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Title: Secondary electron emission properties and characteristic energy losses from some metals
Author: Thomas, Simon
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 1967
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Secondary electron emission yield and characteristic energy losses from a number of metals have been measured in the present investigation. Owing to the known adverse effects of poor vacuum conditions and any consequent contamination of the surface on the secondary emission properties, all experiments have been conducted in a clean ultra-high vacuum environment - typical pressure under operating conditions being < 10⁻⁹ torr and the residual gases analysed by a quadrupole residual gas analyser. Total yield has been measured from Ni, Ag, Pt, Bi and TaC. A quantitative assessment of the variation of the total yield δ with angle of incidence of the primary beam, in the energy range 200-l300eV and of the mean depths of origin of secondary electrons in these materials, has been made. The total yield from TaC, which is currently favoured as a low yield material, and the effect of surface conditions on its yield bave also been investigated. Characteristic energy losses have been measured from Ag, Bi, Be, Ta and TaC by using a spherical retarding field energy analyser coupled with electronic differentiation. This technique involves energy modulating the electron beam and extracting the signal using phase sensitive detection methods. The accurate values of energy losses obtained in this manner, established the validity of such a technique and the potential of the analyser in characteristic energy loss studies. In particular, two losses at 15 and 30eV have been observed in TaC which has not been investigated hitherto. New energy losses at 13.5eV in Ag and 7.9 and 12.5eV in Ta have been found. The various energy losses in the different materials have been attributed to the excitation of volume and surface plasmons and to intertend transitions. Intensity variations with changes in environment have also been noted. Both changes in the intensity and shape of the loss peaks with contamination have emphasised the necessity for maintaining the target surface clean under ultra-high vacuum conditions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics