Enhancing Thermal Stability in CuNi-Sheathed MgB₂ Wires with Copper Core Stabilization

Superconductors like magnesium diboride (MgB₂) hold significant promise for high-power energy systems, MRI devices, and various industrial applications. A recent study of our colleagues from Department of Superconductors explored how the addition of copper into MgB₂ wire structures improves their thermal stability—a crucial factor for high-current applications.
The study compared two types of six-filament MgB₂ wires with CuNi sheath: one with a copper core (W6Cu right) and another with a niobium core (W6Nb left). Although both wires share similar construction, the composition differences had a notable impact on performance. At 40 K, the resistance of the copper-core wires was up to 14 times lower than the Nb-core wires, suggesting improved stability and efficient heat dissipation. This low resistance was achieved thanks to high-purity copper, which constituted about 6% of the wire’s cross-sectional area.
Tests were conducted under extreme low temperatures—in traditional liquid helium (4.2 K) and subcooled water ice—where researchers found that W6Cu wires achieved twice the critical current compared to W6Nb wires, largely due to better heat dissipation. Subcooled ice also proved a cost-effective, safer alternative to helium for cooling in high-current applications.
Researchers also measured the “quench power density” for both wire types. W6Nb, with a niobium core, reached quench at lower currents, leading to increased temperatures and potential damage. In contrast, copper-stabilized W6Cu resisted higher currents without sudden temperature spikes, enhancing reliability and durability for high-power applications. These findings indicate that the CuNi sheath and copper core combination positively impacts MgB₂ wire stability, unlocking new potential for their use in industrial devices.

For further details, see the full study here.

Image Description: Superconducting cable without copper (left) and with copper (right).

Authors: M. Búran, P. Kováč, L. Kopera, I. Hušek