Experimental study on the ionization regions in a multi-cusped field thruster

Abstract The multi-cusped field thruster is a novel electrostatic thruster with significant performance merits in spacecraft propulsion. In this paper, the ion energy distribution function (IEDF) in the plume region and its changing characteristics with anode voltage are tested to study the ionization regions in a two-stage cusped field thruster. Firstly, the IEDFs in two different operating modes are studied, the test result indicates that the plume region could be divided into three angle zones by the discontinuity of IEDFs. Secondly, the changing characteristics of IEDF in each angle zone are studied to analyze the location and the forming process of the corresponding ionization regions. The results show that the two-stage cusped thruster contains three ionization regions. The ions in zone II (from 15 to 40 degrees) are generated in columnar ionization region in discharge channel. The ions in zone III (above 40 degrees) are generated in the exit ionization region. The ions near axis in zone I (from 0 to 15 degrees) are generated in two significant different ionization regions. The high-energy ions are generated in the exit ionization region and the low-energy ions are generated in the plume ionization region. In this study, the number of the ionization regions is validated and the relationships between ion current in plume zones and ionization regions are specified, which is helpful to clarify the complicated ionization processes in the multi-cusped thruster.