Operation of Superconductively Jointed Bi-2212 Solenoidal Coil in Persistent Current Mode

Abstract

A Bi₂Sr₂Ca₁Cu₂O_x (Bi-2212) superconducting solenoidal coil with a persistent current switch (PCS) has been newly designed and fabricated employing an Ag-sheathed Bi-2212 rectangular wire. It is the first superconductively jointed oxide superconducting coil. The operation behavior of the solenoidal coil at 4.2K has been evaluated with the PCS in off and on states. When the PCS was off, the solenoidal coil worked well, generating magnetic fields over 95% of the designed value. After the PCS was turned on, a magnetic field of about 0.01T was continuously generated for 100h and then the PCS was turned off. The residual resistance of the entire circuit is estimated to be below 1.6×10^-11Ω from the relaxation rate of the magnetic field generated during the last 1, 900min (=31.7h) of operation. This resistance value reaches the practical level of commercial metallic superconducting magnets for magnetic resonance spectroscopy operated in the persistent current mode. This study has proved that practical use of the Bi-2212 solenoidal coil for persistent current mode operation is feasible.