Current distribution in thermally degraded superconductor of 2nd generation

The transport current distribution in a simple mono-core non-striated DyBCO tape in LN2 was measured by a contactless non-destructive method based on Hall probe magnetometry. Transport current was gradually increased to 150 A/cm, which is well under a critical current level of 250 A/cm. Nevertheless, due to bad current contact, the sample was overheated and locally degraded. The result of the degradation on the current distribution in the DyBCO tape was studied. The destroyed portion was cut off. The tape was still heavily degraded at its center 3 cm away from the destroyed portion, and the current flowed mostly in the right side of the cross-section with a maximum close to the right edge, exceeding here the local critical current up to 300 A/cm. At a more distant portion, 5 cm along the longitudinal direction, the current distribution was practically normal and matched a maximum level of 250 A/cm, which is typical for an initially non-degraded tape. The damage due to overheating was restricted over a distance of several centimeters. The results of measurement were reproducible and the full current calculated from the magnetic field data matched the full current obtained from the four-probe measurement within one percent.