Experimental Investigation of Ar Inductively Coupled Plasma in a Closed Low-Pressure Chamber

For this paper, an experiment of low-pressure Argon inductively coupled plasma (ICP) was conducted in a closed chamber. Obvious $E$ -$H$ mode transition could be observed in the experiment. To solve the problem that microwave interference diagnosis can only measure the average electron density along the transmission path of the microwave, a new microwave interference diagnosis method based on fluid dynamics modeling is put forward to gain an accurate distribution of electron density. Using this new method, the spatial resolution of electron density could be improved. Finally, the electron density of low-pressure ICP was diagnosed both with this method and the Langmuir probe. The results revealed that the electron density increased with power and the peak value reached $7.8\times 10^{17}\text{m}^{-3}$ at the radio frequency power of 700 W. The consistency in the distribution trend of electron density that resulted from two different methods illustrates that the new method can provide a relatively accurate spatial distribution detail of electron density. The electron temperature was measured via the Langmuir probe and the results show that the temperature declines with power.