Date of Award:
Master of Science (MS)
W. John Raitt
Jan J. Sojka
Secondary electron emission (SEE) and incident-particle backscattering are important processes accompanying the impact of energetic electrons and ions on surfaces. The phenomena play a key role in the buildup of electrical charge on spacecraft surfaces, and are therefore of particular interest to scientists attempting to model spacecraft charging. In response to a demonstrated need for data, techniques for determining total secondary electron (SE) and backscatter (BS) yields 𝛿 and η, and associated scattering-angle-resolved, scattering-energy-resolved, and simultaneous angle-energy-resolved yields have been developed. Further, an apparatus capable of making the necessary measurements for experimental determination of these quantities---for conducting materials in an ultra-high vacuum environment-has been designed, constructed, and partially tested. The apparatus is found to be in working order, though in need of fine-tuning, and the measurement technique successful.
Investigations using a 1-3 keV beam of monoenergetic electrons normally incident on bulk AI have been undertaken with the new apparatus. Electron-stimulated desorption of surface contaminants has been observed, as has been beam-induced carbon deposition, and an empirical model describing the resulting dynamic evolution of (del)is presented. Total 𝛿 and η values obtained in the present investigation are found to be in qualitative agreement with the results of previously reported investigations, though quantitative disagreement of 𝛿-values is substantial. Specifically, evidence is presented suggesting that previously reported SE yields for clean AI under electron bombardment (in the 1-3 Kev energy range) are in error by as much as 30 %.
Davies, Robert, "An Instrument for Experimental Secondary Electron Emission Investigations, with Application to the Spacecraft Charging Problem" (1996). All Graduate Theses and Dissertations. 1697.
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