Optimal Shaping of the Safety Factor Profile in the EAST Tokamak

Tokamaks, which are one of the most promising approaches to energy generation from nuclear fusion, are toroidal devices confining a very hot ionized gas, i.e. plasma, where the nuclear reactions take place. Studies have shown that the shape of the safety-factor profile, which is related to the helical pitch of the magnetic fields used for plasma confinement, is a key factor towards achieving advanced operating conditions characterized by improved confinement, magnetohydrodynamic stability, and possible steady-state operation. In this work, a first-principles-driven, control-oriented model of the safety-factor profile evolution has been used to design linear-quadratic-integral (LQI) controllers for q-profile shaping in combination, in some cases, with plasma-energy regulation. Results based on nonlinear simulations are presented together with some initial experimental results from the EAST tokamak. A general framework for real-time control of both magnetic and kinetic plasma profiles and scalars has been implemented in the EAST Plasma Control System (PCS), enabling in this way the experimental testing of the proposed controllers. These experiments are among the first experiments on safety-factor profile control ever conducted on the EAST tokamak.