Saturation Ion Current Densities in Inductively Coupled Hydrogen Plasma Produced by Large-Power Radio Frequency Generator

An experimental investigation of the saturation ion current densities (J_ions ) in hydrogen inductively coupled plasma (ICP) produced by a large-power (2–32 kW) radio frequency (RF) generator is reported, then some reasonable explanations are given out. With the increase of RF power, the experimental results show three stages: in the first stage (2–14 kW), the electron temperature will rise with the increase of RF power in the ICP, thus, the J_ions increases continually as the electron temperature rises in the ICP. In the second stage (14–20 kW), as some H⁻ ions lead to the mutual neutralization (MN), the slope of J_ions variation firstly decreases then increases. In the third stage (20–32 kW), both the electronic detachment (ED) and the associative detachment (AD) in the ICP result in the destruction of H⁻ ions, therefore, the increased amplitude of the J_ions in the third stage is weaker than the one in the first stage. In addition, with the equivalent transformer model, we successfully explain that the J ions at different radial locations in ICP has the same rule. Finally, it is found that the J_ions has nothing to do with the outer/inner puffing gas pressure ratio, which is attributed to the high-speed movement of hydrogen molecules.