Nonlinear control and optimization of the burn condition in tokamak nuclear fusion reactors

The ITER tokamak, the next experimental step in the development of nuclear fusion reactors, will explore the burning plasma regime in which temperature is sustained mostly by fusion heating. Control of the fusion power through modulation of fueling and heating sources, referred to as burn control, will be essential for achieving and maintaining desired operating points and ensuring stability. We utilize a spatially averaged nonlinear transport model to design a multi-variable nonlinear burn control strategy that can reject large perturbations and move between operating points. The controller uses the available actuation techniques in tandem to ensure good performance, even if one or more of the actuators saturate. We propose the use of a model-based optimization scheme to drive the system to a state that minimizes a given cost function. A simulation study shows the performance of the control scheme with a cost function weighting fusion power and temperature tracking errors.