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  • Articles  (6)
  • 78.70  (6)
  • Springer  (6)
  • 1980-1984  (6)
  • 1980  (6)
  • Physics  (6)
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  • Articles  (6)
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  • Springer  (6)
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  • 1980-1984  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Electric-field effect on positronium formation and decay in some polymers and fused quartz (1980)
    Springer
    Applied physics 22 (1980), S. 317-321 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 71.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effect of static electric field on the formation and annihilation of positronium in polyethylene, polystyrene, teflon, quartz, nylon and perspex has been investigated employing a fast timing spectrometer with prompt resolution (fwhm) ∼200 ps at the positron experimental settings. No significant variation in the lifetime of the long lived pick-off component with electric field has been observed. The intensity of the long-lived pick-off component decreases with increase of the field in all the cases investigated except in nylon and perspex where the intensity remains constant with the field. The results have been discussed in the frame work of the spur reaction model proposed by Mogensen and also in the light of the Ore gap model, as discussed by Brandt and Wilkenfeld. Another interesting correlation seems to exist between positronium formation and dielectric loss factor; in case of increasing loss factor there is a decrease in the effect of electric field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899885
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  • 2
    Electronic Resource
    Electronic Resource
    Positron trapping in electron-irradiated silicon crystals (1980)
    Springer
    Applied physics 22 (1980), S. 415-419 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.60 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The positron lifetime in electron-irradiated undoped and doped silicon crystals is studied as a function of temperature between 90 and 300 K. We show that the temperature dependence of the two lifetime components does not arise from the escape, but from the trapping rate at defects. The temperature dependences of the capture cross sections are deduced. It is concluded that in undoped crystals the positrons interact with negatively charged and neutral defects, probably divacancies and vacancy-oxygen complexes, respectively. In strongly P-doped crystals positron trapping occurs preferably in negatively charged centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00901067
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of geometry on the resolution of a positron annihilation lifetime spectrometer (1980)
    Springer
    Applied physics 23 (1980), S. 149-152 
    Details
    ISSN: 1432-0630
    Keywords: 29 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A detailed study of the prompt resolution curve of a positron annihilation lifetime spectrometer shows that the geometry of the source-detector set-up has great influence on its shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899710
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  • 4
    Electronic Resource
    Electronic Resource
    Diffusion of positrons to surfaces (1980)
    Springer
    Applied physics 21 (1980), S. 323-325 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 71.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Low-energy positrons implanted into a crystal can diffuse to the surface where they may be detected, for instance, by observing the formation of positronium. We describe the positron motion by a one-dimensional diffusion equation, and discuss the measurement of vacancy activation energies, positron diffusion constants, and positron stopping profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00895922
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  • 5
    Electronic Resource
    Electronic Resource
    Brightness enhancement of slow positron beams (1980)
    Springer
    Applied physics 23 (1980), S. 189-191 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The brightness of slow positron beams can be enhanced significantly by repeated stages of moderation, acceleration and focusing. Presently available data suggest that the source spot area should decrease by 10−4 after each stage with only a modest loss of intensity. Beams with very small angular divergence, which could be made with this technique, would be useful for characterizing surfaces by positron diffraction and microscopy. Using such beams it is possible to envision the study of new exotic systems such as thee +-e − plasma and the positronium molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899716
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  • 6
    Electronic Resource
    Electronic Resource
    Stability problems in annihilation photon energy spectroscopy: A case study (1980)
    Springer
    Applied physics 21 (1980), S. 19-24 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Errors caused by instrumental instabilities in annihilation photon energy spectrometers can be much larger than statistical errors. The performance of a typical spectrometer is investigated in detail and both empirical and theoretical approaches to correcting data for residual fluctuations are examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00886478
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