Attempts to enhance a current capacity by a RHQ operation of Nb/Al rectangular strand

We tried to enlarge a Nb/Al strand dimension to enhance a current capacity of RHQT- Nb₃Al further. So far good fsRHQ operation could be made by using the strand dimension of less than φ 1.35 mm. This time we tried to make RHQ operation by using a Nb/Al rectangular strand of 1.45 × 2.2 mm ² which is double cross-section area of φ 1.35 mm. Bcc phases could be formed even in the large cross-section rectangular strand by RHQ operation. The samples were post-annealed at 800°C for transforming into A15. The resultant I_c and core J_c were 232.5 A and 130 A/mm ² at 4.2 K, 22 T, respectively. These values largely surpassed I_c of 57.5 A and J_c of 72.7 A/mm ² at 4.2 K, 22 T for the sample which was made by using a conventional φ 1.35 mm strand.