Comparing Linear Microinstability of the National Compact Stellarator Expriment and a Shaped Tokamak

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One metric for comparing con nement properties of di erent magnetic fusion energy con gurations is the linear critical gradient of drift wave modes. The critical gradient scale length determines the ratio of the core to pedestal temperature when a plasma is limited to marginal stability in the plasma core. The gyrokinetic turbulence code GS2 was used to calculate critical temperature gradients for the linear, collisionless ion tem- perature gradient (ITG) mode in the National Compact Stellarator Experiment (NCSX) and a prototypical shaped tokamak, based on the pro les of a JET H-mode shot and the stronger shaping of ARIES-AT. ... continued below

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J.A. Baumgaertel, G.W. Hammett and D.R. Mikkelsen November 20, 2012.

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One metric for comparing con nement properties of di erent magnetic fusion energy con gurations is the linear critical gradient of drift wave modes. The critical gradient scale length determines the ratio of the core to pedestal temperature when a plasma is limited to marginal stability in the plasma core. The gyrokinetic turbulence code GS2 was used to calculate critical temperature gradients for the linear, collisionless ion tem- perature gradient (ITG) mode in the National Compact Stellarator Experiment (NCSX) and a prototypical shaped tokamak, based on the pro les of a JET H-mode shot and the stronger shaping of ARIES-AT. While a concern was that the narrow cross section of NCSX at some toroidal locations would result in steep gradients that drive instabilities more easily, it is found that other stabilizing e ects of the stellarator con guration o set this so that the normalized critical gradients for NCSX are competitive with or even better than for the tokamak. For the adiabatic ITG mode, NCSX and the tokamak had similar critical gradients, though beyond marginal stability, NCSX had larger growth rates. However, for the kinetic ITG mode, NCSX had a higher critical gradient and lower growth rates until a/LT ≈#25; 1:5 a/LT;crit, when it surpassed the tokamak's. A discussion of the results presented with respect to a/LT vs R/LT is included.

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  • Physics of Plasmas (October 2012)

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  • Report No.: PPPL-4832
  • Grant Number: DE-ACO2-09CH11466
  • DOI: 10.2172/1056355 | External Link
  • Office of Scientific & Technical Information Report Number: 1056355
  • Archival Resource Key: ark:/67531/metadc835783

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  • November 20, 2012

Added to The UNT Digital Library

  • May 19, 2016, 9:45 a.m.

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  • July 18, 2016, 5:25 p.m.

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J.A. Baumgaertel, G.W. Hammett and D.R. Mikkelsen. Comparing Linear Microinstability of the National Compact Stellarator Expriment and a Shaped Tokamak, report, November 20, 2012; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc835783/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.