Third-generation Synchrotron Radiation Research Articles

Using nuclear accelerator technology to make intense X-rays

Electron accelerators, originally developed for nuclear and high energy physics research, have become by far the most intense infrared, ultraviolet and X-ray sources in the world. The increase in availability of these sources (there are now about 60 in operation around the world) has had a revolutionary effect on many branches of basic and applied research resulting in a major impact on science and society in developing countries as well as in technologically well-developed countries. Synchrotron radiation facilities in developing countries have produced hundreds of PhD students who did not have to leave their country, and they have attracted dozens of mid-career scientists to return to their country of origin, where they can continue to perform frontier research. In addition, scientists in these developing countries are able to use intense synchrotron radiation to address local environmental and biomedical issues and concerns. This paper presents: 1) a brief historical account of the development of synchrotron radiation sources from the first to the fourth generation; 2) a summary of the properties of synchrotron radiation; 3) an overview of synchrotron radiation facilities in developing countries; 4) a description of the UNESCO-sponsored Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME) project which is constructing a regional, international third-generation synchrotron radiation research centre in the Middle East in close analogy to CERN.

Operational radiation protection in synchrotron light and free electron laser facilities

The third-generation synchrotron radiation (SR) facilities are storage ring-based facilities with many insertion devices and photon beamlines, and have low injection beam power, but extremely high stored beam power. The fourth-generation X-ray free electron laser (FEL) facilities are based on an electron Linac with a long undulator and have high injection beam power. Due to its electron and photon beam characteristics and modes of operation, storage ring and photon beamlines have unique safety aspects, which are the main subjects of this paper. The shielding design limits, operational modes and beam losses are reviewed. Shielding analysis (source terms and methodologies) and interlocked safety systems for storage ring and photon beamlines (including SR and gas bremsstrahlung) are described. Specific safety issues for storage ring top-off injection and FEL facilities are discussed. Operational safety programme elements, e.g. operation authorisation, commissioning, training and radiation measurements, for SR facilities are also presented.

Directional lithium hydride Compton profiles of 0.1% statistical accuracy

The present status and accuracy of determining the electron momentum density from experimental Compton profiles is reviewed. The new spectrometers operating at third-generation synchrotron radiation sources have made possible measurements with 0.1% statistical accuracy at the Compton peak. A comparable accuracy of the Compton profiles is achieved only after careful corrections for departures from the impulse approximation, effects of multiple scattering, and variations in the analyser response function. Detailed descriptions are given of the correction procedures applied to the data collected by the Johann-type scanning spectrometer that is one of the Compton spectrometers in use at the ESRF. Special attention is paid to the calculation and correction of the glitches that are caused by extra reflections of the analyser crystal. The Fourier transform of the Compton profile, the reciprocal form factor, is calculated, and its use in data treatment and presentation is discussed.

Tomography Observations of Osteoblast Seeding on 3-D Collagen Scaffold by Synchrotron Radiation Hard X-Ray

In recent years, research into three-dimensional (3-D) scaffolds for tissue engineering has become an important topic. To avoid biological rejection, there are many biocompatible materials being developed for in vitro cultivation of autologous cells for implantation into the human body. The 3-D structures of scaffolds are not easily observed using traditional optical or electron microscopes, which only allow examination of the surfaces of samples or ultra thin films, and often require complicated pre-treating processes. The high-brilliance synchrotron radiation (SR) hard X-ray is an emerging technique to acquire tomography. This study involves the successful reconstruction of 3-D images and the animation of the structure of a collagen scaffold. The images were obtained using synchrotron radiation hard X-ray images, which eliminates the need for embedding and microtoming. SR hard X-ray imaging is a non-destructive technique, which has demonstrated a high spatial resolution and transmission, enabling the morphology of osteoblasts adhered on the inner surfaces of the collagen scaffolds to be captured. It is a convenient facility to obtain 3-D tomography images for biomaterial studies. This is the first study to observe the 3-D structures of collagen scaffolds and aquire detailed images of osteoblast attachment on the scaffold, by utilization of third-generation SR hard X-ray radiography.

Measurement of optics for the SSRF storage ring in commissioning

The Shanghai Synchrotron Radiation Facility (SSRF) is a low emittance third-generation synchrotron radiation light source. Some optics parameters of the storage ring were measured when commissioning. This report presents the common methods for measuring some optics parameters of the storage ring, including the betatron tune, beta function, chromaticity, natural chromaticity and dispersion. The results and analysis of measurement for the optics parameters are given here, which are indispensable for the orbit correction of the accelerator and the nonlinear optimization.

Field-free molecular alignment for studies using x-ray pulses from a synchrotron radiation source

A short, intense laser pulse may be employed to create a spatially aligned molecular sample that persists after the laser pulse is over. We theoretically investigate whether this impulsive molecular alignment technique may be exploited for experiments using x-ray pulses from a third-generation synchrotron radiation facility. Using a linear rigid rotor model, the alignment dynamics of model molecular systems with systematically increasing size is calculated utilizing both a quantum density matrix formalism and a classical ensemble method. For each system, the alignment dynamics obtained for a 95 ps laser is compared with that obtained for a 10 ps laser pulse. The average degree of alignment after the laser pulse, as calculated quantum mechanically, increases with the size of the molecule. This effect is quantitatively reproduced by the classical calculations. The average degree of impulsive alignment is high enough to induce a pronounced linear dichroism in resonant x-ray absorption using the intense 100 ps x-ray pulses currently available. However, for structural studies based on elastic x-ray scattering, bright x-ray pulses with a duration of 1 ps or shorter will be required in order to make full use of impulsive molecular alignment.

Increasing Preload Reduced Actin-Myosin Interaction in Isolated Beating Rat Whole Heart Under Hypoxia

Background: Hypoxia reduces cardiac contractile performance. However, there is no direct observation on how preload affects the actinmyosin-interaction (AMI) in beating hearts during hypoxia. Purpose: The aim of this study is to investigate this theme using X-ray-diffraction (XRD) analysis at a third-generation synchrotron radiation facility. Methods: Eight isolated isovolumically contracting rat hearts were paced at 120 bpm after complete heart block, mounted so that the X-ray beam (15.0 keV) passed the deeper layer of left ventricular (LV) free wall, and perfused with Tyrode solution bubbled with 100%O2(Normo) or 100%N2(Hypo). We recorded XRD patterns and LV pressure (LVP) at end-diastolic LVP (EDP) of 0 and 20 mmHg. Results: Under Normo, increasing EDP significantly increased the developed-LVP (EDP0: 104±26mmHg vs. EDP20: 141±25mmHg, p<0.01). Under Hypo, developed LVP and its duration did not show significant differences compared with those in Normo. However, increasing EDP under Hypo significantly decreased developed LVP (72±13mmHg vs. 96±16mmHg, p<0.01). The minimum value of the (1,0)/(1,1) intensity ratio (Imin) provided by the XRD analysis was used as an index of AMI. Imin showed a significantly negative correlation with developed LVP regardless of Normo or Hypo. The diastolic myosin filament lattice spacing (MFL) calculated from the diffraction angle of the (1,0) equatorial reflection would be reduced by increasing EDP. In contrast to a significantly positive MFL-Imin correlation under Normo, we observed the significantly negative MFL-Imin correlation under Hypo. We confirmed that the duration of Ca2 + transient was slightly longer but the amplitude of Ca2 + transient was unchanged under Hypo. Conclusion: These novel findings suggest that under Hypo the probability of AMI decreases even though the MFL was reduced with increasing preload. This is an underlyingmechanism for reduced cardiac contractile performance under hypoxia.

Vacuum space-charge effects in solid-state photoemission

Solid-state photoemission spectroscopy relies to a large part on pulsed photon sources: third-generation synchrotron-radiation sources and ultrafast laser systems in particular. Especially when the photon pulses are intense, Coulombic repulsion between the emitted electrons will be a limiting factor for photoemission experiments aiming at highest energy and angle resolutions. In the present work, the propagation of the photoelectron cloud to the detector is studied with a full $N$-body numerical simulation. The influence of various parameters, in particular number of electrons per pulse, source size, pulse duration, kinetic-energy and emission-angle distributions as well as presence of mirror charges in the sample, is investigated in detail. Previous experimental results obtained with various picosecond and femtosecond light sources are successfully reproduced and the general resolution limits of solid-state photoemission using pulsed photon sources are explored. The results are potentially important for the design and interpretation of photoemission experiments with next-generation light sources, such as free-electron lasers and high-harmonic generation sources.

Post-processing technique for improved assessment of hard tissues in the submicrometer domain using local synchrotron radiation-based computed tomography / Nachbearbeitungstechnik für eine verbesserte Erfassung harten Gewebes im Submikrometerbereich mittels lokaler synchrotronstrahlungsbasierter Computertomographie

During the last two decades micro-computed tomography has become the method of choice for the non-destructive assessment and quantitative morphometry of hard tissues in three dimensions. With the advent of third-generation synchrotron radiation sources, micro-computed tomography in the micrometer range has become feasible and has been employed to analyze local bone tissue properties. However, owing to limitations regarding the tradeoff between object size and spatial resolution, non-destructive conventional global computed tomography of hard tissues, such as bone, remains unachievable in the submicrometer domain so far. Here, we report on a post-processing technique for the assessment of hard tissues using local synchrotron radiation-based computed tomography, which overcomes this experimental limitation.

Irregularity of Autoionizing Rydberg Series in Photoionization Leading to the Si3+ 3l States from the Mg-Like Si2+ Ions

We report the theoretical photoionization cross sections in the low energy region for Mg-like Si 2+ ion, with arousing desire for experiments. With the advent of third-generation synchrotron radiation sources, it is expected to study for this ionic system using merged-beam technique. Since the Mg-like Si 2+ ions are expected to be admixed with the ground-state and several low-lying excited-states, we have calculated the photoionization cross sections from the initial ground-state 3 s 2 1 S , and the excited-states 3 s 3 p 1,3 P , 3 s 3 d 1,3 D , and 3 s 4 s 1,3 S of Mg-like Si 2+ ion. For these calculations, we have used a most elaborate noniterative eigenchannel R -matrix method. We briefly discuss the results for autoionizing resonances and interlopers in the structure of photoionization cross sections, and compare with the previous results of Opacity Project.

Computer simulation of phase-contrast images in white synchrotron radiation using micropipes in silicon carbide

A method of computer simulation of phase-contrast images in white synchrotron radiation has been developed to determine the section parameters of micropipes in silicon carbide. The experiments have been carried out using the third-generation synchrotron radiation source the Pohang Light Source (South Korea). The effective spectrum of the synchrotron radiation that forms of an image has been shown to have a relatively sharp maximum at an energy of 16 keV, which makes it possible to conserve coherency within the required limits. A computer program has been developed that automatically determines the diameters of an elliptic section of a micropipe from the condition of coincidence of calculated and experimental profiles. It has been shown that the studied micropipes have a strongly stretched elliptic section that can twist when moving along the pipe axis.

An assessment of the resolution limitation due to radiation-damage in X-ray diffraction microscopy

X-ray diffraction microscopy (XDM) is a new form of X-ray imaging that is being practiced at several third-generation synchrotron-radiation X-ray facilities. Nine years have elapsed since the technique was first introduced and it has made rapid progress in demonstrating high-resolution three-dimensional imaging and promises few-nanometer resolution with much larger samples than can be imaged in the transmission electron microscope. Both life- and materials-science applications of XDM are intended, and it is expected that the principal limitation to resolution will be radiation damage for life science and the coherent power of available X-ray sources for material science. In this paper we address the question of the role of radiation damage. We use a statistical analysis based on the so-called “dose fractionation theorem” of Hegerl and Hoppe to calculate the dose needed to make an image of a single life-science sample by XDM with a given resolution. We find that the needed dose scales with the inverse fourth power of the resolution and present experimental evidence to support this finding. To determine the maximum tolerable dose we have assembled a number of data taken from the literature plus some measurements of our own which cover ranges of resolution that are not well covered otherwise. The conclusion of this study is that, based on the natural contrast between protein and water and “Rose-criterion” image quality, one should be able to image a frozen-hydrated biological sample using XDM at a resolution of about 10 nm.

Anomalous X-ray scattering studies on superionic glassy (As 2Se 3)-(AgX) systems (X = halides)

Anomalous X-ray scattering experiments for glassy room-temperature superionic conductors (As 2Se 3) 0.4 (AgI) 0.6 and (As 2Se 3) 0.4(AgBr) 0.6 were performed close to the As, Se, Ag, and Br K edges using a third-generation synchrotron radiation facility, ESRF. The differential structure factors, Δ iS ( Q), were obtained from detailed analyses, indicating that Δ As S( Q) and Δ Se S( Q) of both the glassy superionic semiconductors are similar to those of glassy As 2 Se 3 except the prepeak in Δ Se S( Q). The Δ Ag S( Q) spectrum of (As 2Se 3) 0.4 (AgI) 0.6 looks molten salt-like. However, the Δ Ag S( Q) of (As 2Se 3) 0.4(AgBr) 0.6 glass have quite different features from that of (As 2Se 3) 0.4 (AgI) 0.6 glass in the low Q range, and the Δ Br S( Q) has even a pre-shoulder around 13 nm − 1 unlike molten salts. In the differential pair distribution functions Δ i g( r) obtained from the Fourier transforms of Δ iS ( Q), the first peaks of Δ As g( r) and Δ Se g( r) show no correlation with those of Δ Ag g( r) and Δ Br g( r), and vice versa. From these results, it can be concluded that a pseudo-binary mixture of the As 2Se 3 network matrix and AgX-related ionic conduction pathways is a good structural model for these superionic glasses. Differences between the AgBr- and AgI mixtures were found in the second-neighbor structures around the Ag atoms, which may reflect those in the crystal structures of the AgX salts.

Excitation curve calibration for the SSRF booster magnets and applications in the commissioning

The Shanghai Synchrotron Radiation Facility (SSRF) is a low emittance third-generation synchrotron radiation light source under commissioning. The excitation curve calibration for the booster magnets is important to provide the magnet current configurations as reference. Calibration studies give the polynomial coefficients of each type of magnets and provide the magnet current configurations under different beam energies as beam is ramped at speed of 2 Hz. The applications of calibration in booster commissioning which show the accuracy of the magnetic excitation curve calibration are also discussed.

Differential phase contrast with a segmented detector in a scanning X-ray microprobe

Scanning X-ray microprobes are unique tools for the nanoscale investigation of specimens from the life, environmental, materials and other fields of sciences. Typically they utilize absorption and fluorescence as contrast mechanisms. Phase contrast is a complementary technique that can provide strong contrast with reduced radiation dose for weakly absorbing structures in the multi-keV range. In this paper the development of a segmented charge-integrating silicon detector which provides simultaneous absorption and differential phase contrast is reported. The detector can be used together with a fluorescence detector for the simultaneous acquisition of transmission and fluorescence data. It can be used over a wide range of photon energies, photon rates and exposure times at third-generation synchrotron radiation sources, and is currently operating at two beamlines at the Advanced Photon Source. Images obtained at around 2 keV and 10 keV demonstrate the superiority of phase contrast over absorption for specimens composed of light elements.

Transverse coherence properties of X-ray beams in third-generation synchrotron radiation sources

This article describes a complete theory of spatial coherence for undulator radiation sources. Current estimations of coherence properties often assume that undulator sources are quasi-homogeneous, like thermal sources, and rely on the application of the van Cittert–Zernike theorem for calculating the degree of transverse coherence. Such assumption is not adequate when treating third generation light sources, because the vertical (geometrical) emittance of the electron beam is comparable or even much smaller than the radiation wavelength in a very wide spectral interval that spans over four orders of magnitude (from 0.1 up to 10 3 Å ). Sometimes, the so-called Gaussian–Schell model, that is widely used in statistical optics in the description of partially coherent sources, is applied as an alternative to the quasi-homogeneous model. However, as we will demonstrate, this model fails to properly describe coherent properties of X-ray beams from non-homogeneous undulator sources. As a result, a more rigorous analysis is required. We propose a technique, based on statistical optics and Fourier optics, to explicitly calculate the cross-spectral density of an undulator source in the most general case, at any position after the undulator. Our theory, that makes consistent use of dimensionless analysis, allows relatively easy treatment and physical understanding of many asymptotes of the parameter space, together with their region of applicability. Particular emphasis is given to the asymptotic situation when the horizontal emittance is much larger than the radiation wavelength, and the vertical emittance is arbitrary. This case is practically relevant for third generation synchrotron radiation sources.

The barium giant dipole resonance in barite: a study of soft X-ray absorption edges using hard X-rays

Giant dipole resonances are collective phenomena which can be found in systems ranging from atoms through clusters to solids. In atomic and solid state physics such excitations are usually studied by soft X-ray absorption, photoelectron and electron energy-loss spectroscopies. With the advent of third-generation synchrotron radiation sources, nonresonant inelastic X-ray scattering became a prominent tool to study truly bulk sensitive shallow absorption edges with high energy photons. The method is not limited to measuring dipole transitions but allows the study of final states of different symmetry due to monopole and quadrupole transitions employing its momentum-transfer dependence. In this paper the potential of nonresonant inelastic X-ray scattering to probe low-energy excitations is emphasized with the focus on symmetry selectivity, study of liquids and high pressure applications. As an example, nonresonant inelastic X-ray scattering spectra of the barium 4d-f giant dipole resonance in barite are discussed.

Ｘ線分光の現在 ＶＩ．Ｘ線でフォノンを見る―主として不規則系について

Recently, studies of phonons by inelastic x-ray scattering (IXS) technique with a high energy resolution of meV order have considerably developed by using an excellent technique for utilizing third-generation synchrotron radiation facilities and recent progress of semiconductor technique. In this article, the history of studies of phonons using x-rays, the principle of IXS and the advantage (disadvantage) of IXS are briefly reviewed by comparing to inelastic neutron scattering, and an excellent IXS spectrometer installed at the beamline BL35XU of the SPring-8 is introduced. Finally, examples of recent studies performed at BL35XU/SPring-8 are introduced in mainly disordered systems.

The MEM/Rietveld method with nano-applications – accurate charge-density studies of nano-structured materials by synchrotron-radiation powder diffraction

Structural studies of materials with nano-sized spaces, called nano-structured materials, have been carried out by high-resolution powder diffraction. Our developed analytical method, which is the combination of the maximum-entropy method (MEM) and Rietveld refinement, the so-called MEM/Rietveld method, has been successfully applied to the analysis of synchrotron-radiation (SR) powder diffraction data measured at SPring-8, a third-generation SR light source. In this article, structural studies of nano-porous coordination polymers and endohedral metallofullerenes are presented with the advanced technique of SR powder experiment. The structure of the adsorbed guest molecule in the coordination polymer and encapsulated atoms in the fullerene cage are clearly revealed by the MEM charge density. The methodology of MEM/Rietveld analysis is also presented.

Wavelet-based local region-of-interest reconstruction for synchrotron radiation x-ray microtomography

Synchrotron radiation x-ray microtomography is becoming a uniquely powerful method to nondestructively access three-dimensional internal microstructure in biological and engineering materials, with a resolution of 1μm or less. The tiny field of view of the detector, however, requires that the sample has to be strictly small, which would limit the practical applications of the method such as in situ experiments. In this paper, a wavelet-based local tomography algorithm is proposed to recover a small region of interest inside a large object only using the local projections, which is motivated by the localization property of wavelet transform. Local tomography experiment for an Al–Cu alloy is carried out at SPring-8, the third-generation synchrotron radiation facility in Japan. The proposed method readily enables the high-resolution observation for a large specimen, by which the applicability of the current microtomography would be promoted to a large extent.