A numerical model for lithium plasma process in a hybrid microwave ion source

Abstract

Lithium ions are widely used in many scientific fields; in order to get these ions, it is necessary to study lithium plasma process thoroughly. Recently, a hybrid 7Li3+ ion source has been designed and tested at Peking University (PKU). To understand the lithium plasma behaviour inside the plasma chamber and to provide some guidelines for ion source optimization to generate 7Li3+, a numerical model based on the plasma equilibrium equations is developed in this work, which is helpful not only for our ion source, but also for understanding the physical process of lithium plasma from ECR ion sources with different frequencies. This model can describe the density and fraction of lithium ions in various system parameters. The dependences of the Li+, Li2+, and Li3+ ion density and fraction on electron temperature, gas pressure, microwave power, surface ionizer, and the magnetic field are investigated systematically.