Analytical Discharge Model for RF Ion Thrusters

A comprehensive 0-D model of the plasma discharge in magnetic ring-cusp ion thrusters was previously developed. The model utilizes conservation of particles into and out of the ion thruster and conservation of energy into the discharge and out of the plasma, and provided the first closed solution for predicting ion-thruster discharge chamber performance. The 0-D discharge model was benchmarked against the performance measured on several ion thrusters, and successfully predicts the discharge loss as a function of mass utilization efficiency. The analytical model has been modified to handle the discharge chamber configurations and the different magnetic confinement physics found in RF ion thrusters. In these ion thrusters, there is no applied magnetic field to provide confinement of the electrons and ions, but the ac magnetic field induced by the inductively coupled RF coil affects the particle confinement and transport and is important in determining the discharge loss and thruster performance. The modifications to the model required to address the physics of RF thrusters will be discussed, and results showing the predicted ion thruster performance will be presented.