Simultaneous Regulation of the Electron Temperature and Safety Factor Profiles for DIII-D using Optimal Control Methods*

A controller has been designed to simultaneously regulate the electron temperature (T_e) and safety factor (q) profiles on DIII-D.  Future scenario development efforts will require the capability to control both kinetic and magnetic profiles to achieve high performance plasmas while maintaining MHD stability. Optimal control solutions for the regulation of the Te and q profiles individually has been demonstrated for DIII-D [1, 2]; the controller presented here aims to extend these results by controlling both profiles at the same time. The controller is synthesized based on the linearized electron heat transport and magnetic diffusion equations.  Using this model, the Linear Quadratic Integral (LQI) controller is designed to minimize the integrated error between the actual and target profiles.  The controller has been tested in nonlinear simulations using the Control Oriented Transport Simulator (COTSIM).  Predictive simulation results demonstrate the effectiveness of this controller in regulating both the electron temperature and safety factor profiles simultaneously by using the available heating and current drive sources.

[1] S. Morosohk et al., APS Division of Plasma Physics, Spokane, WA, 2022.

[2] W. Wehner et al., Fusion Engineering and Design, vol. 123, pp. 513-517, 2017.