Abstract
For the first time, profiles (0.3<ρ <0.9) of electron temperature and density fluctuations in a tokamak have been measured simultaneously and the results compared to nonlinear gyrokinetic simulations. Electron temperature and density fluctuations measured in neutral beam-heated, sawtooth-free low confinement mode (L-mode) plasmas in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] are found to be similar in frequency and normalized amplitude, with amplitude increasing with radius. The measured radial profile of two fluctuation fields allows for a new and rigorous comparison with gyrokinetic results. Nonlinear gyrokinetic flux-tube simulations predict that electron temperature and density fluctuations have similar normalized amplitudes in L-mode. At ρ =0.5, simulation results match experimental heat diffusivities and density fluctuation amplitude, but overestimate electron temperature fluctuation amplitude and particle diffusivity. In contrast, simulations at ρ =0.75 do not match either the experimentally derived transport properties or the measured fluctuation levels.
| Original language | English |
|---|---|
| Article number | 056116 |
| Journal | Physics of Plasmas |
| Volume | 15 |
| Issue number | 5 |
| DOIs | |
| State | Published - 2008 |
| Externally published | Yes |
Funding
This research is supported by the U.S. Department of Energy under Contract Nos. DE-FG03-01ER54615, JP333701, DE-FG02-89ER53296, DE-FG02-04ER54758, DE-FC02-04ER54698, DE-FG03-97ER54415, and W-7405-ENG-48. A.E.W.’s research was performed under appointment to the Fusion Energy Sciences Fellowship Program administered by Oak Ridge Institute for Science and Education under a contract between the U.S. Department of Energy and the Oak Ridge Associated Universities. We thank the DIII-D team for their support of these experiments. A.E.W. is grateful to Steve Cowley for his many insightful comments and discussions of this work.