Control of the Current Profile Evolution During the Ramp-Up Phase at DIII-D

Setting up a suitable current profile has been demonstrated to be a key condition for advanced scenarios with improved confinement and possible steady-state operation. Experiments at DIII-D focus on creating the desired $q$ profile during the plasma current ramp-up and early flattop phases with the aim of maintaining this profile during the subsequent phases of the discharge. Active feedback control of the $q$ profile evolution at DIII-D has already been demonstrated [1], and an open-loop control scheme has been proposed [2] based on a simplified control-oriented dynamic model [3]. The use of Corsica for both control testing and design is reported, and results of open-loop current profile control experiments are presented.\par \vskip6pt \noindent [1] J.R.\ Ferron, et al., Nucl.\ Fusion {\bf 46} (2006) L13.\hfil\break [2] Y.~Ou, et al., {\em Proc. Am. Control Conf.}, New York (2007).\hfil\break [3] Y.~Ou, et al., Fusion Eng.\ \& Design {\bf 82} (2007) 1153.