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Title: Ion flow and sheath structure near positively biased electrodes

Abstract

What effect does a dielectric material surrounding a small positively biased electrode have on the ion flow and sheath structure near the electrode? Measurements of the ion velocity distribution function and plasma potential near positively biased electrodes were made using laser-induced fluorescence and an emissive probe. The results were compared with 2D particle-in-cell simulations. Both measurements and simulations showed that when the positive electrode was surrounded by the dielectric material, ions were accelerated toward the electrode to approximately 0.5 times the ion sound speed before being deflected radially by the electron sheath potential barrier of the electrode. The axial potential profile in this case contained a virtual cathode. In comparison, when the dielectric material was removed from around the electrode, both the ion flow and virtual cathode depth near the electrode were dramatically reduced. Furthermore, these measurements suggest that the ion presheath from the dielectric material surrounding the electrode may enclose the electron sheath of the electrode, resulting in a virtual cathode that substantially influences the ion flow profile in the region.

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [1];  [1]
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  1. Univ. of Iowa, Iowa City, IA (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Univ. of Iowa, Iowa City, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1916435
Alternate Identifier(s):
OSTI ID: 1332374
Grant/Contract Number:  
SC0016473; AC04-94SL85000; AC05-06OR23100
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 11; 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; sheath; plasma electrode

Citation Formats

Hood, R., Scheiner, B., Baalrud, S. D., Hopkins, M. M., Barnat, E. V., Yee, B. T., Merlino, R. L., and Skiff, F. Ion flow and sheath structure near positively biased electrodes. United States: N. p., 2016. Web. doi:10.1063/1.4967870.
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Hood, R., Scheiner, B., Baalrud, S. D., Hopkins, M. M., Barnat, E. V., Yee, B. T., Merlino, R. L., & Skiff, F. Ion flow and sheath structure near positively biased electrodes. United States. https://doi.org/10.1063/1.4967870
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Hood, R., Scheiner, B., Baalrud, S. D., Hopkins, M. M., Barnat, E. V., Yee, B. T., Merlino, R. L., and Skiff, F. Wed . "Ion flow and sheath structure near positively biased electrodes". United States. https://doi.org/10.1063/1.4967870. https://www.osti.gov/servlets/purl/1916435.
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@article{osti_1916435,
title = {Ion flow and sheath structure near positively biased electrodes},
author = {Hood, R. and Scheiner, B. and Baalrud, S. D. and Hopkins, M. M. and Barnat, E. V. and Yee, B. T. and Merlino, R. L. and Skiff, F.},
abstractNote = {What effect does a dielectric material surrounding a small positively biased electrode have on the ion flow and sheath structure near the electrode? Measurements of the ion velocity distribution function and plasma potential near positively biased electrodes were made using laser-induced fluorescence and an emissive probe. The results were compared with 2D particle-in-cell simulations. Both measurements and simulations showed that when the positive electrode was surrounded by the dielectric material, ions were accelerated toward the electrode to approximately 0.5 times the ion sound speed before being deflected radially by the electron sheath potential barrier of the electrode. The axial potential profile in this case contained a virtual cathode. In comparison, when the dielectric material was removed from around the electrode, both the ion flow and virtual cathode depth near the electrode were dramatically reduced. Furthermore, these measurements suggest that the ion presheath from the dielectric material surrounding the electrode may enclose the electron sheath of the electrode, resulting in a virtual cathode that substantially influences the ion flow profile in the region.},
doi = {10.1063/1.4967870},
journal = {Physics of Plasmas},
number = 11,
volume = 23,
place = {United States},
year = {Wed Nov 23 00:00:00 EST 2016},
month = {Wed Nov 23 00:00:00 EST 2016}
}
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Publisher's Version of Record
https://doi.org/10.1063/1.4967870
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