Christian David

We demonstrate two-dimensional (2-D) imaging and resonant inelastic X-ray scattering (RIXS) spectroscopy in the hν ² “mapping” scheme using a reflection zone plate (RZP) at soft X-rays. Experiments at the PETRA III storage ring (DESY) around the N K _α line (392.4 eV) verify that an RZP can be used in the paraxial regime combined with the 1-D line scanning mode for time-efficient full-field imaging of an extended object with an angular size of 2.5 mrad at low aberrations, even for off-design energies, at a spatial resolution of (14–24) μ m. A similar setup collects the RIXS spectra of acetonitrile within (388.6–401.8) eV for a variable incident photon energy between 399 eV and 400 eV, at a potential resolution of (0.3 ± 0.1) eV. RZPs with their precise manufacturability, efficiency, and strong dispersion can serve as advantageous diffractive optical elements in soft X-ray microscopy or “photon-in vs. photon-out” spectroscopy.

We present a nested Wolter-I mirror design for a neutron condenser, which is based on established X-ray telescope technology. We demonstrate through simulations that it can increase the flux density at the ESS imaging instrument ODIN by up to two orders of magnitude. Experimental measurements of reflectivity and figure errors on a prototype mirror element confirm the technical feasibility of the approach. Then, we introduce design strategies for an imaging objective to fully exploit the condenser specifications while achieving spatial resolutions comparable to those of X-ray micro-computed tomography instruments. Analytically, we show that for monochromatic beams suitable solutions exist employing arrays of hundreds of identical objectives, realized either as compound refractive lenses (CRLs) or Fresnel zone plates (FZPs). To mitigate the inherent chromatic aberration of these optics, each individual objective could be replaced by an achromatic FZP/CRL combination. Key optical properties of the resulting microscope are estimated. This novel full-field microscopy concept for highly divergent, polychromatic neutron beams has the potential to improve temporal and spatial resolution for large samples and sample environments and to enable the simultaneous acquisition of hundreds of projections in neutron tomography.

For the integration of two-dimensional materials in future devices, a fundamental understanding of their response to external stimuli is needed. Toward this goal, we have investigated the electron and spin dynamics in the metallic van der Waals material Fe3GeTe2 (FGT) in its paramagnetic state after ultrafast optical excitation. To this end, we have employed a zone plate streaking technique with probing energies in the extreme ultraviolet range, tuned to the Fe M2,3 and Te N4,5 absorption edges. This approach provides insights into energy-dependent charge dynamics with a sensitivity to transient absorption changes on the order of ∼10−4. We find a slow carrier relaxation time at both elemental edges—up to (2.2±0.6) ps in Te and exceeding several picoseconds in Fe—which is surprising for a metal. To elucidate the complex time-resolved response, we also employ static x-ray absorption spectroscopy at the corresponding elemental edges, in which we find a double feature at the Fe M2,3 edge. We attribute this to different Fe sites in the pristine material and an oxidized surface layer, and we propose that the time-resolved absorption dynamics show a mixture of signals stemming from the different species. Additionally, we conducted time-resolved x-ray magnetic circular dichroism measurements in FGT at room temperature. We do not find clear evidence of the previously observed light-induced ferromagnetic order above TC. Our study lays the groundwork for a deeper understanding of charge and spin dynamics in FGT after optical excitation as part of a roadmap for 2D spintronics.

Neutrons provide exceptional insight into materials, owing to their sensitivity to light elements, isotopic composition, magnetic moments, and high-penetration. However, neutron sources are polychromatic and of low brightness. Neutron optics provides a route to address these limitations by focusing, and to date, various types of neutron optics have been developed based on reflection, refraction, diffraction, and magnetism. Notably, compound refractive lenses and Fresnel zone plates have been demonstrated for imaging, yet their severe chromatic aberration under polychromatic beams has prevented their widespread use and limits progress towards true high-resolution neutron microscopy. Here, we demonstrate an achromatic neutron lens for full-field neutron microscopy. This development overcomes the intrinsic sample-detector distance constraint in pinhole-based radiography. The lens magnification enables the use of efficient detection systems without loss of spatial resolution and establishes a pathway towards high-resolution neutron microscopy. We anticipate the neutron achromat will advance a broad range of neutron methods.

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 (MÖNCH 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 MÖNCH detector (25 µm) 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 MÖNCH 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.

Dark-field X-ray imaging visualizes structural inhomogeneities through small-angle scattering, but existing directional methods are confined to the micrometer scale. While recent advances have extended dark field capabilities to nanoscale transmission X-ray microscopy, directional scattering retrieval – critical for characterizing anisotropic nanostructures – has remained inaccessible for imaging resolutions in the sub-micrometer scale. Here, we demonstrate the first directional dark-field setup for nanoimaging, achieving orientation mapping of scattering features below the spatial resolution limit. Our method is experimentally simple to implement with existing transmission X-ray microscopy setups. We validate its performance by successfully resolving sub-resolution test structure orientations, cross-correlating orientational changes within hierarchical nanoporous materials, and mapping the directional arrangement of hydroxyapatite nanocrystals (30–70 nm) within human tooth enamel. By utilizing shadow regions in the optical configuration, we further extend the detectable scattering vector range, demonstrating a pathway toward size-selective dark-field imaging. This advancement enables the quantitative structural characterization of anisotropic nanomaterials, which are critical to biomineralization, advanced materials, and nanotechnology applications.

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 implementation of full-field transmission X-ray microscopy (TXM) at X-ray tube sources suffers from image blurring due to the chromatic aberration of the lenses and from long exposure times due to the inherent low flux of laboratory sources. Here, we demonstrate the first laboratory full-field TXM system, which combines tailored monocapillary optics, an achromatic X-ray lens, and the MÖNCH hybrid silicon pixel detector to address these challenges. With current optics, this TXM system demonstrates a spatial resolution down to 480 nm using X-ray energies around 10 keV. Despite the large pixel pitch of the MÖNCH detector, high spatial resolution imaging can be achieved by using interpolation methods leveraging charge sharing. In addition, the energy resolving power of the MÖNCH detector allows for the acquisition of elemental information. Bridging the gap between structural and elemental characterizations using X-rays, the concept of this laboratory X-ray microscope provides new opportunities for research in the fields of material science, environmental science, and biology.

Neutrons provide exceptional insight into the structure and dynamics of materials, owing to their sensitivity to light elements, isotopic composition, magnetic moments, and high-penetration capabilities. Neutron sources produce beams that are polychromatic and have low brightness. Neutron optics provides a promising route to mitigate these challenges by guiding and focusing neutron beams, and to date, various types of neutron optics have been developed based on reflection, refraction, diffraction, and magnetism. Notably, compound refractive lenses and Fresnel zone plates have also been demonstrated for imaging and focusing applications, yet their severe chromatic aberration under polychromatic beams has prevented their widespread use and continues to limit progress towards true high-resolution neutron microscopy. Here, we demonstrate an achromatic neutron lens combining a compound refractive lens and a Fresnel zone plate. We experimentally verify its achromatic behaviour and compare its performance to a Fresnel zone plate. We employ the achromatic neutron lens to realise a full-field neutron microscope. This development overcomes the long-standing trade-off between flux and spatial resolution that constrains neutron imaging in a pinhole-based radiography geometry and establishes a pathway towards high-resolution neutron microscopy. We anticipate that this new class of neutron optics will advance a broad range of neutron methods that require or benefit from focused neutron beams.