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Title: Spontaneous healing and growth of locked magnetic island chains in toroidal plasmas

Abstract

Recent experiments have demonstrated that locked magnetic island chains in stellarator plasmas spontaneously heal under certain conditions, and spontaneously grow under others. A formalism initially developed to study magnetic island dynamics in tokamak plasmas is employed to investigate this phenomenon. It is found that island healing/growth transitions can be caused either by a breakdown in torque balance in the vicinity of the island chain, or by an imbalance between the various terms in the island width evolution equation. The scaling of the healing/growth thresholds with the standard dimensionless plasma parameters {beta}, {nu}{sub *}, and {rho}{sub *} is determined. In accordance with the experimental data, it is found that island healing generally occurs at high {beta} and low {nu}{sub *}, and island growth at low {beta} and high {nu}{sub *}. In further agreement, it is found that island healing is accompanied an ion poloidal velocity shift in the electron diamagnetic direction, and island growth by a velocity shift in the ion diamagnetic direction. Finally, it is found that there is considerable hysteresis in the healing/growth cycle, as is also seen experimentally.

Authors:
;  [1]
  1. Department of Physics, Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)
Publication Date:
OSTI Identifier:
22068889
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 11; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ELECTRONS; EXPERIMENTAL DATA; HYSTERESIS; IONS; MAGNETIC ISLANDS; MATHEMATICAL EVOLUTION; PLASMA; SCALING; STELLARATORS; TOKAMAK DEVICES; TOROIDAL CONFIGURATION; TORQUE

Citation Formats

Fitzpatrick, R., and Waelbroeck, F. L. Spontaneous healing and growth of locked magnetic island chains in toroidal plasmas. United States: N. p., 2012. Web. doi:10.1063/1.4766582.
Fitzpatrick, R., & Waelbroeck, F. L. Spontaneous healing and growth of locked magnetic island chains in toroidal plasmas. United States. doi:10.1063/1.4766582.
Fitzpatrick, R., and Waelbroeck, F. L. Thu . "Spontaneous healing and growth of locked magnetic island chains in toroidal plasmas". United States. doi:10.1063/1.4766582.
@article{osti_22068889,
title = {Spontaneous healing and growth of locked magnetic island chains in toroidal plasmas},
author = {Fitzpatrick, R. and Waelbroeck, F. L.},
abstractNote = {Recent experiments have demonstrated that locked magnetic island chains in stellarator plasmas spontaneously heal under certain conditions, and spontaneously grow under others. A formalism initially developed to study magnetic island dynamics in tokamak plasmas is employed to investigate this phenomenon. It is found that island healing/growth transitions can be caused either by a breakdown in torque balance in the vicinity of the island chain, or by an imbalance between the various terms in the island width evolution equation. The scaling of the healing/growth thresholds with the standard dimensionless plasma parameters {beta}, {nu}{sub *}, and {rho}{sub *} is determined. In accordance with the experimental data, it is found that island healing generally occurs at high {beta} and low {nu}{sub *}, and island growth at low {beta} and high {nu}{sub *}. In further agreement, it is found that island healing is accompanied an ion poloidal velocity shift in the electron diamagnetic direction, and island growth by a velocity shift in the ion diamagnetic direction. Finally, it is found that there is considerable hysteresis in the healing/growth cycle, as is also seen experimentally.},
doi = {10.1063/1.4766582},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 11,
volume = 19,
place = {United States},
year = {2012},
month = {11}
}