Simulation Study on Discharge Characteristics of Radio Frequency Ion Thruster with Iodine Working Medium

Iodine, as a potential working medium in space thrusters, has attracted much attention in recent years. Unlike xenon, the discharge products of iodine working medium are more complex, containing small amounts of I⁻, I₂⁺, I²⁺ and I³⁺. Although the content of polyvalent ions is small, it has a great influence on the working performance of thrusters. In this paper, a two-dimensional axisymmetric model is established based on plasma discharge, studying the effects of mass flow rate, RF power and background pressure on two main ionization products, I⁺ and I₂⁺. When the mass flow rate ranges from 20 to 70 mL/min, I⁺ slightly decreases and I₂⁺ slightly increases with the increase of mass flow rate. When the RF power ranges from 100 to 650 W, I⁺ increases rapidly with the increase of RF power, and I₂⁺ decreases slightly. When the background pressure ranges from 0.001 to 0.1 Torr, I⁺ initially increases rapidly with the increase of background pressure and it begins to decrease at around p₀= 0.015 Torr. I₂⁺ has maintained a slow increase. Ignoring the influence of ionization loss, conducting a full factor design of experiment (DOE) of the three influencing factors. When the mass flow rate is 60 mL/min, the RF power is 150 W, and the background pressure is 0.015 Torr, obtaining the optimal product I₂⁺:I⁺=0.204094, which is consistent with the simulation result I₂⁺:I⁺=0.205069, and the error is 0.48%.