Modeling multiple-frequency electron cyclotron resonance heatinga

Electron cyclotron resonance (ECR) heating influences two of the main parameters (electron temperature and, indirectly, density) that determine the charge state of the ions produced in an ECR ion source (ECRIS). Therefore, various schemes to optimize ECR heating in the ECRIS have been pursued such as multiple-frequency heating, the radio-frequency tuning effect, volume heating, or wide-band heating. We investigate two-frequency ECR heating of electrons in a simple magnetic mirror field by right handed circularly polarized waves with infinite phase velocity. The study shows a heating barrier different from the well-know adiabatic barrier. Study also revealed a mechanism whereby multiple frequencies give improved heating. A preliminary interpretation of the study is presented.