NIST discovers how to limit the magnetic substrate effect in coated superconductors. (General Developments).In 2001, NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. researchers showed that magnetic substrates reduced the current carrying capacity carrying capacity the number of animal units that a farm or area will carry on a year round basis, including that needed for conservation of winter feed. Usually stated as dry cows or dry sheep equivalents per hectare. of Y-Ba-Cu-O coated superconductor A material that has little resistance to the flow of electricity. Traditional superconductors operate at absolute zero (-459.67 degrees Fahrenheit or -273.15 degrees Celsius). Experiments in the 1980s raised the temperature to -321 degrees Fahrenheit. tapes when arranged in stacks of two or more layers. They have now discovered that the degradation in critical current due to the magnetic substrate The base layer of a structure such as a chip, multichip module (MCM), printed circuit board or disk platter. Silicon is the most widely used substrate for chips. Fiberglass (FR4) is mostly used for printed circuit boards, and ceramic is used for MCMs. effect can be mitigated significantly if a spacing layer is inserted between the superconductor film and the magnetic cap layer. High-temperature superconducting su·per·con·duct·ing adj. Having, exhibiting, or capable of superconductivity: "a revolutionary superconducting magnetic propulsion system" Colin Nickerson. tapes based upon coatings of Y-Ba-Cu-O on biaxially textured, buffered, magnetic Ni-W-Fe substrates showed a degradation of 12 % in critical current when the superconductor layer was sandwiched between two Ni-W-Fe substrates. The NIST researchers found that this degradation of critical current could be reduced dramatically to less than 1 % if a 300 [micro]m thick Kapton tape was placed between the superconductor film and the magnetic cap layer. Such a spacing layer could naturally be incorporated into the manufacture of Y-Ba-Cu-O coated conductors as an insulating coating. Even a separation of just 50 [micro]m reduces the degradation to 3 %. The magnetic substrate effect resulting from sandwiching Y-Ba-Cu-O between two magnetic layers occurs in applications where the coated conductor needs to be wound or cabled. The spacing tape, which limits the magnetic interaction of the top and bottom Ni-W-Fe layers, represents an engineering solution for limiting performance degradation in low magnetic field applications such as underground power-transmission cables. The separation layer could be an insulatory layer for electrical isolation, or a high conductivity conductivity /con·duc·tiv·i·ty/ (kon?duk-tiv´i-te) the capacity of a body to transmit a flow of electricity or heat; the conductance per unit area of the body. con·duc·tiv·i·ty n. 1. material, such as Cu, to enhance the electrical and thermal stability of the cable. CONTACT: Jack Ekin, (303) 497-5448; ekin@boulder.nist.gov. |
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