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Levitation: Is it Real?

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One hundred years ago, in 1911, a Dutchman by the name of Heike Kamerlingh Onnes discovered superconductivity. He found that mercury had no electrical resistance when cooled to 4.15 kelvins, or -451.93 degrees Fahrenheit. (Dry ice has a surface temperature of -109.3 ºF. Handling dry ice with your bare hand will give you frostbite!)

Today, the race is on to find materials that are superconducting at room temperature. Once this happens, the world-wide web of electronics, power and transportation will be revolutionized.

NSLS supports a rich program of research to understand the basic phenomenon of superconductivity and develop it in ways that will facilitate commercialization.

Often, the work zigzags in unexpected ways. Over a decade ago, scientists using NSLS discovered a low-energy kink in the energy bands of electrons in high-temperature superconductors just as they go through the transition temperature from their normal to superconducting state. Because this kink is a signature for the mechanism that causes superconductivity in low-temperature superconductors, they had hoped that a similar kink in high-temperature superconductors would show the same mechanism at work.

More recent work, however, unveiled a second and much larger kink in the high-temperature superconductors “LBCO” (scientific shorthand for the elements it contains: lanthanum, barium, copper, and oxygen) and “BSCCO” (containing bismuth, strontium, calcium, copper, and oxygen).

And here’s another wrinkle. Scientists have found similar energy scales and gaps in a material that is not a superconductor. The material is a special form of LBCO, where there is exactly one barium atom for every eight copper atoms. With less or more barium, the material acts as a high-temperature superconductor (this was actually the very first high-temperature superconductor discovered). But at the one-to-eight ratio, the material momentarily loses its superconductivity.

So the mystery continues.

But wait! What does this have to do with levitation?

In 1933, 23 years after the Dutchman Onnes discovered superconductivity, the Germans Walther Meissner and Robert Ochsenfeld found that a superconducting material will repel a magnetic field. The effect is so strong that a magnet can actually be levitated over a superconductor.

Maglev trains exploit this property by levitating the cars above the track, eliminating the friction that slows down all forms of land transportation.

JR Tokai, a private railroad company in Japan, is developing plans for a superconducting maglev route between Tokyo and Nagoya. Using a large electrical power source, metal coils lining a track, and large magnets attached to the underside of the cars, these trains would run at 310 miles per hour.

So levitation is real. In fact, magnetic levitation with superconducting magnets was invented and patented by two Brookhaven scientists, James Powell and Gordon Danby. An engineer, Powell came up with the idea while stuck in a traffic jam on the Throgs Neck Bridge, which spans the East River between the Bronx and Queens, boroughs of New York City. He developed the idea with Danby, a physicist, and they were awarded a U.S. patent in 1968. Various demonstration systems have been built through the years.

Research on superconductors at NSLS is funded by the U.S. Department of Energy, which is has a keen interest in understanding the mechanisms of superconducting materials - particularly those that can carry current with zero resistance at higher temperatures - because these materials have many potential applications in improving the efficiency of energy generation and transmission.

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