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(IC/P-08) Drift Reversal Capability in Helical Systems

M. Yokoyama¹⁾, K. Itoh¹⁾, S. Okamura¹⁾, K. Matsuoka¹⁾, N. Nakajima¹⁾, S.-I. Itoh²⁾, G.H. Neilson³⁾, M.C. Zarnstorff³⁾, G. Rewoldt^3)
 
1) National Institute for Fusion Science, Toki, Japan
²⁾ Research Institute for Applied Mechanics, Kyushu University, Kasuga, Japan
³⁾ Princeton Plasma Physics Laboratory, Princeton, NJ, USA

Abstract.  The drift reversal capability has been investigated in innovative helical systems. The unique external knobs for the drift reversal, residual non-axisymmetry of the magnetic field strength for quasi-axisymmetric configurations and magnetic well for quasi-poloidally symmetric ones, are clarified in addition to the magnetic shear contribution in tokamaks. The external controllability of the drift reversal capability is important to perform the systematic study for the impact of magnetic configuration on turbulent transport. These knobs provide additional approach towards improved confinement in addition to those (eg., heating power beyond some threshold value) utilized in previous experiments. The favorable effect of the drift reversal is anticipated to reduce the average bad curvature, so as to reduce growth rate of instabilities like trapped particle modes and temperature gradient modes.

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