A method to evaluate the plasma equivalent resistance of fusion relevant RF ion sources

Abstract

To optimize the RF power transfer process for fusion relevant RF ion sources, the electric models evaluating the plasma equivalent resistance (PER) are used in engineering, such as the transformer model. This paper presents a method to evaluate the PER based on a FEM model, viz. the electromagnetic model describing the RF coupling and numerically solved by the finite element method (FEM). The inductively coupled plasma (ICP) is treated as a lossy dielectric. Then the ICP source loaded by the plasma is modeled in a generic electromagnetic FEM code. The method was applied to two fusion relevant ICP sources. The results showed that PER from the FEM model is quantitatively closer to PER from experiments than PER from other electrical models. Though the error in PER from the FEM model is still large, the method is an alternative to estimate the PER of fusion relevant RF ion sources. The error is mainly due to the stochastic heating model and the neglect of magnetization. Besides, for fusion relevant RF ion sources, the good-conductor approximation does not apply to the plasma and the plasma nonuniformity should be considered in electric models.