Full-field transmission X-ray microscopy (TXM) is a powerful technique for nondestructive nanoscale imaging. In laboratory-based systems, high-resolution full-field TXM remains challenging due to the low brightness and polychromaticity of X-ray tubes. Here, we demonstrate a laboratory TXM instrument composed of a microfocus X-ray source with an integrated multilayer Montel mirror, high-resolution Fresnel zone plates (FZPs), and a charge-integrating direct conversion hybrid pixel detector (M & Ouml;NCH detector). The Montel mirror monochromatizes the X-ray beam and efficiently focuses it onto the sample. Importantly, the numerical aperture of the Montel mirror is matched to that of an FZP with an outermost zone width of 25 nm, thereby ensuring optimal performance in spatial resolution. A central innovation of our work is the replacement of traditional scintillator-based indirect detection schemes with a direct conversion hybrid pixel detector featuring higher detective quantum efficiency. This transition is enabled by the uniquely small pixel size of the M & Ouml;NCH detector (25 & micro;m) and its interpolation capabilities arising from charge sharing between contiguous pixels when an X-ray photon is detected. By integrating our tailored TXM design with the advanced interpolation capabilities of the M & Ouml;NCH detector, features with dimensions down to 34 nm were resolved. Furthermore, the microscope can be operated in Zernike phase-contrast mode, which was applied for imaging of an integrated-circuit chip. This work represents a significant step forward in laboratory-based TXM, introducing a combination of X-ray optics that brings nanoscale imaging in laboratory and industrial environments closer to synchrotron-level resolution. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

An integrated hardware-software platform for three-dimensional electron diffraction (3D ED) has been developed using the JUNGFRAU 1M charge-integrating hybrid pixel detector. The system combines the FPGA-based Jungfraujoch backend with the JFGui graphical interface, providing centralized control of the detector, electron microscope, and data-processing software. This workflow enables synchronized data acquisition, live visualization, and instantaneous post-processing with established programs of crystallography, XDS, DIALS, and SHELX. Applications to l-histidine and PTCDI- C8 crystals are presented including charge-density evaluation employing the recently developed iSFAC (ionic Scattering FACtors) model. The workflow supports continuous rotation measurements at speeds up to 10 ◦ s−1, enabling higher-throughput measurements. Comparative measurement at 100 kV and 200 kV beam energies revealed the trade-off between real-space contrast and diffraction resolution. These developments establish a complete and efficient practical workflow of 3D ED coupled with instrumental evaluation, providing a robust route toward quantitative electron crystallography.

Due to their radiation hardness, kilohertz frame rates, and high dynamic range, hybrid pixel detectors have recently expanded their application range to electron diffraction and recently also electron imaging. However, these detectors typically have pixel sizes about ten times larger than those of direct electron detectors commonly used for imaging and more prominent electron multiple scattering effects. To overcome these limitations, machine learning approaches can be utilized to reconstruct the electron entrance point and achieve super-resolution. As this process is inherently stochastic, and machine learning relies on suitable training data, high-quality, representative training data are essential for developing models that achieve the best possible resolution. In this work, we present two novel experimental methods for generating such training data. The first method employs precise microscope alignment to scan the detector plane using a finely focused electron beam of 2 μm diameter, enabling controlled sub-pixel mapping. The second method utilizes specially designed aperture masks with sub-pixel-sized holes to accurately localize electron entry points. We developed and validated two experimental strategies for collecting training data at acceleration voltages of 60, 80, 120, and 200 keV, which enable sub-pixel labeling for hybrid pixel detectors. Notably, our methodology is broadly applicable to a wide range of hybrid pixel detectors.

JUNGFRAU is a state-of-the-art charge-integrating X-ray detector widely used for imaging, diffraction and spectroscopy experiments at synchrotrons and free electron lasers. The current frame rate is 2.2 kHz, limited by analog signal integrity due to the number of available output pads. With the goal of increasing the frame rate of the detector to over 10 kHz, we have designed a digital 3.125 Gbps high-speed serial readout. Consequently, the development of a fast Analog-To-Digital Converter ADC has become our primary goal to overcome the aforementioned constraints. In addition, on-chip digitization reduces noise pickup and signal distortion caused by wirebonds,traces, and other off-chip components. The ADC has been submitted in June 2024 and arrived at PSI for testing in October 2024. This contribution presents the first characterization results of the new ADC prototype, using standard ADC characterization techniques including statistical histogram testing.

With the evolution of synchrotron light sources to fourth generation (diffraction-limited storage rings), the brilliance is increased by several orders of magnitude compared to third generation facilities. For example, the Swiss Light Source (SLS) has been upgraded to SLS 2.0, promising a horizontal emittance reduced by a factor of 40, and a brilliance up to two orders of magnitude (three at higher energies). A key challenge arising from the increased flux is the heightened accumulated dose in silicon sensors, which leads to a significant increase in radiation damage. This translates into an increase of both noise and dark current, as well as a reduction in the dynamic range for long exposure times, thus affecting the performance of the detector, in particular, for charge-integrating detectors. We have designed sensors with a 4 × 4 mm2 pixel array featuring 16 design variations of 25 µm pitch pixels with different implant and metal sizes and tested them bump-bonded to MÖNCH 0.3, a charge integrating hybrid pixel detector readout ASIC. Following a first assessment of the functionality and performance of the different pixel designs, the assembly has been irradiated with X-rays. The variation in the tested parameters was characterized at different accumulated doses up to 100 kGy at the sensor entrance window side. The annealing dynamics at room temperature have also been measured. The results show that the default pixel design is currently not optimal and can benefit from layout changes (reduction in the inter-pixel gap area with full metal coverage of the implant). Further studies on the metal coverage over large implants could be conducted. The layout changes are, however, not sufficient for future full-sized sensors, requiring improved radiation hardness and long-term stability, and additional strategies such as focusing on detector cooling and changes in sensor technologies would be required.

Soft X-ray experiments at synchrotron light sources are essential for a wide range of research fields. However, commercially available detectors for this energy range often cannot deliver the necessary combination of quantum efficiency, signal-to-noise ratio, dynamic range, speed, and radiation hardness within a single system. While hybrid detectors have addressed these challenges effectively in the hard X-ray regime, specifically with single photon counting pixel detectors extensively used in high-performance synchrotron applications, similar solutions are desired for energies below 2 keV. In this work, we introduce a single photon counting hybrid pixel detector capable of detecting X-ray energies as low as 550 eV, utilizing the internal amplification of Low Gain Avalanche Diode (LGAD) sensors. This detector is thoroughly characterized in terms of Signal-to-Noise Ratio and Detective Quantum Efficiency. We demonstrate its capabilities through ptychographic imaging at MAX IV 4th-generation synchrotron light source at the Fe L3-edge (707 eV), showcasing the enhanced detection performance of the system. This development sets a benchmark for soft X-ray applications at synchrotrons, paving the way for significant advancements in imaging and analysis at lower photon energies. The internal amplification of Low-Gain Avalanche Diode sensors can enhance the signal-to-noise ratio, improving the detection of low-energy X-rays. In this work, the authors demonstrate a single photon counting hybrid pixel detector detecting X-ray energies down to 550 eV, and test it in ptychographic imaging at the Fe L3-edge.

Microstructured foams are emerging as a promising class of targets, with applications ranging from laser-driven particle acceleration to inertial confinement fusion. To unlock their full potential, a deeper understanding of their properties, especially the changes and behavior of the microstructure under extreme conditions, is required. While recently advancing 3D printed foam targets can be observed by X-ray radiography, the microstructure in chemically produced targets is far below the spatial resolution of conventional radiography. To overcome this limitation, we apply grating-based X-ray dark-field imaging to observe structural changes in foams that are rapidly heated by laser-accelerated proton pulses. The experimental data is compared to synthetic dark-field values obtained from hydrodynamic simulations of a simplified foam model. Both experimental and simulation results demonstrate the viability of utilizing grating-based dark-field imaging for observing microstructural changes in foam targets.

Atomic partial charges, integral to understanding molecular structure, interactions and reactivity, remain an ambiguous concept lacking a precise quantum-mechanical definition1,2. The accurate determination of atomic partial charges has far-reaching implications in fields such as chemical synthesis, applied materials science and theoretical chemistry, to name a few3. They play essential parts in molecular dynamics simulations, which can act as a computational microscope for chemical processes4. Until now, no general experimental method has quantified the partial charges of individual atoms in a chemical compound. Here we introduce an experimental method that assigns partial charges based on crystal structure determination through electron diffraction, applicable to any crystalline compound. Seamlessly integrated into standard electron crystallography workflows, this approach requires no specialized software or advanced expertise. Furthermore, it is not limited to specific classes of compounds. The versatility of this method is demonstrated by its application to a wide array of compounds, including the antibiotic ciprofloxacin, the amino acids histidine and tyrosine, and the inorganic zeolite ZSM-5. We refer to this new concept as ionic scattering factors modelling. It fosters a more comprehensive and precise understanding of molecular structures, providing opportunities for applications across numerous fields in the chemical and materials sciences.

Abstract Gotthard-II is a charge-integrating silicon microstrip detector developed for energy-dispersive experiments and X-ray photon beam diagnostics at the European X-ray Free-Electron Laser (EuXFEL). Its one-dimensional geometry, featuring fewer readout channels than pixel detectors, and its fast readout capability make it the only segmented detector able to perform experiments at a 4.5 MHz frame rate while capturing all 2700 X-ray pulses in a bunch train produced by the EuXFEL machine. The Gotthard-II detector was tested for single-photon sensitivity and dynamic range, meeting all specifications. In addition to FEL applications operating at a 4.5 MHz frame rate in burst mode, the detector supports continuous acquisition at up to 400 kHz and counting mode at ≤4.5 MHz for synchrotron applications. Experimental tests with standard samples using X-ray diffraction and X-ray emission spectroscopy were conducted at several beamlines of the Swiss Light Source (SLS) and EuXFEL. The measurement results were compared with those obtained using established detectors at these beamlines, demonstrating the performance of the detector in energy-dispersive experiments.

The single photon counting microstrip detector MYTHEN III was developed at the Paul Scherrer Institute to satisfy the increasing demands in detector performance of synchrotron radiation experiments, focusing on time-resolved and on-edge powder diffraction measurements. Similar to MYTHEN II, the detector installed on the Material Science beamline covers 120° in 2θ. It is based on the MYTHEN III.0 readout chip wire-bonded to silicon strip sensors with a pitch of 50 µm, and it provides improved performance and features with respect to the previous version. Taking advantage of the three independent comparators of MYTHEN III, it is possible to obtain an improvement in the maximum count rate capability of the detector at 90% efficiency from 2.9 ± 0.8 Mphotons s−1 strip−1 to 11 ± 2 Mphotons s−1 strip−1 thanks to the detection of pile-up at high photon flux. The readout chip offers additional operation modes such as pump–probe and digital on-chip interpolation. The maximum frame rate is up to 360 kHz in 8-bit mode with dead-time-free readout. The minimum detectable energy of MYTHEN III is 4.3 ± 0.3 keV with a minimum equivalent noise charge (ENC) of 121 ± 8 electrons and a threshold dispersion below 33 ± 10 eV. The energy calibration is affected by temperature by less than 0.5% °C−1. This paper presents a comprehensive overview of the MYTHEN III detector system with performance benchmarks, and highlights the improvements reached in powder diffraction experiments compared with the previous detector generation.

High-Z compound semiconductors aim to replace silicon as sensor material for X-ray energies above 15 keV thanks to their superior absorption efficiency. However, compared to silicon, high-Z sensors still lack in several aspects such as homogeneity, charge transport properties, charge trapping (leading to polarization and afterglow effects), long ranged fluorescence photons, and others.The aim of this study is to identify sensor materials that can widen the usable energy range of our detector systems at synchrotron sources and free electron lasers (FELs) towards higher photon energies. The main characterization tool was the 75 μm pitch JUNGFRAU charge integrating detector in combination with various high-Z sensors. As charge integrating detectors allow the direct measurement of the collected charge of every single photon with a high spatial resolution, these detectors offer interesting insights into temporal as well as spatial sensor effects which affect the charge collection.As one of the major challenges of the upcoming 4 th generation of synchrotrons or FELs are very intense and potentially pulsed photon beams, the sensors needs to be able to reliably measure highly intense signals and to have no afterglow phenomena after illumination. Measurements performed at the Material Science (MS) beamline of the SLS using photon fluxes up to 5×10 10 ph/(mm 2 • s) and at the FXE beamline of the EuXFEL focused on understanding the dynamic behavior (like signal stability, polarization and afterglow effects) of various high-Z sensor materials like GaAs:Cr (from different suppliers), as well as CdTe (Ohmic and Schottky type) and CdZnTe.The presentation will give an overview of the specific needs of the sensors for the different photon sources and will show how the results obtained fulfill these requirements.

JUNGFRAU is a state-of-the-art charge-integrating detector for high performance experiments at synchrotrons and free-electron lasers. It is currently limited to a frame rate of 2.2 kHz. With the goal to increase the frame rate of the detector to $\gt10 \mathrm{kHz}$, we have designed a 3.125 Gbps high speed serial readout. Thus, the development of a fast Analog-To-Digital Converter (ADC) has become a priority. The design of the current rail-to-rail, fully differential ADC prototype will be presented along simulation results and laboratory evaluation. The prototype targets a sampling rate of $20 \mathrm{MS} / \mathrm{s}$ together with an effective number of bits (ENOB) of equal to or greater than 11 bits. Power and area requirements to reach this goal are currently under evaluation. To meet these demands, a 12-bit Successive Approximation Register (SAR) ADC has been developed and fabricated in the 110 nm UMC CMOS process. We present laboratory characterization results, verifying the design requirements together with a comparison to other ADCs targeting similar use cases.

Hybrid Pixel Detectors (HPDs) are highly suitable in diffraction -based electron microscopy due to their high frame rates (> 1 kHz), high dynamic range, and good radiation hardness. However, their use in imaging applications has been limited by their relatively large pixel size (>= 55 mu m) and high-energy (> 80 keV) electrons scattering over multiple pixels in the sensor layer. To realize the full potential of fast, radiation -hard HPDs across electron microscopy modalities, we developed deep learning techniques to precisely localize the impact point of incident electrons in MUNCH, a charge integrating HPD with 25 mu m pixel size. With neural network models trained using labeled data via simulations and experimental measurements, the best spatial resolution obtained, defined in terms of the root mean squared error, was 0.60 pixels for 200 keV electrons, a three -fold improvement over a simple charge centroid method. This article presents the training sample generation, deep learning model design, training results, and imaging outcomes for a sample containing gold nanoparticles.

Hybrid pixel detectors have become indispensable at synchrotron and X-ray free-electron laser facilities thanks to their large dynamic range, high frame rate, low noise, and large area. However, at energies below 3 keV, the detector performance is often limited because of the poor quantum efficiency of the sensor and the difficulty in achieving single-photon resolution due to the low signal-to-noise ratio. In this paper, we address the quantum efficiency of silicon sensors by refining the design of the entrance window, mainly by passivating the silicon surface and optimizing the dopant profile of the n+ region. We present the measurement of the quantum efficiency in the soft X-ray energy range for silicon sensors with several process variations in the fabrication of planar sensors with thin entrance windows. The quantum efficiency for 250 eV photons is increased from almost 0.5% for a standard sensor to up to 62% as a consequence of these developments, comparable to the quantum efficiency of backside-illuminated scientific CMOS sensors. Finally, we discuss the influence of the various process parameters on quantum efficiency and present a strategy for further improvement.

When first introduced, single-photon counting detectors reshaped crystallography at synchrotrons. Their fast readout speed enabled, for example, shutter-less data collection and fine slicing of the rotation angle and boosted the development of new experimental techniques like ptychography. Under optimal conditions, single-photon counting detectors provide an unlimited dynamic range with image noise only limited by the Poisson statistics of the incoming photons. Counting the pulses from individual photons, essentially what made the detectors so successful, also causes the main drawback, which is the loss of efficiency at high photon fluxes due to pulse pileup in the analog front end. To fully take advantage of diffraction-limited light sources, the next-generation single-photon counters need to improve their count rate capabilities in the same order of magnitude as the increased flux. Moreover, fast frame rates (a few kHz) are required to cope with the shorter dwell time achievable, thanks to the higher flux. Detector architecture with multiple comparators and counters can open new possibilities for energy-resolved imaging, while interpixel communication can overcome the issues arising from charge sharing and reduce the loss of efficiency at the pixel corners. Coupling single-photon counting detectors to high-Z sensors for hard X-ray detection (>20 keV) and to low-gain avalanche diodes (LGADs) for soft X-rays is also necessary to make use of the increased coherence of the new light sources over the full radiation spectrum. In this paper, we present possible strategies to improve the performance of single-photon counting detectors at the fourth-generation synchrotron sources and compare them to charge integrating detectors.

MoNCH is a hybrid pixel detector featuring 25 pm pixel pitch and analogue readout for X-ray imaging at synchrotron radiation (SR) facilities. Sub -pixel spatial resolution has been demonstrated using charge sharing and interpolation algorithms. The current prototype version, MoNCH0.4, features 19 different pixel architectures to assess the design choices and components for an optimised architecture to be used at SR facilities, and to explore the potential use of dynamic gain switching in fine pitch pixels for applications at X-ray free electron lasers (XFELs). Previous characterisation results of the pixel architectures without dynamic gain switching have shown noise levels as low as 21.7 e- r.m.s., which have now been pushed to sub -20 e- r.m.s at room temperature using standard 300 pm -thick silicon sensors. Achieving low noise values however requires high conversion gain and necessitates design choices such as the simplification of the pixel architecture (e.g. by limiting the available choice of in -pixel gains). These compromises ultimately restrain the available dynamic range and prevent the use of MoNCH with low -gain avalanche diodes (LGADs) or high -Z sensors because of the large signals (internal amplification and high photon energies, respectively) and of large leakage currents. In this paper, we will introduce the MoNCH project followed by a description of the current prototype along with characterisation results of the pixel architectures without dynamic gain switching for synchrotron applications with an emphasis on noise and dynamic range. These experimental results will be used to fine-tune the design of MoNCH0.5 to validate the final pixel design. This small prototype should also include additional features from the continuous developments of the PSD detector group towards a full-scale 2 x 3 cm2 MoNCH1.0.

Due to their high frame rates and dynamic range, large area coverage, and high signal-to-noise ratio, hybrid silicon pixel detectors are an established standard for photon science applications at X-ray energies between 2 keV and 20 keV. These properties also make hybrid detectors interesting for experiments with soft X-rays between 200 eV and 2 keV. In this energy range, however, standard hybrid detectors are limited by the quantum efficiency of the sensor and the noise of the readout electronics. These limitations can be overcome by utilizing inverse Low-Gain Avalanche Diode (iLGAD) sensors with an optimized X-ray entrance window. We have developed and characterized a prototype soft X-ray iLGAD sensor bonded to the charge integrating 75 µm pixel JUNGFRAU chip. Cooled to −22°C, the system multiplication factor of the signal generated by an impinging photon is ≥ 11. With this gain, the effective equivalent noise charge of the system is ≤5.5 electrons root-mean-square at a 5 µs integration time. We show that by cooling the system below −50°C, single photon resolution at 200 eV becomes feasible with a signal-to-noise ratio better than 5.

Soft X-ray ptychography was employed to simultaneously image the ferroelectric and antiferromagnetic domains in an 80 nm thick freestanding multiferroic BiFeO_3. The antiferromagnetic spin cycloid was resolved by reconstructing the resonant elastic X-ray scattering and visualised together with mosaic-like ferroelectric domains in a linear dichroic contrast image at the Fe L_3 edge. The measurements reveal a near perfect coupling between the magnetic and ferroelectric ordering by which the propagation direction of the spin cycloid is locked orthogonally to the ferroelectric polarisation. The results provide a direct visualisation of the strong magnetoelectric coupling in BiFeO_3 and of its fine multiferroic domain structure, emphasising the potential of high resolution ptychographic imaging in opening new possibilities for the study of multiferroics and non-collinear magnetic materials with soft X-rays.