A novel real-time feedback compensation system associated with inductive voltage generated by plasma in the EAST PF coil quench detection system

Abstract

Abstract A fast plasma current change can reach up to several or even more than a dozen mega-amperes per second creating a significant voltage signal in the Experimental Advanced Superconducting Tokamak (EAST) Poloidal Field (PF) Quench Detection (QD) circuit. Although co-wound coil has been employed as primary compensation for detecting a signal, its residual noise would still be much greater than the target resistance detection value (about 0.5\u2009V), which calls for secondary noise cancellation to obtain the desired signal-to-noise ratio. Presently, the secondary compensation system uses weighting coefficients to offset the inductive voltage in the quench signal, including plasma-induced perturbations. Unlike the relatively fixed mutual inductance coupling with two PF coils, the one for plasma is time-varying owing to the plasma current’s ever-changing shape and distribution during plasma discharge. A novel Plasma Real-time Feedback Compensation System (PRFCS), designed to cancel the voltage induced by the plasma in PF detecting circuit, was implemented on the EAST. Recent experimental results showed that the PRFCS provided good compensation against fast plasma current changes. Even major disruptions and edge-localized modes did not generate a subsequent false discharge of the PF coils. This paper introduces the basic principle, system setup and test results of the preliminary analysis.