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

摘要

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 x 10(-13) Omega 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. (C) 1998 Elsevier Science Ltd. All rights reserved. [References: 20]