Numerical studies on the nonequilibrium inductively coupled plasma with metal vapor ionization

Nonequilibrium inductively coupled plasma (ICP) where cesium metal atoms contained in argon gas as a seed material are dominantly ionized is investigated with two-dimensional (2-D) numerical calculations which are based on a fully time-dependent (FTD) model and sinusoidal approximation (SA) model. Calculation results with the FTD model indicate that the amplitude of electron temperature oscillation over one radio frequency cycle is below about 120 K for the mean value of about 5600 K, and that of the electron number density is negligible due to its long relaxation time. Results with the SA model coincide with that with the FTD model, and it is valid to predict the plasma properties with the SA model. Under the suitable operating conditions, the region where electron number density is kept constant is formed and extended in the ICP, since the electron temperature ranging from 4000 to 6000 K is realized, and cesium atoms are fully ionized while the ionization of argon atoms is not significant. Since no current is induced at the center axis of ICP, the density profile around the axis is almost determined by the diffusion of electrons from the region of full seed ionization.