Journal of Synchrotron Radiation最新文献

Printer toner is a fine powder material essential for fixing digital information on paper during the electrostatic digital printing process. To achieve fine printing, toner particles are composed of colored pigments, dyes, polymers, charge control agents and other surfactants. Toner particles have approximate dimensions of 5-10 µm. Therefore, the distribution of the constituents cannot be observed by transmission electron microscopy. In this study, we visualized the three-dimensional structure of a 5 µm-sized printer toner particle using cryogenic X-ray diffraction imaging tomography. A particle adsorbed on a silicon nitride membrane was rotated in the angular range from -78° to +78° against the direction of the incident X-rays at an angular step of 0.5°. From the 313 diffraction patterns collected, we reconstructed the three-dimensional electron density distribution of the toner particle at a resolution of 141 nm. The particle was wedge-shaped. The electron density distribution inside the particle was non-uniform. The high-electron-density regions were distributed near the surface. These formed a V-shaped structure at the tip of the wedge. With the help of powder diffraction, the high-electron-density regions were interpreted as microcrystals of silicon dioxide. Silicon dioxide crystals function as cleavage sites for toner particles prepared by the milling method. Based on the present results, we discuss the implications of the structure and methods to visualize it at a higher resolution.

Conventional beam intensity monitor technologies, such as `gold-meshes' and `diamond conductive thin films', currently applied to tender and soft X-ray beams, encounter numerous application challenges, including diffraction effects, low signal strength, non-uniform transparency, and lack of position information. This study explores the potential of very thin (<2 µm) silicon carbide free-standing membranes, as in-line, minimally interfering beam intensity and position monitors, with high-lateral resolution, for soft and tender X-ray beamlines. Initial experimental assessments were conducted at the NanoMAX beamline at MAX IV to analyze the performance of such very thin devices in monitoring tightly focused (<1 µm FWHM) beams. The tests revealed that employing four-quadrant sensor layouts on such thin sensors resulted in significant charge collection losses in the regions between the quadrants and, under high electric field conditions, in charge multiplication effects (avalanche effects). Through Sentaurus TCAD theoretical simulations, the limitations of the four-quadrant design for such applications and the potential of an alternative technology (resistive X-ray beam postion monitor) were clarified.

In the first part of this paper, quantitative aspects of propagation-based phase-contrast imaging (PBI) were investigated using theoretical and numerical approaches, as well as experimental two-dimensional PBI images collected with plane monochromatic X-rays at a synchrotron beamline. In this second part, signal-to-noise ratio, spatial resolution and contrast are studied in connection with the radiation dose in three-dimensional PBI images of breast tissue samples obtained using propagation-based phase-contrast computed tomography (PB-CT) with energy-integrating and photon-counting detectors. The analysis is based on the theory of PBI and PB-CT using the homogeneous Transport of Intensity equation (Paganin's method). A biomedical X-ray imaging quality characteristic, suitable for quantitative assessment of X-ray images of biological samples, is introduced and applied. The key factors leading to high values of the biomedical X-ray imaging quality in PBI and to relatively low values of the same quality metric in CT imaging are identified and discussed in detail. This study is aimed primarily at developing tools for quantitative assessment and optimization of medical PB-CT imaging, initially at synchrotron facilities, with the prospect of subsequent transfer of the technology to medical clinics.

Nano-laminography combines the penetrating power of hard X-rays with a tilted rotational geometry to deliver high-resolution, three-dimensional images of laterally extended, flat specimens that are otherwise incompatible with, or difficult to image using, conventional nano-tomography. In this work, we demonstrate a full-field, X-ray nano-laminography system implemented with the transmission X-ray microscope at beamline 32-ID of the upgraded Advanced Photon Source at Argonne National Laboratory, USA. By rotating the sample around an axis inclined by 20° to the incident beam, the technique minimizes the long optical path lengths that would otherwise generate excessive artifacts when planar samples are imaged edge-on. The efficiency of the technique is demonstrated with 50 nm spatial resolution and minute-scale temporal resolution 3D imaging of a planar integrated circuit sample and targeted imaging of an individual particle within a powder sample, where mounting procedures are typically challenging in regular nano-tomography. The sample mounting strategy, data acquisition, and reconstruction method will also be discussed.

Diffraction anomalous fine structure spectroscopy (DAFS) is a well established technique for characterizing the local structure of elements embedded in complex interfaces and templates when crystallographic and/or site selectivity is needed. DAFS has been effectively applied in the hard X-ray range, where reciprocal space is extended and the absorption edges of the chemical elements are usually well spaced. In this work, we extend the use of DAFS to the tender X-ray range. This energy range is important since it includes the L-edges of second row transition metal elements, which are constituents of functional oxide materials; and some important edges for semiconductors. We present a study of the Nb L-edges in PbSc_0.5Nb_0.5O₃ relaxor ferroelectric oxide, where the use of superstructure reflections provides access to the ordered part of the sample.

The effects of varying intensities of Australian Synchrotron source terahertz (THz) radiation on pheochromocytoma (PC 12) neuronal cells were investigated. PC 12 cells were exposed to THz radiation at beam incident power intensities of 0.25 W m^-2 (low intensity, LI), 0.5 W m^-2 (medium intensity, MI) and 1 W m^-2 (high intensity, HI) for 10 min. After exposure, the morphological and physiological status of the cells was evaluated using scanning electron microscopy (SEM) and confocal laser scanning microscopy. SEM imaging revealed that, after exposure to LI THz radiation, the cells exhibited membrane protrusions (blebs) measuring 70-120 nm in diameter. In contrast, cells exposed to HI THz radiation demonstrated increased uptake of FITC-dextran and nanospheres. Analysis of single-cell populations counterstained with 4',6-diamidino-2-phenylindole (DAPI) showed a decrease in the proportion of DAPI-positive cells, with approximately 90, 80 and 50% remaining positive after exposure to LI, MI and HI THz radiation, respectively. However, only a slight increase in the proportion of dead cells was observed at varying THz intensities. Proteomic analysis of the cell changes following exposure to LI and HI THz irradiation indicated that THz radiation activated the CaN complex and upregulated genes involved in ribosome biogenesis and DNA damage repair.

The Tender X-ray Beamline (TEX), using a bending magnet as a light source, is the first beamline of the High Energy Photon Source (HEPS) to undergo commissioning. It covers an energy range from 2.1 keV to 11 keV. Dynamic diagnostic tools have been installed and can measure the photon flux, energy resolution and position stability. By use of these tools, TEX was found to achieve a photon flux of up to 9 × 10¹¹ photons s^-1, with an energy resolution of 5904 @ 3203.6 eV and position stability lower than ±3 µm (horizontal) × 15 µm (vertical). In this paper, the diagnostic process of the beamline and its performance will be introduced in detail.

In X-ray scattering tensor tomography at large scattering angles, the absorption of scattered X-rays by the sample itself is anisotropic due to the macroscopic geometry of the sample. This effect is mostly ignored or only treated approximately in established reconstruction algorithms. In this paper we perform a simulation study to estimate the severity of the problem and suggest and test a computational approach to correct for this effect. We also investigate experimental scattering data from hydroxyapatite scattering from a piece of beaver tooth where the same trends from the simulations can be observed. We conclude that the conventional approach to transmission correction yields good results at scattering angles and levels of absorption normally used.

The newest seven members of the Editorial Board of Journal of Synchrotron Radiation are introduced.

A sustainable and robust supply chain of rare earth elements (REEs) is necessary to meet our consumer, national security and clean energy goals. However, current intra-REE separation technologies (e.g. solvent extraction) are costly and carry a heavy environmental burden. Therefore, the development of new aqueous based ligands that are selective for individual REEs will be integral in future REE production systems. To develop these ligands, an understanding of how ligand coordination structure relates to selectivity is imperative. We used X-ray absorption spectroscopy (XAS) to observe the local structure around four lanthanide (Ln) ions (La, Ce, Pr and Nd) complexed by water and several relevant chelating ligands [lanmodulin EF-hand 1 peptides (LanM1), ethylenediaminetetraacetic acid (EDTA), aminotris(methylenephosphonic acid) (ATMP) and citric acid]. To collect these liquid-phase XAS spectra, we developed a new flow cell that prevents bubble interference and beam damage to the samples. In the X-ray absorption near-edge structure (XANES), we observed energy shifts in the white line, white line broadening and differences in the white line intensity of different Ln-ligand complexes between ligands. In the extended X-ray absorption fine structure (EXAFS), we distinguished differences in peak intensity and distance between coordinating ligands. Differences in the local coordination structure between Ln-LanM1 peptide complexes were more subtle compared with the other ligands (La-water, La-EDTA, La-ATMP and La-citric acid complexes). Further XANES and EXAFS studies, in combination with modelling and other techniques, could greatly improve our structural knowledge of how these aqueous ligands bind Ln ions and how they can be used to design more selective ligands for more efficient and sustainable REE separations.