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  • 1995-1999  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 1059-1064 
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Element-sensitive tomography produces quality information in the field of medical imaging. This method, also known as dichromatic tomography, can be useful to visualize the distribution of heavy elements, such as actinides, without destroying the sample. One of the problems is to obtain a monochromatic photon beam of sufficiently high energy; the other is to have a way of recording these high-energy photons with a good spatial resolution. Here, the results of a first experiment on uranium mapping with synchrotron radiation are reported. Various natural and artificial samples of a few centimetres in size with uranium concentration between 0.008 g cm−3 and 2 g cm−3 were scanned using photon beams around 115 keV and a specially designed camera. The data were then analysed using a conventional fast reconstruction technique. This yielded excellent results with spatial resolutions down to 50 µm. For the first time it was shown that element-sensitive tomography using synchrotron radiation could be extended to the heaviest natural element. Therefore, in principle, the spatial distribution of any element can now be reconstructed using synchrotron radiation. Extension of this technique to very heavy elements can be important for geology, health physics and nuclear waste storage.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 62 (1996), S. 437-443 
    ISSN: 1432-0630
    Keywords: PACS: 07.85
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Gamma-ray beams of which both the bandwidth and the energy can be tuned were used to perform tomographies. Samples containing heavy elements were rotated and translated in these beams, and the absorption of the beams for each position was measured. Different analysing methods were compared. In contrast to common tomography which uses a continuous spectrum, a technique relying on a monochromatic beam, and a second method which uses as signal the intensity ratio of two monochromatic beams passing through the sample, are presented. When the heavy element under study is present, with the second method the ratio becomes element sensitive if the two energies are such that one is just above and one just below the K-edge of the heavy element under study. An element-sensitive tomography is therefore possible. Different back-projection methods (iterative process, simple back-projection, convolution reconstruction method) were applied on the same data, and their results were compared.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 62 (1996), S. 437-443 
    ISSN: 1432-0630
    Keywords: 07.85
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Gamma-ray beams of which both the band-width and the energy can be tuned were used to perform tomographies. Samples containing heavy elements were rotated and translated in these beams, and the absorption of the beams for each position was measured. Different analysing methods were compared. In contrast to common tomography which uses a continuous spectrum, a technique relying on a monochromatic beam, and a second method which uses as signal the intensity ratio of two monochromatic beams passing through the sample; are presented. When the heavy element under study is present, with the second method the ratio becomes element sensitive if the two energies are such that one is just above and one just below theK-edge of the heavy element under study. An element-sensitive tomography is therefore possible. Different back-projection methods (iterative process, simple back-projection, convolution reconstruction method) were applied on the same data, and their results were compared.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 352 (1995), S. 25-31 
    ISSN: 1434-601X
    Keywords: 21.10 ; 21.60 ; 27.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New experimental data, obtained on73As and74As, were used to test the predictions of the Uπ(6/12)⊗Uν (6/12) supersymmetry scheme in its vibrational limit. The level spectra of 34 74 Se40, 34 75 Se41, 33 73 AS40 and 33 74 As41 supermultiplet nuclei have been calculated using a simple closed energy formula. 44 states in four different nuclei have been reasonably described using only 7 fitted parameters. The existence of supersymmetry was supported also by one-nucleon transfer reaction data, electromagnetic properties, and by a comparison between the supersymmetry and interacting boson-fermion-fermion model wave functions.
    Type of Medium: Electronic Resource
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