Quench Protection Method of HTS and LTS Hybrid Magnet Systems

Abstract

Development of a 1 GHz-class NMR magnet system is going on at the Tsukuba Magnet Laboratory of the National Research Institute for Metals. This magnet will consist of the inner HTS coil and the outer LTS magnet, it is designed to generate a magnetic field of 23. 5 T. We are planning to operate the inner HTS coil and the outer LTS magnet in series in order to obtain high stability of the central magnetic field. To achieve the stability of 0. 01 ppm/h, the critical current of the inner HTS coil must be four times as high as the operating current. Simulation results of usual quench protection methods suggest that there is some possibility that the inner HTS coil is damaged when a quench occurs in the outer LTS magnet.
We designed a new quench protection circuit for the 1 GHz-class NMR magnet and confirmed its adequacy using quench simulation codes. Our new method is valid for any HTS-LTS hybrid magnet.