At the University of Alabama in Huntsville, physicists last month placed a chip of a green, brittle compound inside a thermos-like container, doused it with frigid liquid nitrogen and sent an electric current through it. As the temperature dropped, they took careful measurements of the compound's electrical resistance -- its opposition to the passage of current.*
Suddenly, at 93 Kelvin (-292 degrees F), the resistance dropped precipitously. The substance had become a superconductor, able to transmit current with virtually no loss of energy. "We were so excited and so nervous that our hands were shaking," says Physicist Maw-kuen Wu. "At first we were suspicious that it was an error."
Not so. Wu's group, under the direction of University of Houston Physicist Paul C.W. Chu, had achieved the phenomenon of superconductivity at a higher temperature than ever before. And the National Science Foundation announced last week that Chu's Houston lab had pushed that temperature 5 degrees higher -- to 98 K. Under such conditions -- far less extreme than those required only a few years ago -- superconducting technology might eventually become inexpensive and even commonplace. Possible applications: superconducting cables that could transmit electricity from a power plant to a distant city with essentially no energy loss; practical versions of trains that "fly" ) just above their tracks at hundreds of miles an hour, cushioned on magnetic fields; more widespread use of magnetic resonance imaging machines, which take sharp pictures of the soft tissues of the body. Says Northwestern University Physicist Arthur Freeman: "A barrier has been broken. It's exciting for the physics community and for mankind as a whole."
Superconductivity was discovered in 1911, when Dutch Physicist Heike Onnes cooled the element mercury to near absolute zero (0 Kelvin, or -460 degrees F) and discovered that it had lost its resistance to electric current. Since then more than two dozen chemical elements and hundreds of compounds have been found to be superconductors near that temperature extreme. The only practical way to make something that cold is to bathe it in liquid helium, which exists only at temperatures below 4 K. But helium is rare, and expensive to liquefy. Even so, the efficiency of electromagnets wound with superconducting wires is so great that in certain situations the expense is justified.
For example, giant particle accelerators require extremely powerful magnets to keep the particles confined to a circular track as they move at nearly the speed of light. At Fermilab, near Chicago, the world's most powerful accelerator, known as Tevatron, uses more than 1,000 superconducting magnets cooled with liquid helium at a cost of $5 million a year. But the efficiency of the magnets saves Fermilab an estimated $185 million annually in electric energy costs. The superconducting super collider, a mammoth accelerator 52 miles in circumference, endorsed last month by President Reagan for completion in the 1990s at a projected cost of between $4 billion and $6 billion, will use 10,000 superconducting magnets and save nearly $600 million annually.