Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature
We present inboard (HFS) and outboard (LFS) radial electric field (E[subscript r]) and impurity temperature (T[subscript z]) measurements in the I-mode and H-mode pedestal of Alcator C-Mod. These measurements reveal strong Er wells at the HFS and the LFS midplane in both regimes and clear pedestals...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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IOP Publishing
2015
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| Online Access: | http://hdl.handle.net/1721.1/96826 https://orcid.org/0000-0002-5283-0546 https://orcid.org/0000-0001-8324-4227 https://orcid.org/0000-0002-0349-1736 |
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| author | Landreman, Matthew Joseph Parra, F.I. Theiler, Christian Lipschultz, Bruce Ernst, Darin R. Hughes, Jerry W., Jr. Catto, Peter J. Hutchinson, Ian H. Reinke, Matthew Logan Hubbard, Amanda E. Marmar, Earl S. Churchill, Randy Michael Terry, J. T. Walk, John R. |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Landreman, Matthew Joseph Parra, F.I. Theiler, Christian Lipschultz, Bruce Ernst, Darin R. Hughes, Jerry W., Jr. Catto, Peter J. Hutchinson, Ian H. Reinke, Matthew Logan Hubbard, Amanda E. Marmar, Earl S. Churchill, Randy Michael Terry, J. T. Walk, John R. |
| author_sort | Landreman, Matthew Joseph |
| collection | MIT |
| description | We present inboard (HFS) and outboard (LFS) radial electric field (E[subscript r]) and impurity temperature (T[subscript z]) measurements in the I-mode and H-mode pedestal of Alcator C-Mod. These measurements reveal strong Er wells at the HFS and the LFS midplane in both regimes and clear pedestals in T[subscript z], which are of similar shape and height for the HFS and LFS. While the H-mode E[subscript r] well has a radially symmetric structure, the E[subscript r] well in I-mode is asymmetric, with a stronger ExB shear layer at the outer edge of the E[subscript r] well, near the separatrix. Comparison of HFS and LFS profiles indicates that impurity temperature and plasma potential are not simultaneously flux functions. Uncertainties in radial alignment after mapping HFS measurements along flux surfaces to the LFS do not, however, allow direct determination as to which quantity varies poloidally and to what extent. Radially aligning HFS and LFS measurements based on the T[subscript z] profiles would result in substantial inboard-outboard variations of plasma potential and electron density. Aligning HFS and LFS E[subscript r] wells instead also approximately aligns the impurity poloidal flow profiles, while resulting in a LFS impurity temperature exceeding the HFS values in the region of steepest gradients by up to 70%. Considerations based on a simplified form of total parallel momentum balance and estimates of parallel and perpendicular heat transport time scales seem to favor an approximate alignment of the E[subscript r] wells and a substantial poloidal asymmetry in impurity temperature. |
| first_indexed | 2024-09-23T16:09:41Z |
| format | Article |
| id | mit-1721.1/96826 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T16:09:41Z |
| publishDate | 2015 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/968262022-10-02T06:43:49Z Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature Landreman, Matthew Joseph Parra, F.I. Theiler, Christian Lipschultz, Bruce Ernst, Darin R. Hughes, Jerry W., Jr. Catto, Peter J. Hutchinson, Ian H. Reinke, Matthew Logan Hubbard, Amanda E. Marmar, Earl S. Churchill, Randy Michael Terry, J. T. Walk, John R. Massachusetts Institute of Technology. Department of Physics Massachusetts Institute of Technology. Plasma Science and Fusion Center Hutchinson, Ian H. Theiler, Christian Churchill, Randy Michael Lipschultz, Bruce Ernst, Darin R. Hughes, Jerry W., Jr. Catto, Peter J. Hutchinson, Ian H. Reinke, Matthew Logan Hubbard, Amanda E. Marmar, Earl S. Terry, J. T. Walk, John R. We present inboard (HFS) and outboard (LFS) radial electric field (E[subscript r]) and impurity temperature (T[subscript z]) measurements in the I-mode and H-mode pedestal of Alcator C-Mod. These measurements reveal strong Er wells at the HFS and the LFS midplane in both regimes and clear pedestals in T[subscript z], which are of similar shape and height for the HFS and LFS. While the H-mode E[subscript r] well has a radially symmetric structure, the E[subscript r] well in I-mode is asymmetric, with a stronger ExB shear layer at the outer edge of the E[subscript r] well, near the separatrix. Comparison of HFS and LFS profiles indicates that impurity temperature and plasma potential are not simultaneously flux functions. Uncertainties in radial alignment after mapping HFS measurements along flux surfaces to the LFS do not, however, allow direct determination as to which quantity varies poloidally and to what extent. Radially aligning HFS and LFS measurements based on the T[subscript z] profiles would result in substantial inboard-outboard variations of plasma potential and electron density. Aligning HFS and LFS E[subscript r] wells instead also approximately aligns the impurity poloidal flow profiles, while resulting in a LFS impurity temperature exceeding the HFS values in the region of steepest gradients by up to 70%. Considerations based on a simplified form of total parallel momentum balance and estimates of parallel and perpendicular heat transport time scales seem to favor an approximate alignment of the E[subscript r] wells and a substantial poloidal asymmetry in impurity temperature. United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512) Swiss National Science Foundation 2015-04-28T16:38:49Z 2015-04-28T16:38:49Z 2014-06 2014-02 Article http://purl.org/eprint/type/JournalArticle 0029-5515 1741-4326 http://hdl.handle.net/1721.1/96826 Theiler, C., R.M. Churchill, B. Lipschultz, M. Landreman, D.R. Ernst, J.W. Hughes, P.J. Catto, et al. “Inboard and Outboard Radial Electric Field Wells in the H- and I-Mode Pedestal of Alcator C-Mod and Poloidal Variations of Impurity Temperature.” Nuclear Fusion 54, no. 8 (June 18, 2014): 083017. https://orcid.org/0000-0002-5283-0546 https://orcid.org/0000-0001-8324-4227 https://orcid.org/0000-0002-0349-1736 en_US http://dx.doi.org/10.1088/0029-5515/54/8/083017 Nuclear Fusion Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf IOP Publishing Prof. Hutchinson via Chris Sherratt |
| spellingShingle | Landreman, Matthew Joseph Parra, F.I. Theiler, Christian Lipschultz, Bruce Ernst, Darin R. Hughes, Jerry W., Jr. Catto, Peter J. Hutchinson, Ian H. Reinke, Matthew Logan Hubbard, Amanda E. Marmar, Earl S. Churchill, Randy Michael Terry, J. T. Walk, John R. Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature |
| title | Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature |
| title_full | Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature |
| title_fullStr | Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature |
| title_full_unstemmed | Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature |
| title_short | Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature |
| title_sort | inboard and outboard radial electric field wells in the h and i mode pedestal of alcator c mod and poloidal variations of impurity temperature |
| url | http://hdl.handle.net/1721.1/96826 https://orcid.org/0000-0002-5283-0546 https://orcid.org/0000-0001-8324-4227 https://orcid.org/0000-0002-0349-1736 |
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