Fabrication and characterization of high-Tc tapes and coils made from Ag-clad Bi-2223 superconductors

Abstract

Prereacted Pb-doped Bi-Sr-Ca-Cu-O powders were packed into Ag tubes, drawn, rolled, and given intermediate heat treatment to prepare long lengths of Ag-clad Bi-2223 superconductor tapes. With the use of improved process conditions, transport critical current density (Jc) values exceeding 105 A/cm2 at the temperature of liquid helium (4.2 K) and liquid neon (27 K), and greater than 4 × 104 A/cm2 at liquid nitrogen temperature (77 K), were obtained in zero applied field with short tape samples. Detailed microstructural analysis and Jc measurements in applied fields up to 20 T are reported. Rolled tapes were cut into lengths of up to 10 m, and several such tapes were used in parallel to fabricate small superconducting pancake coils by the “wind-and-react” technique. Recently, we fabricated a test magnet with six pancake coils, each containing three 10-m lengths of rolled tapes and tested at 4.2, 27, and 77 K as a function of applied fields up to 14.5 T. A maximum generated field of 1.25 T was measured in zero applied field at 4.2 T. Detailed measurements made on the pancake coils and test magnets are reported in this paper.