Critical Current Degradation in High-Temperature Superconducting Tapes Caused by Temperature Rise

In the practical application of high-temperature superconductors (HTSs), HTS tapes are frequently exposed to high temperatures during the soldering or epoxy-impregnation process. There is a variety of epoxy resins; high-temperature curing epoxy resin is particularly suitable for superconducting coils because of its high thermal conductivity and low thermal expansion. When applying HTS tapes to magnets, it is necessary to determine the tolerance of the HTS tapes to heat for selecting the epoxy resin. It is also important to gather data on the characteristic changes in the HTS tapes when they are exposed to heat. In this study, we performed experiments to examine the influence of heating on the
I
-
V
characteristics of commercially available YBCO and Bi-2223 tapes. We chose temperature and heating duration as experimental parameters. The sample tapes were heated in a thermostatic chamber, and thermocouples were attached to sample tapes to monitor the rise in temperature. We measured the
I
-
V
characteristics in liquid nitrogen before and after temperature rise treatment.