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It is assumed that the shift of a strong magnetic field region with a positive gradient from exit plane to outside, namely the transit from a normal loaded magnetic field to an aft-loaded one, enhances the multiple ionization process in the magnetically shielded Hall thruster. To confirm this conjecture, a comparative study is carried out numerically with a particle-in-cell method. The simulation results prove that compared with the normal loaded magnetic field, the application of aft-loaded magnetic field enhances the multiple ionization process. This study further analyzes the ionization characteristics of the transition from low-charged ions to high-charged ions under two magnetic field conditions and the influence of the magnetic strength of aft-loaded magnetic field on the multiple ionization characteristics. The study described herein is useful for understanding the discharge characteristics of Hall thruster with an aft-loaded magnetic field.

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Hall thrusters with an internal cathode are widely used due to their ability to enhance efficiency, minimize plume divergence, and eliminate plume asymmetry. In addition, the long-lifetime technology of Hall thrusters typically relocates the intense magnetic-field region outside the channel, known as an “aft-loaded magnetic field,” to mitigate erosion of the discharge channel caused by high-energy ions. However, this exacerbates plume divergence and diminishes overall performance. Therefore, this research focuses on optimizing a Hall thruster with an aft-loaded magnetic field and internal cathode. Given that electrons emitted by the internal cathode initially diffuse onto the magnetic separatrix and subsequently couple with the ion beam in the plume, this study experimentally investigates the impact of the magnetic separatrix shape on the discharge characteristics and plume behavior of the Hall thruster. The experimental findings indicate that expanding the envelope of the magnetic separatrix contributes to improved plume focusing and enhanced performance. Thus, the results of this study highlight the significance of the magnetic field outside the channel as a crucial design factor for long-lifetime Hall thrusters.