HTS Twisted Stacked-Tape Cable Development

Key issues for a twisted stacked-tape cabling concept have been investigated. The issues include: a) tape twisting performance; b) twisted-cable bending performance; c) development of a feasible manufacturing method; and d) YBCO cable termination method. A fabrication method for a twisted stacked tape conductor of 4 mm YBCO tapes has been developed and tested. A 2 m long, 32-YBCO-tape conductor with a 200 mm twist pitch was fabricated. The measured critical current of the straight cable was 1.53 kA which agrees with the expected values estimated from the self-field. The same cable wound on a surface of a 0.5 m diameter disk did not show any degradations. It has been confirmed through tests with single tape and cable tests that it is possible to develop a HTS stacked cable with a 200 mm twist pitch. This cable could be used to make a coil with an innermost turn of at least 0.5 m diameter. A joint method for a multi-tape YBCO cable has been developed and operated at 2.2 kA. The twisted stacked-tape cabling method for YBCO tapes will be very useful for high-current high-field magnets for various applications.