Optimization of the Current Ramp-up Phase in DIII-D via Physics-model-based Control of Plasma Safety Factor Profile Dynamics
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
New Orleans, Lousiana, USA, October 27-31, 2014
Abstract |
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.