On the mechanism of density peak at low magnetic field in argon helicon plasmas

Helicon plasma density may show a non-monotonic dependence on the magnetic field at low strength, so-called low-field peak (LFP). We presented the multiple LFPs and the formation mechanism in argon helicon plasmas in this paper. Propagating conditions of helicon (H) and Trivelpiece-Gould (TG) waves in collisional plasmas were calculated based on the dispersion relation. It is demonstrated that there are two mechanisms during mode transition responsible for LFP, i.e., resonance of H- and TG-waves and anti-resonance of TG-wave. Especially, H-TG resonance of the highest axial mode in the helicon plasma results in a density jump rather than a density peak due to the mode transition from non-wave to co-H/TG-wave mode. Higher plasma density in lower magnetic fields is helpful for achievement of multiple LFPs in argon helicon plasmas. Published under an exclusive license by AIP Publishing.

Automated summary

This paper presents the formation mechanism of multiple low-field peaks (LFP) in argon helicon plasmas. The study calculates the propagating conditions of helicon (H) waves and Trivelpiece-Gould (TG) waves in collisional plasmas based on the dispersion relation. It is demonstrated that resonance and anti-resonance mechanisms of H- and TG-waves contribute to LFP formation in mode transition processes.