2-DIMENSIONAL EFFECTS IN AC LOSSES OF BI2SR2CA2CU3OX TAPES

Two new effects, the existence of the limiting temperature for constan t AC losses with the increase of magnetic field and a node point of mi nimum AC losses, give a clear evidence of predominant two-dimensional nature of dissipation in Bi2Sr2Ca2Cu3Ox tapes. The effects are explain ed in the assumption of exponential suppression of Josephson interacti on in two types of stacks containing two and three well-connected unit -cells. Superconducting layers of isolated unit-cells are intact in ma gnetic field which leads to saturation of the temperature of constant losses at non-zero value. The stacks with more than three unit-cells b ehave in the same way as the ones with three unit cells. Suppression o f Josephson interaction in stacks up to separation of superconducting layers, and the increase of eddy current losses in Ag sheath give the node point of. AC losses in Ag-sheathed tapes near the temperature of Kosterlitz-Thouless transition of single superconducting layer.