The numerical analysis of controllability of EAST plasma vertical position by TSC

Vertical position controllability with EAST vertical instability fast control system in current mode is analyzed using Tokamak Simulation Code (TSC). TSC is a non-linear two-dimensional axisymmetric free boundary simulation code. Maxwell's and MHD equations are used to describe the evolution of magnetic field in a rectangular domain for the plasma. In 2016, the model for VDE free drift and control has been benchmarked against experiments. In this paper, the power supply model for fast VDE control is extended to one with limited maximum control current. VDE controllability with the present system capability is studied. The maximum controllable displacement dZ _max is numerically analyzed, for both ordinary experimental discharge and equilibria with typical β _p and l _i in EAST. It is found that dZ _max inversely grows with β _p and l _i . Rigorous conditions of l _i =1, β _p <0.3 or β _p =0.5, l _i <0.8 are required for dZ _max reaching the safe control level. For operation safety, system capability enhancement is needed. Effects of system delay time, the maximum control current and system current ramp time on VDE controllability are discussed.