Measurements of gas temperature in an argon positive column using acoustic wave propagation

Abstract

Experiments on acoustic wave propagation and gas temperature measurement in an argon discharge are presented. Ultrasonic waves of pulsed or CW (40 kHz) mode were transmitted across the positive column of diameter 4.6 cm, pressure 2-5 Torr and discharge current approximately 200 mA. Line-of-sight average (LSA) values of the gas temperature were obtained from the acoustic speed measurement. A thermocouple was also used to measure gas temperatures in the plasma. It is shown that the LSA gas temperatures are in good agreement with those derived from radial profile measurements by the thermocouple. The measured radial profiles of gas temperature are consistent with the calculated profiles from a model which balances the heat input from the electrons with the loss by thermal conduction in the gas.