High Intensity Synchrotron Radiation Research Articles

Photoemission electron microscopy of arrays of submicron nickel rods in a silicon dioxide matrix

Arrays of Ni rods (∼500 nm diameter) formed by the ion-track technology in combination with electrochemical deposition into a SiO2 matrix on the surface of single-crystal silicon plates have been investigated using photoemission electron microscopy with high-intensity synchrotron (undulator) radiation. An analysis of the Ni L 2,3 X-ray absorption near-edge structure (XANES) spectra has demonstrated that rod-like structures in pores and connecting bridges between the rods are formed by a metallic nickel phase, which is stable to oxidation by atmospheric oxygen. No formation of intermediate compound phases (nickel silicides and oxides) is observed at the Ni/SiO2 heterojunction, whereas oxidized nickel(II) species are identified on the surface of the SiO2 matrix, which presumably can be attributed to nickel silicate and hydroxide compounds formed upon nickel(II) chemisorption in electrochemical deposition electrolytes.

Effect of Al content on the order of phase transition and magnetic entropy change in LaFe11Co0.8(Si1−xAlx)1.2 alloys

The comparative studies of the effect of partial substitution of Al by Si on the structure and magnetic entropy change in LaFe11Co0.8(Si1−xAlx)1.2 alloys produced by arc-melting followed by long time annealing at 1323K were performed. The X-ray diffraction analysis revealed almost single phase composition of annealed samples. The high intensity synchrotron radiation was used for studying the thermal evolution of lattice constant of the La(Fe,Co,Si)13 phase. Furthermore, calculations of temperature dependences of Landau coefficients were used to reveal changes in the character of phase transformation at around the Curie temperature.

Synchrotron studies of SnO2 wire-like crystals

Wire-like micro- and nanocrystals of SnO2 are obtained via gas-transport synthesis. The specifics of the atomic and electronic structure of an array of SnO2 wire-like crystals is revealed using near-edge X-ray absorption and X-ray photoelectron spectra. The method of photoemission electron microscopy with high-intensity synchrotron (undulator) radiation is used to study the morphology of SnO2 wire-like crystals for the first time.

A new double imaging velocity focusing coincidence experiment: i2PEPICO

The vacuum ultraviolet (VUV) beamline of the Swiss Light Source has been upgraded after two years of operation. A new, turntable-type monochromator was constructed at the Paul Scherrer Institut, which allows for fast yaw-alignment as well as quick grating change and exchange. In addition to the original imaging photoelectron photoion coincidence endstation (iPEPICO), a second, complementary double imaging setup (i(2)PEPICO) has been built. Volatile samples can be introduced at room temperature or in a molecular beam, a pyrolysis source allows for radical production, and non-volatile solids can be evaporated in a heated cell. Monochromatic VUV radiation ionizes the sample and both photoelectrons and photoions are velocity map imaged onto two fast position sensitive detectors and detected in delayed coincidence. High intensity synchrotron radiation leads to ionization rates above 10(5) s(-1). New data acquisition and processing approaches are discussed for recording coincidence processes at high rates. The setup is capable of resolving pulsed molecular beam profiles and the synchrotron time structure temporally. The latter is shown by photoelectron autocorrelation, which displays both the 1.04 MHz ring clock frequency as well as resolving the micro-pulses with a separation of 2 ns. Kinetic energy release analysis on the dissociative photoionization of CF(4) indicates a dissociation mechanism change in the Franck-Condon allowed energy range of the first ion state.

Metal micro-detector TimePix imaging synchrotron radiation beams at the ESRF Bio-Medical Beamline ID17

Characterization studies of the metal micro-detector TimePix measuring dose distribution at the Minibeam Radiation Therapy setup (Bio-Medical Beamline ID17, ESRF) were performed. The results obtained for high intensity synchrotron radiation minibeams illustrate an excellent performance of the TimePix providing in real time 2D image of the dose distribution over many beams in a 14×14mm2 area. Peak-to-Valley–Dose–Ratios measured by TimePix and gafhromic films agree well.

Measurement of the linear attenuation coefficients of breast tissues by synchrotron radiation computed tomography

The measurement of the linear attenuation coefficients of breast tissues is of fundamental importance in the field of breast x-ray diagnostic imaging. Different groups have evaluated the linear attenuation coefficients of breast tissues by carrying out direct attenuation measurements in which the specimens were thin and selected as homogeneous as possible. Here, we use monochromatic and high-intensity synchrotron radiation computed tomography (SR CT) to evaluate the linear attenuation coefficients of surgical breast tissues in the energy range from 15 to 26.5 keV. X-ray detection is performed by a custom digital silicon micro-strip device, developed in the framework of the PICASSO INFN experiment. Twenty-three human surgical breast samples were selected for SR CT and histological study. Six of them underwent CT, both as fresh tissue and after formalin fixation, while the remaining 17 were imaged only as formalin-fixed tissues. Our results for fat and fibrous tissues are in good agreement with the published values. However, in contrast to the published data, our measurements show no significant differences between fibrous and tumor tissues. Moreover, our results for fresh and formalin-fixed tissues demonstrate a reduction of the linear attenuation coefficient for fibrous and tumor tissues after fixation.

The high-resolution far-infrared spectrum of methane at the SOLEIL synchrotron

As a tetrahedral molecule, methane has no permanent dipole moment. Its spectrum, however, displays faint absorption lines in the THz region, due to centrifugal distorsion effects. This is important for planetary applications since this region is used to measure methane concentration in some planetary atmospheres, in particular on Titan. Up to now, all measurements relied either on some old low resolution infrared absorption spectra, or on high resolution Stark measurements for low J values only. Even if these results have been reexamined recently [Wishnow EH, Orton GS, Ozier I, Gush HP. The distorsion dipole rotational spectrum of CH 4: a low temperature far-infrared study. J Quant Spectrosc Radiat Transfer 2007;103:102–17], it seemed highly desirable to obtain much more precise laboratory data. The high-intensity synchrotron radiation, combined with a 151.75±0.1 m optical path in a White cell and a Bruker IFS 125 HR FTIR spectrometer at the AILES beamline of SOLEIL, enabled us to record this very weak spectrum at high resolution for the first time. Spectra were obtained in the 50–500 cm −1 wavenumber range at 296 K and 9.91, 20, 50 and 100 mbar with a resolution of 0.00074, 0.00134, 0.0034 and 0.0067 cm −1 (FWHM of the sinc function), respectively. The rotational clusters are fully resolved and the good signal-to-noise ratio has enabled precise measurements of transition intensities (92 cold band lines and 96 Dyad–Dyad hot band lines, with normal abundance intensities in the range 2×10 −26–1×10 −24 cm −1/(mol cm −2)), yielding an accurate determination of the dipole moment derivatives. Such results should allow a better determination of CH 4 concentration in planetary objects.

Synchrotron X-ray Diffraction Investigation of the Anomalous Behavior of Ice During Freezing of Aqueous Systems

Simple aqueous systems, i.e., phosphate-glycine buffers and pure water, were studied at subambient temperatures by X-ray difractometry using a high-intensity synchrotron radiation source at the Advanced Photon Source of Argonne National Laboratory. Complex X-ray diffraction (XRD) patterns, with two or more poorly resolved peaks in place of each of the four diagnostic peaks of hexagonal ice, 100, 002, 101, and 102, referred as "splitting", were observed in the majority of cases. The splitting of up to 0.05 A (d-spacing) was detected for 100, 002, and 101 peaks, whereas 102 peak was less affected. Deformation of the lattice of hexagonal ice, probably due to local stress created on the ice/ice or ice/container interface during water-to-ice transformation, is proposed as a possible mechanism for the observed splitting of XRD peaks. Using molecular modeling, it was estimated that the observed shifts in the peak positions are equivalent to applying a hydrostatic pressure of 2-3 kbars. The splitting can be used to quantify stresses during freezing, which could improve our understanding of the role of water-to-ice transformation on the destabilization of proteins and other biological systems.

High-intensity synchrotron radiation from compact magnetic-plasma structures

As technological devices become more compact, their ability to generate small-scale electric and magnetic structures becomes increasingly important. In most cases, reducing the size of these structures runs into stringent technical limits, especially in terms of the field amplitudes and the shortest length scales attainable. Plasma is an attractive medium in this context because of its ability to sustain strong fields on small spatial scales. Successful examples include high-gradient electrostatic structures—generated by the propagation of an intense laser pulse in a plasma—that are used to accelerate particles to high energies in compact systems.1 Excitation of analogous periodic-magnetostatic structures to drive a plasma magnetic mode (PMM) by colliding a light pulse with a relativistic ionization front had been predicted theoretically,2, 3 but a method to detect and characterize PMMs was designed only recently.4 Propagation of a relativistic electron beam through the PMM can provide ultrashort-wavelength synchrotron radiation,5 in a similar fashion to beam propagation in the undulator structure of a free-electron laser.6 In addition, narrow spectra and, consequently, high-intensity radiation can be generated, since the larger the number of oscillation periods in the structure, the narrower the spectrum of the resulting emission. Development of a compact radiation source would offer a powerful tool to study the dynamics of materials on the timescale of atomic motions7 and for biomolecular imaging.8 We show that controlled excitation of the magnetic structure is possible with existing state-of-the-art laser technology, thus enabling its exploration, in particular, for the generation of high-intensity synchrotron radiation. Figure 1. Schematic setup used to generate synchrotron radiation through the propagation of an electron beam in the plasma-magneticmode (PMM) structure.

MEASUREMENT OF YOUNG'S MODULUS AND POISSON'S RATIO OF THIN FILMS BY SYNCHROTRON X-RAY DIFFRACTION

A new experimental method for determining elastic constants of thin films is proposed. The curvatures of the single crystal substrates before and after depositing thin film are first measured using high-resolution X-ray rocking curve technique with high quality monochromatic and high intensity synchrotron radiation. The residual stress in the film is then calculated from the change in substrate curvature based on the well-known modified Stoney's equation. The formulae for calculating thin film's Young's modulus and Poisson's ratio are deduced based on measured residual stress and the lattice spacing dψ versus sin2ψ curves of the film before and after an unknown mechanical loading. LaNiO3 film grown on single crystal silicon substrate using pulsed laser deposition is employed to demonstrate the measurement method.

Glass transition, thermal expansion and relaxation in B2O3 glass measured by time-resolved X-ray diffraction

In situ heating experiments using high-energy, high-intensity synchrotron radiation, can be successfully designed to study structural evolution with temperature of glassy materials. Coherent diffraction from glassy materials forms a succession of halos or diffraction maxima in reciprocal space and the variation with temperature, of the wave-vector Qmax or angular position of the first diffracted intensity I(Qmax) maximum below Tg can be used to determine the iso-structural volume expansion. In the present work we have obtained synchrotron X-ray diffraction patterns in transmission during in situ heating of a B2O3 glass. Samples were obtained by melting the B2O3 glass rods which were then air-cooled or liquid nitrogen-cooled. The evolution with temperature (and time) of the position of the first diffraction maximum of the diffraction pattern accurately reflected the thermal expansion coefficient and the relaxation behavior of the B2O3 glass. Such results allowed determination by diffraction of the glass transition temperature, Tg, at 580K, as well as information on the structural relaxation during thermal annealing. The total volume changes due to relaxation were measured to be about 1.5vol.% and 2.5vol.%, for the air-cooled and the liquid nitrogen-cooled B2O3 glass, respectively.

Determination of the x-ray elastic constants of solid thin films

A new experimental method for determining the x-ray elastic constants(S1 and (1/2)S2) of thin films is proposed. The curvatures of the single-crystal substrates before and afterdepositing thin films are first measured using a high-resolution x-ray rocking curvetechnique with high-quality monochromatic and high-intensity synchrotron radiation. Theresidual stresses in the films are then calculated from the change in substrate curvaturebased on the well-known modified Stoney’s equation. The formulae for calculation ofS1 and (1/2)S2 are deduced based on measured residual stress and the lattice spacingdψ versus sin2ψ curves before and after a mechanical loading, while the magnitudeof the external loading does not need to be known. Values of(1/2)S2 of films can even be obtained without loading.Pb(Zr0.52Ti0.48) and LaNiO3 films grown on a single-crystal silicon substrate using pulsed laser deposition are employedto demonstrate the measurement method.

Measurement of residual stress of PZT thin film on Si(1 0 0) by synchrotron X-ray rocking curve technique

( l 0 0) oriented Pb(Zr,Ti)O3 (PZT) and LaNiO3 (LNO) thin films were grown on SiO 2/(1 0 0) Si substrate by pulsed laser deposition. The bending of the crystal planes of single crystal substrates is assessed by high-resolution X-ray rocking curve technique (HRRC) with a high quality monochromatic and high intensity synchrotron radiation. The residual stress is then calculated from the change in curvature of the substrate before and after depositing the film based on the well-known modified Stoney's equation. More reliable results can be achieved because they are not affected by surface morphology and reflectivity of the films. HRRC can be applied to all kinds of thin films including randomly oriented polycrystalline, oriented and amorphous films. The residual stress of the ( l 0 0) PZT thin films on SiO 2/(1 0 0) silicon substrate was measured to be 189 MPa.

Structural transitions of the mono-olein bicontinuous cubic phase induced by inclusion of protein lysozyme solutions

Inclusion of protein lysozyme molecules in the lipidic mono-olein cubic phase induces a transition from a Pn3m structure to an Im3m one. The small-angle x-ray scattering method with high-intensity synchrotron radiation enabled us to follow closely the transition depending on the conditions of lysozyme solutions. We show that concentrated lysozyme solutions induced the appearance of the Im3m structure coexisting with the Pn3m structure. From the relation between the lattice parameters of these two structures it is shown that they are related by the Bonnet transformation of the underlying triply periodic minimal surfaces. We found that the transition also occurred at lower lysozyme concentration when NaCl induced an attraction between lysozyme molecules. The origin of the transition was considered as a frustration in the cubic phase where lysozyme molecules were highly confined. A simple estimation of the frustration was given, which took into account the translational entropy of lysozyme molecules. At the highest concentration of lysozyme and NaCl the Im3m structure was found to disappear and left only the Pn3m structure. This was probably either due to the crystallization or phase separation of lysozyme solutions ongoing microscopically, which absorbed lysozyme molecules from channels of the cubic phase and thus removed the frustration.

Metastable Phase Formation in Undercooled Nd-Fe-B Alloys Investigated by In Situ Diffraction Using Synchrotron Radiation

Diffraction experiments on electromagnetically levitated Nd-Fe-B alloys during solidification of the undercooled melt have been performed at the European Synchrotron Radiation Facility (ESRF). By using high intensity synchrotron radiation complete diffraction spectra could be detected within a short period of some seconds thus enabling the observation of metastable solidification products that exhibits a limited lifetime. A metastable phase that crystallizes in wide composition range and that initiates the solidification of the stable Nd2Fe14B1-phase (φ-phase) have been observed.

Simulation of temperature distribution by finite element analysis on different components of the EXAFS beamline at INDUS-II synchrotron source

An extended X-ray absorption fine structure (EXAFS) beamline is being developed for the INDUS-II synchrotron source. Several optical and mechanical components of the beamline are exposed to high intensity synchrotron radiation while in operation. The temperature rise on different components of the beamline on exposure to the synchrotron beam has been simulated by finite element analysis. Design of the cooling mechanism for each of these components has been carried out and estimation of the temperature rise has also been done incorporating the cooling mechanism.

X-ray holography: Atoms in 3D

X-ray holography is a novel method for the investigation of local atomic arrangements in solids. In conventional diffraction experiments, only the intensity of the scattered radiation is measured, its phase is lost. This loss of information makes difficult to reconstruct the atomic arrangements. In holography, both the intensity and the phase information is recorded. Using one of the atoms of the solid as source or detector of the X-radiation, atomic resolution can be reached. A three-dimensional picture of the atoms surrounding the source/detector atom can be easily reconstructed from the measured hologram. While, in principle, the measurement is very simple, in practice the small signal-to-background ratio (∼10 −3) makes it difficult. Using high intensity synchrotron radiation, the measurement time can be reduced and high quality holograms can be recorded. In this paper, we review the principles and experimental techniques of atomic resolution X-ray holography and present a few examples of its application.

大強度放射光用フラックスモニターの開発_-_平行平板電離箱_-_

大強度放射光用フラックスモニターの開発_-_平行平板電離箱_-_

Imaging dislocations in ice.

Three techniques have been used to study dislocations in ice: etch pitting-replication, transmission electron microscopy, and X-ray topography (XT). It is shown that, because ice is a weak absorber of X-rays and can be produced with a low dislocation density, allowing relatively thick specimens to be studied, the most useful technique is XT. The observations that have been made with conventional XT are briefly outlined. However, the introduction of high-intensity synchrotron radiation, with its concomitant short exposure times, showed that images obtained through conventional XT observations were of dislocations that had undergone recovery. The important dynamic observations and measurements that have been made using synchrotron X-ray topography are presented. Dynamic synchrotron X-ray topography observations of ice single crystals undergoing deformation in situ have shown that slip mainly occurs by the movement of screw and 60 degrees (1/3) [1120] dislocations on the basal plane, although non-basal slip by edge dislocations can also occur. The operation of Frank-Read and other dislocation multiplication sources have been clearly demonstrated and dislocation velocities have been measured. In contrast, in polycrystals, dislocation generation occurred at grain boundaries where there are stress concentrations before lattice dislocation generation mechanisms operate. Faulted dislocation loops have been determined to be mainly interstitial in both polycrystals and single crystals.

SAXS/WAXS experiments using extreme sample environments

By using high intensity synchrotron radiation X-ray beam lines it is possible to study the structural evolution of materials exposed to extreme conditions like high temperatures, pressure, etc. This possibility creates scope for real time investigations of structural development relevant to manufacturing conditions. The devitrification of glass with the cordierite composition is one of such processes. This process takes place at temperatures in excess of 1000 °C. Combined small and wide angle X-ray scattering experiments have been performed. From these experiments we have been able to derive temperature parameters required to grow monodisperse crystalline particles in an amorphous matrix. By controlling the amount of crystallisation inducing metal ions and the temperature profile the crystalline volume fraction and particle size can be tailored to the required properties. Another example of the use of extreme conditions is the realignment behaviour of smectic-A liquid crystals under the influence of magnetic fields. This is an interesting subject since smectic liquid crystals are thought to be candidates for faster switching devices in for instance liquid crystal displays. The mechanism of reorientation is still not well understood. Time-resolved X-ray scattering experiments in fields up to 10 T will be described. All the results described in this overview have been recently obtained in collaboration with a number of groups. In this text the emphasis will be on the instrumentation aspects of the work and the importance that sample environments can have for experiments in material science. The full results will be published elsewhere.