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Electron backstreaming determination for ion thrusters

Show simple item record Wirz, Richard E. Katz, Ira Goebel, Dan M. Anderson4, John R. 2015-07-14T17:59:56Z 2015-07-14T17:59:56Z 2008-07-21
dc.identifier.citation 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Hartford, Connecticut, July 21-23, 2008 en_US
dc.identifier.clearanceno 08-2301
dc.description.abstract Electron backstreaming in ion thrusters is caused by the random flux of beam electrons past a potential barrier established by the accel grid. A technique that integrates this flux over the radial extent of the barrier reveals important aspects of electron backstreaming phenomena for individual beamlets, across the thruster beam, and throughout thruster life. For individual beamlets it was found that over 99% of the electron backstreaming occurs in a small annulus at the center of the beamlet that is less than 20% the area of the beamlet at the potential barrier established by the accel grid. For the thruster beam it was found that over 99% of the backstreaming current occurs inside of r = 6 cm for the over 28 cm diameter NSTAR grid. Initial validation against ELT data shows that the technique provides the correct behavior and magnitude of electron backstreaming limit, Vebs. From the sensitivity analyses it is apparent that accel grid chamfering may be the dominant mechanism contributing to the sharp rise in |Vebs| observed in the ELT but does not explain the rise in ion transparency. Grid gap change also contributes to |Vebs| rise and large rises in ion transparency with thruster life for the center gridlet. Screen grid erosion contributes generally to rises in |Vebs| and ion transparency, but for the assumptions used herein, it appears to not have as much of an effect chamfering or grid gap change. Overall, it is apparent that accel grid chamfering, grid gap change, and screen grid erosion are important to the increase in electron backstreaming observed during the ELT. en_US
dc.description.sponsorship NASA/JPL en_US
dc.language.iso en_US en_US
dc.publisher Pasadena, CA : Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2008 en_US
dc.title Electron backstreaming determination for ion thrusters en_US
dc.type Preprint en_US

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