Lore, J., Guttenfelder, W., Briesemeister, A., Anderson, D. T., Anderson, F. S. B., Deng, C. B., Likin, K. M., Spong, D. A., Talmadge, J. N. and Zhai, K. (2010) Internal electron transport barrier due to neoclassical ambipolarity in the helically symmetric experiment. Physics of Plasmas, Vol.17 (No.5). Article: 056101. doi:10.1063/1.3300465 ISSN 1070-664X.
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Abstract
Electron cyclotron heated plasmas in the Helically Symmetric Experiment (HSX) feature strongly peaked electron temperature profiles; central temperatures are 2.5 keV with 100 kW injected power. These measurements, coupled with neoclassical predictions of large "electron root" radial electric fields with strong radial shear, are evidence of a neoclassically driven thermal transport barrier. Neoclassical transport quantities are calculated using the PENTA code [D. A. Spong, Phys. Plasmas 12, 056114 (2005)], in which momentum is conserved and parallel flow is included. Unlike a conventional stellarator, which exhibits strong flow damping in all directions on a flux surface, quasisymmetric stellarators are free to rotate in the direction of symmetry, and the effect of momentum conservation in neoclassical calculations may therefore be significant. Momentum conservation is shown to modify the neoclassical ion flux and ambipolar ion root radial electric fields in the quasisymmetric configuration. The effect is much smaller in a HSX configuration where the symmetry is spoiled. In addition to neoclassical transport, a model of trapped electron mode turbulence is used to calculate the turbulent-driven electron thermal diffusivity. Turbulent transport quenching due to the neoclassically predicted radial electric field profile is needed in predictive transport simulations to reproduce the peaking of the measured electron temperature profile [Guttenfelder , Phys. Rev. Lett. 101, 215002 (2008)]. (C) 2010 American Institute of Physics. [doi:10.1063/1.3300465]
| Item Type: | Journal Article |
|---|---|
| Subjects: | Q Science > QC Physics |
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics |
| Journal or Publication Title: | Physics of Plasmas |
| Publisher: | American Institute of Physics |
| ISSN: | 1070-664X |
| Official Date: | May 2010 |
| Dates: | Date Event May 2010 Published |
| Volume: | Vol.17 |
| Number: | No.5 |
| Number of Pages: | 10 |
| Page Range: | Article: 056101 |
| DOI: | 10.1063/1.3300465 |
| Status: | Peer Reviewed |
| Publication Status: | Published |
| Access rights to Published version: | Restricted or Subscription Access |
| Funder: | DOE |
| Grant number: | DE-FG02-93ER54222 |
| Title of Event: | 51st Annual Meeting of the Division-of-Plasma-Physics of the American-Physics-Society |
| Location of Event: | Atlanta, GA |
| Date(s) of Event: | NOV 02-06, 2009 |
| URI: | https://wrap.warwick.ac.uk/5761/ |
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