Investigation of Flux Pinning and Critical Current Densities in Type II Superconductors.

摘要

The main purpose of this work was to develop and employ new metallurgical techniques for determining the microstructural features controlling the critical current of Type II superconductors. Another purpose was to study the critical current in thin films by magnetization measurements. From the data both the critical current density and magnetic flux pinning force as a function of field were calculated. The study in Appendix I identifies dislocation cell boundaries as the prominent microstructural feature of commercial multifilamentary superconductors. This feature is correlated with critical current and guidelines are provided for critical current enhancement in commercial conductors. The report in Appendix II describes a new technique for measuring grain size and thicknesses of the thin layers on the order of .5micrometer which occur in the fabrication of Nb3Sn by diffusion reactions. The method is rapid and inexpensive compared to competing techniques and will be useful in new conductor development.