Electron heat transport in improved confinement discharges in DIII-D
- Lawrence Livermore National Lab., CA (United States)
- General Atomics, San Diego, CA (United States); and others
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.
- Research Organization:
- General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of California, Los Angeles, CA (United States); Univ. of Texas, Austin, TX (United States); Univ. of Wisconsin, Madison, WI (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC03-99ER54463; W-7405-ENG-48; AC05-96OR22464; FG03-86ER53225; FG03-97ER54415; FG02-92ER54139
- OSTI ID:
- 319673
- Report Number(s):
- GA-A23020; CONF-981127-; ON: DE99001729; TRN: 99:003882
- Resource Relation:
- Conference: 40. annual physics of plasmas meeting, APS Division of Plasma Physics, New Orleans, LA (United States), 16-20 Nov 1998; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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Electron heat transport in improved confinement discharges in DIII-D
Behavior of electron and ion transport in discharges with an internal transport barrier in the DIII-D tokamak