Rotational Temperature in Helium, Argon, and Oxygen Microwave-Induced Plasmas: Comparison with Translational and Solid Surface Temperatures

Abstract

Translational temperature ( T_g), rotational temperature of OH ( T_r), and surface temperature ( T_s are determined in helium, argon, and oxygen plasmas. Measurements are carried out at different pressures and different flow rates as a function of microwave power input by using various methods (line broadening, pressure rise, spectroscopy, thermocouple, pyrometry). The three temperatures depend on the nature of the gas (oxygen < helium > argon) and increase with power input and pressure. Results show that T_g is of the same order of magnitude as T_s. But in all experimental conditions, T_r is always higher than T_g. Therefore, T_r is inadequate for estimating T_g. When no direct determination of T_g is available, T_s seems to give a better estimation of this important parameter.