Spatial structures of different particles in helicon plasma

Abstract

Abstract The spatial structures of different particles (high-energy electron excited ionic and low-energy electron excited neutral particles) in both discharge and plume plasmas of a helicon source have been characterized. These two different populations show different intensity jumps and growth rates with increasing RF input powers. Filters of 480 nm band pass and 600 nm high pass have been used to distinguish these two populations. Results show that the plasmas are generated from both ends of the antenna and transmitted to the middle of the antenna to form an axial particle path. When the wave mode reaches, the axial particle path is formed. The radial distribution of the high-energy electrons is highly concentrated on the center line while that of the low-energy electrons is relatively uniform. The axial distribution of the high-energy electrons is asymmetric, that is the maximum density is located on the one end of the antenna. The reversed magnetic field could reverse their axial distributions. In the plume plasma, the high-energy electrons are highly directional and expand further axial distances compared with the low-energy electrons. The most probable energies of ions derived from the RFEA remain almost the same with an average value of 45 eV. But the IEDF shapes and the relative ion densities change greatly at 700W. It is believed that the IEDFs and ion density jumps are more likely related to the high-energy electron density jumps.