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  • 1
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    Neutron-gamma techniques for planetary exploration (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Chemical analysis of planetary surfaces is necessary for the understanding of the origin and evolutionary processes of the solar system. Orbital lunar geochemical experiments performed during the Apollo 15 and 16 demonstrated that even with a low neutron flux (fast and thermal), reliable results could be extracted. The possibility of using a compact 14 MeV neutron generator for geochemical analysis of planetary surfaces, comets and asteroids is currently studied. This method allows the determination of bulk chemical composition, even in the presence of an atmosphere. This would be possible on the surface of Venus, for example, where alternate methods such as sample return are impractical. This method can be used for continuous monitoring of elemental abundances from a roving vehicle, for example, on the surface of Mars.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Method and apparatus for mapping the distribution of chemical elements in an extended medium (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Contaminants in an extended medium such as the wall of a building are mapped by locating neutron excitation source on one side of the wall and a gamma ray spectrometer, including a gamma ray detector on the opposite side of the wall facing the excitation source. The source and detector are moved in unison in discrete steps over opposing wall surfaces so as to determine the chemical composition of the elements in a hemispheric region of the wall adjacent the detector with the radius of the region being substantially that of the mean free path distance of gamma rays emitted from elements interacting with neutrons on the detector side of the wall. The source and detector are reversed for relatively thick walls for mapping the distribution of elements on the other side of the wall thickness. The output of the detector is fed to a multichannel pulse height analyzer where the intensity of the various gamma ray spectral lines are indicated relative to a dominant constituent element such as silicon. Resolution of anomalies such as the presence of voids and/or determining the bulk density of the medium is achieved by substituting a gamma ray source technique is also applied to metal alloys, such as iron alloys, in either the solid or molten state.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: NAS 1.71:GSC-12808-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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