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Title: Characteristic time for halo current growth and rotation

We report a halo current flows for part of its path through the plasma edge and for part through the chamber walls and during tokamak disruptions can be as large as tenths of the plasma current. The primary interest in halo currents is the large force that they can exert on machine components particularly if the toriodal rotation of the halo current resonates with a natural oscillation frequency of the tokamak device. Halo currents arise when required to slow down the growth of a kink that is too unstable to be stabilized by the chamber walls. The width of the current channel in the halo plasma is comparable to the amplitude of the kink, and the halo current grows linearly, not exponentially, in time. The current density in the halo is comparable to that of the main plasma body. The rocket force due to plasma flowing out of the halo and recombining on the chamber walls can cause the non-axisymmetric magnetic structure produced by the kink to rotate toroidally at a speed compara-ble to the halo speed of sound. Lastly, Gerhardt’s observations of the halo current in NSTX shot 141 687 [Nucl. Fusion 53, 023005 (2013)] illustrate many features ofmore » the theory of halo currents and are discussed as a summary of the theory.« less
Authors:
 [1]
  1. Columbia Univ., New York, NY (United States). Department of Applied Physics and Applied Mathematics
Publication Date:
Grant/Contract Number:
FG02-03ER54696
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 10; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
The Trustees Of Columbia University in The City Of New York Inc (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1469571
Alternate Identifier(s):
OSTI ID: 1224225

Boozer, Allen H. Characteristic time for halo current growth and rotation. United States: N. p., Web. doi:10.1063/1.4933363.
Boozer, Allen H. Characteristic time for halo current growth and rotation. United States. doi:10.1063/1.4933363.
Boozer, Allen H. 2015. "Characteristic time for halo current growth and rotation". United States. doi:10.1063/1.4933363. https://www.osti.gov/servlets/purl/1469571.
@article{osti_1469571,
title = {Characteristic time for halo current growth and rotation},
author = {Boozer, Allen H.},
abstractNote = {We report a halo current flows for part of its path through the plasma edge and for part through the chamber walls and during tokamak disruptions can be as large as tenths of the plasma current. The primary interest in halo currents is the large force that they can exert on machine components particularly if the toriodal rotation of the halo current resonates with a natural oscillation frequency of the tokamak device. Halo currents arise when required to slow down the growth of a kink that is too unstable to be stabilized by the chamber walls. The width of the current channel in the halo plasma is comparable to the amplitude of the kink, and the halo current grows linearly, not exponentially, in time. The current density in the halo is comparable to that of the main plasma body. The rocket force due to plasma flowing out of the halo and recombining on the chamber walls can cause the non-axisymmetric magnetic structure produced by the kink to rotate toroidally at a speed compara-ble to the halo speed of sound. Lastly, Gerhardt’s observations of the halo current in NSTX shot 141 687 [Nucl. Fusion 53, 023005 (2013)] illustrate many features of the theory of halo currents and are discussed as a summary of the theory.},
doi = {10.1063/1.4933363},
journal = {Physics of Plasmas},
number = 10,
volume = 22,
place = {United States},
year = {2015},
month = {10}
}