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In this paper, the numerical study has been performed on the xenon positive column discharges of mercury-free fluorescent lamp. The plasma discharge characteristics are analyzed by numerical simulation based on two-dimensional fluid model. The effects of cell geometry, such as the dielectric layer, the electrode width, the electrode gap, and the cell height, and the filling gas including the pressure and the xenon percentage are investigated in terms of discharge current and discharge efficiency. The results show that a long transient positive column will form in the xenon lamp when applying ac sinusoidal power and the lamp can operate in a large range of voltage and frequency. The front dielectric layer of the cell plays an important role in the xenon lamp while the back layer has little effect. The ratio of electrode gap to cell height should be large to achieve a long positive column xenon lamp and higher efficiency. Increase of pressure or xenon concentration results in an increase of discharge efficiency and voltage. The discussions will be helpful for the design of commercial xenon lamp cells.

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Spectra of SF6 circuit breaker arcs during the arc extinction phase following peak currents up to 53 kA have obtained in the wavelength range 510-517 nm. Copper emission lines and irregularly occurring tungsten emission lines from entrained contact material have been identified and the ratio of the number density of tungsten to copper atoms estimated from the line intensities. An approximate radial distribution of both copper and tungsten line intensities has also been obtained. The irregular occurrence of tungsten in the arc plasma column and the restricted extent of the tungsten line emitting cross section are both believed to be a consequence of the complicated evaporation processes associated with the copper-tungsten contact. An approximate correlation is shown to exist between the occurrence of tungsten line emission at the critical instant of current zero when current interruption is sought and a sharp deterioration in the current interrupting ability of the breaker. The implication of this is that the hitherto neglected presence of tungsten at current zero, as distinct from copper, contributes in combination with the already known effects of flow throttling and nozzle ablation in determining the extent of the degradation of circuit breaker performance.