Robust Control of the Spatial Current Profile in the DIII-D Tokamak

Advanced tokamak operating scenarios, characterized by large noninductively driven plasma currents, typically require active regulation of a specific current density profile. Non-model-based control of the $q$ profile has been tested at DIII-D. However, some present limitations of the controller motivate the design of a model-based controller that accounts for the dynamics of the whole $q$ profile in response to the control actuators. A control-oriented model of the current profile evolution in DIII-D was recently developed and used to design feedforward control schemes. In order to reject the effects of external disturbances to the system, a feedback control input needs to be added to the feedforward input. In this work, we report on the design of a robust feedback controller, on the implementation of the combined model-based feedforward + feedback controller in the DIII-D Plasma Control System, and on the experimental validation of the combined controller in the DIII-D tokamak.