The effect of magnet core size on the performance of a cylindrical Hall thruster with the near-anode cusp magnetic field

Effect of magnet core size on the performance of a cylindrical Hall thruster with the near-anode magnetic field has been investigated. Experiments found that extending magnetic core and rising discharge voltage show similar effects on the ionization process. When the magnetic core ends flush with the anode and discharge voltage is fixed at 240 V, the upstream ionization related with the electron E × B drift is hardly established under an approximately axial magnetic field and the ionization region is located at the near-axial magnetic mirror field, the thruster manifests the highest propellant utilization efficiency (as high as 1.43), the lowest current utilization efficiency (0.54) and beam divergence efficiency (0.52). When the magnet core extends towards the thruster exhaust, the enhancement of upstream ionization results in significant enhancements in the current utilization efficiency (by 14.6%) and the beam divergence efficiency (by 27.1%). However, the reduction of magnetic mirror ionization also led to a reduction of propellant utilization efficiency (by 32.1%). Therefore, the anode efficiency varies non-monotonically (climbing up and then declining) and has an optimal solution: shorter magnet core performs higher anode efficiency in low voltage condition and longer magnet core performs higher anode efficiency in high voltage condition.