Optimization of the Current Ramp-up Phase in DIII-D via Physics-model-based Control of Plasma Safety Factor Profile Dynamics
J.E. Barton, W.P. Wehner, E. Schuster, T.C. Luce, G.L. Jackson, J.R. Ferron, D.A. Humphreys, A.W. Hyatt
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
New Orleans, Lousiana, USA, October 27-31, 2014
Abstract
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Simulations and experimental results in DIII-D are presented to
demonstrate the potential of physics-model-based control of the q
profile to improve the reproducibility of plasma startup conditions by
achieving a specified target q profile at the end of the current
ramp-up. Three different q profiles (qmin of 1.3, 1.65, 2.1 and q95 of
4.4, 5.0, 6.2, respectively) were specified as targets. A feedforward
+ feedback scheme is utilized to control the q profile and is
constructed by embedding a nonlinear, physics-based model of the q
profile dynamics into the control design process. A unique
characteristic of the feedforward trajectories obtained by solving the
optimization problem is the regulation of the plasma current ramp-up
rate to achieve the target q profiles. The feedback controller is
employed to add robustness to the control scheme and account for drifts
due to external plasma disturbances.