Not-So-Common Cold

"Consider a world so cold," says Union Carbide Engineer Roger Thompson, "that the very air you breathe turns to liquid or freezes as solid as a block of ice, where steel is as brittle as glass, a rubber ball shatters when it hits the floor, and lead is an almost perfect conductor of electricity." The odd goings-on described by Engineer Thompson all occur in the far-out world of cryogenics--the science of ultra-low temperatures.

Although it has risen from the status of a laboratory novelty only within the past decade, cryogenics now occupies the attention of hundreds of scientists, has growing applications in industry and science and shows fascinating promise for the near future. Scientists are already talking about cryogenic technology that will make possible transmission lines that conduct electricity without power losses, switching elements that make computers incredibly faster and smaller, and high-speed trains that float on magnetic cushions.

More than Records. The cryogenic temperature range begins at a chilly-- 150DEG F. and plummets to --459.7DEG F., or absolute zero, the point at which all thermal motion of the atom ceases. To attain these temperatures, scientists use expansion engines that compress gases, cool them and allow them to expand again, then repeat the cycle until they liquefy and eventually solidify. As the gases approach absolute zero, a sophisticated magnetization process extracts their remaining reservoir of heat. Because there will always be slight thermal motion of the atomic particles, scientists will never actually achieve absolute zero. But last July, Naval Research Laboratory Physicist Arthur Spohr reported achieving a record low temperature by chilling helium to within a millionth of a degree of absolute zero--3/10 of a millionth of a degree colder than the lowest temperature previously achieved.

More than records are at stake in making the closest possible approach to absolute zero. As the motion of atomic particles decreases with increasing cold, scientists can study the particles more closely and learn more about the forces that bind them together.

Extreme cold also produces the phenomenon of superconductivity, which scientists are putting to work in scores of applications. As temperatures approach absolute zero, the electrical resistance of many elements and compounds suddenly disappears. These substances become highly efficient conductors, and small voltages produce large currents that continue to flow indefinitely even after the power source has been withdrawn. Scientists can now envision a superconductive power-transmission line cooled by liquid helium that could carry 100 billion watts of direct current for hundreds of miles with no appreciable losses.

Closet-Size Shoe Box. Because the large currents that flow in superconductors generate the intense magnetic fields needed in atom smashers and in controlled fusion experiments, superconductors will eventually replace bulky elecromagnets in these areas. A 1-lb. superconducting magnet cooled by a 200-lb. refrigerating system and powered by a 6-volt battery can produce as intense a magnetic field as an iron-core electromagnet weighing several tons and requiring 50 kilowatts of power. Entire trains could be suspended above their roadbeds in strong magnetic fields produced by superconducting magnets, enabling them to travel more smoothly and with less friction at speeds over 300 m.p.h.

Another strange property of superconductors makes them ideal for use in computers; when they are placed in a magnetic field, their electrical resistance reappears. Thus by alternately applying and withdrawing a magnetic field, scientists can turn a superconductor into an on-off switching device many times faster (and many times smaller) than the solid-state semiconductors now used computers. With cryogenic techniques, a closet-size computer could fit in a shoe box. Cryogenics will also make possible such esoteric devices as loss-free superconductive motors with rotors that float in liquid helium, and superconductive gyroscopes that float in frictionless magnetic fields.

Frigid Mud. By chilling electronic equipment to cryogenic temperatures, scientists have already been able to reduce troublesome background noise caused by the random movement of atoms within metallic circuit components; the atoms are literally subdued by lower temperatures. Cryogenically cooled infra-red detectors used in astronomy, aerial mapping and antiaircraft missiles are many more times sensitive to heat than those operated at normal temperatures.

In more familiar applications, liquefied gases freeze food up to six times as fast as conventional freezing and produce smaller ice crystals, thus damaging fewer food cells. Liquid gases are being used in head and neck surgery, and to freeze human and animal semen for later use in artificial insemination.

Liquid oxygen (LOX) is used as an oxidizer in rocket engines and in steel production. Liquid hydrogen has been proposed as the fuel for the supersonic transport and as the propellant in a nuclear rocket. In bubble chambers, it allows scientists to trace the path of sub-atomic particles. Gas companies are liquefying natural gas for more convenient and economical storage, and liquid nitrogen is now used to freeze the earth around excavations so that mud will not slide into the work area.

To avoid shutting down large portions of the city water system when they began installing water meters at every residence, water-department workers in Boulder, Colo., turned to cryogenics. At each house, they poured liquid nitrogen over the inlet pipes, which froze the water inside for 20 minutes and enabled them to install the meter without losing so much as a drip.

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