TSC simulation of vertical position control by the Bang-bang method on EAST

Abstract

Vertical instability is a potentially serious hazard for elongated plasma. Many methods have been proposed to control the plasma vertical position. The Bang-bang method, which is designed for the inside coil (IC) voltage mode based on optimal control theory and the RZIp rigid plasma response model, has been successfully used for plasma vertical position control in the EAST 2014 experimental campaign (Wang et al 2016 Fusion Eng. Des. 112 692–8). The Tokamak Simulation Code (TSC) is a numerical model of tokamak plasma and the associated control systems. It studies the evolution of the magnetic field in a rectangular computational domain using the Maxwell magnetohydrodynamic equations for plasma coupled with the boundary conditions to the circuit equations for the poloidal field coils. In this paper, the numerical model of the Bang-bang method has been implemented in the TSC code, which is used to simulate shot 52444. Simulated trajectories of the vertical position, IC voltage, and current fit the experimental data well. On the basis of benchmarked calculation, a numerical investigation of the Bang-bang controller has been performed using the TSC. This controller was able to work with 8 mm random noise and dz = 41.8 mm displacement. As a predictive tool, the TSC code is used to investigate the the maximum controllable vertical displacement value for different maximum current, and evaluate the ability to control the vertical position by the Bang-bang method.