Characteristic time for halo current growth and rotation

Journal Article · Mon Oct 19 00:00:00 EDT 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4933363· OSTI ID:1469571

Boozer, Allen H. ^[1]

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1. Columbia Univ., New York, NY (United States). Department of Applied Physics and Applied Mathematics

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.

• Research Organization: The Trustees Of Columbia University in The City Of New York Inc (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: FG02-03ER54696
• OSTI ID: 1469571
• Alternate ID(s): OSTI ID: 1224225
• Journal Information: Physics of Plasmas, Vol. 22, Issue 10; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY