Date of Award:

2005

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Physics

Advisor/Chair:

Dr. John R. Dennison

Abstract

Measurements of the electron-induced electron emission properties of insulators are important to many applications including spacecraft charging, scanning electron microscopy, electron sources, and particle detection technology. However, these measurements are difficult to make since insulators can charge either negatively or positively under charge particle bombardment that in turn alters insulator emissions. In addition, incident electron bombardment can modify the conductivity, internal charge distribution, surface potential, and material structure in ways that are not well understood. A primary goal of this dissertation work has been to make consistent and accurate measurements of the uncharged electron yields for insulator materials using innovative instrumentation and techniques. Furthermore, this dissertation reports on the experimental work undertaken by our group to explore insulator charging rates as a function of incident electron energy and fluence. Specifically, these charging studies include: (i) the study of the effectiveness of charge-neutralization techniques such as low-energy electron flooding and UV light irradiation to dissipate both positive and negative surface potentials induced by incident electron irradiation, (ii) the exploration of several noncontacting methods used to determine insulator surface potentials and the insulator first and second crossover energies that are important in determining both the polarity and magnitude of spacecraft material potentials, (iii) the dynamical evolution of electron emissions and sample displacement current as a function of incident charge fluence and energy with ties to evolving surface potentials as an insulator reaches its current steady state condition, and (iv) the slow evolution of electron yields with continuous incident electron bombardment.

These charging data are explained in the context of available insulator charging models. Specific insulator materials tested included chromic acid anodized aluminum, RTVsilicone solar array adhesives, and KaptonTM on aluminum.

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Physics Commons

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