Ion flow and sheath structure near positively biased electrodes

Hood, R.; Scheiner, B.; Baalrud, S. D.; Hopkins, M. M.; Barnat, E. V.; Yee, B. T.; Merlino, R. L.; Skiff, F.

doi:10.1063/1.4967870

Ion flow and sheath structure near positively biased electrodes

Journal Article · Tue Nov 22 23:00:00 EST 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4967870· OSTI ID:1916435

Hood, R. ^[1]; Scheiner, B. ^[2]; Baalrud, S. D. ^[2]; Hopkins, M. M. ^[3]; Barnat, E. V. ^[3]; Yee, B. T. ^[3]; Merlino, R. L. ^[2]; Skiff, F. ^[2]

Univ. of Iowa, Iowa City, IA (United States); University of Iowa
Univ. of Iowa, Iowa City, IA (United States)
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

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.

View Accepted Manuscript (DOE)

Research Organization:: Univ. of Iowa, Iowa City, IA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: SC0016473; AC05-06OR23100

OSTI ID:: 1916435

Alternate ID(s):: OSTI ID: 1332374

Journal Information:: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 11 Vol. 23; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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