Study on impedance matching network characteristics and plasma state identification of RF ion sources

High-precision optical components play an indispensable role in critical fields such as space exploration, advanced weaponry, and semiconductor manufacturing. As a cutting-edge method for ultra-precision manufacturing of optical components, the stability of ion beam figuring (IBF) technology is fundamentally determined by the performance of the ion source, where continuous and accurate impedance matching is the key factor in achieving long-term stability of the removal function. This paper establishes an equivalent circuit model for impedance matching based on the discharge principle of radio frequency (RF) ion sources, and proposes a method for rapid system identification of plasma impedance. By collecting tuning capacitor values and reflected power data and applying least squares fitting, this method can effectively identify the plasma impedance characteristics during the discharge process of RF ion sources. Results show that the state of plasma significantly affects the impedance matching process. Both the ignition phase and excessively high plasma density can lead to large reflected power in the RF circuit, thereby causing instability of the ion source. The tuning capacitor and reflected power data collected from the self-developed ion source used in the experiment are in good agreement with the theoretical calculation results obtained by system identification. The research results have guiding significance for the long-term stable manufacturing of RF ion sources, and provide important theoretical basis and technical support for the development of high-performance RF ion sources