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Wear Mechanisms in Electron Sources for Ion Propulsion, 1: Neutralizer Hollow CathodeUpon the completion of two long-duration life tests of a 30-cm ion engine, the orifice channel of the neutralizer hollow cathode was eroded away to as much as twice its original diameter. Whereas the neutralizer cathode orifice opened significantly, no noticeable erosion of the discharge cathode orifice was observed. Noquantitative explanation of these erosion trends has been established since the completion of the two life tests. A two-dimensional model of the partially ionized gas inside these devices has been developed and applied to the neutralizer hollow cathode. The numerical simulations show that the main mechanism responsible for the channel erosion is sputtering by Xe+. These ions are accelerated by the sheath along the channel and bombard the surface with kinetic energy/charge of about 17 V at the beginning of cathode life. The density of the ions inside the neutralizer orifice is computed to be as high as 2.1 x 10(sup 22) m(sup -3). Because of the 3.5-times larger diameter of the discharge cathode orifice, the ion density inside the orifice is more than 40 times lower and the sheath drop 7 V lower compared with the values in the neutralizer. At these conditions, Xe+ can cause no significant sputtering of the surface.
Document ID
20080044816
Acquisition Source
Jet Propulsion Laboratory
Document Type
Preprint (Draft being sent to journal)
External Source(s)
Authors
Mikellides, Ioannis G.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Katz, Ira
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
July 1, 2008
Publication Information
Publication: Journal of Propulsion and Power
Volume: 24
Issue: 4
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
Paper 5168
Meeting Information
Meeting: 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference
Location: Cincinnati, OH
Country: United States
Start Date: July 8, 2007
End Date: July 11, 2007
Sponsors: American Society for Electrical Engineers, American Inst. of Aeronautics and Astronautics, American Society of Mechanical Engineers, Society of Automotive Engineers, Inc.
Distribution Limits
Public
Copyright
Other
Keywords
ionized gas
ion engines

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