Thesis--Ph. D., University of Hong Kong.

Thesis--Ph. D., University of Hong Kong, 1977.

The goal of this dissertation is to provide experimental insight into the mechanism behind the efficient power absorption of helicon plasmas. This work presents evidence which is consistent with the Radially Localized Helicon (RLH) theory put forth by Breizman and Arefiev. Helicon discharges produce peaked density profiles with radial density gradients creating a potential well that sets up the RLH waves, which we believe is the major power absorption mechanism in the plasma. The experimental data presented in this dissertation must be taken in totality along with parallel efforts in theory and computer simulation. We show photographic evidence along with Langmuir probe measurements of the axial density that shows an asymmetric, right-hand circularly polarized wave being launched in a direction consistent with RLH theory. Additionally, we are able to show, through Langmuir probe measurements, that significant radial density gradients exist in the plasma which is required by the RLH dispersion but contrary to the uniform density assumption of current theory. Furthermore, using the two-dimensional density profile obtained from experiment, we are able to use that data as input into a model which confirms key features of the power absorption in terms of location and magnitude. The time-varying magnetic field is measured and analyzed against the RLH dispersion relation. Using a Fourier decomposition technique, the analysis indicates the proper scaling of the wavenumbers with the RLH dispersion. Finally, using the experimental density as input to a computer model, simulations show very good agreement with the amplitude and phase of the experimentally measured RF magnetic fields. / text

Surface integral equation (SIE) method with the kernel of layered medium Green's function (LMGF) is investigated in details from several fundamental aspects. A novel implementation of discrete complex image method (DCIM) is developed to accelerate the evaluation of Sommerfeld integrals and especially improve the far field accuracy of the conventional one. To achieve a broadband simulation of thin layered structure such as microstrip antennas, the mixed-form thin-stratified medium fast-multipole algorithm (MF-TSM-FMA) is developed by applying contour deformation and combining the multipole expansion and plane wave expansion into a single multilevel tree. The low frequency breakdown of the integral operator is further studied and remedied by using the loop-tree decomposition and the augmented electric field integral equation (A-EFIE), both in the context of layered medium integration kernel. All these methods are based on the EFIE for the perfect electric conductor (PEC) and hence can be applied in antenna and circuit applications. To model general dielectric or magnetic objects, the layered medium Green's function based on pilot vector potential approach is generalized for both electric and magnetic current sources. The matrix representation is further derived and the corresponding general SIE is setup. Finally, this SIE is accelerated with the DCIM and applied in quantum optics, such as the calculation of spontaneous emission enhancement of a quantum emitter embedded in a layered structure and in the presence of nano scatterers. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

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