact of the micrometer‐scale movement of the sample was determined, and a correction methodology was developed. At a photon energy level of 20 keV, a maximum movement of 7.5 µm resulted in a false water thickness of 0.93 cm (9% higher than the maximum amount of water that the experimental apparatus could physically contain). This artefact was corrected by image translations based on the relationship between the false water thickness value and the distance moved by the sample. The implementation of this correction method led to a significant reduction in false water thickness (to ～0.04 cm). Furthermore, to account for inaccuracies in pixel intensities due to the scattering effect and higher harmonics, a calibration technique was introduced for the liquid water X‐ray attenuation coefficient, which was found to be 0.657 ± 0.023 cm^?1 at 20 keV. The work presented in this paper provides valuable tools for artefact compensation and accuracy improvements for dynamic synchrotron X‐ray imaging of fuel cells.     

Synchrotron X‐ray microfluorescence measurement of metal distributions in Phragmites australis root system in the Yangtze River intertidal zone

This study investigates the distributions of Br, Ca, Cl, Cr, Cu, K, Fe, Mn, Pb, Ti, V and Zn in Phragmites australis root system and the function of Fe nanoparticles in scavenging metals in the root epidermis using synchrotron X‐ray microfluorescence, synchrotron transmission X‐ray microscope measurement and synchrotron X‐ray absorption near‐edge structure techniques. The purpose of this study is to understand the mobility of metals in wetland plant root systems after their uptake from rhizosphere soils. Phragmites australis samples were collected in the Yangtze River intertidal zone in July 2013. The results indicate that Fe nanoparticles are present in the root epidermis and that other metals correlate significantly with Fe, suggesting that Fe nanoparticles play an important role in metal scavenging in the epidermis.     

Optimization of L‐shell X‐ray fluorescence detection of lead in bone phantoms using synchrotron radiation

Closely related toxicity and retention mechanisms of lead (Pb) in the human body involve the bone tissues where Pb can accumulate and reside on a time scale ranging from years to tens of years. In vivo measurements of bone Pb can, therefore, play an important role in a comprehensive health risk assessment of Pb exposure. In vivo L‐shell X‐ray fluorescence (LXRF) measurement of bone Pb was first demonstrated over 4 decades ago. Implementation of the method, however, encountered challenges associated with low sensitivity and calibration procedure. In this study, the LXRF measurement was optimized by varying the incident photon energy and the excitation‐detection geometry. The Canadian Light Source synchrotron radiation was used to compare 2 different excitation‐detection geometries of 90^° and 135^° using 3 different X‐ray photon energies: 15.8, 16.6, and 17.5 keV. These energies optimized excitation of the L₃ subshell of Pb and simulated the most intense K‐shell emissions of zirconium, niobium, and molybdenum, respectively. Five rectangular plaster‐of‐Paris bone phantoms with Pb concentrations of 0, 7, 17, 26, and 34 μg/g, and one rectangular 3.1‐mm‐thick resin phantom mimicked the X‐ray attenuation properties of human bone and soft tissue, respectively. Optimal LXRF detection was obtained by the 15.8‐keV energy and the 90^° and 135^° geometries for the bare bone and the bone and soft tissue phantoms, respectively.     

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

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 detected, which decayed and vanished after switching off the X‐ray beam. This demonstrates the usefulness of a SKP for in situ monitoring of surface/interface potentials during X‐ray materials characterization experiments.