Critical Current Degradation Behavior of SSTC YBCO Tapes Under Uniaxial Strain

Abstract

The REBCO tapes with high irreversible field and large current density, which can be industrially produced, have great potential for future fusion reactor. In the high temperature superconductors (HTS) magnets, REBCO tapes will be subjected to various kinds of strain/stress, the research in the effect of uniaxial strain effect on the performance of REBCO tapes is very necessary. The tensile and compressive axial strains dependence of critical current have been investigated at 77K in self-field with the U-spring devices of YBCO tapes, manufactured by Shanghai Superconducting Technologies Co. (SSTC) in China. Until the compressive strain to -8%, no degradation behavior of critical current could be seen, and the n-value of YBCO tapes hardly depended on compressive strain. The irreversible tensile strain limit was ~0.35%. Before reaching irreversible tensile strain limit, the degradation of I c was slight and reversible. When the applied tensile strain exceeded 0.35%, the I c and n-value reduced rapidly and was not recovered back anymore.