Nonlinear Adaptive Control of Deuterium-Tritium Density Ratio in ITER

Active regulation of the deuterium-tritium (DT) density ratio in ITER plasmas is critical for achieving the desired burning plasma scenario and fusion power. A key challenge in designing density ratio controllers is the lack of real-time measurements of critical plasma parameters, such as particle confinement time, and the presence of nonlinear uncertainties in the model. Recently, linear adaptive control techniques have been proposed as an effective solution to handle uncertainties in the particle confinement time. These techniques are designed to update controller gains based on real-time diagnostic measurements to compensate for parameter uncertainties. In this work, an adaptive controller specifically designed to handle nonlinear uncertainties in the model is proposed. In reactor-grade tokamaks like ITER, nonlinear effects, such as contributions from the DT reaction rate, play a critical role in density evolution. To handle uncertainties in these terms, the proposed adaptive controller updates the control law based on real-time diagnostic measurements. The effectiveness of the proposed controller is demonstrated through nonlinear closed-loop simulations.