A diagnosis method for properties of superconducting magnet using fast current discharge

The authors studied a diagnosis method to investigate the properties of superconducting magnets throughout their life. The magnet current, initially held constant, is damped with a short time constant. One can evaluate the properties of the magnet using the normal voltage, which may appear during the damping phase. A bridge circuit, which can adjust both amplitude and phase with over five orders of accuracy, was developed to measure unbalance voltages. Experiments were carried out using a small solenoidal NbTi magnet. By adjusting bridge parameters and numerically processing the voltage waveform, the authors measured the normal transition voltage with the S/N ratio of over 10^-4 in the damping phase. The applicability of the diagnosis method was studied in both numerical simulations and experiments