by Li Sun-wai, Victor. / Title and statement of responsibility also in Chinese. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984. / Bibliography: leaves [44]-45.

An energy analyzer for electron beams, based on a retarding-potential method, has been studied both experimentally and theoretically. In this method a potential energy barrier at right-angles to the beam acts as a high-pass energy filter allowing electrons having energies greater than the barrier height to pass through while turning back electrons of lower energy. The potential barrier in the present study was created by applying a negative potential to an electrode consisting of a 600/inch hexagonal copper mesh or an electrode having a pair of single apertures in series (compound aperture). Two different compound apertures, of diameters 0.4 mm and 1.0 mm, were used. The retarding electrode was mounted between two grounded outer electrodes having openings centered on the axis for entrance and exit of electrons. The barrier height was adjusted by means of a small variable bias voltage between the electron gun cathode and the retarding electrode. Auxiliary electron lenses external to the retarding module were used to satisfy the conditions that the beam be normal to the retarding electrode and, for an imaging filter, that an image plane be focused at the retarding electrode. A beam having a narrow distribution of energies was used to calibrate the energy analyzer as a function of bias voltage for the three different configurations of retarding electrode. The calibration curves were then compared with the transmission curve for a beam having a broadened energy distribution. The feasibility of obtaining a filtered image was explored by observing the image of a fine mesh focused into an aperture of the retarding electrode. The experiments were carried out for a beam voltage of 15 kV. At this beam voltage the energy resolution is poor, being 3. 6 volts for the smaller compound aperture, 3. 7 volts for the mesh, and 5.2 volts for the larger compound aperture. Typically, electrostatic analyzers operate on a beam which has been decelerated to low energies before entering the analyzer, in which case the energy resolution is proportionately better. For example, at 150 V the above resolution figures would be 0.036, 0.037, and 0.052, respectively. In view of the potential for high energy-resolution and the attractive features of in-line, rotationally-symmetric systems, it is felt that the retarding-potential analyzer is a promising candidate for further development.

No description available.

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (p. 108-119). Also available via the World Wide Web.

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2004. / Thesis advisor(s): R.J. Umstattd. Includes bibliographical references (p. 41). Also available online.

Thesis (M.A.)--Ball State University, 2008. / Title from PDF t.p. (viewed on Sept. 01, 2009). Research paper (M.A.), 3 hrs. Includes bibliographical references (p. 30).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 221-227).

Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). "August 2006." Includes bibliographical references (leaves 105-108). Also available via the World Wide Web.

Glow discharge electron guns are used to generate continuous electron beams at 0.5keV-3.0keV in the intermediate range of gas pressures (0.1mb-10.0mb). Cathodes incorporating internal cavities are used to generate distinct electron beam filaments in both Helium and Argon. The formation of such beam filaments has been investigated using a number of different cathode types, and criteria for the production of stable electron beams are established. The production of an electron beam in a glow discharge is largely determined by the motion of electrons in the Cathode dark space sheath region next to the cathode, and other discharge processes in this region. A theoretical model has been developed to simulate electron motion in the sheath region, and in the Negative glow plasma region, of a Helium discharge with a Cathode fall of between 150V and 1000V. It is shown that the electron flux at the 'sheath/Negative glow boundary becomes increasingly monoenergetic as the Cathode fall rises to 1000V. The results are also compared with experimental spatial emission profiles of the glow in the Cathode dark space and Negative glow regions of a helium discharge. In particular, properties of the Cathode glow region in the sheath are discussed. Aspects of the theoretical model and results from the experimental measurements are also used to discuss discharge processes in the sheath region of cathodes incorporating internal cavities, and mechanisms leading to the formation of the electron beam filaments. The production of fast electrons in a glow discharge has a number of applications, including the excitation of gases leading to laser action. Aspects relating to the excitation of high lying energy states in gases, corresponding to known laser transitions, are discussed. It is shown that the production of helium ions, which are responsible for the excitation of metal atoms via asymmetric charge transfer in metal ion lasers, is theoretically more efficient in an electron beam discharge. The results are compared with the theoretical ion production rates in Hollow cathode discharges, and high-voltage Hollow cathode devices. Several electrode geometries using multiple arrays of electron gun cathodes have been developed. Investigations of an electron beam excited argon plasma suggest that Ar II excited states are pumped directly by single electron impacts, even at very low current densities (~10^-3 A cm^-2). From previous calculations using the 'sudden perturbation' approximation, those ion states known to have large cross-sections for direct electron impact excitation (3p44p2P) appear to be favourably pumped in the electron beam plasma.

A wide variety of inelastic scattering and electron attachment phenomena have been studied by directing an electron beam into a gas filled chamber and by observing the results of the interaction. The use of a "monoenergetic" electron beam has permitted the relative cross sections for such processes to be examined in some detail. Three instruments were used to make the measurements, and these instruments were designed and constructed during the course of the work to be described. All three employed a 127° electrostatic electron velocity selector to filter the electron beam. An electron energy analyzer permitted the observation of inelastically scattered electrons, and a monopole or a quadrupole mass filter permitted the measurement of the relative amounts of positive or negative ionization generated by the electron beam in its interaction with the gas. The measurement of the energy dependence of the cross sections was the prime objective of the work, and much care was taken in the design of the instruments to ensure that the cross section curves were not distorted by spurious effects. The forward inelastic scattering spectra of helium and ethylene were recorded using an electron beam having an incident energy of 50 eV . The ionization efficiency curves of singly and doubly charged helium were obtained, and the results are compared with several theoretically derived expressions for electron impact threshold laws. The positive ionization efficiency curves for nitrogen and oxygen were also obtained. An examination of the dissociative capture, non-dissociative capture and ion pair processes has been made by determining the energy dependence of the cross sections for the production of the parent and/or fragment negative ions from nine molecules. Finally, the generation of zero energy electrons from inelastic scattering events has been studied by using sulfur hexafluoride as an electron scavenger in a mixture with the sample gas. The threshold electron impact spectra were obtained for six atomic and molecular species. In all cases, such measurements were carried out below and above the ionization potential of the sample. / Science, Faculty of / Chemistry, Department of / Graduate