Performance of field emission cathodes in xenon environments
Field emission (FE) cathodes are currently being considered to supply electrons in electric propulsion systems for propellant ionization and ion beam neutralization. Hollow cathodes with thermionic electron emitters typically used with Hall and ion thrusters require propellant and heaters for operation. Therefore there are lower limits on their size and power. Because FE cathodes do not require propellant or heaters they can be used with small and micropropulsion systems. The primary concern with integrating these two technologies is cathode lifetime. An FE cathode must be capable of operation in a plasma environment where xenon pressures exceed 2×1O-6 Torr. Experiments were conducted at the Jet Propulsion Laboratory to evaluate the performance of silicon and molybdenum microtip field emission array cathodes, and carbon film cathodes in xenon pressures up to 2×10-5 Torr. Experimental and modeling results were used to determine energy thresholds for sputtering silicon and molybdenum by xenon ions. Experiments and theoretical results are presented for performance degradation in xenon environments.
