In the center panel, the ring is cut, and the magnetic field drops as the electric current ceases to flow. The field distributions of the original ring and the welded ring are very similar, demonstrating the quality of the weld joint. A new welding technique for high-temperature superconductors is adding to the range of practical applications for these materials, which conduct electricity without resistance. High-temperature superconductors, which lose electrical resistance when cooled with liquid nitrogen, were discovered in the late 1980s. They hold the potential for generating more efficient magnetic fields and transmitting electricity without loss to resistance.
Some applications are in use, but most ideas require large components.
Researchers have been unable to grow large high-performance superconducting structures that carry current uniformly and have found it difficult to join smaller sections together without interfering with electrical flow. Now, however, materials scientists at the U.S. Department of Energy's Argonne National Laboratoryhave developed a way to weld components made of these materials with strong bonds that preserve uniform electrical flow across the joint. The materials are heated to a temperature about midway between their melting points. This leads to a weld that preserves the YBCO crystal structure, is mechanically strong and carries high current. Superconductors are materials that lose their resistance to electrical currents at reduced temperatures.