Microwave interference diagnosis of plasma based on fluid dynamics modeling

Abstract

Aim at the problem that microwave interference diagnosis of plasma can only get an average electron density along the transmission path of microwave, this paper put forward a new microwave interference diagnosis method based on fluid dynamics modelling to gain accurate distribution of electron density. In this method, the fluid model of inductively coupled plasma (ICP) is set up by multi-physics coupling method on COMSOL platform. Then a group of Boltzmann equations is introduced to solve the electron energy distribution function (EEDF), diffusion coefficient and transport coefficient. Based on the fluid dynamics model, the bivariate distribution of electron density is obtained by solving the electron drift diffusion equations, electron energy drift diffusion equations and momentum flux conservation equations. Then the profile function of electron density along the transmission path of microwave can be collected from it. And the profile function is discretized to make it easier to calculate the electron density of different parts. At last, an experiment system of ICP in transparent chamber is set up to verify the effectiveness of the new method. The electron density is diagnosed by the new microwave interference diagnosis and Langmuir probe respectively. The results reveal that the electron density rises with power and the peak value can reach 7.8×1017 m-3 at the radio frequency (RF) power of 700 W. The new method makes up for the deficiencies of traditional microwave interference diagnosis and numerical simulation effectively.