Critical Currents in Neutron Irradiated Bi- and Tl-based Tapes

摘要

Experimental results on the magnetic field behavior, including the angular dependence, or the critical current densities in silver-sheathed tapes are presented. The experiments consist of transport measurements in a wide temperature range and in external magnetic fields up to 6 T. In Bi-2223 enhancements of the transport critical current densities J_c are observed at higher magnetic fields after irradiation with fast neutrons, in particular for H||c. This is attributed to an improvement of the flux pinning capability by (he neutron induced defects, but the weak link structure is somewhat damaged as evidenced by the small degradation of J, at low fields. The angular dependence of Jo demonstrates that the "pinning dominated" angular range is extended from H||c towards H||ab and that the overall anisotropy of Jo decreases. These findings are compared with the behavior of various Tl-1223 tapes prior to and following neutron irradiation.