Stability of supercurrents in a BiSrCaCuO (Bi-2212) high-Tc superconductor with artificially created defects

Recent results in a systematic study of the stability of supercurrents in Bi-2212 tapes with randomly oriented, highly splayed columnar defects are presented as a function of defect density. The defects were artificially created by fission fragments of bismuth nuclei, fissioned by irradiation with energetic protons (similar to 0.8 GeV). Significant enhancements in the persistent current density J(p) are observed at all temperatures and fields. Also, a marked shift of the irreversibility line towards higher fields and temperatures improves considerably the capacity of the material for practical applications. Moreover, a significant decrease in the logarithmic decay rate S = dln(J(p))/dln(t) indicates a strong stabilization of the persistent currents. All features point to high effectiveness of this artificial pinning mechanism. However, the optimal proton fluence needs yet to be established. (C) 1998 Academic Press Limited.