Predictive control of the tokamak q profile to facilitate reproducibility of high-qmin steady-state scenarios at DIII-D

We consider control of the q profile while simultaneously regulating the plasma stored energy for the DIII-D tokamak. The main objective is to improve the shot-to-shot reproducibility and facilitate the accessibility of operating conditions that have steady-state potential, i.e. plasmas with large non-inductive current drive fractions. At DIII-D, non-inductive current sources including electron cyclotron current drive (ECCD) and neutral beam injection (NBI) allow the possibility of shaping the plasma current density distribution, and therefore enabling control of the q profile. A feedback controller is designed in a model predictive control framework to regulate the q profile while simultaneously regulating the plasma stored energy. The effectiveness of the control approach is demonstrated with experiments.