Vanishing neoclassical viscosity and physics of the shear layer in stellarators
arXiv:1206.1025 · doi:10.1103/PhysRevLett.109.135003
Abstract
The drift kinetic equation is solved for low density TJ-II plasmas employing slowly varying, time-dependent profiles. This allows to simulate density ramp-up experiments and describe from first principles the formation and physics of the radial electric field shear layer. The main features of the transition are perfectly captured by the calculation, and good quantitative agreement is also found. The results presented here, that should be valid for other non-quasisymmetric stellarators, provide a fundamental explanation for a wealth of experimental observations connected to the shear layer emergence in TJ-II. The key quantity is the neoclassical viscosity, which is shown to go smoothly to zero when the critical density is approached from below. This makes it possible for turbulence-related phenomena, and particularly zonal flows, to arise in the neighborhood of the transition.
arXiv comment5 pages, 5 figures, accepted for publication in Physical Review Letters
References in corpus (2)
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