Download or read book Nanosecond Pulsed Discharge in Water Without Bubbles written by Yohan Seepersad and published by . This book was released on 2015 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: The state of plasma is widely known as a gas-phase phenomenon, but plasma in liquids have also received significant attention over the last century. Generating plasma in liquids however is theoretically challenging, and this problem is often overcome via liquid-gas phase transition preceding the actual plasma formation. In this sense, plasma forms in gas bubbles in the liquid. Recent work at the Drexel Plasma Institute has shown that nanosecond pulsed electric fields can initiate plasma in liquids without any initial cavitation phase, at voltages below theoretical direct-ionization thresholds. This unique regime is poorly understood and does not fit into any current descriptive mechanisms. As with all new phenomena, a complete fundamental description is paramount to understanding its usefulness to practical applications. The primary goals of this research were to qualitatively and quantitatively understand the phenomenon of nanosecond pulsed discharge in liquids as a means to characterizing properties that may open up niche application possibilities. Analysis of the plasma was based on experimental results from non-invasive, sub-nanosecond time-resolved optical diagnostics, including direct imaging, transmission imaging (Schlieren and shadow), and optical emission spectroscopy. The physical characteristics of the plasma were studied as a function of variations in the electric field amplitude and polarity, liquid permittivity, and pulse duration. It was found that the plasma size and emission intensity was dependent on the permittivity of the liquid, as well as the voltage polarity, and the structure and dynamics were explained by a 'cold-lightning' mechanism. The under-breakdown dynamics at the liquid-electrode interface were investigated by transmission imaging to provide evidence for a novel mechanism for initiation based on the electrostriction. This mechanism was proposed by collaborators on the project and developed alongside the experimental work in this research. Finally, analysis of emission spectra obtained from the OH(A-X) band at 308 nm by the excited hydroxyl radical was performed to quantify the temperature parameters of the plasma. Boltzmann analysis was performed to quantify the rotational temperature of OH which correlates well to the liquid temperature, and Stark broadening of the ionic lines belonging to hydrogen and oxygen was analysed to estimate electron temperature. It was found that the liquid temperature remained close to bulk temperature with T_(n,i)