Fabrication of Bi-2212-Ag composite solenoid type superconducting magnet by partial melt process under high PO2

Partial melt process under high oxygen partial pressure (PO2) has been attempted to obtain a well-aligned structure in Bi-2212-Ag composite tapes. Critical current density (Jc) of Bi-2212-Ag composite tapes increased from 4.5 x 104 to 2.2 x 105 A/cm2 at 4.2 K in zero magnetic field with increasing PO2 from 0.1 to 1.0 bar. This process was also effective to improve Jc of round and rectangular conductors. These results were explained by the idea that crystallization of the Bi-2212 system started at the interface between the liquid phase and the oxygen-rich gaseous phase. Jc of the round and rectangular conductors in short length reached 7.8 x 103 and 1.4 x 104 A/cm2 in 21 T at 4.2 K, respectively. Fabrication of a solenoid type magnet has been attempted using a rectangular conductor under PO2=2.4 bar. Jc of this solenoid type magnet reached 4.2 x 104 A/cm2 under generating a self-magnetic field of 0.89 T at 4.2 K. (orig.)