Three-dimensional fluid simulations on a line-shaped microwave plasma

Abstract

A three-dimensional (3D) fluid simulation code has been developed to investigate the discharge characteristics and plasma distribution in a line-shaped microwave plasma device, which consists of a rectangular waveguide with a variable width a, a long quartz discharge tube with a U-shaped cross section partly inserted into the waveguide and the plasma diffusion chamber. The line-shaped plasmas are mainly produced just under the discharge tube surrounded by the complex structure. Experiments have revealed that the axial profile of the plasma density ne can be changed when a and the insertion depth di of the discharge tube into the waveguide are varied. 3D numerical analyses show that the axial distribution of power absorption Pabs depends on a and di and concentrates near the single side of the discharge tube when the high-ne plasma is inserted deeply into the waveguide. 3D simulations show that ne has peaks near the inner edges of the discharge tube and the axial distribution of ne depends on the waveform of the electric fields formed in the waveguide. The change in density profiles due to the variation of a and di observed in the experiment is mostly reproduced qualitatively by the present 3D simulation.