3-D Properties in (RE) BCO Tapes Measured in Fields up to 35T

We have measured the temperature and angular dependence of the upper critical field (B-C2) for three state of the art (RE)BCO HTS tapes using variable-temperature ac susceptibility measurements in applied fields up to 35 T. The three tapes measured were a Fujikura tape without artificial pinning centers and Superpower tapes with and without artificial pinning centers. We have obtained fits to our B-C2(T, theta) data using both the anisotropic Ginzburg-Landau (G-L) and Klemm's models for layered superconductors. Our calculations suggest that these tapes are three-dimensional (3-D) at all temperatures in zero field but become 2-D in magnetic fields above a crossover field of 457/gamma T, where gamma = root m(c)/m(ab) is the G-L anisotropy parameter. The values of gamma were measured and show that the 3-D-2-D crossover fields in these tapes are at least 130 T.