Compact high current rare-earth emitter hollow cathode for hall effect thrusters

A method of emitting electrons, comprising:

• providing a hollow conductive cathode including a cathode orifice in a cathode end having a cathode orifice area smaller than an internal cross sectional cathode area of the hollow conductive cathode such that the cathode end is cupped slightly;
• disposing a hollow rare earth insert within the hollow conductive cathode proximate the cathode end, the hollow rare earth insert having an internal cross sectional insert area no larger than the cathode orifice area of the hollow conductive cathode;
• holding the hollow rare earth insert in position against the cupped cathode end by a retainer and spring disposed behind the hollow rare earth insert;
• and
• applying energy to the hollow rare earth insert resulting in electrons emitted from an inner surface of the hollow rare earth insert and a portion of the electrons flow out the cathode end.

An electron emitter, comprising:

• a hollow conductive cathode means for flowing a gas including an cathode orifice in a cathode end having a cathode orifice area smaller than an internal cross sectional cathode area of the hollow conductive cathode means such that the cathode end is cupped slightly;
• and
• a hollow rare earth insert means for emitting electrons disposed within the hollow conductive cathode proximate the cathode end, the hollow rare earth insert means having an internal cross sectional insert area no larger than the cathode orifice area of the hollow conductive cathode means;
• wherein the electrons emitted from the hollow rare earth insert ionize the gas flowing through the hollow rare earth insert to generate a plasma from the gas and the hollow rare earth insert means is held in position against the cupped cathode end by a retainer and spring disposed behind the hollow rare earth insert means.