Table of Contents
International Journal of Plasma Science and Engineering
Volume 2008, Article ID 693825, 11 pages
Research Article

Hollow Cathode and Low-Thrust Extraction Grid Analysis for a Miniature Ion Thruster

1Propulsion and Materials Section, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
2Aeronautics, California Institute of Technology, Pasadena, CA, USA

Received 3 January 2008; Revised 20 April 2008; Accepted 23 June 2008

Academic Editor: Paul K. Chu

Copyright © 2008 Richard Wirz et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Miniature ion thrusters are well suited for future space missions that require high efficiency, precision thrust, and low contamination in the mN to sub-mN range. JPL's miniature xenon Ion (MiXI) thruster has demonstrated an efficient discharge and ion extraction grid assembly using filament cathodes and the internal conduction (IC) cathode. JPL is currently preparing to incorporate a miniature hollow cathode for the MiXI discharge. Computational analyses anticipate that an axially upstream hollow cathode location provides the most favorable performance and beam profile; however, the hot surfaces of the hollow cathode must be sufficiently downstream to avoid demagnetization of the cathode magnet at the back of the chamber, which can significantly reduce discharge performance. MiXI's ion extraction grids are designed to provide >3 mN of thrust; however, previous to this effort, the low-thrust characteristics had not been investigated. Experimental results obtained with the MiXI-II thruster (a near replica or the original MiXI thruster) show that sparse average discharge plasma densities of 5×10155×1016m-3 allow the use of very low beamlet focusing extraction voltages of only 250–500 V, thus providing thrust levels as low as 0.03 mN for focused beamlet conditions. Consequently, the thrust range thus far demonstrated by MiXI in this and other tests is 0.03–1.54 mN.