Analysis of Damage by Quench and Improvements in Rewinding for a 9.4-T Superconducting NMR Magnet

A NbTi/Cu superconducting magnet for a nuclear magnetic resonance spectrometer has been developed in our laboratory. The magnet reached the designed magnetic field of 9.4 T after several trainings in a test Dewar. However, after the magnet was installed in the final Dewar, the charge of the magnet failed after two trainings. After the magnet was dissembled and two coils were unwound, it is found that local winding close to the former flange is burnt and melted. It is also found that insulating coating on the flange near the burnt area had been damaged. Quench simulation is performed, and the simulation results are analyzed. The two coils are rewound, and some measures are taken to improve the insulation and lower the coil voltages during quench. The magnet is reramped in the final Dewar, and the operating current is reached after five trainings.