Predictive Control of the Rotation Profile using Neutral Beam Injection and Variable 3D Magnetic Fields

W.P. Wehner, M.D. Boyer, D.A. Humphreys, N.C. Logan, E. Schuster

Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)

Fort Lauderdale, FL, USA, October 21-25, 2019

Abstract

Model predictive control (MPC) of the rotation profile using a control-oriented momentum balance model which incorporates empirical models of the NBI and 3D field torques has been developed for DIII-D. Tokamak plasma rotation is widely recognized to significantly affect the energy confinement, plasma stability, and access to high performance operating scenarios. In this work, a generalized control capability for aiding rotation-related physics studies is developed. To obtain a control-oriented model, a simplified version of the momentum balance equation is combined with empirical models of the momentum sources. Recent progress in modeling the torque density profile driven by 3D fields as a function of the non-axisymmetric field coil currents has been embedded into the control design (N.C. Logan EPS 2018). MPC is well suited to a variety of control objectives because it can explicitly incorporate various types of constraints. For example, control of the edge rotation to adjust the ELM suppression threshold while fixing the stabilizing 𝑞=2 rotation. A simulation study is presented to demonstrate the control performance and flexibility of the approach.