Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma
Boundary layer flows in the Alcator C-Mod tokamak are systematically examined as magnetic topology (upper versus lower-null) and plasma density are changed. Utilizing a unique set of scanning Langmuir–Mach probes, including one on the high-field side (HFS) midplane, the poloidal variation of plasma...
| Main Authors: | , , |
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| Format: | Article |
| Language: | en_US |
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IOP Publishing
2014
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| Online Access: | http://hdl.handle.net/1721.1/84061 https://orcid.org/0000-0002-7841-9261 |
| _version_ | 1826205068530024448 |
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| author | Smick, N. Labombard, Brian Hutchinson, Ian Horner |
| author2 | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Smick, N. Labombard, Brian Hutchinson, Ian Horner |
| author_sort | Smick, N. |
| collection | MIT |
| description | Boundary layer flows in the Alcator C-Mod tokamak are systematically examined as magnetic topology (upper versus lower-null) and plasma density are changed. Utilizing a unique set of scanning Langmuir–Mach probes, including one on the high-field side (HFS) midplane, the poloidal variation of plasma flow components in the parallel, diamagnetic and radial directions are resolved in detail. It is found that the plasma flow pattern can be decomposed into two principal parts: (1) a drift-driven component, which lies within a magnetic flux surface and is divergence-free and (2) a transport-driven component, which gives rise to near-sonic parallel flows on the HFS scrape-off layer (SOL). Toroidal rotation, Pfirsch–Schlüter and transport-driven contributions are unambiguously identified. Transport-driven parallel flows are found to dominate the HFS particle fluxes; the total poloidal-directed flow accounts for ~1/3 to all of the ion flux arriving on the inner divertor. As a result, heat convection is found to be an important player in this region, consistent with the observation of divertor asymmetries that depend on the direction of B × ∇B relative to the active x-point. In contrast, the poloidal projection of parallel flow in the low-field SOL largely cancels with E[subscript r] × B flow; toroidal rotation is the dominant plasma motion there. The magnitude of the transport-driven poloidal flow is found to be quantitatively consistent with fluctuation-induced radial particle fluxes on the low-field side (LFS), identifying this as the primary drive mechanism. Fluctuation-induced fluxes on the HFS are found to be essentially zero, excluding turbulent inward transport as the mechanism that closes the circulation loop in this region. |
| first_indexed | 2024-09-23T13:06:16Z |
| format | Article |
| id | mit-1721.1/84061 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T13:06:16Z |
| publishDate | 2014 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/840612023-02-26T02:26:27Z Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma Smick, N. Labombard, Brian Hutchinson, Ian Horner Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Massachusetts Institute of Technology. Plasma Science and Fusion Center Hutchinson, Ian Smick, N. Labombard, Brian Hutchinson, Ian H. Boundary layer flows in the Alcator C-Mod tokamak are systematically examined as magnetic topology (upper versus lower-null) and plasma density are changed. Utilizing a unique set of scanning Langmuir–Mach probes, including one on the high-field side (HFS) midplane, the poloidal variation of plasma flow components in the parallel, diamagnetic and radial directions are resolved in detail. It is found that the plasma flow pattern can be decomposed into two principal parts: (1) a drift-driven component, which lies within a magnetic flux surface and is divergence-free and (2) a transport-driven component, which gives rise to near-sonic parallel flows on the HFS scrape-off layer (SOL). Toroidal rotation, Pfirsch–Schlüter and transport-driven contributions are unambiguously identified. Transport-driven parallel flows are found to dominate the HFS particle fluxes; the total poloidal-directed flow accounts for ~1/3 to all of the ion flux arriving on the inner divertor. As a result, heat convection is found to be an important player in this region, consistent with the observation of divertor asymmetries that depend on the direction of B × ∇B relative to the active x-point. In contrast, the poloidal projection of parallel flow in the low-field SOL largely cancels with E[subscript r] × B flow; toroidal rotation is the dominant plasma motion there. The magnitude of the transport-driven poloidal flow is found to be quantitatively consistent with fluctuation-induced radial particle fluxes on the low-field side (LFS), identifying this as the primary drive mechanism. Fluctuation-induced fluxes on the HFS are found to be essentially zero, excluding turbulent inward transport as the mechanism that closes the circulation loop in this region. United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512) 2014-01-17T16:18:51Z 2014-01-17T16:18:51Z 2013-01 2012-08 Article http://purl.org/eprint/type/JournalArticle 0029-5515 1741-4326 http://hdl.handle.net/1721.1/84061 Smick, N., B. LaBombard, and I.H. Hutchinson. “Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma.” Nuclear Fusion 53, no. 2 (February 1, 2013): 023001. https://orcid.org/0000-0002-7841-9261 en_US http://dx.doi.org/10.1088/0029-5515/53/2/023001 Nuclear Fusion Creative Commons Attribution-Noncommercial-Share Alike 3.0 http://creativecommons.org/licenses/by-nc-sa/3.0/ application/pdf IOP Publishing Prof. Hutchinson via Chris Sherratt |
| spellingShingle | Smick, N. Labombard, Brian Hutchinson, Ian Horner Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma |
| title | Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma |
| title_full | Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma |
| title_fullStr | Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma |
| title_full_unstemmed | Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma |
| title_short | Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma |
| title_sort | transport and drift driven plasma flow components in the alcator c mod boundary plasma |
| url | http://hdl.handle.net/1721.1/84061 https://orcid.org/0000-0002-7841-9261 |
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