Nonlinear Infinite-dimensional Regulation of the Safety Factor Profile in Tokamaks with Moving Electron Cyclotron Drives

S.T. Paruchuri, E. Schuster

SIAM Conference on Control and Its Applications

Philadelphia, PA, USA, July 24-26, 2023

Tokamaks are torus-shaped devices designed to confine hot-ionized gas (commonly referred to as plasma) using strong magnetic fields. The net magnetic field in the tokamaks must be helical to ensure that the charged particles in the plasma remain within the tokamak’s toroidal volume. The pitch of this helical magnetic field is characterized by a plasma property called the safety factor profile. Magnetohydrodynamic studies have shown that maintaining the safety factor profile at the desired level is critical to the stability of the plasma. Conventional controllers designed to maintain the safety factor profile at the desired levels rely on approximating the plasma dynamics. A distributed controller eliminates the need for such finite-dimensional approximation of the safety factor dynamics. However, the infinite-dimensional control law must be translated into physical actuator variables such as the current drive powers and electron-cyclotron deposition locations for practical implementation. This work proposes a nonlinear distributed controller and discusses the steps involved in computing the above-mentioned physical actuator variables from the infinite-dimensional control law. The effectiveness of the controller in a DIII-D tokamak scenario is demonstrated through nonlinear simulations.

*Supported by the US DOE (DE-SC0010537 and DE-SC0010661).