Density profile transition and high-energy electron transport in a magnetically expanding radio frequency plasma

Abstract

The density profile transition and high-energy electron transport in a magnetically expanding radio frequency (RF) plasma were investigated using particle-in-cell and Monte Carlo collision techniques, where both the plasma source and the diffusion region were simulated self-consistently. The simulation results show that the density profile changes from center-peaked to bimodal plasma with increasing magnetic field strength, where bimodal plasma was observed in previous experiments. Then, the density profile transition is discussed with respect to ionization, electron temperature, and high-energy electron density. This indicates that electrons were heated by the RF field and transported radially inward across magnetic field lines. The moving distance of high-energy electrons is explained by an electron-neutral elastic collision. Therefore, the density formation depends on where the electrons are heated and how far the high-energy electrons are transported by an elastic collision, implying the longer existing time of high-energy electrons that move radially inward away from the RF antenna.