Plasma Characterization on Acoustically Structured and Turbulent Plasma-Liquid Interfaces*

Enhancing mass transport at the plasma-liquid interface is an important consideration for the scaling of atmospheric pressure plasma water treatment systems to real world applications. Perturbing the plasma-liquid interface, either in a controlled manner via acoustic excitation of standing waves, or by promoting turbulence, enhances the gas-liquid contact surface area. Such perturbations, along with forced diffusion and mixing, improve the transport of reactive oxygen and nitrogen species (RONS) vital to the mineralization of organic contaminants. Coupled with these hydrodynamic enhancements are plasma chemistry and morphological effects owing to the complex structure of the liquid dielectric. Localized, reduced field (E/N) changes also affect gas phase chemistry and charged particle energetics at the interface. This work experimentally characterizes the effects of these complex surfaces on plasma properties in a pulsed discharge configuration, such as gas temperature and plasma induced optical emission, all of which are functions of E/N. Fast imaging is utilized to resolve length scales induced in turbulent flow relevant to plasma surface attachments. Spatially resolved optical emission spectroscopy is used to infer local E/N changes with interfacial spatial complexity. Finally, a 2D fluid/Monte Carlo model of this system is validated, and used to further generalize experimental results.