The lead is composed of an assembly of 72 ceramic superconducting composites connected to copper and low temperature supeconducting wire. The composites are encapsulated and magnetically shielded by steel spirals. Liquid nitrogen can be used for cooling of the warm end. The lead is designed to conduct large amounts of electrical power to superconducting magnets without transmitting heat from the power source which would interfere with the functioning of the magnets.
During testing, a direct current of 13,200 amperes was fed through a stainless steel pipe with water flowing through it for cooling. Although the pipe became red hot as a result of the current passing through it, the superconducting lead maintained a temperature of between six and forty degrees above absolute zero. The test was the culmination of an international collaboration of private and academic institutions from the U.S., U.K. and Spain. ZerRes of the U.S. and EURUS, an international company, coordinated the project.
According to Zimmerman, "Our lead, made with high transition temperature superconductors, can be cooled by liquid nitrogen. This is vastly more efficient than previous superconducting leads which required cooling by liquid helium--a cooling system which would easily fill a room at a cost $500,000 or more.
"The potential of this technology is enormous," says Zimmerman. "The applications extend to building prototypes of electromagnetic boats, automobiles and elevators. The technology that has been in use requires a tremendous amount of power to keep the magnets cool enough to function properly. High temperature superconducting cables, based on the technology we have developed, have the potential of making these technologies safer and considerably more efficient.
"Right now power is transmitted in cities through 8 inch tubes containing copper wires that are oil cooled," continues Zimmerman. "By replacing the copper wires with superconducting cables, we can replace the oil with liquid nitrogen. With only minor modification to the cooling systems now in use, we would be able to increase the amount of power that can be carried by the cable by a factor of ten."
The Boston University lead was developed for a project of CERN, the European Center for Nuclear Research in Geneva, Switzerland. CERN is in the process of building a Large Haldron Collider which will require millions of amperes to power its superconducting magnets. The accelerator requires the use of high transition temperature superconducting leads to prevent heat leakage which would interfere with the function of the magnets. The Boston University team was one of four working on the project.
Dr. Larry Sulak, chairman of the department of physics at Boston University, applauded the work of the team: "We originally projected a year for the development of the lead, but the team actually built a successful prototype in just three months. It was very exciting to see how well it worked during testing at the Magnetic Field Laboratory."
In addition to the CERN project, the Boston University lead can be used to provide power for Magnetic Resonance Imaging Systems (MRI), and provides a basis for the technology which would allow for generating and transmitting electrical power more efficiently.
Boston University is the third-largest independent institution of higher learning in the United States, with an enrollment of nearly 30,000 students in its 15 schools and colleges. The University offers an exceptional grounding in the liberal arts, a broad range of programs in the arts, science, engineering and professional areas, and state-of-the-art facilities for teaching and research. Located in a city rich in cultural, historical and intellectual attractions, the University, with more than 2,800 faculty members, is one of the nation's preeminent institutions of higher learning.