Enthalpy probe diagnostics of an atmospheric pressure argon microwaveinduced plasma

Abstract

An argon microwave-induced plasma (MIP) at atmospheric pressure wasgenerated in a TE10 mode waveguide. The discharge was sustained bya relatively low absorbed power of around 215 W. An enthalpy probe was used tocharacterize the argon MIP discharge, yielding values of enthalpy, velocityand heavy particle temperature along the jet axis. The theory of the enthalpyprobe operation and calibration is reviewed and the system for itsimplementation is described. The heavy particle temperature is found to beabout 1600 K and the velocity to be about 150 m s-1 at theexit plane of the discharge tube for an argon flow rate of 1.6 l min -1. Although the assumption of local thermodynamic equilibrium isrequired to determine the temperature and velocity in the jet from the enthalpyprobe measurements, it is argued that the values obtained should be reasonableeven if, as expected in MIPs, the electron temperature issignificantly higher than the heavy particle temperature.