Quench Analysis of 5.8 T Conduction-Cooled Superconducting Magnet

A 5.8 T conduction-cooled superconducting magnet has been developed in the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP). The magnet has a warm bore diameter of 190 mm. It consists of four concentric closely compacted NbTi coils with an asymmetrical arrangement. A two-stage Gifford-McMahon cryocooler used to cool down the magnet from room temperature to 4.2 K. The magnet operated in the driving model with total energy 0.63 MJ and the temperature margin only 1 K at operating current 114.5 A, the maximum field up to 7.7 T. A quench protection circuit was designed to avoid damage during the quenching process. The protection circuit has adopted coil subdivision method. A 3D thermal, electromagnetic and electrical circuit coupled model was established to simulate the quenching process. The coupled model was solved by commercial finite element method (FEM) program. Using this model, the hot spot temperature of the coils, the variation of the current, and the voltage can be attained. The effect of a different number of coil subdivision on the quenching process has been studied.