Discharges in and in contact with water for environmental and medical applications

The interest in non-thermal plasma has been growing for a variety of environmental applications. These include the renewed interest in the decomposition of contaminants in water as well as medical applications that involve plasma interacting with liquids containing organic matter. Advancing these applications requires a deeper understanding of plasma processes and the mutual effect of the entire plasma generating system on plasma-liquid interaction. In this presentation, we will discuss the insights gained from a series of projects conducted as a part of the Princeton Collaborative Research Facility in Low Temperature Plasma. Fast frame imaging, electrical and optical measurements were conducted at PCRF. For example, fast imaging was used to demonstrate that nanosecond pulse electrical discharge initiates in the liquid phase even in the presence of macro and microscopic gas bubbles when the conditions for electrostrictive cavitation are met as in deionized water with sharp submerged electrodes. Water conductivity affects discharge initiation and development and hence influences the requirements on the power source characteristics used to generate the discharge. Nanosecond and subnanosecond imaging of microsecond pulsed discharge propagation along the surface of water containing perfluoroalkyl substances with and without bubbles demonstrated faster termination of filaments for low conductivity solutions. A time scale approach aids in understanding of these observations.