White Synchrotron Radiation Research Articles

Large-view x-ray imaging for medical applications using the world’s only vertically polarized synchrotron radiation beam and a single asymmetric Si crystal

Objective. X-ray microangiography provides detailed information on the internal structure and function of a biological subject. Its ability to evaluate the microvasculature of small animals is useful for acquiring basic and clinical medical knowledge. The following three conditions are necessary to attain detailed knowledge of biological functions: (1) high temporal resolution with sufficient x-ray intensity, (2) high spatial resolution, and (3) a wide field of view. Because synchrotron radiation microangiography systems provide high sapatial resolution and high temporal resolution as a result of their high x-ray intensity, such systems have been developed at various synchrotron radiation facilities, starting with the photon factory, leading to numerous medical discoveries. However, the three aforementioned functions are incompatible with the use of synchrotron radiation because the x-ray intensity decreases when a wide field of view is obtained. To overcome these problems, we developed a new x-ray optical system for microangiography in rats using synchrotron radiation x-rays. Approach. Instead of using monochromatic synchrotron radiation x-rays with a conventional double-crystal monochromator, we used white synchrotron radiation x-rays and an asymmetric Si crystal to simultaneously monochromatize the beam and widen the field of view. Main results. The intensity profile and spatial resolution of the x-ray images were then evaluated. The proposed x-ray optics increased the x-ray intensity and beam width by factors of 1.3 and 2.7, respectively, compared with those of conventional monochromatic x-rays. In addition, in vivo studies on microangiography in rats were performed to confirm that the images had sufficient intensity, spatial resolution, and field of view. One of a series of images taken at 50 ms frame−1 was shown as an example. Significance. This x-ray optics provides sufficient x-ray intensity, high spatial resolution, and a wide field of view. This technique is expected providing new insights into the evaluation of the vascular system.

Evaluation of high intensity synchrotron radiation x-ray imaging using Si crystals with lapped surface at 33.3 keV.

In x-ray imaging methods, such as synchrotron radiation microangiography, the x-ray intensity has become more important in recent years for real-time dynamic observations to evaluate temporal changes in samples. Many synchrotron radiation facilities use x-rays monochromated by diffraction from perfect Si crystals to improve the spatial resolution of x-ray images and obtain detailed information about a sample. In this paper, monochromatic synchrotron x-ray images were acquired using Si crystals lapped with abrasives to enhance the x-ray intensity using white synchrotron radiation x-rays for observing dynamic changes in samples. The x-ray intensity, spatial resolution, and contrast noise ratio (CNR) in the acquired x-ray images were quantitatively evaluated using a state-of-the-art high-spatial-resolution detector. The x-ray intensity was substantially increased by a factor of ∼8 when a lapped Si crystal was used. When the lapped Si crystal was used, the spatial resolution of x-ray images in the diffraction-plane direction was ∼70% lower than when an etched Si crystal was used at a spatial resolution of 10 lp/mm. By contrast, the CNR in x-ray images, which is important for observing the interior of a sample, increased threefold when a contrast agent containing iodine at a concentration of 38 wt. % was used. It was confirmed that the combination of white synchrotron radiation x-rays and a lapped crystal produces an intense monochromatic x-ray, providing an important evaluation for the use of optics for each research purpose.

Multi-beam X-ray optical system for high-speed tomography using a σ-polarization diffraction geometry

A multi-beam X-ray optical system using a σ-polarization diffraction geometry is proposed and its potential for high-speed tomography using synchrotron radiation is experimentally evaluated. Projection images of a sample are obtained simultaneously from different directions with X-ray beams generated by diffraction of a white synchrotron radiation beam at silicon single crystals. This makes it possible to record a tomographic dataset without rotation of the sample or X-ray source. Data sets of two samples obtained in a proof-of-principle experiment with an exposure time of 1 ms were successfully reconstructed using an advanced compressed-sensing algorithm.

Development of multi-beam optics for time-resolved X-ray tomography: from π-polarization to σ-polarization

A multi-beam X-ray optics that can image a sample from different directions in a large angular range simultaneously without sample rotation is reported. It consists of 28 thin silicon crystals that are arranged in a σ-polarization diffraction geometry so that the diffracted X-rays from an incident white synchrotron radiation beam pass through the sample. A tomogram of a simple test sample was calculated from projection images recorded with the optics, showing that an alignment accuracy sufficient for X-ray tomography can be achieved.

In-situ investigation of strain relaxation in an Al/Si–MMC using high energy synchrotron radiation

AbstractThermal and mechanical loading induce phase specific strains/stresses in MMCs. At elevated temperature part of the phase-specific strains/stresses relax. The relaxation of the phase-specific strains/stresses is determined by in-situ experiments using white high-energy synchrotron radiation. The experiments reveal that such time-resolved strain measurements are possible and that short-time phenomena can be accessed using white high-energy synchrotron radiation. The elastic strain relaxation behavior is similar for all lattice planes accessed. The influence of the temperature on the characteristic relaxation time is determined. The characteristic relaxation time appears to be independent of the amount of plastic deformation the sample suffers before strain/stress relaxation.

Time-resolved x-ray stroboscopic phase tomography using Talbot interferometer for dynamic deformation measurements.

Time-resolved x-ray phase tomography using a Talbot interferometer and white synchrotron radiation can provide a three-dimensional movie for visualizing the structural change of materials consisting of light elements. In this study, time-resolved x-ray stroboscopic phase tomography using a Talbot interferometer is demonstrated for a vibrating object under 24Hz compression-stretch fatigue loading. Moiré patterns are recorded by synchronizing drivers for a shutter, grating displacement, and sample rotation with an x-ray camera with a 200 µs exposure, and phase tomograms are reconstructed at specific motion phases of the vibration. The measurement lasts for a few minutes and the δ value changes before breaking, which is considered due to plastic deformation of soft materials under external vibration are depicted three-dimensionally.

Development of scanning X-ray fluorescence microscope using KB mirror and white synchrotron radiation at SAGA Light Source

A scanning X-ray fluorescence microscope that uses a Kirkpatrick-Baez (KB) mirror and white synchrotron radiation (SR) was developed for obtaining detailed elemental maps within a micro-meter order. The KB mirror is a total reflection mirror, and the white X-rays are focused at a focus point without chromatic aberration. Therefore, the proposed microscope can use strong white and/or pink SR and enable elemental mapping within a practical measurement time at small synchrotron facilities. A feasibility study on the developed microscope was performed by using white SR at the SAGA Light Source in Tosu, Japan. By using the developed microscope, an X-ray microbeam 1 μm in diameter was successfully formed, and a fine elemental map of a Cu mesh and a seed of eustoma were obtained.

X-ray topographic study of Bridgman-grown CdZnTeSe

We have characterized the structural quality of Cd0.9Zn0.1Te0.93Se0.07 ingot grown by the vertical Bridgman growth technique. The structural quality of Cd0.9Zn0.1Te0.93Se0.07 ingot along the length was investigated via X-ray topography in the reflection mode using a white beam synchrotron radiation source. The X-ray topography data revealed the presence of very few sub grain boundaries and no sub-grain boundary network for the CdZnTeSe samples used in this study.

A multi-beam X-ray imaging detector using a branched optical fiber bundle

We developed a multi-beam X-ray imaging detector, consisting of four scintillator screens connected by a branched optical fiber bundle with a CMOS camera. By using the detector and a multi-beam imaging optics with silicon single crystalline blades designed for a white synchrotron radiation source, we successfully demonstrated multi-beam X-ray imaging with an exposure time of 1 ms. The long and flexible optical fiber bundle used for the detector enables us to realize high-speed multi-beam X-ray imaging with high flexibility at a relatively low cost.

Development of pink-beam 4D phase CT for in-situ observation of polymers under infrared laser irradiation

Four-dimensional phase computed tomography (4D phase CT) by an X-ray Talbot interferometer (XTI) with white synchrotron radiation has ever been demonstrated at a temporal resolution of about 1 s for soft-matter samples. However, the radiation damage to samples caused by white synchrotron radiation occasionally hampers our understanding of the sample dynamical properties. Based on the fact that XTI functions with X-rays of a bandwidth up to ca. 10% with performance comparable to that by monochromatic X-rays, filtering white synchrotron radiation to generate a ‘pink-beam’ of a 10% bandwidth is effective to reduce radiation damage without degrading the image quality and temporal resolution. We have therefore developed pink-beam 4D phase CT at SPring-8, Japan by installing a multilayer mirror with a 10% bandwidth and a 25 keV central photon energy. XTI optimal at this photon energy was built downstream, and a CMOS-based X-ray detector was used to achieve fast image acquisitions with an exposure time of 1 ms (or 0.5 ms) per moiré image. The resultant temporal resolution of pink-beam 4D phase CT was 2 s (1 s). We applied the pink-beam 4D phase CT to in-situ observation of polypropylene, poly(methyl methacrylate), and polycarbonate under infrared laser irradiation (1064 nm). The dynamics of melting, bubbling, and ashing were successfully visualized in 3D movies without problematic radiation damage by synchrotron radiation.

Development of an X-ray imaging system to preventscintillator degradation for white synchrotron radiation.

The high flux of the white X-ray beams from third-generation synchrotron light sources can significantly benefit the development of high-speed X-ray imaging, but can also bring technical challenges to existing X-ray imaging systems. One prevalent problem is that the image quality deteriorates because of dust particles accumulating on the scintillator screen during exposure to intense X-ray radiation. Here, this problem has been solved by embedding the scintillator in a flowing inert-gas environment. It is also shown that the detector maintains the quality of the captured images even after days of X-ray exposure. This modification is cost-efficient and easy to implement. Representative examples of applications using the X-ray imaging system are also provided, including fast tomography and multimodal phase-contrast imaging for biomedical and geological samples.

A Novel and Modern Experimental Approach to Vibrational Circular Dichroism Spectroscopy and Video Spectroscopy Comparative Study on Malignant and Benign Human Cancer Cells and Tissues with the Passage of Time under White and Monochromatic Synchrotron Radiation

A Novel and Modern Experimental Approach to Vibrational Circular Dichroism Spectroscopy and Video Spectroscopy Comparative Study on Malignant and Benign Human Cancer Cells and Tissues with the Passage of Time under White and Monochromatic Synchrotron Radiation

Applications of a pnCCD detector coupled to columnar structure CsI(Tl) scintillator system in ultra high energy X-ray Laue diffraction

Most charge coupled devices (CCDs) are made of silicon (Si) with typical active layer thicknesses of several microns. In case of a pnCCD detector the sensitive Si thickness is 450 μm. However, for silicon based detectors the quantum efficiency for hard X-rays drops significantly for photon energies above 10 keV . This drawback can be overcome by combining a pixelated silicon-based detector system with a columnar scintillator. Here we report on the characterization of a low noise, fully depleted 128×128 pixels pnCCD detector with 75×75 μm2 pixel size coupled to a 700 μm thick columnar CsI(Tl) scintillator in the photon range between 1 keV to 130 keV . The excellent performance of the detection system in the hard X-ray range is demonstrated in a Laue type X-ray diffraction experiment performed at EDDI beamline of the BESSY II synchrotron taken at a set of several GaAs single crystals irradiated by white synchrotron radiation. With the columnar structure of the scintillator, the position resolution of the whole system reaches a value of less than one pixel. Using the presented detector system and considering the functional relation between indirect and direct photon events Laue diffraction peaks with X-ray energies up to 120 keV were efficiently detected. As one of possible applications of the combined CsI-pnCCD system we demonstrate that the accuracy of X-ray structure factors extracted from Laue diffraction peaks can be significantly improved in hard X-ray range using the combined CsI(Tl)-pnCCD system compared to a bare pnCCD.

Nondestructive separation of residual stress and composition gradients in thin films by angle- and energy-dispersive X-ray diffraction. I. Theoretical concepts

Different X-ray measurement and data evaluation concepts are presented, which allow for residual stress analysis in thin films with pronounced gradients in chemical composition. These gradients lead to a variation in the strain-free lattice parameter a 0 with respect to the film thickness and superimpose the lattice strain induced by the film's inherent stresses. Non-consideration of a 0(z) gradients is shown to lead to considerable errors (`ghost stresses') in the residual stress depth profiles. With the simulated example of a TiC x N1−x film with a pronounced carbon gradient, the first part of this series introduces four approaches, which permit the separation of residual stress and composition depth distributions at different levels of approximation. They are based on lattice spacing depth profile measurements performed in either the sin2ψ mode or the scattering vector mode, or in combinations of these two scanning modes. Depending on the approach used for separating the residual stress and composition gradients, angle- or energy-dispersive diffraction has to be applied, employing monochromatic X-ray sources available in the laboratory or either white high-energy synchrotron radiation or the Bremsstrahlung of conventional X-ray tubes, respectively. The methods introduced here assume a biaxial residual stress state within the film. For a triaxial residual stress state with σ33 ≠ 0, a separation of stress and composition gradients is not straightforward, because an a 0(z) gradient cannot be distinguished from the hydrostatic part of the stress tensor.

Application of a pnCCD for energy-dispersive Laue diffraction with ultra-hard X-rays

In this work the spectroscopic performance of a pnCCD detector in the ultra-hard energy range between 40 and 140 keV is tested by means of an energy-dispersive Laue diffraction experiment on a GaAs crystal. About 100 Bragg peaks were collected in a single-shot exposure of the arbitrarily oriented sample to white synchrotron radiation provided by a wiggler at BESSY II and resolved in a large reciprocal-space volume. The positions and energies of individual Laue spots could be determined with a spatial accuracy of less than one pixel and a relative energy resolution better than 1%. In this way the unit-cell parameters of GaAs were extracted with an accuracy of 0.5%, allowing for a complete indexing of the recorded Laue pattern. Despite the low quantum efficiency of the pnCCD (below 7%), experimental structure factors could be obtained from the three-dimensional data sets, taking into account photoelectric absorption as well as Compton scattering processes inside the detector. The agreement between measured and theoretical kinematical structure factors calculated from the known crystal structure is of the order of 10%. The results of this experiment demonstrate the potential of pnCCD detectors for applications in X-ray structure analysis using the complete energy spectrum of synchrotron radiation.

Fast GPU-based absolute intensity determination for energy-dispersive X-ray Laue diffraction

This paper presents a novel method for fast determination of absolute intensities in the sites of Laue spots generated by a tetragonal hen egg-white lysozyme crystal after exposure to white synchrotron radiation during an energy-dispersive X-ray Laue diffraction experiment. The Laue spots are taken by means of an energy-dispersive X-ray 2D pnCCD detector. Current pnCCD detectors have a spatial resolution of 384 × 384 pixels of size 75 × 75 μm2 each and operate at a maximum of 400 Hz. Future devices are going to have higher spatial resolution and frame rates.The proposed method runs on a computer equipped with multiple Graphics Processing Units (GPUs) which provide fast and parallel processing capabilities. Accordingly, our GPU-based algorithm exploits these capabilities to further analyse the Laue spots of the sample. The main contribution of the paper is therefore an alternative algorithm for determining absolute intensities of Laue spots which are themselves computed from a sequence of pnCCD frames. Moreover, a new method for integrating spectral peak intensities and improved background correction, a different way of calculating mean count rate of the background signal and also a new method for n-dimensional Poisson fitting are presented.We present a comparison of the quality of results from the GPU-based algorithm with the quality of results from a prior (base) algorithm running on CPU. This comparison shows that our algorithm is able to produce results with at least the same quality as the base algorithm. Furthermore, the GPU-based algorithm is able to speed up one of the most time-consuming parts of the base algorithm, which is n-dimensional Poisson fitting, by a factor of more than 3. Also, the entire procedure of extracting Laue spots' positions, energies and absolute intensities from a raw dataset of pnCCD frames is accelerated by a factor of more than 3.

Characterization of crystal lattice defects in calcium molybdate single crystals (CaMoO4) by means of X‐ray diffraction topography

Calcium molybdate CaMoO4 crystals are perspective materials for many applications in acoustic‐electronics, acoustic‐optics and nonlinear optics. They are also used as laser hosts, scintillators, different kinds of substrates and active elements of ionizing radiation detectors. For all these applications large‐sized single crystals of high structural quality are required.The samples of CaMoO4 crystals have been investigated by means of synchrotron white beam topography, monochromatic beam topography and conventional X‐ray Lang projection topography. The high‐resolution rocking curves have also been taken using synchrotron and conventional arrangements.The topographs showed a rather good crystallographic perfection of the crystals. In particular, they did not reveal any segregation fringes proving high homogeneity of the chemical composition. Relatively high densities (<104 cm−2) of weak point‐like diffraction contrasts were observed, which can be most probably interpreted as dislocation outcrops.The distinct main imperfection of the investigated crystals was variously developed block structure. The evaluation of lattice misorientation was realized by means of projection and section white beam synchrotron radiation topographs. The evaluated misorientation between various blocks was in the range of several arc minutes. Copyright © 2015 John Wiley & Sons, Ltd.

Resonance effect in white X-ray magnetic diffraction of GdAl2

Using elliptically polarized white synchrotron radiation and an energy-sensitive detector, the 444 reflection from a single-crystal sample of the ferromagnetic compound GdAl2 magnetized along the scattering vector has been measured, and the asymmetry of the diffraction intensity upon the magnetization reversal has been studied in the X-ray energy range across the Gd L II edge. The dependence of the magnetic asymmetry on the scattering angle or on the X-ray energy is understood as the superposition of the sharp near-edge structure and the much broader component arising from the interference between the electric scattering and the resonant and nonresonant magnetic scattering, respectively. To interpret the experimental results, an analytical treatment of the magnetic asymmetry is developed, and in the course of the analysis it is pointed out that in general the pseudo-extinction of the Bragg reflection due to the dispersion effects can be utilized as a technique to raise the magnetic sensitivity in the X-ray scattering from ferromagnetic materials. The potential of an unconventional approach to the resonant X-ray scattering using a white beam, as is clearly demonstrated by the present experiment, is also discussed.

Residual Stress Analysis of Cold-drawn Pearlite Steel Wire Using White Synchrotron Radiation

Residual Stress Analysis of Cold-drawn Pearlite Steel Wire Using White Synchrotron Radiation

Synchrotron radiation x-ray topography and defect selective etching analysis of threading dislocations in GaN

The crystal quality of bulk GaN crystals is continuously improving due to advances in GaN growth techniques. Defect characterization of the GaN substrates by conventional methods is impeded by the very low dislocation density and a large scale defect analysis method is needed. White beam synchrotron radiation x-ray topography (SR-XRT) is a rapid and non-destructive technique for dislocation analysis on a large scale. In this study, the defect structure of an ammonothermal c-plane GaN substrate was recorded using SR-XRT and the image contrast caused by the dislocation induced microstrain was simulated. The simulations and experimental observations agree excellently and the SR-XRT image contrasts of mixed and screw dislocations were determined. Apart from a few exceptions, defect selective etching measurements were shown to correspond one to one with the SR-XRT results.