High field performance tests for Bi-2212 magnets with 30 mm bore

Abstract

Two kinds of compact superconducting magnet with 30 mm inner bore have been fabricated in a wind and react process by using Bi-2212/Ag multifilamentary tapes. One is a double pancake type coil of 78 mm outer diameter and 11 mm height. The other is composed of three double pancake coils of 88 mm outer diameter. As for a reinforcement against large magnetoelectric force, the combination of Ag–Mg alloy tape co-winding and epoxy impregnation is employed in both samples. High field performance of these magnets is examined in backup fields up to 20 T at 4.2 K. The critical current density of double pancake coil at 20 T is 480 A mm −2 and 98 A mm −2 with the criteria of 1×10 −13 Ω m for the oxide part and whole cross-section of the conductor, respectively. The stacked double pancake coil magnet carries 112 A mm −2 with the criterion for conductor and generates 0.95 T in the backup field of 20 T at 4.2 K. The results indicate that the reinforcement is effective against the hoop stress of 120 MPa.