Detection Method for a Local Normal-State Transition in a No-Insulation REBCO Pancake Coil

In this paper, we have proposed a detection method for detecting and locating a local normal-state transition in a meter-class no-insulation (NI) coil that is deployed in next-generation high-field magnetic resonance imaging scanners (MRIs), using a copper pickup coil. There are two schemes for detecting and locating the normal zone: one is a ring pickup coil assembled on the midplane of a central bore and the other consists of several sector pickup coils deployed on the coil winding, namely "scanning pickup coil." To verify the effectiveness of these detection methods, we performed a numerical simulation coupling consisting of a partial element equivalent circuit, a thermal analysis, and a magnetic field analysis. Based on the results of analyses, we reproduced the distributions of the temporal variations of the magnetic flux in the central bore and on the coil winding of the meter-class NI coil, and discussed the effectiveness of these pickup coil schemes for detecting and locating a local normal-state transition in a meter-class NI coil used in next-generation high-field MRIs.