Development of Bi-2212 tapes and coils applying the dip-coating process

We have fabricated Bi-2212 pancake coils using Bi-2212/Ag tapes prepared by the combination of the continuous dip-coating and a melt-solidification processes. The coils were tested at various temperatures and bias magnetic fields. A small double stacked pancake coil was inserted in a metallic superconducting magnet, and the coil generated 0.9T in a bias field of 20.9T. Thus the total field of 21.8T was attained in a full superconducting state. This result demonstrates that Bi-2212 is useful as the conductor for an insert magnet in a high field superconducting magnet system. However, the Ic values of the coils were smaller than those of short Bi-2212/Ag tapes in high magnetic fields because large hoop stress introduced mechanical damage in the oxide layer of the conductors. Adding small amounts of alloying elements to silver significantly improved the mechanical properties of the conductors without seriously degrading Ic. Ic in high fields was higher in a coil made with Ag-Mg-Zr alloy alloy tape than in a coil made with pure silver tape.