van de Kamp T., Schwermann A.H., dos Santos Rolo T., Losel P.D., Engler T., Etter W., Farago T., Gottlicher J., Heuveline V., Kopmann A., Mahler B., Mors T., Odar J., Rust J., Tan Jerome N., Vogelgesang M., Baumbach T., Krogmann L.

in Nature Communications, 9 (2018), 3325. DOI:10.1038/s41467-018-05654-y

Abstract

© 2018, The Author(s). About 50% of all animal species are considered parasites. The linkage of species diversity to a parasitic lifestyle is especially evident in the insect order Hymenoptera. However, fossil evidence for host–parasitoid interactions is extremely rare, rendering hypotheses on the evolution of parasitism assumptive. Here, using high-throughput synchrotron X-ray microtomography, we examine 1510 phosphatized fly pupae from the Paleogene of France and identify 55 parasitation events by four wasp species, providing morphological and ecological data. All species developed as solitary endoparasitoids inside their hosts and exhibit different morphological adaptations for exploiting the same hosts in one habitat. Our results allow systematic and ecological placement of four distinct endoparasitoids in the Paleogene and highlight the need to investigate ecological data preserved in the fossil record.

Rolo T.S., Reich S., Karpov D., Gasilov S., Kunka D., Fohtung E., Baumbach T., Plech A.

in Applied Sciences (Switzerland), 8 (2018), 737. DOI:10.3390/app8050737

Abstract

© 2018 by the authors. An array of compound refractive X-ray lenses (CRL) with 20 × 20 lenslets, a focal distance of 20 cm and a visibility of 0.93 is presented. It can be used as a Shack-Hartmann sensor for hard X-rays (SHARX) for wavefront sensing and permits for true single-shot multi-contrast imaging the dynamics of materials with a spatial resolution in the micrometer range, sensitivity on nanosized structures and temporal resolution on the microsecond scale. The object’s absorption and its induced wavefront shift can be assessed simultaneously together with information from diffraction channels. In contrast to the established Hartmann sensors the SHARX has an increased flux efficiency through focusing of the beam rather than blocking parts of it. We investigated the spatiotemporal behavior of a cavitation bubble induced by laser pulses. Furthermore, we validated the SHARX by measuring refraction angles of a single diamond CRL, where we obtained an angular resolution better than 4 μrad.

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.

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.

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.

Reich S., Gottlicher J., Letzel A., Gokce B., Barcikowski S., dos Santos Rolo T., Baumbach T., Plech A.

in Applied Physics A: Materials Science and Processing, 124 (2018), 71. DOI:10.1007/s00339-017-1503-3

Abstract

© 2017, Springer-Verlag GmbH Germany, part of Springer Nature. Pulsed laser ablation in liquids (PLAL) as an attractive process for ligand-free nanoparticle synthesis represents a multiscale problem to understand the mechanisms and achieve control. Atomic and nanoscale processes interacting with macroscale dynamics in the liquid demand for sensitive tools for in-situ and structural analysis. By adding X-ray methods, we enlarge the available information on millimeter-scale bubble formation down to atomic-scale nanoparticle reactions. X-ray spectroscopy (XAS) can resolve the chemical speciation of the ablated material during the ablation from a zinc wire target showing a first oxidation step from zinc to zinc oxide within some 10 min followed by a slower reaction to hydrozincite. X-ray imaging investigations also give additional information on the bubble dynamics as we demonstrate by comparing the microsecond radiography and optical stroboscopy. We show different features of the detachment of the ablation bubble from a free wire. The location of the first collapse occurs in front of the target. While a first rebound bubble possesses an homogeneous interior, the subsequent rebound consists merely of a cloud of microbubbles.

Hanschke D., Danilewsky A., Helfen L., Hamann E., Baumbach T.

in Physical Review Letters, 119 (2017), 215504. DOI:10.1103/PhysRevLett.119.215504

Abstract

© 2017 American Physical Society. Correlated x-ray diffraction imaging and light microscopy provide a conclusive picture of three-dimensional dislocation arrangements on the micrometer scale. The characterization includes bulk crystallographic properties like Burgers vectors and determines links to structural features at the surface. Based on this approach, we study here the thermally induced slip-band formation at prior mechanical damage in Si wafers. Mobilization and multiplication of preexisting dislocations are identified as dominating mechanisms, and undisturbed long-range emission from regenerative sources is discovered.

Farago T., Mikulik P., Ershov A., Vogelgesang M., Hanschke D., Baumbach T.

in Journal of Synchrotron Radiation, 24 (2017) 1283-1295. DOI:10.1107/S1600577517012255

Abstract

© International Union of Crystallography, 2017. An open-source framework for conducting a broad range of virtual X-ray imaging experiments, syris, is presented. The simulated wavefield created by a source propagates through an arbitrary number of objects until it reaches a detector. The objects in the light path and the source are time-dependent, which enables simulations of dynamic experiments, e.g. four-dimensional time-resolved tomography and laminography. The high-level interface of syris is written in Python and its modularity makes the framework very flexible. The computationally demanding parts behind this interface are implemented in OpenCL, which enables fast calculations on modern graphics processing units. The combination of flexibility and speed opens new possibilities for studying novel imaging methods and systematic search of optimal combinations of measurement conditions and data processing parameters. This can help to increase the success rates and efficiency of valuable synchrotron beam time. To demonstrate the capabilities of the framework, various experiments have been simulated and compared with real data. To show the use case of measurement and data processing parameter optimization based on simulation, a virtual counterpart of a high-speed radiography experiment was created and the simulated data were used to select a suitable motion estimation algorithm; one of its parameters was optimized in order to achieve the best motion estimation accuracy when applied on the real data. syris was also used to simulate tomographic data sets under various imaging conditions which impact the tomographic reconstruction accuracy, and it is shown how the accuracy may guide the selection of imaging conditions for particular use cases.The flexible and efficient framework syris is presented and its capabilities for the simulation of four-dimensional X-ray imaging experiments are demonstrated by two exemplary applications.

Gasilov S., Mittone A., Dos Santos Rolo T., Polyakov S., Zholudev S., Terentyev S., Blank V., Bravin A., Baumbach T.

in Journal of Synchrotron Radiation, 24 (2017) 1137-1145. DOI:10.1107/S1600577517012772

Abstract

© International Union of Crystallography, 2017. In this work a double-crystal setup is employed to study compound refractive lenses made of single-crystal diamond. The point spread function of the lens is calculated taking into account the lens transmission, the wavefront aberrations, and the ultra-small-angle broadening of the X-ray beam. It is shown that, similarly to the wavefront aberrations, the ultra-small-angle scattering effects can significantly reduce the intensity gain and increase the focal spot size. The suggested approach can be particularly useful for the characterization of refractive X-ray lenses composed of many tens of unit lenses.A double-crystal setup is used to quantify aberrations and to assess the influence of ultra-small-angle X-ray scattering on the optical properties of a single-crystal diamond compound refractive lens.

Gasilov S., Dos Santos Rolo T., Mittone A., Polyakov S., Terentyev S., Farago T., Blank V., Bravin A., Baumbach T.

in Optics Express, 25 (2017) 25090-25097. DOI:10.1364/OE.25.025090

Abstract

© 2017 Optical Society of America. Quality of a refractive compound X-ray lens can be limited by imperfections in surfaces of unit lenses and stacking precision. In general case both the lens transmission and optical aberrations define properties of a beam in the lens exit plane; together they can be expressed in terms of the generalized pupil function. In this work we measure this function for a diamond single crystal compound refractive lens. Consequently, we apply the pupil function to evaluate the performance of the examined compound refractive X-ray lens. A number of practically important conclusions can be drawn from such analysis.