Enthalpy probe diagnostics of an atmospheric pressure argon microwave induced plasma

An argon microwave-induced plasma (MIP) at atmospheric pressure was generated in a TE 10 mode waveguide. The discharge was sustained by a relatively low absorbed power of around 215 W. An enthalpy probe was used to characterize the argon MIP discharge, yielding values of enthalpy, velocity and heavy particle temperature along the jet axis. The theory of the enthalpy probe operation and calibration is reviewed and the system for its implementation is described. The heavy particle temperature is found to be about 1600 K and the velocity to be about 150 m s -1 at the exit plane of the discharge tube for an argon flow rate of 1.6 l min -1 . Although the assumption of local thermodynamic equilibrium is required to determine the temperature and velocity in the jet from the enthalpy probe measurements, it is argued that the values obtained should be reasonable even if, as expected in MIPs, the electron temperature is significantly higher than the heavy particle temperature.