Transport current loss and Ic degradation of HTS tapes under mechanical load

Performance of an HTS (high temperature superconductor) tape is evaluated by measuring the critical current I_c, AC loss and mechanical properties of the short samples. However, in coils or magnets for applications, the HTS tapes are under mechanical load caused by winding tension, bending and sometimes twisting. Also thermal contraction by the cooling changes the tension. The mechanical load reduces the critical current of the superconducting wire, and the I_c degradation affects the AC loss of the wire. We measured the I_c degradations and AC losses (transport current loss) of commercial Bi-2223 tapes processed by a PIT (powder in tube) method under tension. The I_c and AC loss measurements are done in the same time with the same voltage taps on the tape conductors. The measurement results and discussions on the relationship between I_c degradation and AC loss are presented.