Effects of Additional Magnetic Fields on the Discharge Characteristics of a Radio-Frequency Ion Thruster

Radio-frequency (RF) ion thrusters, as electrodeless plasma sources, offer significant advantages such as simple structure and long operational lifetime. However, their discharge efficiency is often limited by wall losses and the skin effect. Among various optimization approaches, the application of additional magnetic fields has emerged as an effective method for improving discharge performance. In this study, a compact radio-frequency ion thruster (RIT) was equipped with additional magnetic fields of different configurations. Ion beam currents were systematically measured under various operating conditions. The results show that under a Type-I magnetic field with a strength of approximately 20 G, the ion beam current is significantly enhanced by up to 22.3% at low xenon mass flow rates. Furthermore, plasma parameters inside the discharge chamber, including ion density and electron temperature, were characterized using a double Langmuir probe. The results indicate that appropriately applied additional magnetic fields can reduce ion losses to the walls and partially compensate for the skin effect, thereby improving the beam-current-related discharge characteristics. However, if the magnetic field is too strong, it may overly restrict electron motion and suppress collisionless heating, which in turn negatively affects the discharge process.