Results of High Harmonic Fast Wave Heating Experiments on NSTX

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The study of high-harmonic fast-wave (HHFW) heating and current drive is being conducted on the National Spherical Torus Experiment (NSTX) device to determine the physics of applying radio-frequency (rf) waves at high harmonics (approximately 10-20) of the ion cyclotron frequency in this high-beta plasma regime and to extend the performance of the NSTX plasma. The magnetic field of this low aspect ratio device is lower (less than or equal to 0.35 T for this work) than that for the typical moderate aspect ratio tokamak regime by about an order of magnitude and the plasma densities achieved are typically in the ... continued below

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288 Kilobytes pages

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Hosea, J.C.; Bell, R.E.; Bitter, M.; Bonoli, P.; Carter, M.; Gates, D. et al. August 9, 2001.

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Description

The study of high-harmonic fast-wave (HHFW) heating and current drive is being conducted on the National Spherical Torus Experiment (NSTX) device to determine the physics of applying radio-frequency (rf) waves at high harmonics (approximately 10-20) of the ion cyclotron frequency in this high-beta plasma regime and to extend the performance of the NSTX plasma. The magnetic field of this low aspect ratio device is lower (less than or equal to 0.35 T for this work) than that for the typical moderate aspect ratio tokamak regime by about an order of magnitude and the plasma densities achieved are typically in the mid 10(superscript ''19'') m(superscript ''-3'') range. Thus, the dielectric constant of the plasma, epsilon always equals omega (subscript ''pe'')(superscript ''2'') divided by omega (subscript ''ce'')(superscript ''2''), is of order approximately 50-100 resulting in wave physics properties which favor electron heating by TTMP and Landau damping. Radio-frequency power is applied on NSTX at 3 0 MHz using an antenna array with 12 current straps aligned in the poloidal direction. The antenna can be phased to launch waves with toroidal wave numbers, k(subscript ''T'') between 2 m(superscript ''-1'') and 14 m(superscript ''-1'') and can be phased for current drive with peak toroidal directionality at 7 m(superscript ''-1''). To date most of the HHFW experiments have been carried out using k(subscript ''T'') = 14 m(superscript ''-1'') with 0-pi-0-pi-... phasing of the strap currents. The diagnostic complement on NSTX includes a 30-Hz, 10-spatial-channel Thomson scattering (MPTS) system for measuring profiles of electron temperature and density every 33 msec, and a charge-exchange recombination spectroscopy (CHERS) system for measuring profiles of the impurity ion temperature and toroidal rotation during a neutral-beam blip. Strong electron and ion heating are observed in helium discharges, whereas the heating efficiency is noticeably reduced for deuterium discharges. A detailed comparison between helium and deuterium discharge responses at k(subscript ''T'') = 14 m(superscript ''-1'') is presented here. Also, initial results for different radio-frequency phasing and start-up assist experiments will be discussed briefly.

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288 Kilobytes pages

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INIS; OSTI as DE00787788

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  • Other Information: PBD: 9 Aug 2001

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  • Report No.: PPPL-3595
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/787788 | External Link
  • Office of Scientific & Technical Information Report Number: 787788
  • Archival Resource Key: ark:/67531/metadc725383

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • August 9, 2001

Added to The UNT Digital Library

  • Sept. 29, 2015, 5:31 a.m.

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  • April 18, 2016, 1:03 p.m.

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Hosea, J.C.; Bell, R.E.; Bitter, M.; Bonoli, P.; Carter, M.; Gates, D. et al. Results of High Harmonic Fast Wave Heating Experiments on NSTX, report, August 9, 2001; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc725383/: accessed November 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.