Measurements of Magnetic Field and Temperature Dependence of the Critical Current in Bi-2212 Superconducting Wires
In this paper, we describe our built in-house system for the measurement of the critical current density J c in superconductors. The setup is able to tolerate currents up to 800 A, and works in fields up to 7 T and temperatures from 4.2 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 J c (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 J c ≈ 4 × 10 5 A/cm 2 in self-field at 4.2 K is measured and a J c scaling based on the collective pinning theory is shown to hold above 2 T.