Nonequilibrium in Thermal Plasmas with Applications to Diamond Synthesis

Abstract- Atmospheric pressure plasmas are frequently considered to be in local thermodynamic equilibrium due to the high frequency of collisional processes which drive the plasma state towards a Maxwell-Boltzmann equilibrium. However, various forms of thermodynamic, ionizational, and chemical nonequilibrium have been demonstrated and investigated in atmospheric pressure plasma environments over the last several years, and the nonequilibrium behavior of such systems can be quite significant. The investigation, understanding, and exploitation of atmospheric pressure nonequilibrium plasma chemistry is necessary to the further expansion of plasma-based systems into mainstream manufacturing and processing applications. Several experimental programs to investigate the fundamental processes of atmospheric pressure nonequilibrium plasma chemistry, and the application of this nonequilibrium to various chemical systems have been undertaken in our laboratories. The results of these investigations have shed light on the kinetics behind various forms of atmospheric pressure nonequilibrium chemistry, and provided insights into the beneficial control of nonequilibrium plasma chemistry for processing applications. 1