The line-tying condition at a conducting anode is shown to provide a localized modification to the well-understood 1-D screw pinch equilibrium in the presence of bulk plasma diamagnetism. Diamagnetic currents cannot flow near the conducting anode and are measured to disappear in a localized boundary layer, causing a weak mirror configuration that breaks 1-D equilibrium and causes large parallel pressure gradients suggestive of significant radial outflows. For sufficiently large plasma currents, the paramagnetic nature of parallel current drives the equilibrium to paramagnetism and destroys the mirror effect. At a critical plasma current, the axisymmetric equilibrium is found to transition to a long-lived, rotating, helical 3-D equilibrium state. Internal measurements of this state via multi-point correlation analysis techniques illustrate that it preserves the flux surfaces and pressure profile of the axisymmetric equilibrium. Measurements indicate that despite the fact that the flux surfaces wander at the anode, the line-tied boundary conditions are not necessarily violated.
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Research Article|
May 31 2011
Two-dimensional axisymmetric and three-dimensional helical equilibrium in the line-tied screw pinch
C. Paz-Soldan;
C. Paz-Soldan
Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison
, Wisconsin 53706, USA
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M. I. Brookhart;
M. I. Brookhart
Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison
, Wisconsin 53706, USA
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A. J. Clinch;
A. J. Clinch
Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison
, Wisconsin 53706, USA
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D. A. Hannum;
D. A. Hannum
Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison
, Wisconsin 53706, USA
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C. B. Forest
C. B. Forest
Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison
, Wisconsin 53706, USA
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Phys. Plasmas 18, 052114 (2011)
Article history
Received:
March 16 2011
Accepted:
May 03 2011
Citation
C. Paz-Soldan, M. I. Brookhart, A. J. Clinch, D. A. Hannum, C. B. Forest; Two-dimensional axisymmetric and three-dimensional helical equilibrium in the line-tied screw pinch. Phys. Plasmas 1 May 2011; 18 (5): 052114. https://doi.org/10.1063/1.3592998
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