Hall effect thrusters utilize electric and magnetic fields to extract ions from a plasma discharge. In Hall effect thrusters, the ionization of the propellant gas is achieved by collisions of the neutral propellant gas atoms with the emitted electrons from a cathode, typically a hollow cathode. Besides, the cathode is responsible for the neutralization of the ion beam by emitting an equal number of electrons to prevent spacecraft charging. Proper placement of the cathode strongly affects the neutralization of ions in addition to creating well coupled discharge plasma. Studies from the literature show that the cathode coupling voltage is a function of cathode placement and thruster efficiency. Cathode coupling voltage is related to the external magnetic field lines of the thruster. This study shows that depending on the external magnetic field topology of the thruster, there could be an optimum position for the cathode considering the separatrix region.
You can reach this paper with the following link:
8th Ankara International Aerospace Conference, Ankara, Turkey, September 2015, also AIAC-2015-119.
Some figures from the paper:
