Publications of the ultrafast X-ray imaging group at IPS
Alaribe L., Disch C., Fauler A., Engels R., Keller E., Cecilia A., Rolo T.D.S., Hamann E., Fiederle M.
in IEEE Nuclear Science Symposium Conference Record (2012) 1567-1571, 6154633. DOI:10.1109/NSSMIC.2011.6154633
Currently, there is a great interest in the research and development of SrI 2:Eu 2+ scintillating crystals. The high light yield, high density (4.6 g/cm 3) and high effective atomic number (49.4) make the Eu 2+-activated SrI 2 suitable for use as x-ray and gamma ray detector. SrI 2:Eu 2+-single crystals were grown with the vertical Bridgman technique in silica ampoules to prevent melt hydration and oxygen contamination during the crystal growth. For measurements, crystals were hermetically encapsulated in aluminum containers with quartz glass optical windows. The radioluminescence spectra of the SrI 2:Eu 2+-samples show maximum at 431 nm and 432 nm for the 5% and 6% dopant concentrations respectively. The light yield of the bulk samples was up to 80 000 photons/MeV and up to 119 000 photons/MeV for a 360 μm sample integrated in an x-ray imaging setup. © 2011 IEEE.
Altapova V., Helfen L., Myagotin A., Hanschke D., Moosmann J., Gunneweg J., Baumbach T.
in Optics Express, 20 (2012) 6496-6508. DOI:10.1364/OE.20.006496
Synchrotron laminography is combined with Talbot grating interferometry to address weakly absorbing specimens. Integrating both methods into one set-up provides a powerful x-ray diagnostical technique for multiple contrast screening of macroscopically large flat specimen and a subsequent non-destructive three-dimensional (3-D) inspection of regions of interest. The technique simultaneously yields the reconstruction of the 3-D absorption, phase, and the so-called dark-field contrast maps. We report on the theoretical and instrumental implementation of of this novel technique. Its broad application potential is exemplarily demonstrated for the field of cultural heritage, namely study of the historical Dead Sea parchment. © 2012 Optical Society of America.
Alaribe L., Disch C., Fauler A., Engels R., Keller E., Cecilia A., Dos Santos Rolo T., Fiederle M.
in Materials Research Society Symposium Proceedings, 1341 (2012) 21-26. DOI:10.1557/opl.2011.1275
Eu 2+- activated strontium iodide is a promising material for x-ray and gamma ray detector. A lot of difficulties are though encountered growing strontium iodide crystals due to the high oxygen-sensitivity, hygroscopic property and high impurity concentration. Single crystals of Srl 2:Eu were grown from zone refined starting materials in silica ampoules. The crystals showed good optical qualities. The light yield of two samples cut from the same ingot was determined to be 53 000 photons/MeV and 119±22 photons/keV for a 0.4 cm 3 sample and a 360 μm sample respectively, indicating some level of light trapping in the bulk sample. Keywords: scintillator, Bridgman growth method, energy resolution. © 2011 Materials Research Society.
Chilingaryan S., Kopmann A., Mirone A., Dos Santos Rolo T., Vogelgesang M.
in SC’11 – Proceedings of the 2011 High Performance Computing Networking, Storage and Analysis Companion, Co-located with SC’11 (2011) 51-52. DOI:10.1145/2148600.2148624
X-ray tomography has been proven to be a valuable tool for understanding internal, otherwise invisible, mechanisms in biology and other fields. Recent advances in digital detector technology enabled investigation of dynamic processes in 3D with a temporal resolution down to the milliseconds range. Unfortunately it requires computationally intensive recon- struction algorithms with long post-processing times. We have optimized the reconstruction software employed at the micro-tomography beamlines at KIT and ESRF. Using a 4 stage pipelined architecture and the computational power of modern graphic cards, we were able to reduce the processing time by a factor 75 with a single server. The time required to reconstruct a typical 3D image is reduced down to several seconds only and online visualization is possible for the first time.Copyright is held by the author/owner(s).
Danilewsky A.N., Wittge J., Hess A., Croll A., Rack A., Allen D., McNally P., Dos Santos Rolo T., Vagovic P., Baumbach T., Garagorri J., Elizalde M.R., Tanner B.K.
in Physica Status Solidi (A) Applications and Materials Science, 208 (2011) 2499-2504. DOI:10.1002/pssa.201184264
We describe a rapid digital system for X-ray diffraction imaging and demonstrate its application to the real-time identification of edge defects in a silicon wafer that had been subjected to rapid thermal annealing. The application of the system to the in situ study of slip nucleation at the location of mechanical wafer defects, indents and a thermocouple, and the subsequent dislocation dynamics is presented. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Vagovic P., Korytar D., Mikulik P., Cecilia A., Ferrari C., Yang Y., Hanschke D., Hamann E., Pelliccia D., Lafford T.A., Fiederle M., Baumbach T.
in Journal of Synchrotron Radiation, 18 (2011) 753-760. DOI:10.1107/S090904951102989X
In this work an X-ray imaging system based on a recently developed in-line two-dimensional Bragg magnifier composed of two monolithic V-shaped crystals made of dislocation-free germanium is presented. The channel-cut crystals were used in one-dimensional and in two-dimensional (crossed) configurations in imaging applications and allowed measurement of phase-contrast radiograms both in the edge-enhanced and in the holographic regimes. The measurement of the phase gradient in two orthogonal directions is demonstrated. The effective pixel size attained was 0.17 μm in the one-dimensional configuration and 0.5 μm in the two-dimensional setting, offering a twofold improvement in spatial resolution over devices based on silicon. These results show the potential for applying Bragg magnifiers to imaging soft matter at high resolution with reduced dose owing to the higher efficiency of Ge compared with Si. © 2011 International Union of Crystallography.
Altapova V., Butzer J., Rolo T.D.S., Vagovic P., Cecilia A., Moosmann J., Kenntner J., Mohr J., Pelliccia D., Pichugin V.F., Baumbach T.
in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 648 (2011). DOI:10.1016/j.nima.2010.12.218
One of the most promising methods of phase-contrast imaging is the Talbot grating interferometry. We report about the optimization of the method for fast imaging, requiring reduced exposure times by keeping sufficient imaging contrast. To do this a new Talbot interferometer working with a broad energy bandwidth beam has been installed at the TopoTomo beamline at ANKA. We demonstrate the method with a filtered white beam and without the need of a source grating that is commonly used at moderate-emittance synchrotron sources. Taking advantage of a higher photon flux, the exposure time is significantly reduced. At the same time, images obtained with this setup show a sufficient visibility contrast of 25% on average, which opens the way for new applications in real-time measurements. © 2010 Elsevier B.V. All rights reserved.
Cecilia A., Rack A., Douissard P.-A., Martin T., Dos Santos Rolo T., Vagovic P., Hamann E., Van De Kamp T., Riedel A., Fiederle M., Baumbach T.
in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 648 (2011). DOI:10.1016/j.nima.2010.10.150
Within the project ScinTAX of the 6th framework program (FP6) of the European Commission (SCINTAX – STRP 033 427) we have developed a new thin single crystal scintillator for high-resolution X-ray imaging. The scintillator is based on a Tb-doped Lu2SiO5 (LSO) film epitaxially grown on an adapted substrate. The high density, effective atomic number and light yield of the scintillating LSO significantly improves the efficiency of the X-ray imaging detectors currently used in synchrotron micro-imaging applications. In this work we present the characterization of the scintillating LSO films in terms of their spatial resolution performance and we provide two examples of high spatial and high temporal resolution applications. © 2010 Elsevier B.V. All rights reserved.
Chilingaryan S., Mirone A., Hammersley A., Ferrero C., Helfen L., Kopmann A., Dos Santos Rolo T., Vagovic P.
in IEEE Transactions on Nuclear Science, 58 (2011) 1447-1455, 5766797. DOI:10.1109/TNS.2011.2141686
Advances in digital detector technology leads presently to rapidly increasing data rates in imaging experiments. Using fast two-dimensional detectors in computed tomography, the data acquisition can be much faster than the reconstruction if no adequate measures are taken, especially when a high photon flux at synchrotron sources is used. We have optimized the reconstruction software employed at the micro-tomography beamlines of our synchrotron facilities to use the computational power of modern graphic cards. The main paradigm of our approach is the full utilization of all system resources. We use a pipelined architecture, where the GPUs are used as compute coprocessors to reconstruct slices, while the CPUs are preparing the next ones. Special attention is devoted to minimize data transfers between the host and GPU memory and to execute memory transfers in parallel with the computations. We were able to reduce the reconstruction time by a factor 30 and process a typical data set of 20 GB in 40 seconds. The time needed for the first evaluation of the reconstructed sample is reduced significantly and quasi real-time visualization is now possible. © 2006 IEEE.
Cecilia A., Rack A., Douissard P.-A., Martin T., Dos Santos Rolo T., Vagovic P., Pelliccia D., Couchaud M., Dupre K., Baumbach T.
in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 633 (2011). DOI:10.1016/j.nima.2010.06.192
Within the framework of an FP6 project (SCINTAX)1 we developed a new thin film single crystal scintillator for high resolution X-ray imaging based on a layer of modified LSO (Lu2SiO5) grown by liquid phase epitaxy (LPE) on a dedicated substrate. In this work we present the characterisation of the scintillating LSO films in terms of optical and scintillation properties as well as spatial resolution performances. The obtained results are discussed and compared with the performances of the thin scintillating films commonly used in synchrotron-based micro-imaging applications. © 2010 Elsevier B.V. All rights reserved.