Characterization of Hollow Cathode Performance and Thermal Behavior

Hollow cathodes are one of the main life-limiting components in ion engines and Hall thrusters. Although state-of-the-art hollow cathodes have demonstrated up to 30,352 hours of operation in ground tests with careful handling, future missions are likely to require longer life, more margin and greater resistance to reactive contaminant gases. Three alternate hollow cathode technologies that exploit different emitter materials or geometries to address some of the limitations of state-of-the-art cathodes are being investigated. Performance measurements of impregnated tungsten-iridium dispenser cathodes at discharge currents of 4 to 15 A demonstrated that they have the same operating range and ion production efficiency as conventional tungsten dispenser cathodes. Temperature measurements indicated that tungsten-iridium cathodes also operate at the same emitter temperatures. They did not exhibit the expected reduction in work function at the current densities tested. Hollow cathodes with lanthanum hexaboride emitters operated over a wide current range, but suffered from lower ion production efficiency at currents below about 12.4 A because of higher insert heating requirements. Differences in operating voltages and ion production rates are explained with a simple model of the effect of cathode parameters on discharge behavior.

[1]  Edwin G. Wintucky,et al.  The metallurgical properties of tungsten–iridium cathodes , 1999 .

[2]  John R. Brophy,et al.  Cyclic Endurance Test of an SPT-100 Stationary Plasma Thruster , 1994 .

[3]  D. Goebel,et al.  LaB6 Hollow Cathodes for Ion and Hall Thrusters , 2005 .

[4]  A. Sengupta.  Destructive physical analysis of hollow cathodes from the Deep Space 1 Flight spare ion engine 30,000 hr life test , 2005 .

[5]  A. Grubišić.  Emitter temperature distributions in the NSTAR discharge hollow cathode , 2005 .

[6]  D. Goebel,et al.  Local Neutral Density and Plasma Parameter Measurements in a Hollow Cathode Plume , 2006 .

[7]  Steven R. Oleson,et al.  The Prometheus 1 spacecraft preliminary electric propulsion system design , 2005 .

[9]  David Y. Oh.  Evaluation of Solar Electric Propulsion Technologies for Discovery Class Missions , 2007 .

[10]  B. Lindsay,et al.  Determination of the absolute partial and total cross sections for electron-impact ionization of the rare gases , 2002 .

[11]  S. Oleson.  Electric Propulsion Technology Development for the Jupiter Icy Moons Orbiter Project , 2004 .

[12]  Dan M. Goebel,et al.  Ion source discharge performance and stability , 1982 .

[13]  Michael J. Patterson,et al.  Demonstration of the NSTAR ion propulsion system on the Deep Space One mission , 2001 .

[14]  I. Mikellides,et al.  Driving Processes in the Orifice and Near-Plume Regions of a Hollow Cathode , 2006 .

[15]  D. Goebel,et al.  Hollow cathode and keeper-region plasma measurements , 2005 .

[16]  John R. Brophy,et al.  Status of the Extended Life Test of the Deep Space 1 Flight Spare Ion Engine After 30,000 Hours of Operation , 2003 .

[17]  John R. Anderson,et al.  Performance of the NSTAR ion propulsion system on the Deep Space One mission , 2001 .

[18]  A. M. Shroff,et al.  Performance and life tests of various types of impregnated cathodes , 1981 .

[19]  Timothy R. Sarver-Verhey.  Destructive Evaluation of a Xenon Hollow Cathode after a 28,000 Hour Life Test , 1998 .

[20]  Dan M. Goebel,et al.  High current hollow cathodes for high power ion and hall thrusters , 2005 .

[21]  J. Polk.  The Effect of Reactive Gases on Hollow Cathode Operation , 2006 .

[22]  Edmund Storms,et al.  Phase relationship, vaporization, and thermodynamic properties of the lanthanum-boron system , 1978 .

[23]  John R. Brophy,et al.  NASA's Deep Space 1 ion engine , 2002 .

[24]  Timothy R. Sarver-Verhey.  28,000 Hour Xenon Hollow Cathode LifeTest Results , 1997 .

[25]  J. Polk,et al.  An overview of the Nuclear Electric Xenon Ion System (NEXIS) program , 2003 .

[26]  H. E. Gallagher,et al.  Poisoning of LaB6 Cathodes , 1969 .

[27]  John R. Anderson,et al.  An overview of the results from an 8200 hour wear test of the NSTAR ion thruster , 1999 .

[28]  Timothy R. Sarver-Verhey.  Continuing life test of a xenon hollow cathode for a space plasma contactor , 1994 .

[29]  James E. Polk,et al.  Plasma processes inside dispenser hollow cathodes , 2006 .

[30]  M. Hayashi.  Determination of electron-xenon total excitation cross-sections, from threshold to 100 eV, from experimental values of Townsend's α , 1983 .

[31]  Dan M. Goebel,et al.  Hollow cathode theory and experiment. I. Plasma characterization using fast miniature scanning probes , 2005 .

[32]  B. Thornber,et al.  Temperature distributions in hollow cathode emitters , 2004 .

[33]  J. R. Brophy,et al.  Ion thruster performance model , 1984 .