In this article we present SELUN, a novel X-ray photon counting hybrid pixel detector developed at DECTRIS Ltd for coherent diffraction imaging techniques at synchrotron facilities. Its notable features are a pixel size of 100 µm × 100 µm arranged in a matrix of 192 × 192 elements, the possibility of use of both silicon and high-Z sensors to guarantee high quantum efficiency across a wide range of incoming X-ray energies, fast front-end electronics equipped with instant retrigger technology working in non-paralyzable counting mode, and high frame rates capability up to 120 kfps thanks to two on-chip data-compression mechanisms. Optimized towards speed to cope with the enhanced brilliance of fourth-generation synchrotron sources, it shows remarkable count rate saturation values ranging from about 30 to 60 Mcts s pixel, depending on the sensor material and value of the incoming X-ray energy, and energy-resolution figures of 664 eV r.m.s. for a silicon sensor and 1.22 keV r.m.s. for a cadmium zinc telluride (CZT) sensor.

Refractive X-ray lenses are frequently used components at modern X-ray free-electron laser facilities. This work investigates the temporal effects of refractive optics on ultra-short X-ray pulses, particularly focusing on pulse elongation. We present a model using full Fresnel theory to study the beam profile at the focus in space and time. Refractive X-ray lenses not only change the temporal structure of the pulse, the focus size is also dependent on the incoming pulse duration. Further, we present a simplified ray-tracing model to estimate the pulse stretching effect of compound refractive lenses (CRLs), which we find to be dependent only on the dispersion and the absorption of the CRL material.

We present Gaia, a monolithic array of 96 high-purity germanium pixel detectors integrated with a custom low-noise application-specific integrated circuit (ASIC) and a field-programmable gate array (FPGA)-based data acquisition system. The sensor operates at ∼100 K using a commercial closed-cycle cryocooler, with the in-vacuum electronics thermally isolated from the cold finger to ensure thermal stability. The system demonstrates an average energy resolution of 711 eV at 122 keV, measured using a Co source, and 253 eV at 5.89 keV, measured with Fe across all channels. The readout architecture incorporates a high-performance FPGA paired with a dual-core ARM processor, forming a complete embedded Linux-based computing platform. Communication between the processor and FPGA is handled via memory-mapped I/O, and data are streamed over high-speed gigabit Ethernet. A full-scale 384-pixel Gaia detector, based on this 96-element module, is currently under fabrication.

X-ray imaging is a powerful technique to scan samples in a variety of contexts including biological, environmental and materials science, but commonly requires a synchrotron light source to produce X-rays at sufficient intensity. As these facilities are expensive to operate, the available beam time is limited and always in high demand. Particularly if the illuminated samples are sparse, standard raster scanning methods can be time-consuming, with a majority of that time being spent on areas of the image that carry little information. To increase the efficiency and maximize the information gain for a given time budget, we split the scanning process into a series of steps where previous measurements are used to inform the decision making and adapt the exposure distribution at later stages of the sequence. We formulate this task as a reinforcement learning problem where the goal is to produce a sequence of exposure maps that maximize a predefined scalar metric. We demonstrate the potential of this approach in simulations where the adaptive illumination can accelerate the measurement process by up to an order of magnitude compared with standard raster scanning. Finally, we present the first results from deploying the trained agents on an X-ray fluorescence beamline at the Stanford Synchrotron Radiation Lightsource.

In this paper, we introduce the Modular Adaptive Processing Infrastructure (MAPI), a comprehensive software suite and approach designed to streamline and enhance data analysis workflows in scientific research laboratories. MAPI selects and integrates multiple frameworks and toolkits into a web-based platform, offering a highly modular and adaptable solution for diverse data analysis requirements. By design, MAPI supports distributed processing across heterogeneous backends (edge workstations, on-premises servers, high-performance computing and public cloud), making it suitable for various beamlines and data-processing labs. This blueprint, or `recipe', provides a flexible infrastructure that can be tailored to specific experimental needs. We showcase MAPI's application through its successful implementation on the X-ray computed tomography (CT) beamline, resulting in a system for tomographic processing (STP3). The case study demonstrates MAPI's effectiveness in meeting complex computational demands, highlighting its potential for widespread adoption in scientific research environments. Most of the results reported in the paper are from a production deployment on Elettra's SYRMEP beamline using two on-premises GPU servers, but two additional ongoing deployments on different beamlines are discussed.

Gaining insight into structural and compositional transformations occurring at the electrode/electrolyte interface during the operation of electrochemical systems is fundamental to understanding and, thus, optimizing their performance. Such an analysis must be performed in operando conditions, owing to the potential, electrolyte and time dependence of these transformations. Here, the use of X-ray photoelectron spectroscopy (XPS) is particularly attractive due to its surface sensitivity and ability to provide quantitative information on the oxidation state and chemical environment of an element. In specific instrumental configurations [e.g. in `dip-and-pull' (D&P) or `meniscus' setup], it can be used to analyse not only the electrode but also the electrolyte side of the interface, under in situ/operando conditions. In this article, we discuss how D&P XPS can provide unique information on both sides of the electrode/electrolyte interface, briefly review publications demonstrating its capabilities, highlight the challenges the method faces, and share our views on its future developments. This article aims to provide a practical guide to new D&P synchrotron users and help them to understand the technique, and physical phenomena that may impede the acquisition of reliable data.

The Single-Particle, Clusters and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) scientific instrument at the European X-Ray Free-Electron Laser (EuXFEL) became operational with user experiments in September 2017. The unique properties and capabilities of the EuXFEL, enabling megahertz data collection rates, provide more rapid data collection with improved statistics compared with other XFEL facilities. This improves the feasibility of obtaining multiple data points in time-resolved experiments and hence enables the observation of reactions in greater detail (molecular movies). In collaboration with the SFX User Consortium (SFX UC), the SPB/SFX instrument was designed to further increase user access and research outcomes. Focusing the pulses downstream of the first interaction region [described previously (Mancuso et al., 2019)], a second experiment plane is enabled, which allows for greater optimization and more efficient usage of available beam time. Additionally, the SFX UC provided further instrumentation to provide improved capabilities on SPB/SFX. The aim for additional and extended functionality for the second interaction region was to enable sample-efficient data collection at atmospheric pressure in an environment where the sample temperature and humidity can be controlled. This paper describes the extended capabilities of the downstream interaction region of the SPB/SFX instrument and its major components, in particular its X-ray focusing optics, vacuum to atmospheric pressure out-coupling, available sample delivery methods and 2D detector, and the supporting optical laser systems for pump-probe experiments.

Corrigendum to the article by Feuer-Forson et al. [(2024). J. Synchrotron Rad. 31, 698-705].

Understanding the chemical processes that occur during the solvothermal synthesis of functional nanomaterials is essential for their rational design and optimization for specific applications. However, these processes remain poorly understood, primarily due to the limitations of conventional ex situ characterization techniques and the technical challenges associated with in situ studies, particularly the design and implementation of suitable reactors. Here, we present a versatile reactor suitable for in situ X-ray scattering, X-ray spectroscopy and infrared spectroscopy studies performed during solvothermal synthesis under autoclave-like, inert conditions. The reactor enables precise control of the temperature between -20°C and 200°C, pressure up to 8 bar, magnetic stirring, and injection of gas or liquids. The reactor's capabilities are demonstrated by comprehensively studying the solvothermal synthesis of magnetite nanoparticles from iron acetylacetonate in benzyl alcohol through in situ X-ray scattering and spectroscopy, and attenuated total reflection infrared (ATR-IR) spectroscopy.

This article reports an operando X-ray absorption spectroscopy (XAS) cell and its set-up for the photocatalytic reduction of CO in the gas phase. Details about the cell and set-up development and configuration are provided. The operando cell and set-up are validated from a photocatalytic point of view: the performances of two photocatalysts are successfully benchmarked with those obtained on an already existing gas phase photoreactor unit. The cell is also validated from an XAS point of view as measured Mo K-edge spectra of the photocatalyst loaded in the cell are similar to those measured for ex situ samples, prepared in a capillary. Finally, a detailed example of an operando photocatalytic experiment shows the potentiality of the developed cell to monitor photocatalysts under working conditions for gas phase CO photoreduction, making the link between a shift in the absorption edge due to Mo species evolution and the deactivation of the photocatalyst. Additionally, the developed operando cell, available at Synchrotron SOLEIL on the ROCK beamline, is versatile and may actually be used for any photocatalytic gas phase reaction.

With the start of the user program at the European XFEL in 2017, and more recently with the LCLS-II upgrade, the X-ray repetition rate at X-ray free-electron lasers (XFELs) has been pushed into the kilo- and megahertz regimes. These high X-ray repetition rates provide an increase in the integrated flux at these facilities by orders of magnitude, potentially facilitating measurements that were previously infeasible due to signal-to-noise constraints. However, the high repetition rates lead to new challenges for sample delivery and a shorter time for the sample to recover between X-ray pulses. For solution-phase techniques, the X-ray-sample interactions will strongly perturb or even vaporize the sample jet. Although the sample can be replenished, up to X-ray repetition rates of ∼100 kHz, by flowing the jet at high speeds, this does not completely mitigate the jet perturbations. In this work, we present a characterization of the jet perturbations induced by the high X-ray repetition rates at the European XFEL. We show how these can introduce background signals in time-resolved X-ray solution scattering data measured at the Femtosecond X-ray Experiments (FXE) instrument. We show that it is possible to mitigate these experimental artifacts by employing an alternating excitation scheme combined with careful background subtraction and that implementing this approach in the experimental design outperforms more simple background subtraction schemes. The methodology, the observations and analysis results are discussed in relation to the evolving landscape of XFEL sources.

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 (low intensity, LI), 0.5 W m (medium intensity, MI) and 1 W m (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.

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.

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 WTe. 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.

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.

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 × 10 photons s, 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.

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.

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.

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.

We present a Python toolbox for holographic and tomographic X-ray imaging. It comprises a collection of phase retrieval algorithms for the deeply holographic and direct contrast imaging regimes, including non-linear approaches and extended choices of regularization, constraint sets and optimizers, all implemented with a unified and intuitive interface. Moreover, it features auxiliary functions for (tomographic) alignment, image processing and simulation of imaging experiments. The capability of the toolbox is illustrated by an example of a catalytic nanoparticle, imaged in the deeply holographic regime at the `GINIX' instrument of the P10 beamline at the PETRA III storage ring (DESY, Hamburg, Germany). Due to its modular design, the toolbox can be used for algorithmic development and benchmarking in a lean and flexible manner, or be interfaced and integrated in the reconstruction pipeline of other synchrotron or X-ray free-electron laser instruments for phase imaging based on propagation.

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