Composition Profiles and Upper Critical Field Measurement of Internal-Sn and Tube-Type Conductors

Two standard internal-Sn type rod-in-tube (RIT) and two newly developed tube type conductors were investigated. Both types of strand were doped with Ta. A series of heat-treatments with varying temperature and duration time were performed to study their influence on the microstructure and properties. In this work, the fully reacted strands were analysed. Non-Cu J_c was measured and B_c2 values were estimated via Kramer plot extrapolation. B_c2 values were also measured by resistive transitions at high magnetic fields, and compared with the values from Kramer plot extrapolations. High resolution scanning electron microscopy (SEM) was used to observe the cross-section and the composition across the strands´ cross-section was measured by using energy dispersive spectroscopy (EDS). scanning transmission electron microscopy (STEM) was used to measure the composition variation in the individual filaments in the RIT strands. Superconducting properties were correlated to strand composition.