Dependences of AC Loss in Stacked REBa₂Cu₃O_y Superconducting Tapes on the Interval among Tapes under Perpendicular Magnetic Field

In this study, we focused on the dependence of the AC loss in REBa₂Cu₃O_y (REBCO, RE = rare earth, Y, Eu, Gd) superconducting tapes stacked perpendicular to the tape face on the interval between the superconducting layers. The AC loss of the 2-layer stacked tapes with various interval in perpendicular field was investigated by pickup-coil method. The AC loss for external applied magnetic field, B _m, below the penetration field, B _p, increases with increasing the interval. In the case that the ratio of the distance between the neighboring superconducting layer, D, to the width of the tape, w, (D/w) is smaller than 0.1, the AC loss of 2-layer tapes decreased to 1/2 of that of 1-layer tape. On the other hand, in the case of D/w being larger than 0.1, the AC loss of 2-layer tapes was larger than 1/2 and it approached the AC loss of 1-layer tape with increasing D/w. From the result obtained in this study, it is predicted that, for B _m below B _p, the AC loss of stacked REBCO tapes with large D/w, such as multifilamentary tapes, is larger than the AC loss of stacked non-scribed REBCO tapes. However, for B _m above B _p: a large AC loss region, it is known that the AC loss of the multifilamentary tapes decreases compared with that of non-scribed tapes. Next step, AC loss of the multifilamentary tapes for B _m below B _p will be investigated experimentally and theoretically. (paper)