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Analytical and experimental studies of thermionically emitting electrodes in contact with dense, seeded plasmas

Koester, John K. and Sajben, Miklos and Zukoski, Edward E. (1970) Analytical and experimental studies of thermionically emitting electrodes in contact with dense, seeded plasmas. In: Engineering Aspects of Magnetohydrodynamics. , Pasadena, CA, pp. 54-60.

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Interactions are considered between a moving, alkali-metal seeded, dense plasma and a metallic electrode whose surface properties are influenced by the absorption of seed particles. The plasma behavior is governed by a set of differential equations, which are coupled to the surface through the boundary conditions. These conditions are obtained by utilizing the particle desorption rate expressions of Levine and Gyftopoulos. The solution of the problem yields the state of the surface as well as the spatial distribution of plasma properties. In particular, electrode voltage drops are predicted, which indicate whether the electrode operates in a thermionic or arc mode. The method has been applied to a potassiwn-seeded argon plasma in contact with a tungsten electrode in a stagnation flow geometry. The results show that the plasma - surface interaction may lead to large electrode currents at moderate voltage drops. These currents can be up to an order of magnitude greater than what the random electron current would be at the surface under conditions of perfect thermodynamic equilibrium at the surface temperature. R.esults of a comparable experiment show reasonably good agreement with the theory.

Item Type:Book Section
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Additional Information:© 1970. Supported in part by the U. S. Air Force Office of Scientific Research under Contract AF 49(638)-1285.
Group:Guggenheim Jet Propulsion Center
Funding AgencyGrant Number
Air Force Office of Scientific ResearchAF 49 (638)-1285
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Guggenheim Jet Propulsion CenterUNSPECIFIED
OSTI ID4601156
Record Number:CaltechAUTHORS:20101220-133221838
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21445
Deposited By: Ruth Sustaita
Deposited On:04 Jan 2011 18:19
Last Modified:03 Oct 2019 02:24

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