Is the Landau damping plays a crucial role in high density and low magnetic field helicon plasma

By employing warm plasma model and considering the cyclotron harmonic effect in the dielectric tensor elements, the power deposition properties of the azimuthally symmetric mode of the helicon and Trivelpiece-Gould (TG) waves due to collisional and kinetic damping in high density (~1×10¹³ cm^-3), low magnetic field (~30-50 G) and low to moderate neutral gas pressure (~ 0.5-10 mTorr) helicon plasma are investigated. Theoretical calculations indicate that the magnetic field imposed significant influence on the mode coupling surface properties between the helicon and TG waves; in typical helicon plasma electron temperature range, T_e ∈(3, 5) eV, there exist the critical neutral gas pressure, below or above which, different waves due to different damping mechanism play dominant role in the power deposition, meanwhile, in low neutral gas pressure (~0.5 mTorr) circumstances, TG wave due to Landau damping dominates the power deposition and this dominance gradually becomes intensified as the magnetic field increases.