Intrinsic momentum transport in up-down asymmetric tokamaks
Recent work demonstrated that breaking the up-down symmetry of tokamak flux surfaces removes a constraint that limits intrinsic momentum transport, and hence toroidal rotation, to be small. We show, through MHD analysis, that ellipticity is most effective at introducing up-down asymmetry throughout...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
Institute of Physics Publishing
2014
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| _version_ | 1826258740565770240 |
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| author | Ball, J Parra, F Barnes, M Dorland, W Hammett, G Rodrigues, P Loureiro, N |
| author_facet | Ball, J Parra, F Barnes, M Dorland, W Hammett, G Rodrigues, P Loureiro, N |
| author_sort | Ball, J |
| collection | OXFORD |
| description | Recent work demonstrated that breaking the up-down symmetry of tokamak flux surfaces removes a constraint that limits intrinsic momentum transport, and hence toroidal rotation, to be small. We show, through MHD analysis, that ellipticity is most effective at introducing up-down asymmetry throughout the plasma. We detail an extension to GS2, a local $\delta f$ gyrokinetic code that self-consistently calculates momentum transport, to permit up-down asymmetric configurations. Tokamaks with tilted elliptical poloidal cross-sections were simulated to determine nonlinear momentum transport. The results, which are consistent with experiment in magnitude, suggest that a toroidal velocity gradient, $(\partial u_{\zeta i} / \partial \rho) / v_{th i}$, of 5% of the temperature gradient, $(\partial T_{i} / \partial \rho) / T_{i}$, is sustainable. Here $v_{th i}$ is the ion thermal speed, $u_{\zeta i}$ is the ion toroidal mean flow, $\rho$ is the minor radial coordinate normalized to the tokamak minor radius, and $T_{i}$ is the ion temperature. Since other intrinsic momentum transport mechanisms scale poorly to larger machines, these results indicate that up-down asymmetry is the most feasible method to generate the current experimentally-measured rotation levels in reactor-sized devices. |
| first_indexed | 2024-03-06T18:38:45Z |
| format | Journal article |
| id | oxford-uuid:0c2dd014-30c5-409b-a080-1e11693d5053 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T18:38:45Z |
| publishDate | 2014 |
| publisher | Institute of Physics Publishing |
| record_format | dspace |
| spelling | oxford-uuid:0c2dd014-30c5-409b-a080-1e11693d50532022-03-26T09:33:32ZIntrinsic momentum transport in up-down asymmetric tokamaksJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:0c2dd014-30c5-409b-a080-1e11693d5053EnglishSymplectic Elements at OxfordInstitute of Physics Publishing2014Ball, JParra, FBarnes, MDorland, WHammett, GRodrigues, PLoureiro, NRecent work demonstrated that breaking the up-down symmetry of tokamak flux surfaces removes a constraint that limits intrinsic momentum transport, and hence toroidal rotation, to be small. We show, through MHD analysis, that ellipticity is most effective at introducing up-down asymmetry throughout the plasma. We detail an extension to GS2, a local $\delta f$ gyrokinetic code that self-consistently calculates momentum transport, to permit up-down asymmetric configurations. Tokamaks with tilted elliptical poloidal cross-sections were simulated to determine nonlinear momentum transport. The results, which are consistent with experiment in magnitude, suggest that a toroidal velocity gradient, $(\partial u_{\zeta i} / \partial \rho) / v_{th i}$, of 5% of the temperature gradient, $(\partial T_{i} / \partial \rho) / T_{i}$, is sustainable. Here $v_{th i}$ is the ion thermal speed, $u_{\zeta i}$ is the ion toroidal mean flow, $\rho$ is the minor radial coordinate normalized to the tokamak minor radius, and $T_{i}$ is the ion temperature. Since other intrinsic momentum transport mechanisms scale poorly to larger machines, these results indicate that up-down asymmetry is the most feasible method to generate the current experimentally-measured rotation levels in reactor-sized devices. |
| spellingShingle | Ball, J Parra, F Barnes, M Dorland, W Hammett, G Rodrigues, P Loureiro, N Intrinsic momentum transport in up-down asymmetric tokamaks |
| title | Intrinsic momentum transport in up-down asymmetric tokamaks |
| title_full | Intrinsic momentum transport in up-down asymmetric tokamaks |
| title_fullStr | Intrinsic momentum transport in up-down asymmetric tokamaks |
| title_full_unstemmed | Intrinsic momentum transport in up-down asymmetric tokamaks |
| title_short | Intrinsic momentum transport in up-down asymmetric tokamaks |
| title_sort | intrinsic momentum transport in up down asymmetric tokamaks |
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