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To improve the performance of thrusters by using two permanent ring-shaped magnets to push a magnetic field downward, we propose an annular–cylindrical combined-channel Hall thruster and numerically study its performance. The results indicate that, compared with simple annular channels, the annular–cylindrical combined channel can effectively increase the neutral gas density contained within it and increase the degree of ionization, efficiency, thrust, and specific impulse. Moreover, the sputtering zone of discharge channel is in front of the permanent magnets, i.e., wall erosion occurs upon ion bombardment during discharge. However, ions cannot bombard the permanent magnetic rings, thus guaranteeing a constant magnetic field and long discharge lifetime. [ABSTRACT FROM AUTHOR]

A time-resolved optical measurement method is applied to examine the gas discharge process inside the discharge channel during a Hall thruster ignition. The results show that the excitation and ionization processes in the working gas begin near the exit of the channel and then propagate upstream along the channel. The change in energy of electrons moving toward the anode leads to the alternating dominance of ionization and excitation processes, which is the main reason for the changes in light intensity in different regions of the channel during the thruster startup. [ABSTRACT FROM AUTHOR]