|Abstract:||Ball plasmoid discharges are uniquely long-lived plasmas that are generated by a pulse of several kiloJoules of stored energy over the surface of a grounded volume of water. The plasmoid has a visible lifetime on the order of a few hundred milliseconds, part of which appears to persist without power input. Predictions of the recombination time of ball plasmoids using air plasma models dictate that the system should dissipate within a millisecond-- this discrepancy indicates that there is likely some unexplained mechanism (physical, chemical, or otherwise) by which ball plasmoids are stabilized. The search for this potential mechanism has motivated the work described in this thesis for the past several years.
Ball plasmoid discharges are considered to be laboratory analogues of ball lightning, a naturally-occurring and still unexplained phenomenon. To date, ball lightning has not been reproduced in the laboratory, therefore studies aimed at explaining the formation and lifetime of ball lightning must rely on laboratory analogues. Like ball plasmoids, the reported lifetime of ball lightning (seconds) is several orders of magnitude longer than what would be expected at atmospheric pressure. An understanding of the mechanism(s) responsible for the long lifetime of ball plasmoids could perhaps provide insight into the stability of ball lightning.
To gain a comprehensive understanding of the chemistry that occurs during a ball plasmoid discharge, several techniques were implemented to analyze various physico-chemical properties of the plasmoid. Experiments using mass spectrometry, emission spectroscopy, microwave interferometry, and electrical analyses in ambient air and other gases are described throughout this thesis. The combination of these results furthers our understanding of the composition of these plasmoids. We have identified the major ions present in the plasmoid and have shown through statistical analysis of water clusters that the electrolyte contributes to the formation more than the ambient environment. Emission spectroscopy reveals emission from a wide variety of molecular and atomic species, including OH and NH radicals, H-α, H-ß, O I, N I, W I, Cu I, Fe I, Cu II, and Fe II, and facilitates a deeper discussion of molecular excitation and dissociation processes than has been presented to date in the literature. Finally, preliminary measurements of plasmoid discharges in argon indicate that the resistance of the plasmoid is significantly different in a rare-gas atmosphere compared to ambient air.
While this work does not answer all of the questions surrounding the stability of ball plasmoids, unexplored avenues of experimentation and analysis were investigated at higher energies than previously reported. Results inferred from these experiments provide a foundation from which further studies of this system can be undertaken.