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Author(s):
M. Yokoyama, N. Nakajima and M. Okamoto
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Title:
Nonlinear Incompressible Poloidal Viscosity in L=2 Heliotron and Quasi-Symmetric Stellarators
Date of publication:
Nov. 1997
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Key words:
nonlinear incompressible poloidal viscosity, L = 2 heliotron, quasi-symmetric stellarators, Boozer coordinates, Hamada coordinates, helicity induced local maximum (HM), toroidicity induced local maximum (TM)
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Abstract:
The possibility of occurence of the L-H transition is examined in L = 2 heliotron and quasi-symmetric (QS) stellarators based on the nonlinear incompressible poloidal viscosity for the plateau to Pfirsch-Schluter regime. Fourier spectra of the magnetic field strength |B| in the Hamada coordinates are employed for the calculation. The appearance of the local maxima of poloidal viscosity as a function of poloidal flow velocity greatly depend on the relative amplitudes between the toroidicity and helicities in the magnetic field. Effects of magnetic configuration control such as the inward magnetic axis shift and quadrupole field control on the poloidal viscosity are investigated in the Large Helical Device (LHD)-1ike L = 2 heliotron. Finite beta effects are also briefly studied based on the fixed boundary magnetohydrodynamic (MHD) equilibria. Due to the well suppressed non-symmetric magnetic spectra in the Boozer coordinates for QS configurations, QS properties are well maintained even in the Hamada coordinates. Therefore, the single clear local maximum can be obtained for QS configurations.
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