Non-existence of Normal Tokamak Equilibria with Negative Central Current

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Recent tokamak experiments employing off-axis, non-inductive current drive have found that a large central current hole can be produced. The current density is measured to be approximately zero in this region, though in principle there was sufficient current-drive power for the central current density to have gone significantly negative. Recent papers have used a large aspect-ratio expansion to show that normal MHD equilibria (with axisymmetric nested flux surfaces, non-singular fields, and monotonic peaked pressure profiles) can not exist with negative central current. We extend that proof here to arbitrary aspect ratio, using a variant of the virial theorem to derive ... continued below

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Hammett, G.W.; Jardin, S.C. & Stratton, B.C. February 18, 2003.

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Recent tokamak experiments employing off-axis, non-inductive current drive have found that a large central current hole can be produced. The current density is measured to be approximately zero in this region, though in principle there was sufficient current-drive power for the central current density to have gone significantly negative. Recent papers have used a large aspect-ratio expansion to show that normal MHD equilibria (with axisymmetric nested flux surfaces, non-singular fields, and monotonic peaked pressure profiles) can not exist with negative central current. We extend that proof here to arbitrary aspect ratio, using a variant of the virial theorem to derive a relatively simple integral constraint on the equilibrium. However, this constraint does not, by itself, exclude equilibria with non-nested flux surfaces, or equilibria with singular fields and/or hollow pressure profiles that may be spontaneously generated.

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1.3 Megabytes pages

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INIS; OSTI as DE00812029

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  • Other Information: PBD: 18 Feb 2003

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  • Report No.: PPPL-3788
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/812029 | External Link
  • Office of Scientific & Technical Information Report Number: 812029
  • Archival Resource Key: ark:/67531/metadc733795

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  • February 18, 2003

Added to The UNT Digital Library

  • Oct. 18, 2015, 6:40 p.m.

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  • April 15, 2016, 9:47 p.m.

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Hammett, G.W.; Jardin, S.C. & Stratton, B.C. Non-existence of Normal Tokamak Equilibria with Negative Central Current, report, February 18, 2003; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc733795/: accessed December 13, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.