Development of 10 kA Bi2212 conductor for fusion application

Recently, superconducting properties of high Tc superconductors (HTS) have been highly improved and using performance of HTS a conceptual design of a fusion device was performed by Japan Atomic Energy Research Institute (JAERI). HTS has a capability to produce a magnetic field of higher than 16 T, which is required in such a fusion power reactor. Aiming at development of the conductor, a trial fabrication of a 10-kA 12-T conductor was started using round Ag-alloy sheathed Bi-2212 strands, which has best performance at 4.2 K, 16 T at present. The conductor has about 34-mm diameter, and is composed of 729 HTS strands. Operating temperature is designed at not only 4 K but also 20 K. The cable of the conductor is solder-coated on the surface to use specific heat of the lead as much as possible, which at 20 K is almost comparable with specific heat of SHe at 4.5 K, 0.6 MPa. From the tests of the conductor, the fabrication of large HTS conductor and 10 kA operation at 12 T, 18 K ∼ 20 K were successfully performed and the first step of developing work of HTS conductor for fusion application was achieved.