Laboratory Researchers Achieve High Temperature Superconductor Milestone

Superconducting tapes can efficiently carry vast amounts of electrical current with no resistive losses. A single, one-centimeter-wide, thin foil of Los Alamos superconducting tape exhibits a current density - the amount of electrical current that can be passed through a cross section of the material - of more than one million amps per square centimeter. This means a single piece of superconducting tape can carry 200 times the electrical current of an equivalent copper wire.

As the world market for superconducting tape in electric power technologies - projected up to $50 billion by the year 2020 - is realized, tremendous energy savings and emission reductions also will result, said Dean Peterson, director of Los Alamos' Superconductivity Technology Center. "Electric motors, transformers, transmission cables and levitated trains will be some of the applications demanding hundreds of kilometers of these flexible superconducting tapes each year," said Peterson.

The latest achievement was attained by replacing cubic zirconia with magnesium oxide as the template material for the superconducting film, thereby speeding up the template deposition process by 100 times.

Said James Daley, manager of the Superconductivity Program for Electric Systems for DOE, "Being able to reduce the fabrication time in a continuous process will increase U.S. industry interest in scaling-up the manufacturing process and in bringing new products to market more quickly."

Los Alamos researchers in 1995 achieved world-record performance by depositing a film of a superconducting ceramic, known as yttrium barium copper oxide or YBCO, on inexpensive nickel alloy tape by first applying a buffer layer of cubic zirconia. The zirconia layer was deposited using ion beams in a process known as Ion Beam Assisted Deposition. The first beam removes material from a zirconia target and deposits it onto the nickel tape. A second ion beam, aimed at the tape, orients zirconia grains as they are deposited. Subsequent pulsed-laser deposition of YBCO on top of the aligned zirconia template allows growth of a nearly perfect crystalline superconducting film from one to six millionths of a meter thick.

Extending this Ion Beam Assisted Deposition-pulsed-laser deposition approach in a continuous process, Los Alamos researchers were able to produce meter lengths of YBCO superconducting tapes with critical current exceeding 100 amps and current densities of one million amps per square centimeter at liquid nitrogen temperatures.

"None of the competing processes for producing coated conductors have succeeded in achieving such results on long tapes," said Peterson.

Magnesium oxide addresses the need for a fast and reliable template formation process that is required to produce the high-performance YBCO-coated conductors economically. It also permits timely manufacturing of kilometers of high-performance superconductor tape that will enable the development of an array of energy-conserving and more powerful electrical technologies for use in the electric power industry.

Los Alamos researchers have also recently made the exciting discovery that superconductor multilayers carry unprecedented amounts of current - potentially 1,000 amperes in a one-centimeter-wide strip through a coating only one tenth the thickness of a human hair. This new film deposition technology is now being incorporated in producing superconducting tapes with superior current carrying ability.

To accelerate commercial development of high-temperature superconducting tape, Los Alamos is collaborating with American Superconductor Corp., 3M Corp. and Intermagnetics General Corp.

Los Alamos' Superconductivity Technology Center is one of three national centers funded by the Department of Energy to develop high-temperature superconductor technologies in collaboration with American industry and universities.

Additional information about high temperature superconducting tape development and applications is available at http://www.lanl.gov/superconductivity online.

Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.