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Title: A current-driven resistive instability and its nonlinear effects in simulations of coaxial helicity injection in a tokamak

Abstract

An instability observed in whole-device, resistive magnetohydrodynamic simulations of the driven phase of coaxial helicity injection in the National Spherical Torus eXperiment is identified as a current-driven resistive mode in an unusual geometry that transiently generates a current sheet. The mode consists of plasma flow velocity and magnetic field eddies in a tube aligned with the magnetic field at the surface of the injected magnetic flux. At low plasma temperatures (~10–20 eV), the mode is benign, but at high temperatures (~100 eV) its amplitude undergoes relaxation oscillations, broadening the layer of injected current and flow at the surface of the injected toroidal flux and background plasma. The poloidal-field structure is affected and the magnetic surface closure is generally prevented while the mode undergoes relaxation oscillations during injection. Furthermore, this study describes the mode and uses linearized numerical computations and an analytic slab model to identify the unstable mode.

Authors:
 [1];  [2]
  1. Woodruff Scientific, Inc., Seattle, WA (United States)
  2. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1328138
Alternate Identifier(s):
OSTI ID: 1343838; OSTI ID: 1421100
Report Number(s):
LLNL-JRNL-698022
Journal ID: ISSN 1070-664X; TRN: US1701570
Grant/Contract Number:  
AC52-07NA27344; AC02-05CH11231; FC02-05ER54813
Resource Type:
Published Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 10; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION

Citation Formats

Hooper, E. B., and Sovinec, C. R. A current-driven resistive instability and its nonlinear effects in simulations of coaxial helicity injection in a tokamak. United States: N. p., 2016. Web. doi:10.1063/1.4964292.
Hooper, E. B., & Sovinec, C. R. A current-driven resistive instability and its nonlinear effects in simulations of coaxial helicity injection in a tokamak. United States. doi:10.1063/1.4964292.
Hooper, E. B., and Sovinec, C. R. Thu . "A current-driven resistive instability and its nonlinear effects in simulations of coaxial helicity injection in a tokamak". United States. doi:10.1063/1.4964292.
@article{osti_1328138,
title = {A current-driven resistive instability and its nonlinear effects in simulations of coaxial helicity injection in a tokamak},
author = {Hooper, E. B. and Sovinec, C. R.},
abstractNote = {An instability observed in whole-device, resistive magnetohydrodynamic simulations of the driven phase of coaxial helicity injection in the National Spherical Torus eXperiment is identified as a current-driven resistive mode in an unusual geometry that transiently generates a current sheet. The mode consists of plasma flow velocity and magnetic field eddies in a tube aligned with the magnetic field at the surface of the injected magnetic flux. At low plasma temperatures (~10–20 eV), the mode is benign, but at high temperatures (~100 eV) its amplitude undergoes relaxation oscillations, broadening the layer of injected current and flow at the surface of the injected toroidal flux and background plasma. The poloidal-field structure is affected and the magnetic surface closure is generally prevented while the mode undergoes relaxation oscillations during injection. Furthermore, this study describes the mode and uses linearized numerical computations and an analytic slab model to identify the unstable mode.},
doi = {10.1063/1.4964292},
journal = {Physics of Plasmas},
number = 10,
volume = 23,
place = {United States},
year = {2016},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1063/1.4964292

Citation Metrics:
Cited by: 1 work
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