Current-density enhancements of the highest-T_c superconductors with GeV protons

In several Tl- and Hg-based high-Tc. superconducting materials, vortex-pinning defects were formed by irradiation with 0.8 GeV protons. The protons cause heavy constituent nuclei (Tl, Hg, Bi, ...) to fission, which generates randomly oriented tracks. These columnar defects lead to significant enhancements in the current-conducting properties. We investigated bulk materials and thin films, irradiated with or without Pb or Au "amplifier foil" overlayers, which increase the number of column-creating fission fragments. © 1997 American Institute of Physics.