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Painting with superconductors.

Painting with superconductors

The new high-temperature superconductingmaterials are brittle and ceramic and only recently have been found to have technological potential, but already people have drawn wires and films from them and made rings out of them. The latest news from IBM, in whose laboratories the first of them was discovered, is that scientists at its Thomas J. Watson Research Center in Yorktown Heights, N.Y., have managed to make superconducting circuits called SQUIDs (superconducting quantum interference devices) out of the new materials and have developed a technique for spray painting them onto surfaces. This photograph shows such a pattern of superconducting lines.

Because SQUIDs can sense quantum-by-quantumchanges in magnetic fields, they are frequently employed as high-sensitivity magnetometers. The Josephson junctions that are the basic elements in SQUIDs have many actual and potential uses in microcircuity, particularly as switches in computer circuitry. However, previous Josephson junctions needed refrigeration by liquid helium to a temperature of 4 kelvins to operate, and that limited their prospects. These new IBM SQUIDs are fully superconducting at 68 kelvins and so can operate with refrigeration by liquid nitrogen. Liquid nitrogen temperature is normally 77 kelvins, but adjusting the pressure can reduce it to 68 K, IBM says.

The new superconducting substances,which are compounds of copper oxide with yttrium and barium, are amenable to the technique known as plasma spraying, IBM scientists have found. In plasma spraying the substance is heated until it is ionized and then quickly deposited on a suitable surface and cooled. After annealling, the painted substance is completely superconducting, again at 68 K. IBM researchers have managed to coat preformed shapes such as wires, contoured and flat surfaces, and even tubes. They can paint lines with the superconductors on substrates commonly used in making conventional printed circuitry. Such superconducting lines could someday form connections in computer circuitry, thus eliminating some serious hindrances to computer speed and data-processing volume.
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Title Annotation:superconducting quantum interference devices
Publication:Science News
Date:May 9, 1987
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