Hall thruster with absorbing electrodes

Control of the electric field profile in the Hall thruster through the positioning of an additional electrode along the channel is theoretically shown to enhance the efficiency. The reduction of the potential drop near the anode increases the plasma density there, through the increase of the electron and ion transit times. As a result, the ionization is increased in the vicinity of the anode, thus enhancing the propellant and energy utilizations. This resulting separation of the ionization and acceleration regions is enhanced by forcing the sonic transition to occur at the additional electrode. The sonic transition is then abrupt and is accompanied by the presence of a large (theoretically infinite) electric field. The large electric field induced by the additional electrode allows us a further control of the electric field profile. In particular, when the electron temperature is high, a large abrupt voltage drop is induced at the vicinity of the additional electrode, a voltage drop that can comprise a significan part of the applied voltage. This ability to separately control the electric and the mgnetic field profiles is a great advantage, in addition to the efficiency enhancement demonstrated in the present paper.