Search Results - (Author, Cooperation:F. E. Christensen)

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  1. 1
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    Publication Date:
    2015-02-24
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
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    http://www.aaas.org/

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  2. 2
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    Publication Date:
    2015-05-09
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
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    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.aaas.org/

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  3. 3
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    Publication Date:
    2014-10-10
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.nature.com/

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  4. 4
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    Publication Date:
    2015-05-01
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
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    Published by:
    http://www.nature.com/

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  5. 5
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    Publication Date:
    2013-03-01
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  6. 6
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    Publication Date:
    2014-02-21
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  7. 7
    Christensen, F. E. ; Hornstrup, A. ; Frederiksen, P. ; Nilsson, C. ; Grundsøe, P. ; Ørup, P. ; Jacobsen, E. ; Schnopper, H. W. ; Lewis, R. ; Hall, C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1992
    Staff View
    ISSN:
    1089-7623
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Electrical Engineering, Measurement and Control Technology
    Notes:
    The detailed study of the performance of full scale x-ray optics often requires the illumination of large areas. This paper describes a beam expander facility at the Daresbury Synchrotron Radiation Facility. It combines monochromatization and beam expansion in one dimension. The beam expansion is obtained from an extremely asymmetric reflection in a large single crystal of Si. An expansion of a factor of 50 was obtained in one dimension. The expanded beam of ∼85 mm is limited only by the crystal size. The facility is installed in a 12-m-long hutch. A specific application, in which a high throughput x-ray telescope will be studied, is described in detail.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1143124

    Articles: DFG German National Licenses
  8. 8
    Priedhorsky, W. C. ; Christensen, F. E.
    Springer
    Published 1995
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    ISSN:
    1572-9508
    Keywords:
    hard x-rays ; x-ray telescopes ; all-sky surveys
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract We discuss a hard x-ray telescope for the range 25–70 keV based on a one-dimensional lobster-eye telescope and x-ray supermirror coatings. This approach enables wide field-of-view imaging. A telescope suitable for a large balloon payload, with a 50×100 cm frontal area, could have an effective area of 50–100 cm2 and a 100×100 field of view, and thereby detect AGN that are 0.5 milliCrab in the soft x-rays in a 104 second exposure. 29% of the sky could be surveyed to this limit in a 2-week balloon flight, reaching 6 times fainter than the HEAO A-4 all-sky survey.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF00421129

    Articles: DFG German National Licenses
  9. 9
    Staff View
    ISSN:
    1572-9508
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract It is shown that compact designs of multifocus, conical approximations to highly nested Wolter I telescopes, as well as single reflection concentrators, employing realistic graded period W/Si or Ni/C multilayer coatings, allow one to obtain more than 1000 cm2 of on-axis effective area at 40 keV and up to 200 cm2 at 100 keV. The degree of concentration is defined by a focusing factor i.e., the effective area divided by the half power focal area. For the cases studied, this is 400 at 40 keV and 200 at 100 keV for a 2 arcmin imaging resolution. This result is quite insensitive to the specifics of the telescope configuration provided that mirrors can be coated to an inner radius of 3 cm. Specifically we find that a change of focal length from 5 to 12 m affects the effective area by less than 10%. In addition the result is insensitive to the thickness of the individual mirror shell provided that it is smaller than roughly 1 mm. The design can be realized with foils as thin (≤0.4 mm) as used for ASCA and SODART or with closed, slightly thicker (∼1.0 mm) mirror shells as used for JET-X and XMM. The effect of an increase of the inner radius is quantified on the effective area for multilayered mirrors up to 9 cm. The calculated Field of View (full width at half maximum), ranges from 9 arcmin at 1 keV to ≥5 arcmin at 60 keV. Finally, the continuum sensitivity of the design assuming a signal to noise ratio of 5 and a 10% energy bandwidth has been calculated. For a balloon flight observation of 104 sec. with a telescope having 2 arcmin imaging resolution the point source sensitivity is ∼3 · 10−6 photons/cm2/s/keV up to 70 keV for a W/Si coated telescope and up to ∼100 keV for a Ni/C coated telescope. For a satellite observation time of 105 sec and an imaging resolution of 1 arcmin the sensitivity is ∼10−7 photons/cm2/s/keV which demonstrates the great potential of this hard X-ray imaging telescope in the energy range up to 100 keV.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF00419256

    Articles: DFG German National Licenses