Researchers at the US Department of Energy’s Los Alamos National Laboratory have developed a new process for producing high-performance superconducting tape that operates at the temperature of liquid nitrogen.
Superconducting tapes are said to efficiently carry vast amounts of electrical current with no resistive losses. A single, one-centimetre-wide, thin foil of Los Alamos superconducting tape exhibits a current density of more than one million amps per square centimetre. This means a single piece of superconducting tape can carry 200 times the electrical current of an equivalent copper wire.
The world market for superconducting tape in electric power technologies is estimated to be worth $50 billion by the year 2020 and the development could lead to tremendous energy savings and emission reductions, said Dean Peterson, director of Los Alamos’ Superconductivity Technology Centre.
‘Electric motors, transformers, transmission cables and levitated trains will be some of the applications demanding hundreds of kilometres of these flexible superconducting tapes each year,’ said Peterson.
The latest achievement from Los Alamos was attained by replacing cubic zirconia with magnesium oxide as the template material for the superconducting film. This speeded up the template deposition process by 100 times.
In 1995 Los Alamos researchers achieved world-record performance by depositing a film of yttrium barium copper oxide (YBCO) on cheap nickel alloy tape by first applying a buffer layer of cubic zirconia.
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 centimetre at liquid nitrogen temperatures.
Magnesium oxide is said to address the need for a fast and reliable template formation process that is required to produce the high-performance YBCO-coated conductors economically.
Los Alamos researchers have also recently discovered that superconductor multilayers carry unprecedented amounts of current – potentially 1,000 amperes in a one-centimetre-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.