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Extending the capillary wave model to include the effect of bending rigidity: X-ray reflectivity and diffuse scattering
No full textThe surface roughness of a thin film at a liquid interface exhibits contributions of thermally excited fluctuations. This thermal roughness depends on temperature (), surface tension (), and elastic material properties, specifically the bending modulus () of the film. A nonzero suppresses the thermal roughness at small length scales compared to an interface with zero , as expressed by the power spectral density of the thermal roughness. The description of the x-ray scattering of the standard capillary wave model (CWM), which is valid for zero , is extended to include the effect of . The extended CWM (eCWM) provides a single analytical form for both the specular x-ray reflectivity (XRR) and the diffuse scattering around the specular reflection, and recovers the expression of the CWM at its zero limit. This theoretical approach enables the use of single-shot grazing incidence x-ray off-specular scattering (GIXOS) measurements for characterizing the structure of thin films on a liquid surface. The eCWM analysis approach decouples the thermal roughness factor from the surface scattering signal, providing direct access to the intrinsic surface-normal structure of the film and its bending modulus. Moreover, the eCWM facilitates the calculation of reflectivity at any desired resolution (pseudo-XRR approach). The transformation into pseudo-XRR provides the benefit of using widely available XRR software to perform GIXOS analysis. The extended range of the vertical scattering vector () available with the GIXOS pseudo-XRR approach allows for a higher spatial resolution than with conventional XRR. Experimental results are presented for various lipid systems, showing strong agreement between conventional specular XRR and pseudo-XRR methods. This agreement validates the proposed approach and highlights its utility for analyzing soft, thin films
Effects of the compression rates on the lattice parameters in Zn investigated by dynamic diamond anvil cell
No full textHigh-pressure experiments allow us to induce and control chemical reactions or synthesize materials of unique properties. Furthermore, they are our primary means to replicate the conditions of geological processes and thus of studying, measuring, and understanding compositions and conditions in planetary interiors or asteroid impacts and subduction, etc. In all those experiments, time is a critical factor, as the compression rate or strain rate defines and alters the sample environment. Until recently, most experiments have been performed with either quasistatic strain rates, , in diamond anvil cell and large volume press apparatus, or at very high strain rates, , using gas gun, laser shock, and ramp compression. The work presented here focuses on intermediate compression rates applied to hcp Zn, using the dynamic diamond anvil cell. The evolution of the lattice parameters depends on the choice of the pressure transmitting medium. Nevertheless, at nonhydrostatic conditions we observe a significant change in the evolution of the lattice parameter when compressed at strain rates of or . At , the c/a ratio does not correlate with the results of slow, nonhydrostatic experiments, but its trend resembles closer with hydrostatic, quasistatic data. The deviation indicates that strain rates of interfere with the otherwise predominant deformation mechanism at quasistatic conditions
OSCARS: Consolidation of Services in the Photon and Neutron Open Science Cluster
No full textThe EU project OSCARS (Open Science Clusters’ Action for Research and Society) brings research data to new audiences and targets new use-cases in a broad range of scientific clusters including Photon and Neutron Sciences (PaN). As recommended by a new White Paper from the user organisations, ESUO and ENSA, adherence to the FAIR principles (Findable, Accessible, Interoperable, Reusable) facilitates the use of research data in novel ways, with increased citations acknowledging original researchers and facilities that provided that data. Further, increased (meta)data and software findability and accessibility promotes a better use of resources by reducing the duplication of experiments. We recently completed the task of consolidating the achievements of the PaN Open Science Cluster (PaNOSC), integrating knowledge and skills from various contexts to create a more comprehensive understanding. This was achieved by cataloguing existing resources to gain an overview of available services and data sources. For PaNOSC, we created the portfolio from scratch, starting with collections from key Research Infrastructures (RIs). Representatives from various RIs within PaNOSC, established under OSCARS, significantly contributed by adding new resources and updating information on existing ones, resulting in a portfolio of over 500 resources. The services and data sources identified are candidates for being on-boarded to the thematic PaNOSC EOSC node, which has been selected for implementation in the EOSC Federation. The portfolio serves as a foundation for identifying services needed for specific tasks within typical research scenarios. We have gathered a selection of PaNOSC-typical scenarios that can be streamlined and enhanced by composing the relevant services. We will highlight several key aspects of these scenarios that show high potential for composability. One or two of these aspects will be developed as demonstrators within the project, while others will be addressed through the OSCARS Open Call funded projects
Influence of an AlO Capping Layer on the Thermal Reduction of the NativeNiobium Oxide: An In situ X-ray Reflectivity Study
No full textSuperconducting radio-frequency cavities, critical components of modern particle accelerators andquantum computing hardware, rely fundamentally on the surface properties of niobium. However,native oxide formation and impurity uptake in the near-surface region can degrade superconductingperformance and increase RF losses during operation. In this study, we present a systematic in situX-ray reflectivity investigation of (110) niobium single crystal surfaces with and without an atomiclayer deposited AlO capping layer under ultra-high vacuum conditions up to 650 °C. Our resultsreveal a temperature-dependent reduction of the native niobium oxide layers in both capped anduncapped samples, with similarities in the overall behavior but clear differences in the reductionpathways. The AlO capping layer modifies the reduction process, prevents oxide regrowth uponair exposure, and protects the niobium surface against impurity uptake during thermal treatment.These findings demonstrate that AlO capping is an effective strategy to suppress native oxideformation during thermal cycling, offering clear benefits for the performance and operational lifetimeof superconducting radio-frequency cavities and related quantum computing technologies
Insight into the carbon monoxide reduction reaction on Cu(111) from operando electrochemical X-ray photoelectron spectroscopy
No full textIn this work, we introduce a modified dip-and-pull ECXPS approach that offers new mechanistic insight into the alkaline CORR over a Cu(111) single crystal surface. We tackle two major unresolved questions in the CORR mechanism that persist in the literature. Firstly, we address the mechanism for methane formation on Cu(111) and show that the mechanism likely proceeds via atomic carbon, which subsequently couples, leading to the accumulation of amorphous carbon on the surface. Secondly, we provide insight into whether the mechanism for acetate formation occurs entirely on the surface or partially within the solution phase, showing that acetate is present on the surface, indicating a surface-based reaction. These insights into surface-based mechanisms provide a handle for designing future catalysts that can efficiently target the binding of specific intermediates. Furthermore, we expect that our modified approach to dip-and-pull ECXPS - in which we have changed the electrode geometry, the method of introducing the reactant gas, and used hard x-rays - will significantly expand the technique’s applicability, enabling studies of the CO(2)RR and beyond
Covalent Organic Framework Solid Solutions for Combined Near-Infrared Photodynamic and Drug Delivery Cancer Therapy
No full textCovalent organic frameworks (COFs) have been emerging as versatile reticular materials due to their tunable structures and functionalities, enabled by precise molecular engineering at the atomic level. While the integration of multiple compotents into COFs has substantially expanded their structural complexity, the strategic engineering of diverse functionalities within a single framework via the random distribution of linkers with varying lengths remains largely unexplored. Here, we report a series of highly crystalline COF solid solutions synthesized using azobenzene and bipyridine as linkers, where tuning the ratio of linkers and incorporating palladium effectively modulates the balance between near-infrared (NIR) light absorption and catalytic sites for NIR-generation of hydrogen peroxide (H2O2). Capitalizing on the deep tissue penetration of NIR light and the generated H2O2 as reactive oxygen species, the optimal COF solid solution reduces breast cancer cell viability by almost 90% after 1 hour of irradiation in a combined in vitro photodynamic and drug delivery therapy
Substrate material studies for PCB-based electro-optical bunch arrival-time monitors for XFELs
No full textThe all-optical synchronization system used in many X-ray free-electron laser facilities (XFELs) relies on electro-optical bunch arrival-time monitors (EO-BAM) for measuring the single bunch arrival time with regards to an optical reference. An upgrade of the established EO-BAM is intended to achieve a sensitivity that enables stable operation with bunches down to charges of 1 pC, or to significantly increase the resolution in normal operation. Therefore, the pickup structure, the RF path and the electro-optical modulators are undergoing a fundamental redesign. The novel concept of the pickup structure comprises planar pickups on a printed circuit board (PCB) with integrated combination network and a bandwidth of up to 100 GHz. The theoretical jitter charge product of the preliminary concept has been estimated to be in the order of 9 fs pC and the concept was proven experimentally with a 67-GHz demonstrator at ELBE. In this contribution, we compare ceramic and glass substrates in terms of radiation hardness, sensitivity, and manufacturing capabilities. The achievable bandwidth and sensitivity are influenced by material losses and varying tolerances due to different fabrication methods
Towards Differentiable Beam Dynamics Modeling in BLAST/ImpactX
No full textDifferentiable simulations are in demand in accelerator physics, demonstrating order-of-magnitude improvements for complex tasks such as many-parameter optimization for accelerator working points and reconstruction of hard-to-measure quantities. At its core, a differentiable simulation does not only solve a forward problem, but additionally provides gradients of output parameters (e.g. beam parameters) with respect to input parameters (e.g. beamline or source parameters).How to effectively program large dynamic simulations differentiably is still an open question, but there is general consensus that a “single-source” approach aided by automatic differentiation (AD) is desirable. Addressing this, there are a) emerging domain-specific languages in machine learning that are intrinsically differentiable, and b) highly-performing & scalable, general-purpose languages like ISO C++ of existing codes. The challenge of approach a) is syntax specialization, which can limit ease of implementation & performance for physics algorithms, while b) requires additional work for AD.Performance is important for modeling high-order beam dynamics and collective effects in accelerators. We compare the fast, modern codes ImpactX (C++/Python) and Cheetah (PyTorch) using traditional, gradient-free modeling. We then show progress in introducing single-source differentiability in ImpactX using modern compiler techniques, producing performant executables for gradient-based and gradient-free modeling
Smith-Purcell and Transition Radiation Based Charged Particle Beam Diagnostics for the Femtosecond-Range
No full textWe will give an overview of the Smith-Purcell and transition radiation based longitudinal diagnostic methods employed at the ARES (Accelerator Research Experiment at SINBAD) linear accelerator to characterize femto-second long electron bunches. The Smith-Purcell radiation mechanism has been studied for the case of metallic gratings, but not much experimental data has been published yet with respect to dielectric gratings as charged particle beam diagnostic devices. We expect a number of advantages in the detection of the radiation at the substrate side and the spectral properties of the radiation tailored by the geometric shape of the grating structures. Due to the advances in lithographic techniques dielectric gratings can be produced with optical wavelength periodicities and the shapes can be controlled with nano-meter precision. For femto-second bunch lengths the coherence of transition radiation starts to reach the near-infrared to optical regime. This opens up the possibility of characterizing the spectrum with readily available high sensitivity semi-conductor based detectors to draw conclusions on the form factor and measure bunch lengths
Annotated Logbook Dataset for Binary Issue Detection in Laser Operations (2022–2024)
No full textThis dataset contains annotated operator logbook entries collected between 2022 and 2024 at DESY. Each entry documents routine observations or potential issues during laser system operation. The dataset has been manually annotated for the task of binary issue detection, distinguishing between “issue” and “non-issue” entries. All personal identifiers and sensitive information have been anonymized according to PUBDB guidelines. The dataset supports research on automated anomaly and issue detection using large language models (LLMs) in scientific facility operations