No description available.

No description available.

No description available.

Bibliography: p. 174-183. / ix, 183 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Aims to contribute to the understanding of the first excited electronic state of NaI / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1999

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics and Mathematical Physics, 1999. / Bibliography: p. 174-183.

Bibliography: p. 174-183. Aims to contribute to the understanding of the first excited electronic state of NaI

No description available.

No description available.

This thesis investigates the relevance between the acoustic resonance and power harmonics on a metal halide lamp. First, a sinusoidal current ranging from 20 kHz to 400 kHz is used to drive a 70 W metal halide lamp. Second, a hybrid-current test circuit is designed to generate a current waveform consisting of a low-frequency square-wave and a high-frequency sinusoidal wave. Both of the frequency and the amplitude can be adjusted independently. The test lamp is deliberately driven at its acoustic-resonance eigen-frequencies to observe the effect of the power spectrum on the degree of the acoustic resonance. The experimental results indicate that the occurrence of acoustic resonance is indeed affected by the DC level and related power harmonics. The power harmonic spectrum that elucidates the initiation of acoustic resonance is deduced from the observations. It is found that the power harmonics that excites acoustic resonance can be divided into three categories. The first is independent of the average lamp power; it excites acoustic resonance only if the magnitude of its power exceeds a specific level. The thresholds of power harmonics belong to the second category are proportional to their DC powers. One can also find those remaining power harmonics belong to the third category. The power harmonic spectrum of the acoustic resonance is demonstrated by driving the test lamp with quasi-square-wave and triangle-wave currents. This work helps advance the understanding of the phenomena and mechanism of acoustic resonance in a metal halide lamp.

Conventionally, metal halide lamps were ignited by striking the lamp electrodes several times with high voltage pulses. Such a starting scenario causes uncomfortable light strobes to users. To solve this problem, this thesis attempts to ignite small-wattage metal halide lamps with a single pulse strike. At first, the forms of the high voltage pulses required for breaking down the electrodes are investigated. After being broken down, a continuous current is critical for sustaining the lamp arc. With conventional electronic ballasts, however, the lamp current tends to resonate to zero resulting in break of the lamp arc. This problem can be solved by adding an extra switch to remove the capacitor of the output filter during the ignition stage. An electronic ballast is designed and tested on 70 W metal halide lamps with an associated switch for single pulse striking. Experiments have demonstrated that the proposed ignition criteria can start up the lamps successfully with a single-pulse high voltage.