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Taylor relaxation and lambda decay of unbounded, freely expanding spheromaks

Yee, J. and Bellan, P. M. (2000) Taylor relaxation and lambda decay of unbounded, freely expanding spheromaks. Physics of Plasmas, 7 (9). pp. 3625-3640. ISSN 1070-664X. https://resolver.caltech.edu/CaltechAUTHORS:YEEpop00

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Abstract

A magnetized coaxial gun is discharged into a much larger vacuum chamber and the subsequent evolution of the plasma is observed using high speed cameras and a magnetic probe array. Photographic results indicate four distinct regimes of operation, labeled I–IV, each possessing qualitatively different dynamics, with the parameter lambdagun = µ0Igun/Phibias determining the operative regime. Plasmas produced in Regime II are identified as detached spheromak configurations. Images depict a donut-like shape, while magnetic data demonstrate that a closed toroidal flux-surface topology is present. Poloidal flux amplification shows that Taylor relaxation mechanisms are at work. The spatial and temporal variation of plasma lambda= µ0Jphi/Bphi indicate that the spheromak is decaying and expanding in a manner analogous to a self-similar expansion model proposed for interplanetary magnetic clouds. In Regime III, the plasma is unable to detach from the gun due to excess bias flux. Analysis of toroidal and poloidal flux as well as the lambda profile shows that magnetic flux and helicity are confined within the gun for this regime.


Item Type:Article
ORCID:
AuthorORCID
Bellan, P. M.0000-0002-0886-8782
Additional Information:© 2000 American Institute of Physics. (Received 4 February 2000; accepted 22 May 2000) This work was taken from the doctoral dissertation of one of the authors (J.Y.). The research was supported by U.S. Department of Energy Grant No. DE-FG03-98ER54461. The ICCD camera was purchased in part by a Powell equipment grant. The authors wish to thank F. T. Cosso for technical assistance.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-98ER54461
Subject Keywords:plasma toroidal confinement; plasma production; plasma guns; plasma diagnostics; plasma probes
Issue or Number:9
Record Number:CaltechAUTHORS:YEEpop00
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:YEEpop00
Alternative URL:http://dx.doi.org/10.1063/1.1287137
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1868
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:21 Feb 2006
Last Modified:02 Oct 2019 22:47

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