Abstract
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 dZmax is numerically analyzed, for both ordinary experimental discharge and equilibria with typical βp and li in EAST. It is found that dZmax inversely grows with βp and li. Rigorous conditions of li=1, βp<0.3 or βp=0.5, li<0.8 are required for dZmax 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.
Published Version
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