A Study on Joint Resistance between Nb-Ti Superconducting Wires for MRI Magnet

The joints between the superconducting wires are inevitably needed from the requirement of a high magnetic stability with respect to time in the superconducting MRI magnet. In this study, a new superconducting joint using Cu/Nb-Ti sleeve has been tried on the MR1 type Nb-Ti superconducting wires. The transformer induction type apparatus was made and applied to measure the joint resistance. A very low joint resistance of 10^(-15) Ω could be successfully obtained from this joint method. It was confirmed that the initial rapid current decay occurs before the very stable current decay due to only superconducting joint. Some unstable part in the joint like exposed filaments causes the initial induced current to lower and influence on the increase of the joint resistance.