Tokamak parameter regimes with low toroidal momentum diffusivity

McMillan, B. F.; Dominski, J.

doi:10.1017/S0022377819000333

Tokamak parameter regimes with low toroidal momentum diffusivity

Journal Article · Mon May 20 00:00:00 EDT 2019 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/S0022377819000333· OSTI ID:1558751

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Univ. of Warwick, Coventry (United Kingdom)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

The strong, sharp flow structures that are seen frequently in tokamak cores, and large amplitude spontaneous global toroidal rotation are both surprising in light of current theories where toroidal flow evolution is dominantly diffusive. Mechanisms for spontaneously generating strong poloidal shear flows have been extensively investigated, but these processes were thought not to apply to toroidal flows. We confirm, however, that there is a regime with near-zero toroidal momentum diffusivity, where toroidal flow structures are spontaneously generated, as shown in earlier global gyrokinetic simulations. This allows strong rotation with negligible applied external torque, and the regime where this occurs is also favourable for strong turbulence stabilisation by rotation. In conclusion, the transition to low momentum diffusivity occurs for tight aspect ratio, low safety factor and at low levels of heat flux, in agreement with a simple zero-dimensional model for the flow–turbulence interaction.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: Partially supported by EPSRC grants EP/N035178/1 and EP/R034737/1

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1558751

Journal Information:: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 3 Vol. 85; ISSN 0022-3778

Publisher:: Cambridge University PressCopyright Statement

Country of Publication:: United States

Language:: English

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