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barium depletion in the nstar discharge cathode after 30,000 hours of operationDispenser hollow cathodes rely on a consumable supply of barium released by impregnant materials in the pores of a tungsten matrix to maintain a low work function surface. Examinations of cathode inserts from long duration ion engine tests show deposits of tungsten at the downstream end that appear to block the flow of barium from the interior. In addition, a numerical model of barium transport in the insert plasma indicates that the barium partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant barium-producing reaction, and it was postulated previously that this would suppress barium loss in the upstream part of the insert. New measurements of the depth of barium depletion from a cathode insert operated for 30,352 hours reveal that barium loss is confined to a narrow region near the downstream end, confirming this hypothesis.
Document ID
20150008916
Document Type
Conference Paper
External Source(s)
Authors
Polk, James E.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Capece, Angela M.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
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
May 26, 2015
Publication Date
July 25, 2010
Subject Category
Spacecraft Propulsion and Power
Meeting Information
AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit(Nashville, TN)
Distribution Limits
Public
Copyright
Other
Keywords
plasma transport
Hollow cathodes