Surface temperature and thermal balance of probes immersed in high density plasma

Abstract

The surface temperatures of thermal probes immersed in a low pressure inductively coupled argon discharge have been measured over a wide range of gas pressure. At a fixed discharge power, the measured temperature increases with gas pressure and decreases with increasing probe diameter. At a discharge power of 100 W, the surface temperature of a 0.4 mm diameter probe in the centre of the discharge ranges from C at 0.3 mTorr to C at 1 Torr. This temperature is considerably higher than the gas temperature. An analysis of the energy balance on a probe surface shows that plasma particle bombardment is the dominant heating process while radiation is the dominant cooling process. Probe temperatures found from an energy balance are in reasonable agreement with those measured in experiment.