2016 Laufer Lecture
Hans W. Liepmann Professor of Aeronautics
Professor of Bioinspired Engineering
Director of Graduate Aerospace Laboratories
Division of Engineering and Applied Science
California Institute of Technology, Pasadena, CA
Title: “On the Generation of Toroidal Micro-Plasmas in the Flow Field of Impinging Water-Jets”
There is a renewed interest in atmospheric pressure plasma (APP), also known as atmospheric pressure corona, for its broad scientific and industrial applications. As a weakly ionized non-equilibrium plasma, APP has no defined shape or volume and, in general, is unstable and non-uniform. Therefore, it is desirable to have a source of stable and uniform APP with defined morphologies for scientific investigations that could take advantage of the highly collisional state of the plasma medium. Here, we report an approach to produce atmospheric pressure micro-plasmas in which the plasma cloud presents a stable, and topologically-connected and self-confined toroidal shape. We show that this unique toroidal APP morphology can be uniquely generated when a high-speed laminar micro-jet of de-ionized water impinges on a di-electric solid surface. This toroidal micro-plasma shows a unique and previously unreported plasma resonance mode characterized by a strong and discrete radio frequency emission.