Experimental and numerical simulation study of the effect for the anode positions on the discharge characteristics of 300 W class low power Hall thrusters

Low-power Hall thruster (LHT) generally has poor discharge efficiency characteristics due to the large surface-to-volume ratio. Aiming to further refine and improve the performance of 300 W class LHT in terms of thrust and efficiency, and to obtain the most optimal operating point, the experimental study of the discharge characteristics for three different anode positions was conducted under the operation of various discharge voltages (100–400 V) and anode mass flow rates (0.65 mg·s^-1 and 0.95 mg·s^-1). The experimental results indicated that the thruster has the most excellent performance in terms of thrust and efficiency etc at a channel length of 27 mm for identical operating conditions. In addition, particle in cell simulations, employed to reveal the underlying physical mechanisms, show that the ionization and acceleration zone is pushed downwards towards the channel exit as the anode moves towards the exit. At the identical operating point, when the channel length is reduced from 32 to 27 mm, the ionization and acceleration zone moves towards the exit, and the parameters such as thrust and efficiency increase due to the high ionization rate, ion number density, and axial electric field. When the channel length is further moved to 24 mm, the parameters in terms of thrust (F) and efficiency (${\eta }_{\mathrm{a}}$) are reduced as a result of the decreasing ionization efficiency (${\eta }_{\mathrm{m}}$) and the larger plume divergence angle ($\alpha$). In this paper, the results indicated that an optimum anode position ($\mathrm{∆}L=27$ mm) exists for the optimum performance.