Abstract

Microdischarges are plasmas confined to very small gaps and have contributed to a new direction in plasma science and engineering during the last couple of decades with applications including electronics, nanomaterial synthesis, lighting to name a few. The microscale dimensions of these devices make experimental measurements of spatial profiles of plasma properties difficult even with the development of optical diagnostics. As a result, the role of computations in understanding the operating characteristics of microplasmas in both direct current and microwave regimes cannot be stressed enough. Simulating real microplasma devices is best performed in two and three dimensions thereby requiring the use of computational techniques that deliver the right combination of accuracy and efficiency. Non-equilibrium plasmas are typically simulated using two broad classes of techniques – continuum and kinetic. In this talk, we summarize our recent work on comparing continuum and kinetic simulations for direct current argon and microwave microplasmas. Specifically, the standard approach of using a 0-dimensional Boltzmann equation solver to determine reaction rates that are provided as input to the continuum solver is shown to lead to severe under-prediction of plasma number densities in direct current microplasmas. This is attributed to the presence of secondary emitted electrons that are accelerated in the sheath region thereby leading to an over-population of the high-energy tail as shown in the kinetic simulations. On the other hand, microwave microplasmas that are driven predominantly by ionization processes in the bulk are shown to lead to better agreement between the continuum and kinetic simulations particularly at low current densities/powers. The talk will also discuss the frequency response and impedance characteristics of microwave microplasmas ignited at various power levels.

Bio
Venkattraman Ayyaswamy is currently an Assistant Professor of Mechanical Engineering at the University of California, Merced where he leads a group with interests in the broad area of non-continuum fluid mechanics and plasma physics. An aerospace engineer by training, he received his PhD in Aero & Astro from Purdue University in 2012 after receiving his Master’s (also from Purdue) in 2009. Prior to coming to the US for graduate education, he got his Bachelor’s degree from the Indian Institute of Technology (IIT) Madras in 2007. Before his current position, he held visiting faculty appointments at Purdue as well as IIT Madras. He also spent a summer at the Lawrence Livermore National Lab during his graduate school. Venkatt is a recipient of the Ramanujan Fellowship (by the Department of Science and Technology (India)), was Purdue’s finalist for Chorafas Foundation Awards, Magoon Award for Excellence in Teaching as well as a Young Engineer Fellowship from the Indian Institute of Science.