Vortex pinning in high-Tc materials via randomly oriented columnar defects, created by GeV proton-induced fission fragments

Extensive work has shown that irradiation with 0.8 GeV protons can produce randomly oriented columnar defects (CD's) in a large number of HTS materials, specifically those cuprates containing Hg, Tl, Pb, Bi, and similar heavy elements. Absorbing the incident proton causes the nucleus of these species to fission, and the recoiling fission fragments create amorphous tracks, i.e., CD's. The superconductive transition temperature Tc decreases linearly with proton fluence and we analyze how the rate depends on the family of superconductors. In a study of Tl-2212 materials, adding defects decreases the equilibrium magnetization Meq(H) significantly in magnitude and changes its field dependence; this result is modeled in terms of vortex pinning. Analysis of the irreversible magnetization and its time dependence shows marked increases in the persistent current density and effective pinning energy, and leads to an estimate for the elementary attempt time for vortex hopping, tau ~ 4x10^(-9) s.Comment: Submitted to Physica C; presentation at ISS-2001. PDF file only, 13 pp. tota

Stability of supercurrents in a BiSrCaCuO (Bi-2212) high- Tcsuperconductor with artificially

J. G. Ossandon. Facultad de Ingeniera, Universidad de Talca, Curicó, Chile.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 (0.8 GeV). Significant enhancements in the persistent current density Jpare 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 (Jp) /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

Equilibrium magnetization of the high-TC Superconductor TL2Ca2Ba2Cu3O10+Delta and fluctuation effects

Ossandon, J.G. Faculty of Natural Resources, University de Talca, Curicó, Chile

Vortex Fluctuations, Magnetic Penetration Depth, and HC2 in Hg-based and TL-based hight-T(C) superconductors

Ossandon, J.G. Faculty of Natural Resources, University de Talca, Curicó, Chile

Equilibrum Superconducting properties of grain-aligned HgBa2Ca2Cu3O8+DELTA

Ossandon, J.G. Faculty of Natural Resources, University de Talca, Curicó, Chile

Influence of neutron-irradiation damage on the equilibrium properties of the polycrystalline BI1.8Pb0.3Sr2Ca2Cu3O10 superconductor

Ossandon, J.G. Faculty of Natural Resources, University de Talca, Curicó, Chile

Comparative study of the characteristic length scales and fields of Hg-based high-T-c superconductors

Ossandon, J.G. Department of Engineering Sciences, Universidad de Talca, Curicó, Chil

Quantum tunneling of vortices in Bi-2212 with randomly oriented columnar defects

Ossandon, J.G. Department of Engineering Sciences, Universidad de Talca, Curicó, Chile

Quantum constraints on technological superconductors

Ossandon, J.G. Department of Engineering Sciences, Universidad de Talca, Curicó, Chil