Improvement of superconducting properties of Bi-2212 round wire and primary test results of large capacity Rutherford cable

We have developed HTS cables using Bi-2212 round wires, which have high mechanical strength and an average J_c of 200 kA/cm² at 4.2 K in self-field. Four designs of cables were fabricated in this work and those tables could carry I_c values from 1 kA to 10 kA at 4.2 K and self-field depending on the number of strands. A 70m-long 20-strand Rutherford cable was successfully manufactured. Optimization of heat treatment conditions was effective to reduce I_c degradation observed in the case of heat treatment with a long length. I_c values of a Rutherford cable were measured under loading at 4.2 K in 4 T. The critical values of the stress on face loading and edge loading were 60 MPa and 100 MPa, respectively. We successfully obtained high J_c value of 500 kA/cm², which was almost double that of the conventional wires capitalize “Rutherford”