Niehues G., Brosi M., Briindermann E., Casclle M., Funkncr S., Kehrer B., Nasse M.J., Patil M., Rota L., Steinmann J.L., Weber M., Muller A.-S.
in International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, 2018-September (2018), 8510133. DOI:10.1109/IRMMW-THz.2018.8510133
© 2018 IEEE. A key bottleneck for investigations of ultrafast processes is a detection scheme to record all individual spectra with high repetition rates to avoid averaging and to improve the signal-to-noise ratio. Here, we present spectral measurements of fs laser sources used for electro-optical detection with a KIT-developed linear sensor array and DAQ system adapted to light sources with MHz repetition rates. This system can be equipped with different sensor types covering a broad wavelength range. It can therefore be used for various applications and scientific questions. The presented exemplary applications range from accelerator-based diagnostics to table-top laser experiments.
Kehrer B., Brosi M., Steinmann J.L., Blomley E., Brundermann E., Caselle M., Funkner S., Hiller N., Nasse M.J., Niehues G., Rota L., Schedler M., Schonfeldt P., Schuh M., Schutze P., Weber M., Muller A.-S.
in Physical Review Accelerators and Beams, 21 (2018), 102803. DOI:10.1103/PhysRevAccelBeams.21.102803
© 2018 authors. Published by the American Physical Society. To understand and control dynamics in the longitudinal phase space, time-resolved measurements of different bunch parameters are required. For a reconstruction of this phase space, the detector systems have to be synchronized. This reconstruction can be used for example for studies of the microbunching instability which occurs if the interaction of the bunch with its own radiation leads to the formation of substructures on the longitudinal bunch profile. These substructures can grow rapidly – leading to a sawtooth-like behavior of the bunch. At KARA, we use a fast-gated intensified camera for energy spread studies, Schottky diodes for coherent synchrotron radiation studies as well as electro-optical spectral decoding for longitudinal bunch profile measurements. For a synchronization, a synchronization scheme is used which compensates for hardware delays. In this paper, the different experimental setups and their synchronization are discussed and first results of synchronous measurements presented.
Evangelista Y. et al.
in Journal of Instrumentation, 13 (2018), P09011. DOI:10.1088/1748-0221/13/09/P09011
© 2018 IOP Publishing Ltd and Sissa Medialab. Multi-pixel fast silicon detectors represent the enabling technology for the next generation of space-borne experiments devoted to high-resolution spectral-timing studies of low-flux compact cosmic sources. Several imaging detectors based on frame-integration have been developed as focal plane devices for X-ray space-borne missions but, when coupled to large-area concentrator X-ray optics, these detectors are affected by strong pile-up and dead-time effects, thus limiting the time and energy resolution as well as the overall system sensitivity. The current technological gap in the capability to realize pixelated silicon detectors for soft X-rays with fast, photon-by-photon response and nearly Fano-limited energy resolution therefore translates into the unavailability of sparse read-out sensors suitable for high throughput X-ray astronomy applications. In the framework of the ReDSoX Italian collaboration, we developed a new, sparse read-out, pixelated silicon drift detector which operates in the energy range 0.5-15 keV with nearly Fano-limited energy resolution (≤150 eV FWHM @ 6 keV) at room temperature or with moderate cooling (∼0°C to +20°C). In this paper, we present the design and the laboratory characterization of the first 16-pixel (4 × 4) drift detector prototype (PixDD), read-out by individual ultra low-noise charge sensitive preamplifiers (SIRIO) and we discuss the future PixDD prototype developments.
Blank T., Pfistner P., Leyrer B., Caselle M., Simons C., Schmidt C.J., Weber M.
in 2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018 (2018) 288-292. DOI:10.23919/ICEP.2018.8374306
© 2018 Japan Institute of Electronics Packaging. The Compressed Baryonic Matter Experiment (CBM) investigates highly compressed nuclear matter, utilizing a Silicon Tracking System comprising 896 silicon sensors modules packed in eight layers with an overall area of four sqm. Each module consists of one sensor, 16 Read-Out Chips and 16 double-layer micro flex-cables, which are connected to the top and bottom side of the sensor. The cables are up to 50 cm long. They carry 128 signal traces on two layers at a pitch of 100 μm and a line-width of 25 μm. The layers are separated by a meshed core to reduce the cable capacity to 0.44 pF/cm. The cables are bonded onto one sensor by a pick and place flip-chip machine. The interconnection is realized by gold stud-bumps on the silicon and SAC solder bumps on the cable. The status of the sensor module and cable production process are presented.
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
© 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.
Ametova E., Ferrucci M., Chilingaryan S., Dewulf W.
in Measurement Science and Technology, 29 (2018), 065007. DOI:10.1088/1361-6501/aab1a1
© 2018 IOP Publishing Ltd. The recent emergence of advanced manufacturing techniques such as additive manufacturing and an increased demand on the integrity of components have motivated research on the application of x-ray computed tomography (CT) for dimensional quality control. While CT has shown significant empirical potential for this purpose, there is a need for metrological research to accelerate the acceptance of CT as a measuring instrument. The accuracy in CT-based measurements is vulnerable to the instrument geometrical configuration during data acquisition, namely the relative position and orientation of x-ray source, rotation stage, and detector. Consistency between the actual instrument geometry and the corresponding parameters used in the reconstruction algorithm is critical. Currently available procedures provide users with only estimates of geometrical parameters. Quantification and propagation of uncertainty in the measured geometrical parameters must be considered to provide a complete uncertainty analysis and to establish confidence intervals for CT dimensional measurements. In this paper, we propose a computationally inexpensive model to approximate the influence of errors in CT geometrical parameters on dimensional measurement results. We use surface points extracted from a computer-aided design (CAD) model to model discrepancies in the radiographic image coordinates assigned to the projected edges between an aligned system and a system with misalignments. The efficacy of the proposed method was confirmed on simulated and experimental data in the presence of various geometrical uncertainty contributors.
Reich S., Dos Santos Rolo T., Letzel A., Baumbach T., Plech A.
in Applied Physics Letters, 112 (2018), 151903. DOI:10.1063/1.5022748
© 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
© 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
© 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.
Ametova E., Ferrucci M., Chilingaryan S., Dewulf W.
in Precision Engineering (2018). DOI:10.1016/j.precisioneng.2018.05.016
© 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.