Critical currents in uranium doped Tl-1223 superconductors

Tl-1223 films were doped with small amounts of 235U. Irradiation by thermal neutrons causes fission of uranium into two fission products, which create fission tracks. These defects, which are randomly oriented and homogeneously distributed, significantly improve flux pinning. The superconducting properties of the samples are determined by dc transport measurements in fields up to 6 T at temperatures between 40 and 77 K. Rotation of the sample in the horizontal field of a split-coil magnet allows us also to measure the angular dependence of Jc. Enhancements of the critical current densities and the irreversibility lines as well as a change of the Jc anisotropy are found after irradiation. The results are compared to data on U-doped Bi-2223 tapes.