Authors: J-K. Park and N.C. Logan

Abstract: Toroidal torque is one of the most important consequences of non-axisymmetric fields in tokamaks.The well-known neoclassical toroidal viscosity (NTV) is the second-order toroidal force by the anisotropic pressure tensor in the presence of these asymmetries. This work shows that first-order force originating from the same anisotropic pressure tensor, despite having no flux surface average, can significantly modify the local perturbed force balance and thus must be included in perturbed equilibrium self-consistent with NTV. The force operator with an anisotropic pressure tensor is not self-adjoint when the second-order torque is finite, and thus is solved directly for each component. This approach yields a modified, non-self-adjoint Euler-Lagrange equation, that can be solved using a variety of common drift-kinetic models in generalized tokamak geometry. The resulting energy and torque integral provides a unique way to construct a torque response matrix, which contains all the information of self-consistent NTV torque profiles obtainable by applying non-axisymmetric fields to the plasma. This torque response matrix can then be used to systematically optimize non-axisymmetric field distributions for desired NTV profiles.

Submitted to: Physics of Plasmas
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Download PPPL-5358  1.4 MB (37 pp)
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