Development and Implementation of Integrated q-profile+beta_N Feedback Control Strategies for Access to Advanced Scenarios in EAST

E. Schuster, H. Wang, Z. Wang, Y. Huang, Z. Luo, B. Xiao, Q. Yuan, D.A. Humphreys, A. W. Hyatt, M.L. Walker, W.P. Wehner

28th IAEA Fusion Energy Conference

Nice, France, October 12-17, 2020 -> May 10-15, 2021 (Remote)

Abstract

Experiments on integrated q-profile and βN closed-loop control have been recently conducted for the first time ever in EAST. In order to achieve advanced modes of oper- ation, characterized by confinement improvement and possible steady-state operation, it is critical to count with robust control capabilities for shaping the spatial profile of the toroidal current density, or equivalently the safety factor q or the gradient of the poloidal magnetic flux, and simultaneously regulating a measure of the plasma internal energy such as βN . Several model-based and non-model-based controllers have been designed with the capability of either regulating several points of the q profile, minimizing the integrated squared error between actual and target profiles, or controlling integral properties such as the internal plasma inductance li, while at the same time regulating βN. To enable the experimental testing of many of these controllers, a general framework for real-time feedforward + feedback control of magnetic and kinetic plasma profiles and scalars has been implemented in the EAST Plasma Control System (PCS). Moreover, critical actua- tors including the ohmic coils, two Lower Hybrid Wave (LHW) sources, and four Neutral Beam Injection (NBI) sources have been placed under the PCS command. The q profile at 11 points and βN have been reconstructed in real-time by pEFIT, an equilibrium re- construction code exploiting the massively parallel processing cores of graphic processing units (GPUs). These initial experiments show successful regulation of the q profile at several points. Further development work, which includes the increase of the number of actuators, the improvement of the quality of the real-time plasma-state reconstruction, and the enhancement of the plasma-response models, is planned to make this control capability a routine enabler of long-pulse, disruption-free, high-performance operation in the EAST tokamak.