Combined Rotation Profile and Plasma Stored Energy Control for the DIII-D Tokamak via MPC
W.P. Wehner, J.E. Barton, E. Schuster, M.L. Walker, D.A. Humphreys
American Control Conference
Seattle, WA, USA, May 24-26, 2017
Abstract
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Tokamak plasma rotation is widely recognized for its importance to heat
confinement and plasma stability. In this work we consider control of
the plasma rotation profile with the aim of building a control strategy
suitable for testing various rotation profiles for stability
characteristics and reaching desired operating conditions. To obtain
a control-oriented model of the toroidal rotation profile evolution, a
simplified version of the momentum balance equation is combined with
scenario-specific models for the momentum sources. Various momentum
sources including on-axis and off-axis neutral beam injection and the
non-axisymmetric field coils, which provide rotation damping, allow not
only control of the bulk plasma rotation, but also control of the
profile shape. A feedback controller is designed in a model predictive
control framework to regulate the rotation profile while satisfying
constraints associated with the desired plasma stored energy and beta
(kinetic to magnetic pressure ratio) limits.