Investigation on the optimal configuration design and discharge characteristics of the helicon plasma tube

Abstract

Helicon discharge is characterized by its high ionization efficiency. In order to obtain the desired density, the configuration design of the helicon discharge tube is carried out, and the discharge characteristics are then studied to explore the correlation between the plasma parameters and the input discharge parameters. Finite‐length helicon discharge theory is employed to calculate the plasma resistance Rp, and then the optimal tube length Ls, the radius rp, and the tube–antenna gap d are confirmed. The partial and energy loss mechanisms of the tube are investigated based on low‐pressure discharge particle collision theory. The results show that, for a 10‐cm‐long Nagoya III type antenna, with a tube radius of 4 cm and length of 20 cm, the Rp versus ne curves have peak values at ne higher than 1012 cm−3 when the magnetic field intensity B0 ≥ 200 G. We find that a local minimum of Ploss exists when p0 is ∼1.5–3.0 mTorr; meanwhile, the radial confinement reduces Te and Ploss at constant p0.