C Grünzweig

Publications (11)65.08 Total impact

• Source

  Available from: John Banhart

  Article: Three-dimensional imaging of magnetic domains.

  I Manke, N Kardjilov, R Schäfer, A Hilger, M Strobl, M Dawson, C Grünzweig, G Behr, M Hentschel, C David, A Kupsch, A Lange, J Banhart
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  ABSTRACT: Magnetic domains have been the subject of much scientific investigation since their theoretical existence was first postulated by P.-E. Weiss over a century ago. Up to now, the three-dimensional (3D) domain structure of bulk magnets has never been observed owing to the lack of appropriate experimental methods. Domain analysis in bulk matter thus remains one of the most challenging tasks in research on magnetic materials. All current domain observation methods are limited to studying surface domains or thin magnetic films. As the properties of magnetic materials are strongly affected by their domain structure, the development of a technique capable of investigating the shape, size and distribution of individual domains in three dimensions is of great importance. Here, we show that the novel technique of Talbot-Lau neutron tomography with inverted geometry enables direct imaging of the 3D network of magnetic domains within the bulk of FeSi crystals.
  Nature Communications 11/2010; 1:125. · 7.40 Impact Factor
• Source

  Available from: nist.gov

  Article: Neutron dark-field tomography.

  M Strobl, C Grünzweig, A Hilger, I Manke, N Kardjilov, C David, F Pfeiffer
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  ABSTRACT: We report how a grating interferometer yields neutron dark-field scatter images for tomographic investigations. The image contrast is based on ultrasmall-angle scattering. It provides otherwise inaccessible spatially resolved information about the distribution of micrometer and submicrometer sized structural formations. Three complementary sets of tomographic data corresponding to attenuation, differential phase, and small-angle scattering can be obtained from one measurement. The method is compatible with conventional imaging and provides significantly higher efficiency than existing techniques.
  Physical Review Letters 10/2008; 101(12):123902. · 7.37 Impact Factor
• Article: Neutron decoherence imaging for visualizing bulk magnetic domain structures.

  C Grünzweig, C David, O Bunk, M Dierolf, G Frei, G Kühne, J Kohlbrecher, R Schäfer, P Lejcek, H M R Rønnow, F Pfeiffer
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  ABSTRACT: Here we introduce a novel neutron imaging method, which is based on the effect that the spatial coherence of the neutron wave front can be changed through small-angle scattering of neutrons at magnetic domain walls in the specimen. We show that the technique can be used to visualize internal bulk magnetic domain structures that are difficult to access by other techniques. The method is transferable to a wide variety of specimens, extendable to three dimensions, and well suited for investigating materials under the influence of external parameters, as, e.g., external magnetic field, temperature, or pressure.
  Physical Review Letters 08/2008; 101(2):025504. · 7.37 Impact Factor
• Source

  Available from: actedi.net

  Article: Hard-X-ray dark-field imaging using a grating interferometer.

  F Pfeiffer, M Bech, O Bunk, P Kraft, E F Eikenberry, Ch Brönnimann, C Grünzweig, C David
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  ABSTRACT: Imaging with visible light today uses numerous contrast mechanisms, including bright- and dark-field contrast, phase-contrast schemes and confocal and fluorescence-based methods. X-ray imaging, on the other hand, has only recently seen the development of an analogous variety of contrast modalities. Although X-ray phase-contrast imaging could successfully be implemented at a relatively early stage with several techniques, dark-field imaging, or more generally scattering-based imaging, with hard X-rays and good signal-to-noise ratio, in practice still remains a challenging task even at highly brilliant synchrotron sources. In this letter, we report a new approach on the basis of a grating interferometer that can efficiently yield dark-field scatter images of high quality, even with conventional X-ray tube sources. Because the image contrast is formed through the mechanism of small-angle scattering, it provides complementary and otherwise inaccessible structural information about the specimen at the micrometre and submicrometre length scale. Our approach is fully compatible with conventional transmission radiography and a recently developed hard-X-ray phase-contrast imaging scheme. Applications to X-ray medical imaging, industrial non-destructive testing and security screening are discussed.
  Nature Material 03/2008; 7(2):134-7. · 32.84 Impact Factor
• Article: Highly absorbing gadolinium test device to characterize the performance of neutron imaging detector systems.

  C Grünzweig, G Frei, E Lehmann, G Kühne, C David
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  ABSTRACT: We report on the fabrication and application of a novel neutron imaging test device made of gadolinium. It is designed for a real time evaluation of the spatial resolution, resolution direction, and distortions of a neutron imaging detector system. Measurements of the spatial resolution of (6)LiF doped ZnS scintillator screens with different thicknesses and of imaging plates were performed. The obtained results are in good agreement with comparison measurements using the standard knife edge detection method.
  Review of Scientific Instruments 06/2007; 78(5):053708. · 1.37 Impact Factor
• Article: Grating interferometer based scanning setup for hard X-ray phase contrast imaging.

  C Kottler, F Pfeiffer, O Bunk, C Grünzweig, C David
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  ABSTRACT: In x-ray radiography, particularly for technical and industrial applications, a scanning setup is very often favorable when compared to a direct two-dimensional image acquisition. Here, we report on an efficient scanning method for grating based x-ray phase contrast imaging with tube based sources. It uses multiple line detectors for staggered acquisition of the individual phase-stepping images. We find that the total exposure time does not exceed the time needed in an equivalent scanning setup for absorption radiography. Therefore, we conclude that it should be possible to implement the method into a scanning system without affecting the scanning speed or significant increase in cost but with the advantage of providing both the phase contrast and the absorption information at once.
  Review of Scientific Instruments 05/2007; 78(4):043710. · 1.37 Impact Factor
• Article: Grating based x-ray phase tomography for improved contrast in x-ray brain imaging

  F Pfeiffer, O Bunk, C Grünzweig, C David, M Bech, Le G Duc, A Bravin
  Phys. Med. Biol. 01/2007; 52:6923-6930.
• Source

  Available from: Gabriel Frei

  Article: Neutron phase imaging and tomography.

  F Pfeiffer, C Grünzweig, O Bunk, G Frei, E Lehmann, C David
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  ABSTRACT: We report how a setup consisting of three gratings yields quantitative two- and three-dimensional images depicting the quantum-mechanical phase shifts of neutron de Broglie wave packets induced by the influence of macroscopic objects. Since our approach requires only a little spatial and chromatic coherence it provides a more than 2 orders of magnitude higher efficiency than existing techniques. This dramatically reduces the required measurement time for computed phase tomography and opens up the way for three-dimensional investigations of previously inaccessible quantum-mechanical phase interactions of neutrons with matter.
  Physical Review Letters 07/2006; 96(21):215505. · 7.37 Impact Factor
• Source

  Available from: Gabriel Frei

  Article: Bulk magnetic domain structures visualized by neutron dark-field imaging

  C Grünzweig, C David, O. Bunk, M Dierolf, G. Frei, G Kühne, R Schäfer, S. Pofahl, H.M.R. Rønnow, F. Pfeiffer
• Article: Phase contrast X-ray imaging of large samples using an incoherent laboratory source

  C. Kottler, F. Pfeiffer, O. Bunk, C Grünzweig, J. Bruder, R. Kaufmann, T. Tlustos, H. Walt, I. Briod, T. Weitkamp, C David
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  ABSTRACT: An interferometric method to record quantitative X-ray phase contrast images has been developed that can be used at polychromatic and incoherent X-ray sources such as laboratory tubes. With respect to previously presented results, in this work we report on recent developments and results that have been achieved in view of potential future applications such as in medicine or biology. In particular, due to improvements in the fabrication process large area diffraction gratings with high aspect ratio were achieved. Thereby, the field of view of the interterometer has been drastically increased to 64 x 64 mm(2) and the design value of the photon energy for the gratings could be increased up to 28 keV. Moreover, the use of a Medipix2 single photon-counting pixel detector shows a considerable improvement in image quality and sensitivity over the integrating detector used so far.
• Source

  Available from: psi.ch

  Article: Fabrication of diffraction gratings for hard X-ray phase contrast imaging

  C. David, J. Bruder, T. Rohbeck, C. Grünzweig, C. Kottler, A. Diaz, O. Bunk, F. Pfeiffer
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  ABSTRACT: We have developed a method for X-ray phase contrast imaging, which is based on a grating interferometer. The technique is capable of recording the phase shift of hard X-rays travelling through a sample, which greatly enhances the contrast of low absorbing specimen compared to conventional amplitude contrast images. Unlike other existing X-ray phase contrast imaging methods, the grating interferometer also works with incoherent radiation from a standard X-ray tube. The key components are three gratings with silicon and gold structures, which have dimensions in the micrometer range and high aspect ratios. The fabrication processes, which involve photolithography, anisotropic wet etching, and electroplating, are described in this article for each of the three gratings. An example of an X-ray phase contrast image acquired with the grating interferometer is given.
  Microelectronic Engineering.