Journal of Synchrotron Radiation最新文献

Due to their superior fatigue strength, martensitic steels are the material of choice for high cyclic loading applications such as coil springs. However, crack propagation is influenced by residual stresses and their interaction is poorly understood. In fact, linear elastic fracture mechanics predicts unphysical singularities in the strain around the crack tip. In this study, we have combined synchrotron-based X-ray diffraction, X-ray fluorescence and optical microscopy to map the factual strain fields around crack tips with micrometre spatial resolution. X-ray fluorescence and optical images were co-registered to locate the crack in the X-ray diffraction maps. Observed crystal recovery close to cracks confirmed that the diffraction signal originates at least in part from the cracks. The retrieved local strain field around the crack was further improved by averaging information over carefully selected diffraction peaks. This procedure provided strain maps around crack tips with a spatial resolution of about 1 µm and may enable heuristic predictions of further crack growth.

The BL46XU beamline of SPring-8 has been reorganized into a beamline dedicated to hard X-ray photoelectron spectroscopy (HAXPES) to meet the increasing demand for various HAXPES based measurements. Two specialized HAXPES instruments, namely, (i) a high-throughput HAXPES system specialized for automated measurements and (ii) an ambient pressure HAXPES system with a focus on measurements under a gas atmosphere, provide advanced capabilities for characterizing bulk-sensitive electronic and chemical states in a variety of research fields. To enhance the capabilities further, several X-ray optical instruments have been introduced. Two types of double channel-cut monochromators [Si(220) and Si(311)] have been installed in the optics hutch, allowing users to select the optimum energy resolution and flux in a wide photon-energy range (4.9-21.8 keV) while keeping a fixed-exit condition. In addition, a focusing mirror to provide a high-flux microbeam has been arranged for each HAXPES system. In this article, the design and performance of the beamline as well as some recent scientific results are outlined.

The Ultrafast Transient Experimental Facility (UTEF) at Chongqing University is constructing a next-generation angle-resolved photoemission spectroscopy (ARPES) beamline designed to simultaneously achieve sub-meV energy resolution, continuous photon energy tunability (10-40 eV), high photon flux (>10¹² photons s^-1 at the sample position), full polarization control, and ultra-low-temperature sample environments (<1.5 K). Leveraging the unique advantages of UTEF's low-energy (0.5 GeV), high-beam-current (500-1000 mA) storage ring, the beamline is capable of generating high-flux EUV radiation, enabling detailed exploration of complex quantum materials. The beamline employs two high-groove-density gratings and one low-groove-density grating to achieve, respectively, an energy resolving power exceeding 100000 and photon fluxes greater than 5×10¹³ photons s^-1. A dual-endstation layout enables flexible operation for both ultra-high-resolution measurements at ultra-low temperatures and large-angle, high-flux spin-resolved experiments. Through comprehensive optical optimization-including mirror coatings, customized grating groove profiles and precision focusing geometry-the system can deliver photon flux exceeding 10¹⁴ photons s^-1 (0.1% bandwidth)^-1 with a spatial beam spot size of approximately 30 µm, while maintaining sub-0.4 meV energy resolution. This work presents the optical design and projected performance of the UTEF ARPES beamline.

In this contribution, we present a compact differential pumping unit with apertures ≥500 µm. It allows windowless operation for in-air sample environments as well as to connect low-quality in-vacuum sample environments to the beamline UHV (≤10^-8 mbar) section. The unit also protects the UHV section of the beamline from accidental venting due to operator errors. To simplify the design, an adjustment-free series of pinholes is used. The positioning of the apertures relies on tight machining tolerances. The assembly consists of just eight parts: one main aluminium body, four threaded cylinders with apertures and three covers with links to pumping units assembled with Viton seals. The overall footprint is restricted to 368 mm on the beam axis.

This study develops an integrated X-ray absorption spectroscopy (XAS) photoemission electron microscopy (PEEM) platform on beamline BL09U at the Shanghai Synchrotron Radiation Facility (SSRF), enabling nanoscale characterization of complex materials through energy-resolved imaging and local-area XAS. By using the wide range of energy tunability, full access to different polarizations and PEEM's surface sensitivity, we have established a gap-monochromator control system under the EPICS framework to synchronize the elliptically polarized undulator (EPU) gap and monochromator energy dynamically, optimizing photon flux stability for absorption fine structure analysis. Combining X-ray magnetic circular dichroism (XMCD) and X-ray magnetic linear dichroism (XMLD) with PEEM and local-area XAS, this platform achieves concurrent mapping of electronic structures and magnetic domains in ferromagnetic nano-patterns, as demonstrated through our studies of Ni₈₀Fe₂₀ Permalloy using this system. The dual-modal approach bridges synchrotron radiation technology and surface science, offering nanometre-scale spatial resolution in XAS with magnetic domain sensitivity through linearly and circularly polarized X-ray excitation, providing researchers with advanced tools for functional materials analysis through synergistic XAS-PEEM techniques and dynamic control systems.

We present a series of novel X-ray imaging systems designed specifically for the soft X-ray energy range, optimized for operation in ultra-high-vacuum environments and compactness. These systems achieve micrometre-level spatial resolution with high collection efficiency of visible light by using high numerical aperture optics. Comprehensive characterization of the systems' response was performed, including linearity assessments and X-ray sensitivity measurements, across X-ray photon densities ranging from 1 nJ m^-2 to 10^-4 nJ m^-2. The imaging system was employed for caustic measurements to characterize the X-ray focal spot and to demonstrate its capabilities. Finally, grating interferometry was used to measure the wavefront distortion, yielding a pitch resolution as fine as 3.1 µm. These results underscore the system's potential for high-resolution soft X-ray imaging and wavefront characterization applications.

We present a laser reaction chamber that we have developed for in situ/operando X-ray diffraction measurements at the NSLS-II 28-ID-2 X-ray powder diffraction beamline. This chamber allows for rapid and dynamic sample heating under specialized gas environments, spanning ambient conditions down to vacuum pressures. We demonstrate the capabilities of this setup through two applications: laser-driven heating in polycrystalline iron oxide and in single-crystal WTe₂. Our measurements reveal the ability to resolve chemical reaction kinetics over minutes with 1 s time resolution. This setup advances opportunities for in situ/operando X-ray diffraction studies of both bulk and single-crystal materials.

Synchrotron light sources are powerful platforms for cutting-edge, multidisciplinary research, with dozens currently in operation, construction or commissioning worldwide. It is widely recognized that different research areas have specific demands for source capabilities. For the majority of synchrotron facilities, delivering high-brightness, high-flux synchrotron radiation stably through high-current electron beams is the primary mode of operation. However, there is also a significant demand for timing experiments to study dynamic processes. In response, many synchrotron facilities offer specialized or hybrid timing modes. In this paper, we propose a novel method that combines a double RF system and deflecting cavities to generate pairs of X-ray pulses in electron storage rings with adjustable transverse separation and time delay. This approach holds the potential to enable new experimental possibilities, such as X-ray pump and X-ray probe studies, or capturing information from two temporal points in a dynamic process using two X-ray probes simultaneously. We analyze the fundamental characteristics of this method, present a conceptual design, and demonstrate through simulations that the scheme can achieve adjustable transverse separation of the two X-ray pulses with tunable time delay on the order of 100 ps.

An automated alignment procedure, based on wavefront measurement with a single-grating interferometer, has been developed for precise tuning of Kirkpatrick-Baez nanofocusing mirrors for X-ray free-electron lasers (XFELs). This approach optimizes focus size and maximizes peak intensity while minimizing aberrations. Wavefront errors are quantitatively correlated with alignment deviations - incidence angle, perpendicularity and astigmatism - via Legendre polynomial analysis. These errors are subsequently corrected through a straightforward optimization process. Implemented at the SPring-8 Angstrom Compact Free-Electron Laser (SACLA), the system consistently achieves a reproducible XFEL focus below 150 nm × 200 nm within 10 min. Routine operation at SACLA demonstrates the reliability and efficacy of this method, enabling rapid restoration of optimal nanofocusing conditions.

The lung is a complex organ with a hierarchical structure, containing four times more air than tissue. It is in constant contact with environmental factors such as pollution and pathogens, leading to pathological alterations at various hierarchical levels. Because of its intricate structure and continuous movement, lung imaging presents significant challenges for most existing techniques. Recent advancements in phase-contrast computed tomography and photon-counting detectors have greatly enhanced lung imaging capabilities. Specifically, propagation-based imaging (PBI), a phase-contrast method that does not require optical elements, has proven particularly effective at low X-ray dose rates due to the strong phase shifts between lung tissue and aerated regions. This study introduces an in situ imaging approach for large-scale lungs using PBI at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron. We investigated optimal conditions for PBI, including energy and propagation distance settings, and found that an X-ray beam energy of 70 keV combined with a 7 m propagation distance yields the highest image quality in terms of contrast-to-noise ratio while also delivering the lowest radiation dose. Furthermore, Monte Carlo simulations were performed on the reconstructed volume to calculate absorbed radiation doses in tissues. These findings provide valuable insights for designing future experiments aimed at minimizing radiation exposure and potentially enable in vivo applications in larger animals or even humans.