Trapped Electron Stabilization of Ballooning Modes in Low Aspect Ratio Toroidal Plasmas

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The kinetic effects of trapped electron dynamics and finite gyroradii and magnetic drift motion of ions are shown to give rise to a large parallel electric field and hence a parallel current that greatly enhances the stabilizing effect of field line tension for ballooning modes in low aspect ratio toroidal plasmas. For large aspect ratio the stabilizing effect increases (reduces) the {beta}(= 2P/B{sup 2}) threshold for the first (second) stability of the kinetic ballooning mode (KBM) from the MHD {beta} threshold value by a factor proportional to the trapped electron density fraction. For small aspect ratio the stabilizing effect can ... continued below

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912 Kilobytes pages

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Gorelenkov, C.Z. Cheng and N.N. March 18, 2004.

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The kinetic effects of trapped electron dynamics and finite gyroradii and magnetic drift motion of ions are shown to give rise to a large parallel electric field and hence a parallel current that greatly enhances the stabilizing effect of field line tension for ballooning modes in low aspect ratio toroidal plasmas. For large aspect ratio the stabilizing effect increases (reduces) the {beta}(= 2P/B{sup 2}) threshold for the first (second) stability of the kinetic ballooning mode (KBM) from the MHD {beta} threshold value by a factor proportional to the trapped electron density fraction. For small aspect ratio the stabilizing effect can greatly increase the {beta} threshold of the first stability of KBMs from the MHD {beta} threshold by S{sub c} {approx_equal} 1 + (n{sub e}/n{sub eu}){delta}, where n{sub e}/n{sub eu} is the ratio of the total electron density to the untrapped electron density, and {delta} depends on the trapped electron dynamics and finite gyroradii and magnetic drift motion of ions. If n{sub e}/n{sub eu} >> 1 as in the National Spherical Torus Experiment (NSTX) with an aspect ratio approximately equal to 1.4, the KBM should be stable for {beta} {le} 1 for finite magnetic shear. Therefore, unstable KBMs are expected only in the weak shear region near the radial location of the minimum of the safety factor in NSTX reverse shear discharges.

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912 Kilobytes pages

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INIS; OSTI as DE00827762

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  • Other Information: PBD: 18 Mar 2004

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  • Report No.: PPPL-3934
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/827762 | External Link
  • Office of Scientific & Technical Information Report Number: 827762
  • Archival Resource Key: ark:/67531/metadc781670

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  • March 18, 2004

Added to The UNT Digital Library

  • Dec. 3, 2015, 9:30 a.m.

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  • June 10, 2016, 6:16 p.m.

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Gorelenkov, C.Z. Cheng and N.N. Trapped Electron Stabilization of Ballooning Modes in Low Aspect Ratio Toroidal Plasmas, report, March 18, 2004; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc781670/: accessed September 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.