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 ion and electron thermal transport within much of the plasma. As previously reported, the region for improved ion transport seems well characterized by the condition OE~B>Y-, where SERB is the ExB flow shear, calculated from measured quantities, and y,, is the maximum linear growth rate for ion temperature gradient (ITG) modes in the absence of flow shear. Within a limited region just inside the ITB, the electron ... continued below

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Stallard, B. W. November 24, 1998.

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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 ion and electron thermal transport within much of the plasma. As previously reported, the region for improved ion transport seems well characterized by the condition OE~B>Y-, where SERB is the ExB flow shear, calculated from measured quantities, and y,, is the maximum linear growth rate for ion temperature gradient (ITG) modes in the absence of flow shear. 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 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 Te 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-l), 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.

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1.7 Megabytes

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  • 40th Annual American Physical Society Meeting, Division of Plasma Physics, New Orleans, LA, November 16-20, 1998

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  • Other: DE00003388
  • Report No.: UCRL-JC-132585
  • Grant Number: W-7405-Eng-48
  • Office of Scientific & Technical Information Report Number: 3388
  • Archival Resource Key: ark:/67531/metadc684762

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  • November 24, 1998

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  • July 25, 2015, 2:20 a.m.

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  • Feb. 24, 2016, 3:49 p.m.

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Stallard, B. W. Electron heat transport in improved confinement discharges in DIII-D, article, November 24, 1998; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc684762/: accessed September 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.