Journal
PLASMA PHYSICS AND CONTROLLED FUSION
Volume 56, Issue 9, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0741-3335/56/9/095014
Keywords
tokamaks; gyrokinetics; intrinsic rotation; up-down asymmetry
Categories
Funding
- US DoE [DE-SC008435]
- RCUK Energy Programme [EP/I501045]
- European Union's Horizon research and innovation programme
- EURATOM within the framework of the European Fusion Development Agreement
- Fundacao para a Ciencia e Tecnologia [Pest-OE/SADG/LA0010/2011]
- NFL [IF/00530/2013, PTDC/FIS/118187/2010]
- Office of Science of the US Department of Energy [DE-AC02-05CH11231]
- Helios supercomputer at IFERC-CSC under project GKMSC
- Engineering and Physical Sciences Research Council [EP/G049718/1] Funding Source: researchfish
- EPSRC [EP/G049718/1] Funding Source: UKRI
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Recent work has 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 the experiment in magnitude, suggest that a toroidal velocity gradient, (partial derivative u(zeta i)/partial derivative rho)/nu(thi), of 5% of the temperature gradient, (partial derivative T-i/partial derivative rho)/T-i, is sustainable. Here nu(thi) 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. Though other known core intrinsic momentum transport mechanisms scale poorly to larger machines, these results indicate that up-down asymmetry may be a feasible method to generate the current experimentally measured rotation levels in reactor-sized devices.
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