Study of Joint Resistance in ${\hbox{Nb}}_{3}{\hbox{Al-NbTi}}$ Superconducting Joint for High Field NMR

We have developed a novel superconducting joint method for Nb
₃
Al conductors, which can be used for the innermost coil of a 1-GHz NMR magnet. First, we optimized the joint property; then, we prepared a closed circuit with an NbTi coil and a pair of Nb
₃
Al-NbTi joints; finally, we determined the joint resistance by using the field decay of the persistent current. A joint resistance of 1.27 times 10
^-12
Omega was obtained, which is sufficiently low for high field NMR.