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Item type:Publication, Access status: with files , Equilibrium shape and surface termination of supported magnetite nanoparticles(Nature Publishing Group, 2026-12-01); ; ; ; The equilibrium shape and surface termination of magnetite nanoparticles (NPs) are fundamental properties that determine the physical and chemical properties of the supercrystal structure of oleic acid-coated magnetite NPs. Here, we studied the equilibrium shape of magnetite (Fe3O4) NPs supported by Al2O3(0001) single-crystalline surfaces. We report the growth of epitaxial (111)-oriented NPs exhibiting a triangular shape with a height-to-diameter aspect ratio of 0.42 over a wide growth temperature range. We probed the surface termination of the NP facets by adsorbing formic acid as a prototypical molecule representing the adsorption behavior of oleic acid. We identified infrared absorption bands characteristic of dissociative adsorption on (111) facets with the iron tetrahedral (Fetet1) termination, as well as on mixed-terminated (100) side facets. Our experimental findings are supported by predictions of the NP shape using surface-free energy calculations from ab initio thermodynamics. The experimentally observed nanoparticle shape can only be rationalized by the presence of bulk-terminated {100} type facets. Such a fundamental understanding of the shape and surface terminations of oxide nanoparticles is crucial for tailoring the properties of hybrid hierarchical materials and drug carriers and for their development.Publicationtype: Journal Article60 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Beyond the size: Assessing the influence of synthesis parameters on ZIF-8 monolith degradation in aqueous environments(Elsevier, 2026-08-28); ; ; 15 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Experimental verification of soft X-ray imaging and RIXS mapping with a reflection zone plate(Optica Publishing Group, 2026-08-05); ; ; We demonstrate two-dimensional (2-D) imaging and resonant inelastic X-ray scattering (RIXS) spectroscopy in the hν2 “mapping” scheme using a reflection zone plate (RZP) at soft X-rays. Experiments at the PETRA III storage ring (DESY) around the N Kα 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) μm. 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.Publicationtype: Journal Article31 22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , CT-based assessment of 3D-printed clay elements(Springer, 2026-06); ; ; ; Clay-based 3D printing has emerged as a low-carbon alternative to cementitious additive manufacturing in construction. However, pore space, inhomogeneities, shrinkage, and crack formation in clay-sand-water mixtures are still poorly understood, particularly with respect to their influence on the structural integrity of clay-printed elements. This paper investigates the use of X-ray computed tomography (CT) for specimen-scale analysis of clay-sand-water mixtures used in additive manufacturing. One printed specimen and two manually prepared reference specimens in the wet and dried state were scanned with the ENCI CT system. The reconstructed and segmented volumes were used to quantify pore volume, equivalent spherical diameter, sphericity, a derived specific pore surface, and spatial porosity distribution. The printed sample exhibited markedly smaller pores than the manually prepared dried sample, indicating compaction during extrusion and layer deposition, while the dried sample showed larger and more crack-like pores consistent with shrinkage during drying. Local porosity maps and their coefficients of variation were further used to identify heterogeneous zones that may act as mechanically weaker regions. The results demonstrate the feasibility of CT-based assessment for characterizing internal porosity and heterogeneity in 3D-printed clay elements.Publicationtype: Conference Paper13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A physics-informed AI model for on-demand design of complex optical coatings(SPIE, 2026-05-28); ; ; ; The inverse design of multilayer optical coatings is a computationally intensive, non-convex optimization problem. We address this using a neural network framework trained to directly generate physical layer structures from target spectra. Our approach couples a ‘design’ network with a parameter-free, differentiable Transfer Matrix Method (TMM) model. During training, the network proposes a layer stack, the TMM model calculates its optical response, and the network’s parameters are adjusted to minimize the difference between this response and the target. This end to-end process allows the network to learn the physics of optical design directly without relying on any prior design data. Using this approach, we have generated a broadband dispersive mirror with performance characteristics comparable to those obtained by established commercial optimization tools. Building on this validated approach, we now show that this framework can be used to create a general, pre-trained model that rapidly generates initial designs for new problems, functioning as a powerful tool for optical coating design. Furthermore, the model architecture is inherently adaptable; it can be quickly fine-tuned on specific, user-defined design problems to further enhance its performance. This work demonstrates a practical pathway towards fast, generalizable, and continually improving AI tools for optical system design.Publicationtype: Conference Paper46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Data-model-guided framework for systemic emittance minimization in high brightness photoinjectors(American Physical Society (APS), 2026-05-08); ; ; ; Bunch shaping in electron linear accelerators is of critical importance, as it enables the realization of prescribed projection profiles along specific coordinates of the bunch distribution for linac-based x-ray free-electron laser (XFEL) applications. It is evident that temporally flattop electron bunches yield more uniform slice properties, reduced emittance growth, and enhanced FEL gain compared to conventional Gaussian profiles. In this work, we present a data- and model-guided framework that consists of a physics-informed model and an inverse emittance model for minimizing the bunch emittance through laser pulse shaping and the control of laser and accelerator parameters in high-brightness photoinjectors. With a temporal flattop laser shape selected, a flat slice emittance distribution along the bunch has been experimentally obtained at the European XFEL. A measured central slice emittance of about 0.4 μm at 250 pC is achieved using a 20 ps flattop laser pulse at the photocathode. Here we present the results of a commissioning experiment, marking a practical application of temporally flattop-shaped electron bunches for stable photon delivery in a user experiment week at the facility. Within limited tuning time, a pulse energy of 1.7 mJ has been achieved at photon energies of 7.1 and 7.6 keV for the two hard x-ray undulator beamlines, surpassing the user requirements. Such a data- and model-driven framework opens up new opportunities for end-to-end optimization of machine parameters, thereby enhancing the capabilities of large-scale FEL facilities.Publicationtype: Journal Article40 26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Estimation of superconducting cavity bandwidth and detuning using a Luenberger observer(American Physical Society (APS), 2026-05-08); ; ; ; Enabled by progress in superconducting technology, several continuous wave linear accelerators are foreseen in the next decade. For these machines, it is of crucial importance to track the main cavity parameters, such as the resonator bandwidth and detuning. The bandwidth yields information on the superconducting state of the cavity. The detuning should be minimized to limit the required power for operation of the cavity. The estimation of these parameters is commonly implemented in the digital electronics of the low-level rf control system to minimize the computation delay. In this proceedings paper, we present a way to compute the bandwidth and detuning using a Luenberger observer. In contrast to previous methods, the state observer yields estimations at the native control system sample rate without explicitly filtering the input signals. Additionally, the error convergence properties of the estimations can be controlled intuitively by adjusting gain parameters. Implementation considerations and test results for the derived observer are presented in the manuscript.Publicationtype: Journal Article27 7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Revealing formic acid adsorption geometries on magnetite (001) and (111) surfaces by IRRAS line shape analysis(RSC Publ, 2026-05-05); ; ; The sign and intensity of infrared (IR) bands on oxide surfaces strongly depend on light polarization and the adsorption geometry of surface species. In this study, we investigate formic acid adsorption on single crystalline magnetite Fe<inf>3</inf>O<inf>4</inf>(001) and Fe<inf>3</inf>O<inf>4</inf>(111) surfaces, which being neither perfect metals nor insulators exhibit characteristic Fano shaped IR line profiles. Using both s- and p-polarized infrared reflection absorption spectroscopy (IRRAS), we identify distinct spectral features and reveal vibrational bands that were previously unobserved in experiments employing unpolarized or solely p-polarized light. Complementary density functional theory (DFT) calculations provide structural and vibrational insights into the adsorbed species. On Fe<inf>3</inf>O<inf>4</inf>(001), a new band at 1555 cm<sup>−1</sup> observed with p-polarized light is attributed to the asymmetric OCO stretching vibration of formate bound to octahedral Fe sites with tetrahedral Fe<inf>tet1</inf> underneath. On Fe<inf>3</inf>O<inf>4</inf>(111), a band at 1730 cm<sup>−1</sup> detected in both unpolarized and s-polarized light corresponds to the CO stretch of a monodentate species. These results highlight the crucial role of light polarization in IRRAS for elucidating adsorption geometries and electronic properties of oxide surfaces.Publicationtype: Journal Article17 14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Optimizing the iterative reprojection phase retrieval algorithm Via Angle sampling(IEEE, 2026-05); ; ; ; Coherence-based imaging with synchrotron radiation offers spatial resolutions beyond the limits of conventional X-ray imaging and enables quantitative mapping of the refractive index. In nanotomography experiments with phase contrast, reconstruction is commonly performed in a two-step procedure, namely phase retrieval and computer tomography. One may enforce a 3D consistency constraint by repeatedly switching between both steps through a reprojection of the tomogram, which comes at a high computational cost. In this study, we accelerate the reprojection approach by updating the phase retrieval step on a subset of the projection angles. We show that the improvement is also reflected on the rest of angles through the tomographic reconstruction. We present an exemplary phantom to show that the angle sampling both accelerates convergence and helps reconstruction of challenging angles.Publicationtype: Conference Paper21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Auto-generating ageing self-tests with hardware in the loop for commercial microcontrollersMicrocontrollers in critical systems require monitoring of hardware ageing to avoid unexpected malfunctioning. We previously introduced a deployable timing-based method with self-tests for ageing monitoring in commercial microcontrollers that relies solely on user-level information. While effective, manually constructing computing payloads for system-level tests can limit scaling and coverage of hardware-specific critical paths or subsystems. In this paper, we complement our technique with an automated generation of the self-test firmware. We explore several approaches for generation using hardware in the loop (HiL) evaluation on commercial microcontrollers, including a random generation and evolutionary strategies. In the evolutionary approach, we investigate two mutation mechanisms: random selection, and contextual bandits. Our evaluations on real hardware and a surrogate model show the impact of evaluation budget and algorithm selection on the effectiveness of automatic self-test generation. Results reveal that random generation is well suited to reduced HiL explorations, while evolutionary strategies benefit from extended evaluations. Our Hil-based technique is able to produce firmwares with up to double the degradation sensitivity as the functional tests provided by the vendor.Publicationtype: Conference Paper15