TY - JOUR A1 - Kupsch, Andreas A1 - Müller, Bernd R. A1 - Lange, Axel A1 - Bruno, Giovanni T1 - Microstructure Characterization of Ceramics via 2D and 3D X-Ray Refraction Techniques N2 - 3D imaging techniques are very fashionable nowadays, and allow enormous progress in understanding ceramic microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this feature article, we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. While the techniques are limited by the X-ray absorption of the material under investigation, we demonstrate showcases of ceramics and composite materials, where understanding of process parameter influence or simply of microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography. KW - X-ray refraction KW - Porosity KW - Specific surface KW - Crack detection KW - Composites PY - 2017 DO - https://doi.org/10.1016/j.jeurceramsoc.2016.12.031 SN - 0955-2219 SN - 1873-619X VL - 37 IS - 5 SP - 1879 EP - 1889 PB - Elsevier CY - Amsterdam AN - OPUS4-39094 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Kupsch, Andreas A1 - Müller, Bernd R. T1 - Correction of diffuse X-ray detector based background N2 - A novel approach to strongly suppress artifacts in radiography and computed tomography caused by the effect of diffuse background Signals (“backlight”) of 2D X-ray detectors is suggested. Depending on the detector geometry the mechanism may be different, either based on the optical scattering of the fluorescent screen materials into optical detection devices or Compton or X-ray fluorescence scattering by the detector components. Consequently, these erroneous intensity portions result in locally different violations of Lambert Beer’s law in single projections (radiographs). When used as input data for computed tomography these violations are directly observed via modulation of the projected mass as a function of the rotation Phase and the sample’s aspect ratio (dynamics). The magnitude of the diffuse Background signal depends on the detector area covered by the projected sample. They are more pronounced the smaller the shaded area and the stronger the total attenuation. Moreover, the local intensity mismatch depends on the attenuation of the sample. We present very basic reference data measured with multiple metal foils at a synchrotron radiation source. Beam hardening artifacts can be excluded due to the monochromatic radiation. The proposed correction procedure assumes a constant (non-local) scattering mechanism. T2 - DIR 2011 - International symposium on digital industrial raidology and computed tomography CY - Berlin, Germany DA - 20.06.2011 KW - Backlight KW - X-ray detector KW - Fluorescence screen KW - Synchrotron radiography KW - Computed tomography PY - 2011 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-243589 SN - 978-3-940283-34-4 IS - DGZfP-BB 128 (Poster 24) SP - 1 EP - 7 PB - Deutsche Gesellscahft für Zerstörungsfreie Prüfung e.V. (DGZfP) AN - OPUS4-24358 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Kupsch, Andreas T1 - Bewertung von CT-Rekonstruktionen mit DIRECTT N2 - Modellrechnungen mit dem CT-Algorithmus DIRECTT (Direkte iterative Rekonstruktion computertomographischer Trajektorien) haben die Vorteile gegenüber anderen Ansätzen bezüglich Ortsauflösung und Dichte gezeigt, insbesondere auch für unvollständige Datensätze wie Limited View- und Region of Interest-Szenarien. Entsprechend dem Normalfall werden hier jedoch vollständige Datensätze von Modellen und Messungen und ihre Rekonstruktionen bewertet. Die Qualität von DIRECTT wird mit der Gefilterten Rückprojektion anhand der Modulations-Transfer-Funktion (MTF) sowie integraler Kenngrößen im Radon- und im Ortsraum verglichen. Zur Überprüfung der Rekonstruktionsgenauigkeit experimenteller Daten werden Mustermessungen einfacher Probengeometrien unter definierten physikalischen Bedingungen durchgeführt. Diese betreffen Monochromasie, Unterdrückung von Kantenartefakten und radiometrische Intensitätsbestimmung mit Einkanaldetektor. T2 - DGZfP-Jahrestagung 2013 CY - Dresden, Germany DA - 06.05.2013 KW - Computertomographie KW - DIRECTT KW - Modulations-Transfer-Funktion KW - CT-Algorithmus PY - 2013 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-286933 SN - 978-3-940283-49-8 IS - Poster 13 SP - 1 EP - 10 PB - Deutsche Gesellschaft für zerstörungsfreie Prüfung e.V. (DGZfP) AN - OPUS4-28693 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Manke, I. A1 - Kardjilov, N. A1 - Schäfer, R. A1 - Hilger, A. A1 - Grothausmann, R. A1 - Strobl, M. A1 - Dawson, M. A1 - Grünzweig, C. A1 - Tötzke, C. A1 - David, C. A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Banhart, J. T1 - Three-dimensional imaging of magnetic domains with neutron grating interferometry N2 - This paper gives a brief overview on3D imaging of magnetic domains with shearing grating neutron tomography. We investigated the three-dimensional distribution of magnetic domain walls in the bulk of a wedge-shaped FeSi single crystal. The width of the magnetic domains wasanalyzed at different locations within the crystal. Magnetic domains close to the tip of the wedge are much smaller than in the bulk. Furthermore, the three-dimensional shape of individual domains wasinvestigated. We discuss prospects and limitations of the applied measurement technique. KW - Neutron imaging KW - Tomography KW - Magnetic domains KW - Grating interferometry KW - Darkfield imaging KW - Shearing gratings KW - Talbot-Lau KW - Three-dimensional data quantification KW - Tomographic reconstruction PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-341919 DO - https://doi.org/10.1016/j.phpro.2015.07.057 SN - 1875-3892 VL - 69 SP - 404 EP - 412 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-34191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Lange, Axel A1 - Grothausmann, R. A1 - Manke, I. T1 - Application of the DIRECTT algorithm to sub-nanometer electron tomography N2 - Tomography data obtained from transmission electron microscopes are especially attractive due to their unrivaled spatial resolution in the nanometer range or even less, but they require enormous efforts in sample preparation and suffer from a diverse accumulation of experimental restrictions, which unavoidably result in fundamental reconstruction artifacts. These restrictions refer to: partial opacity, a limited view (limited angle or missing wedge), very few angles (with respect to the detector size), limited to a region of interest (ROI; due to the sample size), variable angular increments as well as sample degradation due the interactions with the electron beam. An advanced version of the DIRECTT (Direct Iterative Reconstruction of Computed Tomography Trajectories) algorithm proves to cope with most of these severe deviations from ideal CT measuring conditions. However, careful data preprocessing is required in order to exploit the capabilities of the algorithm. Nanometer sized Ruthenium catalyst particles for fuel cell applications are 3D imaged at a few Ångström resolution in order to estimate their partial free surface on carbon black supports, which rule the efficiency of the catalytic activity. Comparisons of DIRECTT reconstructions to the conventional filtered back projection, prove the significant improvements. T2 - DIR 2011 - International symposium on digital industrial raidology and computed tomography CY - Berlin, Germany DA - 20.06.2011 KW - Electron tomography KW - Computed tomography KW - Reconstruction algorithms PY - 2011 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-243577 SN - 978-3-940283-34-4 IS - DGZfP-BB 128 (Tu.3.3) SP - 1 EP - 6 PB - Deutsche Gesellscahft für Zerstörungsfreie Prüfung e.V. (DGZfP) AN - OPUS4-24357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lange, Axel A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Lück, S. A1 - Schmidt, V. A1 - Grothausmann, R. A1 - Hilger, A. A1 - Manke, I. T1 - Reduzierung von Missing-Wedge-Artefakten mit DIRECTT N2 - Wir stellen eine Prozedur vor, mit der typische 'Missing Wedge' (MW)-Artefakte in CT-Rekonstruktionen effektiv unterdrückt werden können. Dazu wird der iterative DIRECTT-Algorithmus (Direkte Iterative Rekonstruktion Computertomographischer Trajektorien) mit einigen Zyklen diskreter Rekonstruktion eingesetzt. Die Kernfunktionen des Algorithmus', die wiederholte Auswahl und Gewichtung von Elementen einer Zwischenkonstruktion, werden beibehalten. Abgesehen von Sonderfällen der Röntgen- und Neutronentomographie tritt die MW-Restriktion (neben einer Vielzahl anderer) in Standardkonfigurationen der Elektronentomographie auf. Um den MW-Effekt isoliert zu untersuchen und beurteilen zu können, werden hier vollständige experimentelle Datensätze einer bekannten Porenstruktur um einen Sektor beschnitten sowie MW-Rekonstruktionen von Porenmodellen erzeugt. Die Ergebnisse werden mit zurzeit verbreiteten Algorithmen (Gefilterte Rückprojektion (FBP) und ART-Varianten) verglichen. Die Bewertung im Fourierraum zeigt, dass DIRECTT die fehlende Information im MW erfolgreich ergänzt. Zur quantitativen Bewertung der lokalen Rekonstruktionsqualität werden Methoden der räumlichen Statistik eingesetzt. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 26.05.2014 KW - Computertomographie (CT) KW - Rekonstruktionsalgorithmus KW - DIRECTT KW - Missing Wedge KW - Statistische Bewertung PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-312977 SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Poster 18, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-31297 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Lange, Axel A1 - Müller, Bernd R. T1 - Röntgen-Interface-Radiographie im Dunkelfeld N2 - Es wird ein Verfahren zur Röntgenabbildung schwach absorbierender Objekte vorgestellt. Als kontrastgebender Effekt wird die Röntgenrefraktion an Ober- und Grenzflächen ausgenutzt. Zur Erzeugung eines sogenannten Dunkelfeldes wird ein schwach gekrümmter Transmissionskristall eingesetzt, der lokal, d.h. in einem kleinen Ausschnitt des Einstrahlquerschnitts, die Bragg-Bedingung erfüllt. Innerhalb dieser Zone erscheinen die durch Refraktion abgelenkten Strahlkomponenten als hell leuchtende Interface-Strukturen. Die Synthese mehrerer Dunkelfeldstreifen ergibt hochaufgelöste 2D Beispiel von biologischen und technischen Mikrostrukturen. T2 - DGZfP-Jahrestagung 2013 CY - Dresden, Germany DA - 06.05.2013 KW - Refraction enhanced imaging (REI) KW - Radiographie KW - Dunkelfeldabbildung KW - Röntgenrefraktion PY - 2013 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-286900 SN - 978-3-940283-49-8 IS - Di.3.C.1 SP - 1 EP - 7 PB - Deutsche Gesellschaft für zerstörungsfreie Prüfung e.V. (DGZfP) AN - OPUS4-28690 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Grothausmann, R. A1 - Manke, I. T1 - Verbesserte Elektronen-Tomographie mittels DIRECTT-Algorithmus N2 - Tomographische Messungen in Transmissions-Elektronenmikroskopen beziehen ihren Reiz aus der hohen Ortsauflösung im Nanometerbereich. Allerdings bringen sie neben dem hohen Aufwand bei der Probenpräparation auch eine außerordentliche Häufung von Restriktionen der Messung mit sich, die bei Verwendung herkömmlicher Rekonstruktionsalgorithmen zu erheblichen Artefakten führen. Diese Restriktionen betreffen: partielle Nichtdurchstrahlbarkeit, einen eingeschränkten Winkelbereich, wenige Projektionen in Bezug auf die Detektorgröße, Probenabbildungen größer als der Detektor, instabile Rotationsachse, variierende Winkelinkremente sowie Probenveränderungen während der Messung. Der DIRECTT-Algorithmus (Direkte iterative Rekonstruktion computertomographischer Trajektorien) kann, abgesehen von der Probenveränderung, sämtliche dieser Restriktionen geeignet berücksichtigen. Die auftretenden, teils unvollständigen Bahnen lassen sich mittels einer Treffertabelle und geeigneter Auswahl iterativ behandeln. Außerdem kann das Rekonstruktionsvolumen über die Detektorlänge hinaus erweitert werden. Damit gelingt eine weitgehende Unterdrückung von Rekonstruktionsartefakten, insbesondere der sonst dominanten Streifenartefakte, und eine deutliche Erhöhung der Ortsauflösung. Die Verbesserung der Rekonstruktionsqualität wird anhand von Modell- und experimentellen Daten gezeigt. T2 - DGZfP-Jahrestagung 2011 CY - Bremen, Germany DA - 30.05.2011 KW - Elektronen-Tomographie KW - Computer-Tomographie KW - Rekonstruktionsalgorithmen PY - 2011 SN - 978-3-940283-33-7 IS - DGZfP-BB 127 (P8) SP - 1 EP - 7 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-25004 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lück, S. A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Schmidt, V. T1 - Statistical analysis of tomographic reconstruction algorithms by morphological image characteristics N2 - We suggest a procedure for quantitative quality control of tomographic reconstruction algorithms. Our task-oriented evaluation focuses on the correct reproduction of phase boundary length and has thus a clear implication for morphological image analysis of tomographic data. Indirectly the method monitors accurate reproduction of a variety of locally defined critical image features within tomograms such as interface positions and microstructures, debonding, cracks and pores. Tomographic errors of such local nature are neglected if only global integral characteristics such as mean squared deviation are considered for the evaluation of an algorithm. The significance of differences in reconstruction quality between algorithms is assessed using a sample of independent random scenes to be reconstructed. These are generated by a Boolean model and thus exhibit a substantial stochastic variability with respect to image morphology. It is demonstrated that phase boundaries in standard reconstructions by filtered backprojection exhibit substantial errors. In the setting of our simulations, these could be significantly reduced by the use of the innovative reconstruction algorithm DIRECTT. KW - Tomography KW - Computed tomography KW - Reconstruction algorithm KW - Morphological image analysis KW - Phase boundary KW - Metrology KW - Non-destructive testing PY - 2010 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-210710 DO - https://doi.org/10.5566/ias.v29.p61-77 SN - 1580-3139 SN - 1854-5165 VL - 29 SP - 61 EP - 77 CY - Ljubljana, Slovenia AN - OPUS4-21071 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lange, Axel A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Müller, Bernd R. T1 - Straightforward correction of X-ray detector backlighting N2 - A novel approach to strongly suppress artifacts in radiography and computed tomography caused by the effect of diffuse background signals ('backlighting') of 2D X-ray detectors is suggested. Depending on the detector geometry the mechanism may be different, either based on the optical scattering of the fluorescent screen materials into optical detection devices or Compton or X-ray fluorescence scattering by the detector components. Consequently, these erroneous intensity portions result in locally different violations of Lambert Beer’s law in single projections (radiographs) as function of the detector area coverage and the magnitude of the attenuation. The absorption of multiple metal sheets is investigated by monochromatic synchrotron radiation, thus excluding beam hardening. The proposed correction procedure simply requires the individual subtraction of one and the same fraction of the primary and transmitted mean intensity, as a constant (non-local) scattering mechanism is assumed. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - X-ray detector backlighting KW - Radiography KW - Fluorescent screen KW - Diffuse background KW - Computed tomography PY - 2012 UR - http://www.ndt.net/article/wcndt2012/papers/205_wcndtfinal00205.pdf SN - 978-0-620-52872-6 SP - 1 EP - 8(?) AN - OPUS4-25835 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lange, Axel A1 - Kupsch, Andreas A1 - Müller, Bernd R. A1 - Hentschel, Manfred P. T1 - Edge artefacts of radiographic images by X-ray refraction N2 - The relevance of nano sized structures and interfaces in upcoming technologies requires new non-destructive Xray techniques exploiting attenuation as well as scattering. In the course of driving the resolution and the contrast of modern radiography into micro and nano metre dimension the inevitable scattering effects require increased attention. Several radiologists interpret the observed edge artefacts simply by 'phase contrast' due to different X-ray path lengths within the sample and others refer to Fresnel scattering. The ultra small angle scattering is of high intensity and may reach the level of the primary beam. We present monochromatic synchrotron measurements on rather simply shaped objects (such as plates and cylinders) which prove clearly the dominance of refraction intensity over total reflection and coherent small angle scattering. The refraction conditions hold for angles of incidence of several degrees to the surface, but typical deflection angles range from several seconds to minutes of arc. Additionally to the concept of 'phase contrast' of the primary beam its deflection becomes the essential issue. The appropriate removal of the attenuation contribution enables the imaging of inner surfaces and interfaces by refraction scanning topography. The presented measurements of reference particles demonstrate the reliability of laboratory refraction scanners applying X-ray tubes. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - X-ray refraction KW - Small angle scattering KW - Phase contrast radiography KW - Refraction topography KW - Nanostructures KW - Nanocracks PY - 2012 UR - http://www.ndt.net/article/wcndt2012/papers/274_wcndtfinal00274.pdf SN - 978-0-620-52872-6 SP - 1 EP - 11 AN - OPUS4-25836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Grothausmann, R. A1 - Arlt, Tobias A1 - Manke, I. T1 - High quality reconstruction of insufficient tomographic data by a new iterative procedure N2 - In order to demonstrate the challenging tasks in current R&D applications in the field of renewable energy sources experimental neutron and electron tomographic data sets of PEM fuel cell components are processed by an advanced version of the DIRECTT algorithm. The neutron measurements of the water distribution suffer from several intrinsic limitations such as massive position dependent focal smearing due to the large primary neutron beam aperture. Electron (TEM) tomography allows characterisation of nanometre sized catalyst particles but is hampered by the following restrictions: partial opacity, a limited sector of projections (missing wedge), very few projections, samples exceeding the detector size (region of interest) and improper angular alignment. Beyond the capabilities of other algorithms DIRECTT proves to overcome these essential reconstruction problems, in comparison to FBP and SIRT. Nevertheless, careful data pre-processing is an inevitable requirement in order to fully exploit the algorithm's potentials. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - Iterative reconstruction KW - DIRECTT KW - Neutron tomography KW - Electron tomography KW - Focal smearing KW - Limited View KW - Opacity KW - Fuel cell KW - Renewable energy PY - 2012 UR - http://www.ndt.net/article/wcndt2012/papers/207_wcndtfinal00207.pdf SN - 978-0-620-52872-6 SP - 1 EP - 8 AN - OPUS4-25833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -