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Title: Non-existence of Normal Tokamak Equilibria with Negative Central Current

Abstract

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.

Authors:
; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
812029
Report Number(s):
PPPL-3788
TRN: US0303304
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 18 Feb 2003
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASPECT RATIO; CURRENT DENSITY; MAGNETIC SURFACES; NON-INDUCTIVE CURRENT DRIVE; VIRIAL THEOREM; EQUILIBRIUM; EQUILIBRIUM, MHD-TOROIDAL; MAGNETOHYDRODYNAMICS (MHD); RECONNECTION

Citation Formats

Hammett, G W, Jardin, S C, and Stratton, B C. Non-existence of Normal Tokamak Equilibria with Negative Central Current. United States: N. p., 2003. Web. doi:10.2172/812029.
Hammett, G W, Jardin, S C, & Stratton, B C. Non-existence of Normal Tokamak Equilibria with Negative Central Current. United States. doi:10.2172/812029.
Hammett, G W, Jardin, S C, and Stratton, B C. Tue . "Non-existence of Normal Tokamak Equilibria with Negative Central Current". United States. doi:10.2172/812029. https://www.osti.gov/servlets/purl/812029.
@article{osti_812029,
title = {Non-existence of Normal Tokamak Equilibria with Negative Central Current},
author = {Hammett, G W and Jardin, S C and Stratton, B C},
abstractNote = {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.},
doi = {10.2172/812029},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {2}
}