Reich S., Dos Santos Rolo T., Letzel A., Baumbach T., Plech A.

in Applied Physics Letters, 112 (2018), 151903. DOI:10.1063/1.5022748

Abstract

© 2018 Author(s). We demonstrate the fabrication of a 2D Compound Array Refractive Lens (CARL) for multi-contrast X-ray imaging. The CARL consists of six stacked polyimide foils with each displaying a 2D array of lenses with a 65 μm pitch aiming for a sensitivity on sub-micrometer structures with a (few-)micrometer resolution in sensing through phase and scattering contrast at multiple keV. The parabolic lenses are formed by indents in the foils by a paraboloid needle. The ability for fast single-exposure multi-contrast imaging is demonstrated by filming the kinetics of pulsed laser ablation in liquid. The three contrast channels, absorption, differential phase, and scattering, are imaged with a time resolution of 25 μs. By changing the sample-detector distance, it is possible to distinguish between nanoparticles and microbubbles.

Cavadini P., Weinhold H., Tonsmann M., Chilingaryan S., Kopmann A., Lewkowicz A., Miao C., Scharfer P., Schabel W.

in Experiments in Fluids, 59 (2018), 61. DOI:10.1007/s00348-017-2482-z

Abstract

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. To understand the effects of inhomogeneous drying on the quality of polymer coatings, an experimental setup to resolve the occurring flow field throughout the drying film has been developed. Deconvolution microscopy is used to analyze the flow field in 3D and time. Since the dimension of the spatial component in the direction of the line-of-sight is limited compared to the lateral components, a multi-focal approach is used. Here, the beam of light is equally distributed on up to five cameras using cubic beam splitters. Adding a meniscus lens between each pair of camera and beam splitter and setting different distances between each camera and its meniscus lens creates multi-focality and allows one to increase the depth of the observed volume. Resolving the spatial component in the line-of-sight direction is based on analyzing the point spread function. The analysis of the PSF is computational expensive and introduces a high complexity compared to traditional particle image velocimetry approaches. A new algorithm tailored to the parallel computing architecture of recent graphics processing units has been developed. The algorithm is able to process typical images in less than a second and has further potential to realize online analysis in the future. As a prove of principle, the flow fields occurring in thin polymer solutions drying at ambient conditions and at boundary conditions that force inhomogeneous drying are presented.

A N Danilewski, J Becker, T Baumbach, D Hänschke, A Kopmann, V Asadchikov, M Kovalchuk

Final report, BMBF Programme: “Development and Use of Accelerator-Based Photon Sources (2014)”

Project duration: 01.10.2014 – 30.09.2017

Executive summary

Within the STROBOS-CODE project, partners from two German (KIT, University Freiburg (UFREI)) and two Russian (Shubnikov Institute of Crystallography (SHUB), Kurchatov Institute (KUR)) institutions developed and optimized a novel methodology for correlative 2D, 3D, and 4D characterization of crystalline materials, based on X-ray diffraction imaging. In short, the joint work comprised the theoretical description of the measurement principles, the derivation of the measurement procedures, the specification, design, and construction of the corresponding instrumentation, the formulation and implementation of the data analysis algorithms, as well as the experimental demonstration of the methodology.

The driving application within the project is the in situ investigation of crystals and devices, aiming for a fundamental understanding of structure, nucleation, arrangement, propagation, and extension of defects like dislocations or cracks. In this context, the results of the STROBOS-CODE project will open new perspectives to improve prediction, control, and avoidance of critical defects during the industrial growth and processing of technologically relevant crystals, in particular semi-conductor wafers e.g. for microelectronic devices or solar cells. For several selected use cases, the methodology developed within the STROBOS-CODE project has already been demonstrated, successfully.

The core element of the methodical development is X-ray imaging based on Bragg diffraction contrast, which is highly sensitive to local elastic and plastic deformation of crystal lattices as typically associated with crystal defects. Based on the results of the preceding UFO project and on the prior development of the basic 3D X-ray diffraction laminography (XDL), within STROBOS-CODE an advanced methodology has been made available for correlative characterization and with in situ capabilities. The correlative analysis of data obtained by complementary techniques like X-ray white-beam topography or visible light microscopy now allows creating an unprecedented comprehensive picture of crystalline defects like dislocation networks.
The adaption and optimization of laminographic 3D reconstruction algorithms to the specific requirements of X-ray Bragg diffraction contrast imaging has been performed. Aiming for in situ ca-pabilities, particular interest was put on the reduction of the number of projections required for XDL reconstruction, which could be successfully reduced from about 700 to 50-100 by the appropriate utilization of DART-based algorithms. This progress in data processing resulted in a substantial reduction of the measurement time, for the first time enabling quasi in situ characterization of dislocation dynamics with 3D XDL scans interleaved with a step-wise thermal treatment of the investigated samples.

A concept for a mobile instrument suited for general purpose full-field X-ray diffraction imaging, referred to as the CODE station, has been worked out. A first prototype was successfully realized, served as a test instrument, and enabled first experiments. The results were used to further improve the methodology. Despite the constraints due to the compact and lightweight design, an angular precision and stability of all critical elements better than 1.5e-4 degree was successfully demonstrated. The components of the final instrumentation have been specified and ordered and the final assembly will be performed by UFREI during its extended project run-time until 2019. Afterwards, the highly flexible and mobile CODE-instrumentation will be available for routine experiments at all suitable synchrotron end stations, like e.g. at PETRA III or at the ESRF.

For the STROBOS-instrumentation in Moscow a modular camera system has been developed, constructed, implemented, and tested in cooperation with the Russian partners. It is designed to enable a continuous data streaming with up to 5GB/s. Depending on the application case, differ-ent image sensors can be installed: Sensors with 2, 4, and 20 megapixel are presently available, with a read-out speed of up to 330 frames/s. A sub-zero cooling system has been developed and the camera has been mechanically and electrically integrated for use within the STROBOS set-up.

Within the STROBOS-CODE project, several experiments demonstrated successfully the unique capabilities of the proposed concept for the instrumentation as well as of the developed methodology for correlative and quasi in situ characterization of crystal defects in technologically relevant samples like semiconductor wafers. An unprecedented, comprehensive picture of the onset of thermally driven plastic deformation of silicon wafers could be obtained and provided novel insight into the involved mechanisms. Moreover, for the first time the dynamics of dislocation nucleation and evolution could be monitored in 3D by interleaving XDL measurements and controlled step-wise annealing. Finally, also the applicability of the developed diffraction imaging methodology to higher absorbing materials could be demonstrated by the 3D visualization of dislocation cell structures in a GaAs wafer.
The results of the STROBOS-CODE project have been reported at several national and international workshops and conferences and in more than 10 peer-reviewed publications. In close collaboration, the German and Russian partners have advanced the development on the field of photon science and the methodological progress for large-scale facilities. The methodology and instrumentation developed (improve the research infrastructure at the Kurchatov Institute (STROBOS) and at KIT and other synchrotron infrastructures (CODE). The consortium created for the STROBOS-CODE project will exists beyond the project duration and will extend the cooperation and partnership of Russian and German institutions, in particular on the field of X-ray analytics, algorithms, image processing, and the characterization of crystalline materials and components. In Germany, STROBOS-CODE supports the research partnership of KIT and UFREI within the joint virtual institute “BIRD” and intensifies and strengthens their close collaboration on the field of materials science and microsystem technology.

Zakharova M., Vlnieska V., Fornasier H., Borner M., dos Santos Rolo T., Mohr J., Kunka D.

in Applied Sciences (Switzerland), 8 (2018), 468. DOI:10.3390/app8030468

Abstract

© 2018 by the authors. Single-shot grating-based phase-contrast imaging techniques offer additional contrast modalities based on the refraction and scattering of X-rays in a robust and versatile configuration. The utilization of a single optical element is possible in such methods, allowing the shortening of the acquisition time and increasing flux efficiency. One of the ways to upgrade single-shot imaging techniques is to utilize customized optical components, such as two-dimensional (2D) X-ray gratings. In this contribution, we present the achievements in the development of 2D gratings with UV lithography and gold electroplating. Absorption gratings represented by periodic free-standing gold pillars with lateral structure sizes from 5 μm to 25 μm and heights from 5 μm to 28 μm have shown a high degree of periodicity and defect-free patterns. Grating performance was tested in a radiographic setup using a self-developed quality assessment algorithm based on the intensity distribution histograms. The algorithm allows the final user to estimate the suitability of a specific grating to be used in a particular setup.

Rota L., Caselle M., Brundermann E., Funkner S., Gerth C., Kehrer B., Mielczarek A., Makowski D., Mozzanica A., Muller A.-S., Nasse M.J., Niehues G., Patil M., Schmitt B., Schonfeldt P., Steffen B., Weber M.

in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2018). DOI:10.1016/j.nima.2018.10.093

Abstract

© 2018 Synchrotrons and modern FEL light sources operate with bunch repetition rates in the MHz range. The profile of the electron beam inside the accelerator can be characterized with indirect experimental techniques where linear array detectors are employed to measure the emitted synchrotron radiation or the spectrum of a near-IR laser. To improve the performance of modern beam diagnostics we have developed KALYPSO, a detector system operating with a continuous frame rate of up to 2.7 MHz. To facilitate the integration in different experiments, a modular architecture has been adopted. Different semiconductor micro-strip sensors can be connected to front-end ASICs to optimize the quantum efficiency at different photon energies, ranging from visible light up to near-IR. The front-end electronics are integrated within an heterogeneous DAQ consisting of FPGAs and GPUs, which allows scientists to implement real-time data processing algorithms. The current version of the detector is in operation at the KARA synchrotron light source and at the European XFEL. In this contribution we present the detector architecture, the performance results and the on-going technical developments.

Asadchikov V., Buzmakov A., Chukhovskii F., Dyachkova I., Zolotov D., Danilewsky A., Baumbach T., Bode S., Haaga S., Hanschke D., Kabukcuoglu M., Balzer M., Caselle M., Suvorov E.

in Journal of Applied Crystallography (2018). DOI:10.1107/S160057671801419X

Abstract

© International Union of Crystallography, 2018 This article describes complete characterization of the polygonal dislocation half-loops (PDHLs) introduced by scratching and subsequent bending of an Si(111) crystal. The study is based on the X-ray topo-tomography technique using both a conventional laboratory setup and the high-resolution X-ray image-detecting systems at the synchrotron facilities at KIT (Germany) and ESRF (France). Numerical analysis of PDHL images is performed using the Takagi–Taupin equations and the simultaneous algebraic reconstruction technique (SART) tomographic algorithm.

Miko I., van de Kamp T., Trietsch C., Ulmer J.M., Zuber M., Baumbach T., Deans A.R.

in PeerJ, 2018 (2018), e5174. DOI:10.7717/peerj.5174

Abstract

© 2018 Mikó et al. Ceraphronoids are some of the most commonly collected hymenopterans, yet they remain rare in the fossil record. Conostigmus talamasi Mikó and Trietsch, sp. nov. from Baltic amber represents an intermediate form between the type genus, Megaspilus, and one of the most species-rich megaspilid genera, Conostigmus. We describe the new species using 3D data collected with synchrotron-based micro-CT equipment. This non-invasive technique allows for quick data collection in unusually high resolution, revealing morphological traits that are otherwise obscured by the amber. In describing this new species, we revise the diagnostic characters for Ceraphronoidea and discuss possible reasons why minute wasps with a pterostigma are often misidentified as ceraphronoids. Based on the lack of ceraphronoid characteristics, we remove Dendrocerus dubitatus Brues, 1937, Stigmaphronidae, and Radiophronidae from Ceraphronoidea and consider them as incertae sedis. We also provide some guidance for their future classification.

Sakraker Ozmen I., Joshi A., Bohrk H., Hanschke D., Cecilia A.

in 2018 Joint Thermophysics and Heat Transfer Conference (2018), AIAA 2018-3588. DOI:10.2514/6.2018-3588

Abstract

© 2018 by Isil Sakraker Özmen, Archana Joshi, Hannah Boehrk, Daniel Haenschke, Angelica Cecilia. Published by the American Institute of Aeronautics and Astronautics, Inc. The cork based DLR Cork and low density DLR ZURAM materials were exposed to heat while being monitored by x-ray radiation in a synchrotron facility. A portable furnace was manufactured to provide the low pressure conditions of the atmospheric entry and the high stagnation heat fluxes. A total of 4 samples were exposed to radiative heating at 10.4 mbar pressure. The sample was rotated inside the furnace by a miniature servomotor to allow for 3D image reconstruction. Furthermore, 2D radiography sequences were also acquired with stationary samples. The charring, char front propagation and volumetric expansion were prominent in the case of DLR Cork. Even though the ZURAM sample did not significantly char, volumetric phenomena were observed even in the virgin regions. 3D image sequences are provided for ablating DLR Cork material, where the surface topology evolution can be observed. Furthermore, individual cork granules could be tracked throughout the ablation. An optical flow analysis was applied to track the carbon fibers following the volumetric phenomena inside the DLR ZURAM samples.

Ametova E., Ferrucci M., Chilingaryan S., Dewulf W.

in Precision Engineering (2018). DOI:10.1016/j.precisioneng.2018.05.016

Abstract

© 2018 Elsevier Inc. X-ray computed tomography (CT) is an imaging technique that allows the reconstruction of an imaged part in the form of a three-dimensional attenuation map. The CT data acquisition process consists of acquiring X-ray transmission images from multiple perspectives. Analysis of the reconstructed attenuation map can provide dimensional and material information about the measured part(s). Therefore, CT is recognized as a solution for quality control tasks, for example dimensional inspection of complex objects with intricate inner geometries. CT measurements can suffer from various sources of error in the measurement procedure. One such influence is the geometrical alignment of the CT instrument components. Typical tomographic reconstruction algorithms impose strict requirements on the relative position and orientation of the three main components: X-ray source, rotation axis of the sample stage, and X-ray detector. Any discrepancy in the actual CT geometry from the geometry assumed by the reconstruction algorithm will contribute to errors in measurements performed on the reconstructed data. There is currently no standardized or easily implementable method for users to compensate geometrical misalignments of the CT instrument. In many cases, the procedure of mechanical adjustment of CT instrument is time consuming and impractical. In this paper, we show that software-based compensation of deviations in CT instrument geometry is an effective alternative to mechanical adjustment of CT instrument. Through computer simulations, we compare qualitatively and quantitatively two methods to compensate CT instrument misalignment: radiographic re-binning (interpolation) and a modified conventional reconstruction algorithm with embedded misalignment compensation.

Jerome N.T., Kopmann A.

in VISIGRAPP 2018 – Proceedings of the 13th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications, 3 (2018) 341-348.

Abstract

© 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved. With the advancement of instrument precision, research facilities are generating data at an unprecedented rate. These experimental results are stored in a digital library platform which the contents are later accessible from within the facility or the public. However, the sheer volume of collected data is overwhelming the capacity of researchers and impedes the process of browsing for the desired data. In this paper, we present a concept of Digital Visual Exploration Library (DVEL) based on the confluence of two major research domains-digital library and visualisation-that enables efficient browsing of the growing data within a digital library. We complement the current state-of-the-art textual metadata description by integrating visual exploration to address big complex data, i.e., data of large size, multimodal data and multivariate data. We describe our concept based on use cases from three unique domains: climate research with Doppler wind lidar, X-ray-imaging for entomology research, and medical imaging with ultrasound computer tomography.