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.

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.

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.

Aggleton R. et al.

in Journal of Instrumentation, 12 (2017), P12019. DOI:10.1088/1748-0221/12/12/P12019

Abstract

© 2017 CERN. A new tracking detector is under development for use by the CMS experiment at the High-Luminosity LHC (HL-LHC). A crucial requirement of this upgrade is to provide the ability to reconstruct all charged particle tracks with transverse momentum above 2-3 GeV within 4 μs so they can be used in the Level-1 trigger decision. A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are reconstructed using a projective binning algorithm based on the Hough Transform, followed by a combinatorial Kalman Filter. A hardware demonstrator using MP7 processing boards has been assembled to prove the entire system functionality, from the output of the tracker readout boards to the reconstruction of tracks with fitted helix parameters. It successfully operates on one eighth of the tracker solid angle acceptance at a time, processing events taken at 40 MHz, each with up to an average of 200 superimposed proton-proton interactions, whilst satisfying the latency requirement. The demonstrated track-reconstruction system, the chosen architecture, the achievements to date and future options for such a system will be discussed.

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.

Kopmann A., Chilingaryan S., Vogelgesang M., Dritschler T., Shkarin A., Shkarin R., Dos Santos Rolo T., Farago T., Van De Kamp T., Balzer M., Caselle M., Weber M., Baumbach T.

in 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop, NSS/MIC/RTSD 2016, 2017-January (2017), 8069895. DOI:10.1109/NSSMIC.2016.8069895

Abstract

© 2016 IEEE. New imaging stations aim for high spatial and temporal resolution and are characterized by ever increasing sampling rates and demanding data processing workflows. Key to successful imaging experiments is to open up high-performance computing resources. This includes carefully selected components for computing hardware and development of advanced imaging algorithms optimized for efficient use of parallel processor architectures. We present the novel UFO computing platform for online data processing for imaging experiments and image-based feedback. The platform handles the full data life cycle from the X-ray detector to long-term data archives. Core components of this system are an FPGA platform for ultra-fast data acquisition, the GPU-based UFO image processing framework, and the fast control system “Concert”. Reconstruction algorithms implemented in the UFO framework are optimized for the latest GPU architectures and provide a reconstruction throughput in the GB/s-range. The control system “Concert” integrates high-speed computing nodes and fast beamline devices and thus enables image-based control loops and advanced workflow automation for efficient beam time usage. Low latencies are ensured by direct communication between FPGA and GPUs using AMDs DirectGMA technology. Time resolved tomography is supported by cutting edge regularization methods for high quality reconstructions with a reduced number of projections. The new infrastructure at ANKA has dramatically accelerated tomography from hours to second and resulted in new application fields, like high-throughput tomography, pump-probe radiography and stroboscopic tomography. Ultra-fast X-ray cine-tomography for the first time allows one to observe internal dynamics of moving millimeter-sized objects in real-time.

Aggleton R. et al.

in 2017 27th International Conference on Field Programmable Logic and Applications, FPL 2017 (2017), 8056825. DOI:10.23919/FPL.2017.8056825

Abstract

© 2017 Ghent University. The Compact Muon Solenoid (CMS) experiment at CERN is scheduled for a major upgrade in the next decade in order to meet the demands of the new High Luminosity Large Hadron Collider. Amongst others, a new tracking system is under development including an outer tracker capable of rejecting low transverse momentum particles by looking at the coincidences of hits (stubs) in two closely spaced sensor layers in the same tracker module. Accepted stubs are transmitted off-detector for further processing at 40 MHz. In order to maintain under the increased luminosity the Level-1 trigger rate at 750 kHz, tracker data need to be included in the decision making process. For this purpose, a system architecture has to be developed that will be able to identify particles with transverse momentum above 3 GeV/c by building tracks out of stubs, while achieving an overall processing latency of maximum 4us. Targeting these requirements the current paper presents an FPGA-based track finding architecture that identifies track candidates in real-time and bases its functionality on a fully time-multiplexed approach. As a proof of concept, a hardware system has been assembled targeting the MP7 MicroTCA processing card that features a Xilinx Virtex-7 FPGA, demonstrating a realistic slice of the track finder. The paper discusses the algorithms’ implementation and the efficient utilisation of the available FPGA resources, it outlines the system architecture, and presents some of the hardware demonstrator results.