Date of Award:

5-1996

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Physics

Committee Chair(s)

John R. Dennison

Committee

John R. Dennison

Committee

W. John Raitt

Committee

Jan J. Sojka

Abstract

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 S and n, 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 Al 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 S is presented. Total S and n values obtained in the present investigation are found to be in qualitative agreement with the results of previously reported investigations, though quantitative disagreement of S-values is substantial. Specifically, evidence is presented suggesting that previously reported SE yields for clean Al under electron bombardment (in the 1-3 ke V energy range) are in error by as much as 30 %.

Checksum

d40a98f0290808fdbf52dbeeb1d3f82c

Included in

Physics Commons

Share

COinS