Speaker
Nikolas Logan
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1037.pdf
Optimizing 3D spectra for rotation control
N.C. Logan1, S.R. Haskey1, B.A. Grierson1, R. Nazikian1, C. Chrystal2, C. Paz-Soldan2
1
Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA
2
General Atomics, PO Box 85608, San Diego, CA 92186, USA
A new matrix formulation utilizing the multi-modal plasma response to optimize multi-coil
spectra for desired neoclassical toroidal viscosity (NTV) torque profiles has been developed in
the Generalized Perturbed Equilibrium Code (GPEC) and applied in experimental
optimization on the DIII-D tokamak. The new GPEC formulation [1] solves the single-fluid
quasi-neutral anisotropic pressure perturbed equilibrium in the first gyro-radius ordering,
representing the nonlinear torque as a function of coil array currents; τ(ψ) = Ic · T(ψ) · Ic. With
this representation in hand, the optimal coil configuration for localized torque between any
two surfaces ψ1 and ψ2 is immediately calculable as the first eigenvector and of Tb-1[T1 - T2],
where Tb is the boundary matrix. A single perturbed equilibrium calculation thus provides the
optimal coil configurations for the maximum, minimum, core localized, and edge localized
NTV torque profiles. Experiments have validated this model in nonresonant field space,
providing accurate predictions of quiescent (having little impact on density and energy
confinement) braking profiles that could be used in rotation control algorithms with little
impact on the particle or energy confinement. Large edge resonant magnetic perturbations,
however, caused large density pumpout not accounted for in the neoclassical model,
significantly distorting the equilibrium from the perturbative model prediction. The impact of
the pumpout is quantified here and used to motivate future work using integrated 3D (GPEC)
and 2D (TRANSP) transport models for full momentum profile evolution predictions. This
experimental application and test of the new GPEC torque matrix predictions represents a
significant step in building successful error field correction models towards new practical
applications for rotation profile control. The torque profile manipulation with the poloidal 3D
field spectrum is a direct application of the multi-mode phenomena [2, 3] for concrete
performance enhancements, and validated predictions provide a path towards reduced rotation
profile control schemes for the optimization of tokamak stability and performance.
This work is supported by US DOE contracts DE-AC02-09CH11466 & DE-FC02-04ER54698.
[1] J.-K. Park and N.C. Logan, Physics of Plasmas 24, 32505 (2017).
[2] C. Paz-Soldan, et al., Physical Review Letters 114, 105001 (2015).
[3] N.C. Logan, C. Paz-Soldan, J. Park, and R. Nazikian, Physics of Plasmas 23, 56110 (2016).
