Quantifying AC Losses in YBCO Coated Conductor Coils

In superconducting coils tapes are often closely packed in a configuration similar to a ldquoz-stackrdquo, which strongly influences the AC losses with respect to when tapes can be considered as separate objects: losses are reduced in the presence of externally applied AC magnetic field, but are increased in the presence of AC transport current. In this paper, we quantify the magnitude of the tape interaction and the AC losses of these two cases, both experimentally and by means of finite-element method simulations. We also discuss the experimental issues arisen with the utilized AC loss measurement technique.