Electron heat transport in improved confinement discharges in DIII-D

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In DIII-D tokamak plasmas with an internal transport barrier (ITB), the comparison of gyrokinetic linear stability (GKS) predictions with experiments in both low and strong negative magnetic shear plasmas provide improved understanding for electron thermal transport within the plasma. Within a limited region just inside the ITB, the electron temperature gradient (ETG) modes appear to control the electron temperature gradient and, consequently, the electron thermal transport. The increase in the electron temperature gradient with more strongly negative magnetic shear is consistent with the increase in the ETG mode marginal gradient. Closer to the magnetic axis the T{sub e} profile flattens ... continued below

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22 p.

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Stallard, B.W.; Greenfield, C.M. & Staebler, G.M. January 1, 1999.

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Description

In DIII-D tokamak plasmas with an internal transport barrier (ITB), the comparison of gyrokinetic linear stability (GKS) predictions with experiments in both low and strong negative magnetic shear plasmas provide improved understanding for electron thermal transport within the plasma. Within a limited region just inside the ITB, the electron temperature gradient (ETG) modes appear to control the electron temperature gradient and, consequently, the electron thermal transport. The increase in the electron temperature gradient with more strongly negative magnetic shear is consistent with the increase in the ETG mode marginal gradient. Closer to the magnetic axis the T{sub e} profile flattens and the ETG modes are predicted to be stable. With additional core electron heating, FIR scattering measurements near the axis show the presence of high k fluctuations (12 cm{sup {minus}1}), rotating in the electron diamagnetic drift direction. This turbulence could impact electron transport and possibly also ion transport. Thermal diffusivities for electrons, and to a lesser degree ions, increase. The ETG mode can exist at this wavenumber, but it is computed to be robustly stable near the axis. Consequently, in the plasmas the authors have examined, calculations of drift wave linear stability do not explain the observed transport near the axis in plasmas with or without additional electron heating, and there are probably other processes controlling transport in this region.

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22 p.

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INIS; OSTI as DE99001729

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  • 40. annual physics of plasmas meeting, APS Division of Plasma Physics, New Orleans, LA (United States), 16-20 Nov 1998

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  • Other: DE99001729
  • Report No.: GA--A23020
  • Report No.: CONF-981127--
  • Grant Number: AC03-99ER54463;W-7405-ENG-48;AC05-96OR22464;FG03-86ER53225;FG03-97ER54415;FG02-92ER54139
  • Office of Scientific & Technical Information Report Number: 319673
  • Archival Resource Key: ark:/67531/metadc674775

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  • January 1, 1999

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  • July 25, 2015, 2:20 a.m.

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  • Aug. 1, 2016, 6:45 p.m.

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Stallard, B.W.; Greenfield, C.M. & Staebler, G.M. Electron heat transport in improved confinement discharges in DIII-D, article, January 1, 1999; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc674775/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.