R&D on passive stabilization loop at EAST

The passive stabilization loop (PSL) is part of the plasma stabilization system built in the EAST. Its purpose is to provide passive feedback control of the plasma vertical instability on short time scales. To accommodate with the new stage for high performance plasma and enhance the control of vertical stabilization in EAST, the project of PSL has been carried out. The eddy currents are induced by the vertical displacement events (VDEs) and disruption. The distribution of the eddy currents depend on the structure of the PSL and the formation of the induction. The global model is created and meshed by the ANSYS software. Based on the simulation of plasma VDEs and disruption, the distribution and decay curve of the eddy currents on the PSL are obtained. The stress and the strain caused by the eddy currents and the magnetic field are calculated. To decrease the resistance of the joint and enhance anti-corrosion of the joint surface, the silvered craft is used. In the experiment of test model, the resistance is decreased to half after silvered with the same matrix material and under the same preload. The PSL is insulated from the vacuum vessel at the supports of passive stabilizers. The insulation structure is designed and tested with ceramic material. The PSL is designed, fabricated and assembled with the total resistance 150 μΩ. It can supply passive feedback control to the plasma by the eddy currents induced by the VDEs, which could enhance the vertical placement control of plasma.