急熱急冷・変態法Nb₃Al線材の開発

抄録

Nb₃Al superconducting wires fabricated by the RHQT (rapid-heat, quench, and transformation) process show excellent superconducting properties in high magnetic fields. To prove the uniformity of the Nb₃Al superconducting monolith wire in a longitudinal direction, we made a small solenoid coil by using a Nb₃Al monolith wire 0.5mm in diameter, 137m long, and 169A/mm² in J_c (21T, 4.2K). The quench current of the coil was almost equal to the I_c of a short sample for this coil. As a next step, we tried to develop a Nb₃Al superconducting wire with a large current capacity. We successfully produced a Nb₃Al monolith wire with a diameter of 1.25mm and a Nb-matrix ratio of 0.52, which showed the I_c (21T, 4.2K) of 166A and the J_c (21T, 4.2K) of 207A/mm². We also attempted to make a compacted strand cable as an alternative. The Nb₃Al compacted strand cable showed a large current capacity without degradation, compared with the I_c summation of the original strand wires. These results indicate that the RHQT-processed Nb₃Al superconducting wire has great potential for large-scaled and high-field applications.