Researchers at Florida State University have discovered a way to improve the performance of electrical wires used as high-temperature superconductors.
The team’s research on superconductor wires, which was published in the journal Superconductor Science and Technology, holds the potential to power the next generation of particle accelerators.
Researchers used high-resolution scanning electron microscopy to comprehend how processing techniques influence grains in bismuth-based superconducting wires (known as Bi-2212). The Bi-2212 grains form the underlying structures of high-temperature superconductors, and scientists viewing them at the atomic scale have now successfully optimised their alignment in a process that makes the material more effective at carrying a superconducting current, or supercurrent.
The team found that the grains have a long rectangular shape, with their longer side pointing along the same axis as the wire. They are positioned in a circular pattern following the path of the wire, so that orientation is only apparent at very small scale. Together, these properties give the Bi-2212 grains a quasi-biaxial texture, which resulted in being a perfect configuration for supercurrent flow.
Abiola Temidayo Oloye, a doctoral candidate at the FAMU-FSU College of Engineering, researcher at the National High Magnetic Field Laboratory (MagLab) and the paper’s lead author, commented: “By understanding how to optimise the structure of these grains, we can fabricate the High-temperature superconductor (HTS) round wires that carry higher currents in the most efficient way.”
Unlike standard conductors like copper, superconductors can transport electric with perfect efficiency, as the electrons do not encounter any friction whist traveling in the superconductor wire.
Bi-2212 wires are part of a new generation of high-field superconductors for constructing superconducting magnets, which are crucial tools for scientific research at labs around the world, including the National High Magnetic Field Laboratory, where the team of researchers conducted their experiments.
High-temperature superconductors, such as Bi-2212 are capable of conducting current at significantly higher magnetic fields than low-temperature superconductors. They are also crucial to the designs of powerful particle accelerators at the Large Hadron Collider at the European Organization for Nuclear Research (CERN).
“We optimised the Bi-2212 round wires to carry more current, while keeping in mind the scale difference between the lab and manufacturer,” Oloye explained. “The process we develop in the lab has to scale to the manufacturing level for the technology to be commercially viable and we were able to do that in the study.”
Previous work done by Fumitake Kametani, an associate professor of mechanical engineering at the FAMU-FSU College of Engineering, MagLab researcher, and principal investigator for the study, illustrated the significance of quasi-biaxial texture in Bi-2212 round wires for currents. This paper continued the premise and showed the factors needed to achieve optimal quasi-biaxial texture.
“The microstructural characterisation used is unique in analysing the crystal structure of Bi-2212 round wires,” Kametani said. “The technique is usually used for analysing metals and alloys, and we have adapted it to develop novel sample preparation methods to further the optimization of Bi-2212 HTS wire technologies.”
Going forward, the researchers plan on using Bi-2212 round wires for high-field magnet applications.
“Since it is the only high-temperature superconductor available in round wire form, the material can more easily replace existing technologies using LTS wires made from other materials,” Oloye added. “Other HTS such as REBCO and Bi-2223 are only available in tape form, which adds a layer of complexity to magnet design.”
