Researchers at the Universitat Autònoma de Barcelona, the Materials Science Institute of Barcelona (ICMAB-CSIC), and various German and North American institutions have developed what they claim is a simple method for measuring the maximum current that coated superconductors can carry. The material will, most likely, be used to manufacture the superconductor wires of the future. The research was published in the journal, Applied Physics Letters.
Electric currents pass through superconductor materials without resistance - a property with many technological applications - but this is only possible when the materials are cooled below a certain temperature and when the current does not exceed a certain value.
According to the researchers, the superconductor materials that will most likely be used for wires that transport electric energy are called 'coated conductors'. They are formed by the deposition of a film of high-temperature superconductor material on a metallic band. They say the main advantage with respect to other types of superconductors is that they allow large quantities of electric current to move through them without the need for excessive cooling, yet they keep their superconductor qualities.
The principal limitation of these new generation materials is, however, that their microscopic structure is in the form of small grains, which limits movement through them and makes it more difficult in each case, to know what the maximum current is that the material can carry and yet still retain its characteristics of superconductivity. The team's simple method for measuring the maximum current (called critical current) that coated superconductors can carry is based on measuring the response of the coated superconductor to the application of magnetic fields. The material undergoes a magnetic field with cyclical variations so that different maximum values are obtained, making it possible to measure its critical current. Thus engineers can calculate, in a simple way, the maximum intensity of electric current that a superconductor wire can carry without superconductivity being lost. The difference from other methods is that the technique is non-invasive, ie, it is not necessary to enter into contact with the material.
Furthermore, the results obtained will make it possible to analyse how to improve the granular structure of the superconductor material so as to increase the current that can move through it, thereby obtaining the values required in applications such as superconductor wires for the transmission of electricity, new motors, more efficient and lighter generators, magnetically levitated trains or magnetic resonance image-generating apparatus for the human body.
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