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Title: Properties of the electrostatically driven helical plasma state

Abstract

A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a ($m=1,n=1$) (helical) symmetry where $$m$$ and $$n$$ represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius $$r < r_w$$ and helical angle $u=mθ-nζ$, where θ is the poloidal angle, and $ζ=z/R$ is the normalized axial coordinate in the context of a periodic cylinder. In this reference, the strongly driven form of the state was found to have a strong axial mean current density, with a mean-field line safety factor $$q_0(r)$$ just above the pitch of the electrodes m/n=1 in the interior, where the plasma is nearly force-free. However, at the edge the current density has a component perpendicular to the magnetic field B. This perpendicular current density drives nearly Alfvénic helical plasma flows, a notable feature of these states. This state is being studied for its possible application in $DC$ electrical transformers. We present results on several issues of importance for these applications: the transient leading to the steady state; the twist and writhe of the field lines and their relation with the current density; the properties of the current density streamlines and length of the current density lines connected to the electrodes; the sensitivity to changes in the velocity boundary conditions; the effect of varying the radial resistivity profile; and the effects of a concentrated electrode potential

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Tibbar Plasma Technologies, Los Alamos, NM (United States)
Publication Date:
Research Org.:
Tibbar Plasma Technologies, Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
OSTI Identifier:
1524593
Alternate Identifier(s):
OSTI ID: 1419704
Grant/Contract Number:  
AR0000677
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 2; 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

Akçay, Cihan, Finn, John M., Nebel, Richard A., Barnes, Daniel C., and Martin, Neal. Properties of the electrostatically driven helical plasma state. United States: N. p., 2018. Web. doi:10.1063/1.5006902.
Akçay, Cihan, Finn, John M., Nebel, Richard A., Barnes, Daniel C., & Martin, Neal. Properties of the electrostatically driven helical plasma state. United States. https://doi.org/10.1063/1.5006902
Akçay, Cihan, Finn, John M., Nebel, Richard A., Barnes, Daniel C., and Martin, Neal. Tue . "Properties of the electrostatically driven helical plasma state". United States. https://doi.org/10.1063/1.5006902. https://www.osti.gov/servlets/purl/1524593.
@article{osti_1524593,
title = {Properties of the electrostatically driven helical plasma state},
author = {Akçay, Cihan and Finn, John M. and Nebel, Richard A. and Barnes, Daniel C. and Martin, Neal},
abstractNote = {A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a ($m=1,n=1$) (helical) symmetry where $m$ and $n$ represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius $r < r_w$ and helical angle $u=mθ-nζ$, where θ is the poloidal angle, and $ζ=z/R$ is the normalized axial coordinate in the context of a periodic cylinder. In this reference, the strongly driven form of the state was found to have a strong axial mean current density, with a mean-field line safety factor $q_0(r)$ just above the pitch of the electrodes m/n=1 in the interior, where the plasma is nearly force-free. However, at the edge the current density has a component perpendicular to the magnetic field B. This perpendicular current density drives nearly Alfvénic helical plasma flows, a notable feature of these states. This state is being studied for its possible application in $DC$ electrical transformers. We present results on several issues of importance for these applications: the transient leading to the steady state; the twist and writhe of the field lines and their relation with the current density; the properties of the current density streamlines and length of the current density lines connected to the electrodes; the sensitivity to changes in the velocity boundary conditions; the effect of varying the radial resistivity profile; and the effects of a concentrated electrode potential},
doi = {10.1063/1.5006902},
journal = {Physics of Plasmas},
number = 2,
volume = 25,
place = {United States},
year = {Tue Feb 06 00:00:00 EST 2018},
month = {Tue Feb 06 00:00:00 EST 2018}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

FIG. 1 FIG. 1: Evolution of the helical flux $χ$ (top row), parallel current density $λ$ (middle row), and helical field g (bottom row) during the transient stage that leads to the time-asymptotic state with a flat $q$0($r$) ≥ 1.0 in the plasma interior. Parameters are identical to those of the nominalmore » state in AFNB. The plotted frames from left to right correspond to approximate times for the linear ramp phase, the peak helicity (and nearly peak injected power), and the beginning of the steady-state phase, respectively. For this case, the chosen times representative of these three stages are $t$/$τ$$A$ = 1.5, 5.7, and 11. The helical perturbation is ramped up over a period of $τ$ramp = 2.5$τ$$A$ . The contour $λ$= 0 (black) is also superposed in (a)–(f).« less

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Works referencing / citing this record:

Geometric scalings for the electrostatically driven helical plasma state
text, January 2017