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With the development of electric space propulsion and all-electric propulsion technologies, the application range of the Hall effect thruster (HET) has gradually expanded. As an important part of the HET, the magnetic field plays a decisive role in its performance. In the development of versatile HETs, it is necessary to comprehensively and thoroughly understand the effects of the magnetic field on the HET discharge characteristics. In this paper, a HEP-100X thruster with multiple degrees of freedom in terms of magnetic field control is used to study the effects of the peak magnetic field position on the thruster discharge characteristics. The results indicate that the peak magnetic field position can effectively control the main ionization zone position and affect the ionization rate. The thruster has the best comprehensive discharge performance when the peak magnetic field position is located near the channel exit. Further analysis reveals that the performance improvement is mainly due to the reduced ion loss on the wall surface and plume divergence half-angle, and the increased current utilization efficiency and voltage utilization efficiency. The HEP-100X shows the above trends under various flow conditions, and the anode efficiency is the highest when the anode flow is 50 sccm. In this condition, the propellant is sufficiently ionized and the ion loss on the wall surface is small. This research provides the necessary support for a comprehensive understanding of the role and significance of the magnetic field in the thruster discharge process, and has important significance for the design optimization of multifunctional Hall thrusters and subsequent research. [ABSTRACT FROM AUTHOR]

Abstract HET72-VC is a kW-class Hall effect thruster with a variable channel characterized by high thrust and power densities. In this work, an experimental study of the effect of magnetic field configuration on the discharge characteristics of HET72-VC is carried out. By separately adjusting the current through the front and rear coils to change the magnetic field configuration inside the channel, a change in the plume is observed and the discharge performance parameters are measured. Experimental results show that the effects of reducing the front coil current and increasing the rear coil current on the thruster discharge are consistent. The plume gradually changes from a hollow cone with a clear boundary into a solid cone, the thrust increases by about 3%, and the anode efficiency increases by about 2.5%. Theoretical analysis shows that the degree of inclination of the magnetic lines of force plays an important role on the electron conduction and ion acceleration. When the angle between the magnetic lines of force and the channel centerline becomes larger, the discharge performance improves. This study helps in providing a deeper understanding of the working characteristics of this type of thruster, and can provide important guidelines for its structure design and optimization. Highlights • Plume shape is strongly modulated by magnetic field configuration. • Plume shape of a solid cone rather than a hollow cone represents good performance. • Magnetic field configuration impeding electrons strongly yields good performance. [ABSTRACT FROM AUTHOR]

The large height-radius ratio design of the Hall thruster increases the difference of radial distributions of magnetic field and plasma parameters in the channel, so that the optimal discharge effect of the thruster cannot be guaranteed under the symmetrical magnetic field configuration relative to the channel centerline. In this work, the effects of the unsymmetrical magnetic field on discharge characteristics of Hall thruster with large height-radius ratio were studied through experiments and PIC simulations. The results show that the thruster can realize stable discharge in a wide power range under unsymmetrical magnetic fields. Also, the unsymmetrical magnetic field plays a positive role in improving the discharge performance and prolonging the service life of the thruster. The inward-inclined magnetic field can effectively improve the discharge performance of the thruster, and the discharge efficiency can be increased by 1.5% under the rated working condition compared with the symmetrical magnetic field. The advantage in performance is mainly attributed to the improvement of ionization efficiency of propellant. The outward-inclined magnetic field is more conducive to prolong the service life of the thruster, and the peak value of ion power deposition on the inner wall can be reduced by 40% under the rated working condition due to the outward inclination of the ionization zone and the reduction of the radial electric field. However, under unsymmetrical magnetic field, the ionization zone deviates from the channel center, and the high ionization rate zone is more dispersed in distribution, thus leading to the increase in plume divergence angle. This study verifies that the unsymmetrical magnetic field has certain advantages under the structure of large height-radius ratio, which could be used as a guidance for the optimal design of Hall thruster with large height-radius ratio. • Hall thruster can operate in a wide power range under unsymmetrical magnetic fields. • Inward-inclined magnetic field can improve thruster discharge performance. • Outward-inclined magnetic field is conducive to prolong thruster service life. [ABSTRACT FROM AUTHOR]