MAGNETIC-FIELD DEPENDENCE OF DC CRITICAL CURRENT FOR LARGE SAMPLES OF TEXTURED BULK Y-BA-CU-O

Large samples of textured Y-Ba-Cu-0 were prepared at the Texas Center for Superconductivity using a continuous process. These were cut into a rectangular shape with typical dimensions 4.0 cm x 0.5 cm x 0.25 cm. The large physical size of these samples and their ability to carry high currents particularly in zero magnetic field required low resistance contacts to avoid Joule heating at the sample current-electrode interface. Accordingly, low resistance metal contact pads for current and voltage electrodes were applied at NIST Boulder, using a sputter etch, sputter deposition, thermal evaporation and oxygen anneal procedure. Transport critical current density measurements at 77 K, and in magnetic fields up to 6 T were performed at NRL. A holder was designed to hold the samples securely in such a way that would allow for contraction during cool-down and to support them against the anticipated large Lorentz forces. The highest critical current measured with no external field was 393 A. This corresponds to a critical current density of 1871 A cm-2. At 1 T, these values decreased to 229 A or 1090 A cm-2. These critical current values, found in material that was fabricated using a technique capable of being scaled up for larger sizes, demonstrate a potential usefulness in large scale applications.