AC Loss Properties of Stacked REBCO Superconducting Tapes

REBCO superconducting tapes have excellent critical current properties even at high temperature and high magnetic field. Many projects for the research and development of superconducting machines and devices with REBCO tapes are in progress worldwide. The important problem to realize them is the ac loss reduction of REBCO superconducting tapes since the most part of thermal load of cryocoolers is the ac loss. The evaluation of the induced ac loss in the windings is also quite important to design the superconducting system, especially the cooling system. In this study, we investigated the applicability of the scaling law to the stacked tapes using the currently fabricated REBCO superconducting tapes. We defined the number of stacked tapes asn, and the temperature asT. The ac loss forB_m\,< \,B_pedecreased with increasingndue to the influence of diamagnetic field, whereas the ac losses forB_m\,> B_peagreed with each other regardless ofn. By definingIcaround zero field at the respective temperature, in the respective number of stacked tapes asIc0(T,\,n),I_c-B normalized by usingIc0(T,\,n). The normalizedI_c-Bcurves coincided with one master curve for everynregardless ofT. The normalized M-H curves and ac loss curves against the field amplitude by usingIc0(T,\,n)also coincided with one master curves for everynregardless ofT. It was verified that the scaling law ofMand ac loss was available even if the REBCO tapes stacked into multilayers.