Marginal Stability of Microturbulence near ITB Onset on Alcator C-Mod

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Insight into microturbulence and transport in tokamak plasmas is being sought using linear simulations of drift waves near the onset time of an internal transport barrier (ITB) on Alcator C-Mod. Microturbulence is likely generated by instabilities of drift waves and causes transport of heat and particles. This transport is studied because the containment of heat and particles is important for the achievement of practical nuclear fusion. We investigate nearness to marginal stability of ion-temperature-gradient (ITG) modes for conditions in the ITB region at the trigger time for ITB formation. Data from C-Mod, analyzed by TRANSP (a time-dependent transport analysis code), ... continued below

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844 Kilobytes pages

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Baumgaertel, J.A.; Redi, M.H.; Budny, R.V.; McCune, D.C.; Dorland, W. & Fiore, C.L. August 23, 2004.

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Insight into microturbulence and transport in tokamak plasmas is being sought using linear simulations of drift waves near the onset time of an internal transport barrier (ITB) on Alcator C-Mod. Microturbulence is likely generated by instabilities of drift waves and causes transport of heat and particles. This transport is studied because the containment of heat and particles is important for the achievement of practical nuclear fusion. We investigate nearness to marginal stability of ion-temperature-gradient (ITG) modes for conditions in the ITB region at the trigger time for ITB formation. Data from C-Mod, analyzed by TRANSP (a time-dependent transport analysis code), is read by the code TRXPL and made into input files for the parallel gyrokinetic model code GS2. Temperature and density gradients in these input files are modified to produce new input files. Results from these simulations show a weak ITG instability in the barrier region at the time of onset, above marginal stability; the normalized critical temperature gradient is 80% of the experimental temperature gradient. The growth rate increases linearly above the critical value, with the spectrum of ITG modes remaining parabolic up to a multiplicative factor of 2. The effect of varying density gradients is found to be much weaker and causes the fastest growing drift mode to change from ITG to trapped-electron mode character. Simulations were carried out on the NERSC [National Energy Research Supercomputer Center] IBM 6000 SP using 4 nodes, 16 processors per node. Predictive simulations were examined for converged instability after 10,000-50,000 time-steps in each case. Each simulation took approximately 30 minutes to complete on the IBM SP.

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844 Kilobytes pages

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INIS; OSTI as DE00834530

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  • Other Information: PBD: 23 Aug 2004

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  • Report No.: pppl-3999
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/834530 | External Link
  • Office of Scientific & Technical Information Report Number: 834530
  • Archival Resource Key: ark:/67531/metadc783264

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  • August 23, 2004

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  • Dec. 3, 2015, 9:30 a.m.

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  • June 10, 2016, 6:04 p.m.

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Baumgaertel, J.A.; Redi, M.H.; Budny, R.V.; McCune, D.C.; Dorland, W. & Fiore, C.L. Marginal Stability of Microturbulence near ITB Onset on Alcator C-Mod, report, August 23, 2004; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc783264/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.