Date of Award
Doctor of Philosophy
Dr. John A. Tanis
Dr. N. Stolterfoht
Dr. A. Kayani
Dr. P. Ari-Gur
Transmission of electrons through an insulating single cylindrically-shaped glass capillary of microscopic dimension has been investigated. Samples made with Borosilicate glass (PYREX 7740) were subjected to bombardment of 300-1000 eV electrons. Transmitted electrons were analyzed using a parallel-plate spectrometer coupled to a channel electron multiplier.
The transmitted electron intensity was found to decrease with increasing sample tilt angle relative to the direction of the primary beam. Two regions of transmission were found: direct where there is no interaction of the beam with the inner capillary wall, and indirect where the beam does interact with the wall. The rate of transmission falloff in the direct region was independent of the primary beam energy, whereas a maximum in the rate for 500 eV was observed for the indirect region. Rutherford scattering was found to be dominant at lower energies (< 500 eV), while Coulombic repulsion due to charge deposition took over at higher energies. When the same experiment was repeated using an angular resolution spectrometer with ten times better resolution, the transmitted electron intensities revealed two distinct regions with different characteristics within the indirect region instead of just one. The region of lower sample tilt angles was dominated by transmission due to Coulombic repulsion, while for larger tilt angles inelastic scattering of incoming electrons at the capillary wall dominated the transmission. Charge deposition inside the capillary was also studied as a function of time and found to be time (charge) dependent, confirming the existence of transmission based on Coulombic repulsion. The transmission intensity showed oscillatory behavior in the indirect region at equilibrium, suggesting a sudden discharge of the capillary followed by slower recovery as the charge build up goes toward equilibrium. Stable transmission equilibrium was never reached due to repeated sudden partial discharge of the inner capillary from time to time. Evidence of initial beam deflection due to charge accumulation at the capillary entrance is in agreement with observations on slow highly charged ions.
Dassanayake, Buddhika Senarath, "Electron Transmission Characteristics and the Production of Narrow Beams Using Glass Optics" (2011). Dissertations. 394.