Conductor Characterization of YBCO Twisted Stacked-Tape Cables

Cable performances of a flat high temperature superconductor (HTS) tape cable fabricated by twisted stacked-tape cable (TSTC) method were experimentally evaluated under various bending diameters at 77 and 4.2 K in self-field. The straight conductor was made with 32 YBCO tapes and twisted using the TSTC method. The 32-tape YBCO TSTC straight conductor was soldered, and then the critical currents were tested at various bending diameters between 1 m and 140 mm. The critical current at a bending diameter of 140 mm was about 6% lower than the straight cable. The same cable with a bending diameter of 250 mm was charged to 10 kA in one second in liquid helium. A new magnet winding technique, stacked-tape twist-wind (STTW), of YBCO tapes using the TSTC concept has been developed, and a 2.3-m, 50-tape YBCO tape coil fabricated with this method was tested. Its critical current was 4.0 kA at 100 μV/m at 19.7 T in liquid helium. It was observed that for an electromagnetic Lorentz force of 50 kN/m the soldered YBCO cable started degrading. A curved saddle coil winding using a STTW technique was demonstrated.