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 - TY - JOUR A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Kupsch, Andreas A1 - Müller, Bernd R. T1 - Numerical 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 by 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 shadowed area and the stronger the total attenuation. This implies that the reconstruction suffers from additional anisotropic artifacts caused by elongated sample structures. This issue is studied simply by absorption of flat plates in a conventional laboratory radiography set-up and at a synchrotron radiation facility. In the latter case beam hardening artifacts can be excluded due to the monochromatic radiation. The proposed correction procedure requires simple integral intensity offsets as a constant (non-local) light scattering mechanism is assumed. KW - Detector backlighting KW - X-ray detector scattering KW - Fluorescent screen KW - Diffuse background KW - Computed tomography PY - 2012 DO - https://doi.org/10.3139/146.110659 SN - 1862-5282 VL - 103 IS - 2 SP - 174 EP - 178 PB - Carl Hanser CY - München AN - OPUS4-25553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grothausmann, R. A1 - Zehl, G. A1 - Manke, I. A1 - Fiechter, S. A1 - Bogdanoff, P. A1 - Dorbandt, I. A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Hentschel, Manfred P. A1 - Schumacher, G. A1 - Banhart, J. T1 - Dreidimensionale Charakterisierung von Katalysatornanopartikeln N2 - We present transmission electron microscope (TEM) tomography investigations of ruthenium-based fuel cell catalyst materials as employed in direct methanol fuel cells (DMFC). The digital three-dimensional representation of the samples not only enables detailed studies on number, size, and shape but also on the local orientation of the ruthenium particles to their support and their freely accessible surface area. The shape analysis shows the ruthenium particles deviate significantly from spherical symmetry which increases their surface to volume ratio. The morphological studies help to understand the structure formation mechanisms during the fabrication as well as the high effectiveness of these catalysts in the oxygen reduction reaction at the cathode side of fuel cells. KW - Radiography KW - Tomography KW - Neutrons KW - Polymer electrolyte membrane fuel cell (PEMFC) KW - Fuel cell stack PY - 2012 SN - 1862-5282 VL - 103 IS - 1 SP - 135 EP - 136 PB - Carl Hanser CY - München AN - OPUS4-25976 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Markötter, Henning A1 - Manke, I. A1 - Kuhn, R. A1 - Arlt, Tobias A1 - Kardjilov, N. A1 - Hentschel, Manfred P. A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Hartnig, C. A1 - Scholta, J. A1 - Banhart, J. T1 - Neutron tomographic investigations of water distributions in polymer electrolyte membrane fuel cell stacks N2 - Neutron tomography was applied to study the 3D water distribution in full polymer electrolyte membrane fuel cell (PEMFC) stacks. The water distribution after switch-off of the fuel cell was analyzed over a period of 36 h. We found a slowly increasing water amount in the fuel cell, but only few changes within a time period of 5 h, which is about the time necessary for neutron tomography. In this way, the requirement for successful tomography was obtained. It is demonstrated how the quasi in-situ tomography technique enables us to study the water content in individual flow field channels of three-fold stacks. Flow field as well as stack design issues are addressed by this visualization method showing weak points due to a non-uniform water distribution that can be identified by means of neutron imaging. KW - Radiography KW - Tomography KW - Neutron imaging KW - Polymer electrolyte membrane fuel cell (PEMFC) KW - Manifold stack KW - Water management PY - 2012 DO - https://doi.org/10.1016/j.jpowsour.2012.07.043 SN - 0378-7753 VL - 219 SP - 120 EP - 125 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-26317 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -