Profile Modifications Resulting from Early High-harmonic Fast Wave heating in NSTX

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Experiments have been performed in the National Spherical Torus Experiment (NSTX) to inject high harmonic fast wave (HHFW) power early during the plasma current ramp-up in an attempt to reduce the current penetration rate to raise the central safety factor during the flattop phase of the discharge. To date, up to 2 MW of HHFW power has been coupled to deuterium plasmas as early as t = 50 ms using the slowest interstrap phasing of k|| approximately equals 14 m(superscript)-1 (nf = 24). Antenna-plasma gap scans have been performed and find that for small gaps (5-8 cm), electron heating is ... continued below

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364 Kilobytes pages

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Mendard, J.E.; LeBlanc, Wilson, J.R.; Sabbagh, S.A.; Stutman, D. & and Swain, D.W. May 18, 2001.

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Experiments have been performed in the National Spherical Torus Experiment (NSTX) to inject high harmonic fast wave (HHFW) power early during the plasma current ramp-up in an attempt to reduce the current penetration rate to raise the central safety factor during the flattop phase of the discharge. To date, up to 2 MW of HHFW power has been coupled to deuterium plasmas as early as t = 50 ms using the slowest interstrap phasing of k|| approximately equals 14 m(superscript)-1 (nf = 24). Antenna-plasma gap scans have been performed and find that for small gaps (5-8 cm), electron heating is observed with relatively small density rises and modest reductions in current penetration rate. For somewhat larger gaps (10-12 cm), weak electron heating is observed but with a spontaneous density rise at the plasma edge similar to that observed in NSTX H-modes. In the larger gap configuration, EFIT code reconstructions (without MSE [motional Stark effect]) find that resistive flux consumption is reduced as much as 30%, the internal inductance is maintained below 0.6 at 1 MA into the flattop, q(0) is increased significantly, and the MHD stability character of the discharges is strongly modified.

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364 Kilobytes pages

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INIS; OSTI as DE00784550

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  • Other Information: PBD: 18 May 2001

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  • Report No.: PPPL-3564
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/784550 | External Link
  • Office of Scientific & Technical Information Report Number: 784550
  • Archival Resource Key: ark:/67531/metadc722681

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  • May 18, 2001

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  • Sept. 29, 2015, 5:31 a.m.

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  • April 15, 2016, 9:51 p.m.

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Mendard, J.E.; LeBlanc, Wilson, J.R.; Sabbagh, S.A.; Stutman, D. & and Swain, D.W. Profile Modifications Resulting from Early High-harmonic Fast Wave heating in NSTX, report, May 18, 2001; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc722681/: accessed December 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.