Performance Test of Superconducting Switch for NMR Magnet

A superconducting switch with an off-state resistance of 10 Ω, operating current of about 67 A, for a NMR magnet in persistent current operation to obtain higher field stability is designed and manufactured. The superconducting switch is solenoid type which consists of four parts: bobbin, superconductor, heater and adiabatic part. And NbTi/CuNi superconducting wire with higher resistance is used and wound on the switch bobbin in a bifilar manner for low inductance and minimum field perturbation. Numerical simulations by FEM method for the switching performance of temperature distribution during heating and cooling cycles are performed. Finally the switching performance tests were carried out and the results show that the minimum heating power is about 0.69 W and the off-time is less than 10 s.