As part of an effort to establish the principles and application of F K-edge X-ray absorption spectra to complex inorganic systems, the F K-edge spectra of a range of glasses, minerals and synthetic crystalline compounds are presented and discussed in terms of the F environments present. Crystalline fluorides often display richly detailed spectra as a result of the small core-hole broadening at the F K-edge, and the analysis of the spectra is presented by way of examining trends in material structure and bonding, spectral fingerprinting, and linear combination fitting. The benefits and drawbacks of each method of analysis are discussed, and recommendations for collection of high quality spectra are presented. The speciation of F in three oxide glasses is established by comparison of the observed F K-edge spectra with the spectra of suitable crystalline reference material. The F environments determined this way are in excellent agreement with previous works that utilized other methods of probing the F speciation, though in one case ambiguity in the observed spectrum does prevent definitive identification. F K-edge spectra were also calculated using the FEFF software package, with the aim of calculating spectra that reproduce the experimental spectra accurately with a minimum of prior knowledge and assumptions. The spectrum of CaF2 was calculated with a wide range of simulation parameters, and comparisons with experimental data are made to facilitate a simple computational workflow, that is validated by application to the simulation of the spectrum of Ca4Si2O7F2. Observations and recommendations are made that will assist other experimenters in the collection and analysis of future high-quality F K-edge spectra. The data and analyses presented establish F K-edge X-ray absorption spectroscopy as a powerful tool for the characterization of F speciation and environments in complex inorganic materials.
We have developed an X-ray scattering setup capable of capturing time-resolved small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) images spanning q = 0.02 to over 5.2 Å-1 on a single, large area Rayonix MX340-HS detector with time resolution as short as 120 ps. A key feature of this setup is a 0.51 mm-diameter partially transmissive beamstop that enables non-invasive, image-by-image recording of direct beam position and intensity during acquisition. This beamstop attenuates 12 keV undulator radiation by approximately eight orders of magnitude while suppressing off-axis second harmonic radiation. Continuous monitoring of the direct beam position facilitates long-term beam alignment and allows datasets acquired at different times to be placed on a common absolute scale prior to differencing. The accuracy of the difference scattering curves is ultimately limited by the performance of the large area, fiber-taper X-ray detector used in this study. To address accuracy issues, we present a detailed statistical characterization of the detector readout noise and responsivity and introduce a variance-per-count statistic that enables identification of zinger-free averages, generation of precise uniformity corrections, and statistically weighted conversion of two-dimensional scattering images into near shot-noise-limited one-dimensional scattering curves. The detector point-spread function and its effects on resolution and scaling are examined using scattering data from a fused silica plate and from apoferritin solution in a capillary. The ability to acquire high accuracy, high precision scattering curves over a broad range of q and temperatures provides a robust foundation for time-resolved studies of biomolecular structure and dynamics in solution.
The paper presents a comprehensive description of a new setup implemented and commissioned at the SEXTANTS beamline of Synchrotron SOLEIL for absorption and scattering experiments with X-ray beams carrying an orbital angular momentum, also known as twisted X-ray beams. Two alternative methods have been implemented, based on the use of either spiral zone plates or fork grating devices, and we show how they can be used for both defining and assessing the orbital angular momentum of an X-ray beam. We also demonstrate that cascading multiple devices enables integer operations on the orbital angular momentum of the resulting X-ray beam. Finally, we report the results of the first resonant scattering pilot experiments in transmission and reflection mode, intended to assess the feasibility of future users' measurements. The availability of twisted soft X-rays complements the range of experimental techniques in elastic, resonant and coherent scattering available at the SEXTANTS beamline.
The structural biology method of X-ray footprinting mass spectrometry (XFMS) is available at two national synchrotron beamlines in the USA: one at the Advanced Light Source (ALS) on the West Coast and the other at the National Synchrotron Light Source II on the East Coast. XFMS is a solution-state technique that utilizes oxidative modifications of proteins at micromolar concentrations in aqueous buffer to extract structural information. X-rays are employed to generate hydroxyl radicals in situ, which covalently modify specific protein side chains. These modifications are subsequently quantified using liquid chromatography and mass spectrometry. Ratiometric changes in modification levels between two protein states (e.g. with and without ligand) generate a relative solvent accessibility map of the protein pairs, which serves to reveal structural features. Up until recently, the XFMS capability was available as part of a shared program at the ALS without a dedicated beamline. In this article, we describe the commissioning of ALS beamline 3.3.1, dedicated to XFMS, including the installation of a new focusing mirror, the design and construction of a new endstation with automated sample handling and exposure capabilities, and the use of accurate empirical dose calculations using Gafchromic film. Finally, we showcase the new beamline capabilities using two protein systems.
In situ observations of high-temperature transformations, not compromised by reactivity with a crucible, have recently become accessible by integrating containerless processing with the time-resolved diffraction of synchrotron X-rays. The presented electromagnetic levitator (EML) has been designed for mobility and ease of operation during beamline experiments while enabling stable processing of a wide range of materials. Developed to work with area detectors, the facility's capabilities are demonstrated by measurements of the structural changes during melting and solidification of pure Fe and Fe-Co samples. The direct observations of the metastable phase formation in the Fe-Co system, accessible through containerless processing, have been accomplished for the first time due to the improved acquisition rate of modern area detectors. The diffraction patterns and associated artifacts characteristic of crystal structure measurements during levitation are examined. Moreover, an analytical description of the measured instrumental resolution of the diffraction setup is presented along with a survey of the corrections and associated measurements necessary for an accurate total scattering analysis of the disordered states, such as liquids or glasses. This provides a base for the conceptual planning of diffraction experiments suitable for various levitation methods, including electrostatic, aerodynamic and acoustic levitation.
This study presents a comprehensive comparison of image quality between synchrotron-based and laboratory-based nano-computed tomography (nano-CT) systems, using a standardized 3D test phantom composed of monodisperse silica spheres. A round-robin approach was employed across multiple international facilities to benchmark performance across various imaging modalities and setups, including absorption and phase contrast techniques. Image quality was quantitatively assessed using three-dimensional signal-to-noise ratio (SNR3D), detection effectiveness (DE3D) and modulation transfer function (MTF3D) metrics. The results reveal that, while synchrotron-based nano-CT consistently delivers superior spatial resolution and shorter scan times, laboratory-based systems demonstrate competitive image quality at the cost of extended acquisition durations. Beyond the experimental comparison, the main contribution of this work is a standardized, open-source analysis framework that quantifies nano-CT image quality using SNR3D, DE3D and MTF3D of a specific phantom. This combination of metrics provides a reproducible basis for cross-platform benchmarking of synchrotron and laboratory nano-CT implementations and can be readily applied to future instruments.
Objective.Microbeam radiation therapy (MRT) exploits spatially fractionated, micrometer-scale x-ray beam arrays that deliver high-dose (peak) and low-dose (valley) regions. At beamline P61A of the PETRA III synchrotron (DESY, Hamburg, Germany), MRT delivery has been limited to a fixed 2 mm wide field and single-direction irradiation. This study aimed to implement stereotactic multi-port MRT (STX-MRT) with lateral field extension and to quantify the spatial reproducibility of the microbeam arrays during patched and multi-angle delivery.Approach.A custom motorized stage providing vertical and lateral translation and rotation was developed to enable discrete lateral patching and sequential delivery from multiple ports (1-9). Each microbeam array comprised five peaks with a beam width of 50µm and a center-to-center spacing of 400µm. Spatial accuracy was assessed with Gafchromic™ HD-V2 film scanned at 7.9µm resolution. Fifteen films (three per geometry), corresponding to 225 patched arrays, were included to determine the spatial accuracy.Main results.Beam delivery was highly reproducible. In 88% of the microbeam arrays, deviations were below the detection limit (⩽7.9µm). Detectable displacements occurred in 12% of arrays and ranged from 33 to 258µm, typically localized to individual patches or ports. The rotational isocenter remained stable across all configurations, and increasing the number of ports and delivery speed did not introduce systematic alignment errors.Significance.Reliable lateral field patching and multi-port MRT delivery with micrometer-scale precision was achieved, extending the usable irradiation field and enabling STX-MRT at beamline P61A. This technical capability broadens the range of irradiation of different target sizes and supports advanced preclinical studies of MRT.
FLASH radiotherapy involves delivering relatively high radiation doses at ultra-high dose rates (UHDRs) that are several orders of magnitude greater than those used in conventional radiotherapy (40 Gy s-1 versus 0.5-5 Gy min-1, respectively). Previous in vivo studies have shown that doses delivered with such UHDRs result in significant tumour killing while having less effect on normal tissues. Most of these in vivo studies were based on the use of charged particles such as electrons and protons. In this study we exposed cells [human epidermal melanocytes (HEM), MM96L melanoma cells, CCD841 colon epithelial cells and CaCo2 colorectal adenocarcinoma cells] grown in vitro to synchrotron-based X-ray beams delivered at either low dose rates or UHDRs to validate the FLASH effect. The FLASH effect that has been reported to occur under hypoxic conditions was also investigated using HEM and MM96L cells. Significant cell killing was observed at 48 h post-irradiation, when the cells were exposed to high dose (≥10 Gy) UHDRs compared with low dose rate beams in both groups of cells. MM96L melanoma cells were ∼10% less resistant to UHDR than were HEM cells. A similar result was observed in CCD841 and CaCo2 cells. When the hypoxic melanocytes (HEM) were exposed to (≥10 Gy) UHDRs a minimal loss of cell viability was observed; however, when hypoxic MM96L cells were irradiated, significant cell losses were observed. These results show that a FLASH effect is evident in these skin and colon cells. Moreover, when MM96L melanoma cells were pretreated with 1 mM gold nanoparticles and exposed to 10 Gy UHDR X-rays there was a 50% dose enhancement observed where only 15% was observed at low dose rates.
Scanning small-angle X-ray scattering (sSAXS) has found multiple applications as a technique to probe the nanostructure in soft tissues and pathologies thereof. However, fresh tissue is fragile and prone to the quick onset of decomposition and autolysis. It lacks the firmness required for uniform and thin sectioning, resulting in the loss of 2D resolution offered by focused X-ray beams, because the signal would be integrated through thick and/or irregular sections. Tissue processing, that includes fixation and embedding, is used to mitigate these issues but can by itself introduce structural changes in the tissues and impede the correct interpretation of sSAXS data. Here the extent of these structural changes in the SAXS signal caused by common tissue preservation methods on the example of skeletal muscle tissue, consisting of both muscle and surrounding connective tissue, was studied. This can guide an informed choice of preservation method tailored for specific experimental requirements. While some techniques performed better than others, all tissue-processing methods induced structural changes to a certain degree. The choice of preservation method is therefore a balance between sectioning requirements and type of tissue used, as well as targeted structural information.
Here, a compact two-electrode field-emission X-ray source employing a blade-type tungsten cathode was designed for soft X-ray spectroscopy. The device suppressed filament-derived optical and thermal background that is intrinsic to thermionic tubes, while providing stable and tunable output. The cathode-anode spacing was optimized and an optimal gap was identified at 150 µm, enabling the source to reach 400 µA at 4 kV without short circuits at <1 × 10-7 mbar. Spatial intensity mapping with targets tilted at 30°, 45° and 60° showed that smaller tilts yielded a more concentrated flux, with full width at half-maximum values of 28°, 54° and 76° at 2.5 kV, respectively, while the peak emission direction remained near 30° independent of the applied voltage and the tilt angle. Energy-resolved measurements with a silicon drift detector showed that the high-energy cutoff of the Bremsstrahlung continuum shifted linearly with the applied acceleration voltage, and that a reproducible Cu Lα peak appeared at 927.7 eV, confirming stable and proper operation of the source. High signal-to-noise soft X-ray emission spectroscopy of Ti Lα and O Kα lines were obtained using the source integrated at the Ultrafast X-ray Spectroscopy (UXS) endstation of the Shanghai Soft X-ray Free-Electron Laser (SXFEL) facility. The blade cathode and simplified architecture improve manufacturability and cost efficiency, providing a laboratory-scale low-background source for element-specific soft X-ray spectroscopy and pre-beamline experiments.
Scanning fluorescence X-ray microscopy lets one non-destructively and quantitatively map the distribution of most biologically important metals in cells and tissues. For studies on large-scale tissues and organs, a spatial resolution of several micrometres is often sufficient; in this case, bending magnets at synchrotron light sources provide abundant X-ray flux. We describe here the use of bending magnet beamline 8-BM-B at the Advanced Photon Source with two distinct microscopy stations: a pre-existing one with Kirkpatrick-Baez (KB) mirror optics for slightly higher throughput and the ability to accommodate samples tens of centimetres across, and a new prototype station with an axially symmetric, single-bounce, capillary optic with slightly less flux, but finer resolution at similar fluence per time. The KB station provides δres = 10.5 µm spatial resolution at a per-pixel exposure time of tdwell = 100 ms and a fluence per time of 5.8 × 107 photons µm-2 s-1, while the prototype capillary station provides δres = 6.5 µm at tdwell = 50 ms and a fluence per time of 5.6 × 107 photons µm-2 s-1. We used image power spectral density to estimate the achieved spatial resolution δres from individually acquired images, with δres depending on the optic, the fluorescence signal strength of the sample being imaged, and the method used to process raw fluorescence spectral data.
A novel approach to soft X-ray fluorescence-yield absorption spectroscopy is presented using a superconducting tunnel junction (STJ) X-ray detector, a new type of detector for the soft X-ray region. The STJ detector offers superior energy resolution compared with silicon drift detectors and higher detection efficiency than grating-based spectrometers, both of which are widely used in soft X-ray spectroscopy. The STJ detector can simultaneously detect multiple fluorescence lines in a single measurement, even on a bending-magnet beamline, which enables medium-energy-resolution fluorescence detected X-ray absorption spectroscopy (XAS) without the need for large-scale emission spectrometers. Using these characteristics, the Ti Lα/Lℓ XAS and O Kα XAS of SrTiO3 were measured, where Ti Lℓ XAS are expected to reflect the intrinsic Ti 3d electronic states without being affected by orbital anisotropy, providing a more accurate picture of the transition-metal electronic structure. These results demonstrate that the STJ detector is effective for probing anion electronic states of carbides, nitrides and oxides.
X-ray diffraction (XRD) combined with in situ mechanical testing is a powerful, non-destructive technique that provides valuable information on structural evolution and defect formation during deformation. Unlike many other characterization methods, XRD does not impose constraints on sample dimensions, does not require a vacuum environment, and can be applied to a wide range of materials with periodic structures. However, such experiments present significant challenges due to the need for precise synchronization between independently controlled systems: one managing mechanical loading and the other handling X-ray measurements. In this work, we report on the successful software-level integration of a nanoindenter control system directly into the beamline control system. This integration enables full control of both mechanical and diffraction measurements from a single user interface, allowing real-time synchronization and automation of complex in situ experiments. We demonstrate the capabilities of this setup through uniaxial compression tests on α-Ti micropillars. Mechanical data from the nanoindenter and XRD patterns were collected simultaneously in an automated mode. Raster scans were performed on the micropillar in its pristine state, at two intermediate deformation stages, and post-mortem. This approach enabled detailed analysis of mechanical behavior and structural evolution under load, illustrating the effectiveness of the integrated system for advanced in situ studies.
The ClearXCam detector is a new video rate imaging in-beam monitor based on a diamond sensor. Imaging with 2304 effective pixels is achieved by sequentially biasing one of 48 metal stripes on one side of a diamond sensor, while reading out the current from 48 stripes on the other side of the sensor. This system was characterized for real-time X-ray beam diagnostics at synchrotron beamline 17-BM at the National Synchrotron Light Source II. Significant results include: detection of in-beam structure via the imaging mode, beam focusing in one minute with real-time imaging feedback during a focusing event, linearity over five orders of magnitude, validation of a fast mode operating at 100 Hz, and sub-micron beam-positioning resolution. The system is now available commercially.
Phase contrast and dark-field imaging are relatively new X-ray imaging modalities that provide additional information to conventional attenuation-based imaging. However, this new information comes at the price of a more complex acquisition scheme and optical components. Among the different techniques available, such as grating interferometry or edge illumination, modulation-based and more generally single-mask/grid imaging techniques simplify these new procedures to obtain phase and dark-field images by shifting the experimental complexity to the numerical post-processing side. This family of techniques involves inserting a membrane into the X-ray beam that locally modulates the intensity to create a pattern on the detector which serves as a reference. However, the topological nature of the mask used seems to determine the quality of the reconstructed phase and dark-field images. We present in this article an in-depth study of the impact of the membrane parameters used in a single-mask imaging approach. A spiral topology seems to be an optimum both in terms of resolution and contrast-to-noise ratio compared with random and regular patterns.
Angle-resolved photoemission spectroscopy (ARPES) was developed in the 1970s to 1990s as a momentum-resolved probe of the electronic structure of solids, with its basic principles summarized in early seminal works and classic reviews. The basic ARPES result is currently almost exclusively associated with the two-dimensional intensity distribution with coordinate axes labeled as `Binding energy' and `Momentum'. Such datasets are usually directly compared with band structure calculations along high symmetry directions of the Brillouin zone. Here it is shown that this is the result of an oversimplified treatment of the ARPES data leading to incorrect interpretations of the experimental results. Practical ways of how to avoid this in both data collection and analysis are suggested.
In this article, we present the experimental protocol and data-processing framework for megahertz X-ray Photon Correlation Spectroscopy (MHz-XPCS) experiments on soft matter samples implemented at the Materials Imaging and Dynamics (MID) instrument of the European X-ray Free-Electron Laser (EuXFEL). Due to the introduction of a standard configuration and the implementation of a highly automated data-processing pipeline, MHz-XPCS measurements can now be conducted and analyzed with minimal user intervention. A key challenge lies in managing the extremely large data volumes generated by the Adaptive Gain Integrating Pixel Detector (AGIPD) - often reaching several petabytes within a single experiment. We describe the technical implementation, discuss the hardware requirements related to effective parallel data processing and propose strategies to enhance data quality, in particular related to data reduction strategies and an improvement of the signal-to-noise ratio. Finally, we address strategies for making the processed data FAIR (Findable, Accessible, Interoperable, Reusable), in alignment with the goals of the DAPHNE4NFDI project.
In coherent diffraction imaging (CDI), the coherence properties of photons play critical roles in obtaining structural information from specimens without using lenses. While the impact of coherence has been widely studied in CDI, it has not been systematically investigated within the specific framework of X-ray free-electron laser (XFEL)-CDI. Here, we examined the relationship between the transverse and temporal coherence of XFEL pulses and the quality of image reconstruction using XFELs. Specifically, we investigated the properties of self-amplified spontaneous emission and self-seeding beams at an X-ray energy of 5 keV by collecting diffraction patterns from a single gold nanoparticle. Furthermore, the quality of the reconstructed images obtained using the two beam modes was compared. Our results demonstrate that the self-seeding beam offers more reliable image reconstruction that is attributable to the narrower bandwidth of the incident X-rays. This study highlights the advantages of utilizing a self-seeding beam in CDI experiments, particularly for enhancing the reliability and quality of image reconstruction.
X-ray phase-contrast tomography can efficiently image brain tissue at subcellular resolution. However, current sample preparation methods are not optimized to exploit the full potential of X-ray contrast mechanisms. Here we propose to replace interstitial material by air to enhance X-ray phase contrast of the ultrastructural features. Critical point drying (CPD) of heavy-metal-stained mouse brain tissue produced samples with preserved ultrastructure, a nanofoam-like material that remains compatible with follow-up conventional resin embedding. Using two synchrotron-based setups, namely, a high-throughput microtomography beamline and a nanoscale holographic tomography beamline, we found that CPD samples consistently showed 2-4× stronger phase-shift signal than samples embedded in resin. CPD offers a versatile route for preparing tissue for subcellular and ultrastructural-resolution X-ray imaging. It retains structural detail while improving signal, and is compatible with follow-up protocols involving femtosecond laser milling or electron microscopy, paving the path for biological tissue imaging beyond the mm3 scale.
Due to their high penetration depth, X-rays enable us to obtain information from the interior of whole unsliced cells. Scanning small-angle X-ray scattering (SAXS), in particular, reveals real-space images in dark-field representation as well as structural information in reciprocal space. However, obtaining information on anisotropy and orientation from cells in an aqueous, close-to-physiological environment remains challenging. Here, we extend the recently introduced fast-scanning SAXS mode with short exposure times of a few milliseconds to such hydrated samples by combining a newly developed X-ray compatible microfluidic chamber and innovative data analysis that includes an effective noise-filtering method. This strategy enables the systematic analysis of radiation damage by quantifying the SAXS signal. Our results demonstrate that scanning SAXS can be used to obtain intracellular information of fixed-hydrated cells and the approach may in the future be applicable to living cells as well.