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Characteristics of Plasma Probes in an MHD Working Fluid

Conference:

Abstract

In this paper an attempt is made to formulate a theory of electrostatic probes in a high-pressure plasma in which an external electrical field may be imposed. Such a situation exists in high-pressure arc discharges and in MHD channels. First, it is shown that an adequate theory must include the ionization and recombination phenomena which were ignored in almost all previous theories. Secondly, due to the preferred direction induced by the presence of the electric field, the probe problem is no longer a symmetrical one. The analysis is based on the assumption that the three-body recombination and ionization is the dominant process. In a typical MHD working fluid, say an argon gas seeded with caesium at 2000 Degree-Sign K and one atmosphere of pressure, the penetration length I of ions and electrons, i.e. the distance that an ion or electron diffuses before recombination, is of the order of 10{sup -3} cm. (It is to be noted that ambipolar diffusion prevents the electrons from travelling much faster than the ions. ) We thus have a situation where Script-Small-L /L << 1, d/ Script-Small-L << 1, {lambda}/L <<1, and {lambda}/d >> 1, where L is the characteristic dimension of the probe {lambda}  More>>
Authors:
Whitman, A. M.; Hsuan, Yeh [1] 
  1. Towne School of Civil and Mechanical Engineering, University of Pennsylvania (United States)
Publication Date:
Oct 15, 1966
Product Type:
Conference
Report Number:
IAEA-SM-74/250
Resource Relation:
Conference: Symposium on Magnetohydrodynamic Electrical Power Generation, Salzburg (Austria), 4-8 Jul 1966; Other Information: 12 refs., 5 figs.; Related Information: In: Electricity from MHD. Vol. I. Proceedings of a Symposium on Magnetohydrodynamic Electrical Power Generation| 728 p.
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; AMBIPOLAR DIFFUSION; ANALYTICAL SOLUTION; ARGON; BOUNDARY LAYERS; CESIUM; DEBYE LENGTH; ELECTRIC FIELDS; ELECTRIC POTENTIAL; ELECTRON DENSITY; ELECTRONS; ELECTROSTATIC PROBES; MAGNETOHYDRODYNAMICS; MEAN FREE PATH; MHD CHANNELS; PLASMA; PRESSURE RANGE MEGA PA 10-100; THREE-BODY PROBLEM; WORKING FLUIDS
OSTI ID:
22113802
Research Organizations:
International Atomic Energy Agency, Vienna (Austria); European Nuclear Energy Agency of the OECD, Issy-les-Moulineaux (France)
Country of Origin:
IAEA
Language:
English
Contract Number:
Grant NSG-316
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M1688070784
Submitting Site:
INIS
Size:
page(s) 127-144
Announcement Date:
Jul 20, 2013

Conference:

Citation Formats

Whitman, A. M., and Hsuan, Yeh. Characteristics of Plasma Probes in an MHD Working Fluid. IAEA: N. p., 1966. Web.
Whitman, A. M., & Hsuan, Yeh. Characteristics of Plasma Probes in an MHD Working Fluid. IAEA.
Whitman, A. M., and Hsuan, Yeh. 1966. "Characteristics of Plasma Probes in an MHD Working Fluid." IAEA.
@misc{etde_22113802,
title = {Characteristics of Plasma Probes in an MHD Working Fluid}
author = {Whitman, A. M., and Hsuan, Yeh}
abstractNote = {In this paper an attempt is made to formulate a theory of electrostatic probes in a high-pressure plasma in which an external electrical field may be imposed. Such a situation exists in high-pressure arc discharges and in MHD channels. First, it is shown that an adequate theory must include the ionization and recombination phenomena which were ignored in almost all previous theories. Secondly, due to the preferred direction induced by the presence of the electric field, the probe problem is no longer a symmetrical one. The analysis is based on the assumption that the three-body recombination and ionization is the dominant process. In a typical MHD working fluid, say an argon gas seeded with caesium at 2000 Degree-Sign K and one atmosphere of pressure, the penetration length I of ions and electrons, i.e. the distance that an ion or electron diffuses before recombination, is of the order of 10{sup -3} cm. (It is to be noted that ambipolar diffusion prevents the electrons from travelling much faster than the ions. ) We thus have a situation where Script-Small-L /L << 1, d/ Script-Small-L << 1, {lambda}/L <<1, and {lambda}/d >> 1, where L is the characteristic dimension of the probe {lambda} is the mean free path and d the Debye length. Because of the last condition, i. e, d << {lambda}, the space charge region is contained wholly in a ''free-falling'' zone in the immediate neighbourhood of the probe. Since, also, (d/ Script-Small-L ) << 1, the region outside of the ''free-falling'' zone is in a state of ''quasi-neutrality'', i.e. the number densities of electrons and ions are approximately equal. In this latter region, the mechanisms of diffusion and recombination are both important. The two regions must of course be matched at their connecting boundaries. Furthermore, the external boundary of the ''quasi-neutrality'' region must be matched to the discharge field. Using the approximations of the classical boundary layer theory, analytic solutions are obtained in closedform. It was found that the predictions of the theory agreed, in all the cases considered, with existing experimental findings. A notable success of the theory was the prediction of the correct value of ion saturation current obtained experimentally by Rohatgi and Emmons for a typical MHD working fluid. Another contribution of the theory is a theoretical current-voltage characteristic that includes the effect of sheath voltage-drop. (author)}
place = {IAEA}
year = {1966}
month = {Oct}
}