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Spontaneous tokamak rotation: observations turbulent momentum transport has to explain

Date: 
Thursday 22nd July 2010 - 09:45 to 10:30
Venue: 
INI Seminar Room 1
Session Title: 
Momentum transport rotation, ITBs - Tokamaks
Abstract: 
Ideal tokamaks have axisymmetric magnetic fields that, by symmetry, cannot impart toroidal angular momentum. Yet, even without obvious external sources of momentum, such as neutral-beams, they rotate at speeds up to a substantial fraction of the ion thermal speed. This spontaneous rotation is an unequivocal signature of momentum transport (presumably turbulent) *up* the velocity gradient --- that is, in the opposite direction to any supposed shear viscosity. Theoretical suggestions for the mechanisms producing spontaneous rotation exist; but even qualitative confrontation of theory with experiment is at a rudimentary stage. This presentation will summarize some key experimental observations that require explanation. Understanding the spontaneous rotation is vital for future devices like ITER, where beam-driven rotation will be small, and might be relevant also in the space and astrophysical context.
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Presentation Material: 
University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons