Measurements of Magnetic Field and Temperature Dependence of the Critical Current in Bi-2212 Superconducting Wires

In this work we describe our built in-house system
for the measurement of the critical current density Jc in
superconductors. The set up is able to tolerate currents up to
800 A, and works in fields up to 7 T and temperatures from 4.2 K
to 40 K. The peculiarity of our system lies in its versatility: we
can measure a high variety of superconducting samples up to
15 cm in length, testing their performance also at temperatures
achievable by cryocoolers.
Magnetic field and temperature dependencies of critical
current density Jc(H, T) are measured in Bi-2212 round wires. Bi-
2212 wires are fabricated by applying the new GDG (grooverolling
/drawing /groove-rolling) process consisting of the
alternation of groove-rolling and drawing techniques, which
densifies the filaments already during the working procedure
prior to the heat treatment. A Jc ? 4×105 A/cm2 in self-field at
4.2 K is measured and a Jc scaling based on the collective pinning
theory is shown to hold above 2 T.