L-H Mode Transitions in the National Spherical Torus Experiment

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Edge data from plasmas in the National Spherical Torus Experiment (NSTX) [S. Kaye et al., Fusion Technology 36 (1999) 16] have been compared to theories of transport suppression that have been used to develop a physics framework for low-confinement (L) to high-confinement (H) mode transitions. The NSTX data were obtained in low aspect ratio (R/a approximately equal to 1.3) discharges taken from a variety of discharge phases, including L-modes, L-H transitions, and H-modes with and without edge localized modes (ELMs). The comparisons show that the group of points taken just before the L-H mode transition are well mixed with the ... continued below

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Kaye, S.M.; Bush, C.E.; Fredrickson, E.; LeBlanc, B.; Maingi, R. & Sabbagh, S.A. July 24, 2003.

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Description

Edge data from plasmas in the National Spherical Torus Experiment (NSTX) [S. Kaye et al., Fusion Technology 36 (1999) 16] have been compared to theories of transport suppression that have been used to develop a physics framework for low-confinement (L) to high-confinement (H) mode transitions. The NSTX data were obtained in low aspect ratio (R/a approximately equal to 1.3) discharges taken from a variety of discharge phases, including L-modes, L-H transitions, and H-modes with and without edge localized modes (ELMs). The comparisons show that the group of points taken just before the L-H mode transition are well mixed with the purely L-mode group to within the measurement uncertainties, indicating that changes in these parameters leading up to the transition are subtle. One of the theory parameters, alpha{sub MHD} = -R{sub q}{sup 2}dbeta{sub t/dr}, does show a clear threshold alpha{sub MHD} = 1 to 2 between the H-mode grouping of points and those remaining in the L-mode or taken just prior to the transition. Additionally, there is no evidence for an edge temperature threshold necessary for transitioning into the H-mode. NSTX data indicate further a possible connection between L-H transitions and non-ambipolar beam ion losses.

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1 MB pages

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INIS; OSTI as DE00814726

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  • Other Information: PBD: 24 Jul 2003

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  • Report No.: PPPL-3745
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/814726 | External Link
  • Office of Scientific & Technical Information Report Number: 814726
  • Archival Resource Key: ark:/67531/metadc737394

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  • July 24, 2003

Added to The UNT Digital Library

  • Oct. 18, 2015, 6:40 p.m.

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  • April 15, 2016, 10:01 p.m.

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Kaye, S.M.; Bush, C.E.; Fredrickson, E.; LeBlanc, B.; Maingi, R. & Sabbagh, S.A. L-H Mode Transitions in the National Spherical Torus Experiment, report, July 24, 2003; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc737394/: accessed October 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.