Hall effect thruster with anode having magnetic field barrier

A Hall effect ion accelerator having an annular gas discharge channel including an exit end portion, discharge of gas through the exit end portion defining a downstream direction, said accelerator comprising:

• an inner magnetic pole located at the inside of and encircled by the annular gas discharge area adjacent to the exit end portion;
• an outer magnetic pole located at the outside of and encircling the annular gas discharge area adjacent to the exit end portion, the inner and outer magnetic poles being magnetically coupled by a first magnetic path;
• a first magnetic field source associated with the first magnetic path for producing a generally radially extending magnetic field between the inner pole and the outer pole at the exit end portion of the gas discharge channel;
• an anode located upstream of the exit end portion of the gas discharge channel;
• a gas source for supplying an ionizable gas to the gas discharge channel for flow in a downstream direction toward the exit end portion;
• an electron source for supplying free electrons for introduction through the exit end portion of the gas discharge channel in a generally upstream direction;
• an electric field source for producing an electric field extending from the anode in a downstream direction toward the exit end portion of the gas discharge channel, interaction between the ionizable gas from the gas source and free electrons from the electron source providing ions accelerated in a downstream direction by the electric field;
• an outer shell of magnetic material having a downstream end adjacent to the innermost part of the outer pole and extending upstream therefrom along an outer portion of the gas discharge channel;
• an inner shell of magnetic material having a downstream end adjacent to the outermost part of the inner pole and extending upstream therefrom along an inner portion of the gas discharge channel, the outer and inner shells being magnetically coupled behind the anode to define a second magnetic path, and
• a second magnetic field source associated with the second magnetic path and generating magnetic flux therealong sufficient to generate magnetic field lines extending generally axially of the gas discharge channel from a location adjacent to the anode and downstream toward the exit end portion of the gas discharge channel.