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Title: Floating potential of emitting surfaces in plasmas with respect to the space potential

Abstract

The potential difference between a floating emitting surface and the plasma surrounding it has been described by several sheath models, including the space-charge-limited sheath, the electron sheath with high emission current, and the inverse sheath produced by charge-exchange ion trapping. Our measurements reveal that each of these models has its own regime of validity. We determine the potential of an emissive filament relative to the plasma potential, emphasizing variations in emitted current density and neutral particle density. The potential of a filament in a diffuse plasma is first shown to vanish, consistent with the electron sheath model and increasing electron emission. In a denser plasma with ample neutral pressure, the floating filament potential is positive, as predicted by a derived ion trapping condition. In conclusion, the filament floated negatively in a third plasma, where flowing ions and electrons and nonnegligible electric fields may have disrupted ion trapping. Depending on the regime chosen, emitting surfaces can float positively or negatively with respect to the plasma potential.

Authors:
 [1]; ORCiD logo [2]
  1. Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1430533
Alternate Identifier(s):
OSTI ID: 1426846
Grant/Contract Number:  
AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 3; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Kraus, B. F., and Raitses, Y. Floating potential of emitting surfaces in plasmas with respect to the space potential. United States: N. p., 2018. Web. doi:10.1063/1.5018335.
Kraus, B. F., & Raitses, Y. Floating potential of emitting surfaces in plasmas with respect to the space potential. United States. doi:10.1063/1.5018335.
Kraus, B. F., and Raitses, Y. Mon . "Floating potential of emitting surfaces in plasmas with respect to the space potential". United States. doi:10.1063/1.5018335. https://www.osti.gov/servlets/purl/1430533.
@article{osti_1430533,
title = {Floating potential of emitting surfaces in plasmas with respect to the space potential},
author = {Kraus, B. F. and Raitses, Y.},
abstractNote = {The potential difference between a floating emitting surface and the plasma surrounding it has been described by several sheath models, including the space-charge-limited sheath, the electron sheath with high emission current, and the inverse sheath produced by charge-exchange ion trapping. Our measurements reveal that each of these models has its own regime of validity. We determine the potential of an emissive filament relative to the plasma potential, emphasizing variations in emitted current density and neutral particle density. The potential of a filament in a diffuse plasma is first shown to vanish, consistent with the electron sheath model and increasing electron emission. In a denser plasma with ample neutral pressure, the floating filament potential is positive, as predicted by a derived ion trapping condition. In conclusion, the filament floated negatively in a third plasma, where flowing ions and electrons and nonnegligible electric fields may have disrupted ion trapping. Depending on the regime chosen, emitting surfaces can float positively or negatively with respect to the plasma potential.},
doi = {10.1063/1.5018335},
journal = {Physics of Plasmas},
number = 3,
volume = 25,
place = {United States},
year = {2018},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 5 works
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Figures / Tables:

FIG. 1. FIG. 1. : A series of potential profile cartoons, representative of the emissive sheath models from the text. The parameter Δ$\phi$ is here defined as $\phi$(r) – $\phi$$P$, where $\phi$$P$ is the plasma potential far from the surface. Potential magnitudes are approximate but have realistic signs and relative sizes.

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      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.