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 (BC
₂
) 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 , θ) 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/γ T, where γ = √m
_c
/m
_ab
is the G-L anisotropy parameter. The values of γ were measured and show that the 3-D-2-D crossover fields in these tapes are at least 130 T.