Combined Current Profile and beta_N Control to Facilitate Accessibility and Reproducibility Testing of High-qmin Steady-State Scenarios

W.P. Wehner, J.E. Barton, M.E. Lauret, E. Schuster, C.T. Holcomb, B. Victor, J.R. Ferron, T.C. Luce, R. La Haye, F. Turco and W. Solomon

Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)

Savannah, GA, USA, November 16-20, 2015

Abstract

The capability of combined current profile and βN control to enable access and repeatability of steady-state scenarios for high qmin > 1.5 discharges is studied in both nonlinear simulations and experiments. The presentation focuses on model-predicted q-profile+βN control, which numerically solves successive optimal control problems over a receding time horizon by exploiting efficiently solvable quadratic programming techniques. One of the key advantages of this control approach is that it allows for explicit incorpo- ration of state/input constraints to prevent the controller from driving the plasma outside of stability/performance limits and obtain, as closely as possible, steady state conditions in the q profile. To characterize the q profile+βN response, empiri- cal correlations are combined with first-principles laws to arrive at a control-oriented model, which captures the dominant physics that is necessary for model-based optimal control design.