Cold Magnet

One of the most pervasive and mysterious phenomena in the universe is magnetism. As the scientist knows it, magnetism is the invisible pull that surrounds magnets, electric currents and even the electrons that circle the heart of the atom. Physicists do not wholly understand it, but they use it constantly. All the hundreds of thousands of electrical devices in the modern world have fields of magnetic force coursing through them. Any discovery that promises stronger or better controlled magnetism is immensely important to both practical industry and theoretical science. Such a discovery has just been made: four Bell Telephone Laboratories scientists* have found a new way to generate magnetic fields of fantastic strength.

Electromagnets, which are the essential parts of electric motors and many other devices, are made of coils of wire with electric current flowing through them. The stronger the current, the stronger is the magnetic field that the coils generate. But this increase in magnetic power is practicable only up to a point: ordinary metal wires, such as copper, offer resistance to electricity, and so will carry only a limited amount of current before melting. The strength of electromagnets cannot be increased indefinitely by pushing more current through the coils.

A promising escape from this difficulty is "superconductivity"--the scientists' way of saying that certain materials, when cooled close to absolute zero (--460DEGF.), allow current to flow through them without the slightest hindrance, as light flows through empty space. Superconducting wires, even though very thin, can carry large currents, so coils made of them should be able to generate very strong magnetic fields. But when scientists eagerly tried this obvious trick to increase magnetic strength, they discovered that it simply did not work: magnetism itself, even if only moderately powerful, destroyed the superconductive qualities of all materials that the scientists had tried.

Thin Core. In 1954 Bell Labs found that a compound of niobium and tin becomes superconductive at the comparatively high temperature of 18DEGK (--428DEGF.)./- Later work hinted that the compound might keep its superconductivity in strong magnetic fields. Since it is extremely brittle and cannot be drawn into wires, it was put on the shelf for a while, but eventually Bell Lab scientists patiently learned how to make a tube out of pure niobium, fill it with a mixture of powdered niobium and tin, draw it down to a wire, then heat it to make the powder react chemically, forming a thin core.

When cooled close to absolute zero, this core becomes superconductive, does not show a trace of electrical resistance even when placed in the strongest magnetic field that Bell Labs can generate, 88,000 gauss (the unit of magnetism). It can carry more than 1,000 times as much current as a copper wire of the same size at normal temperature. Bellmen believe that it can be coiled into a superpowerful electromagnet with a field of at least 100,000 gauss.

The Key? No such supermagnet has yet been built. For one thing, it will surely prove to be extremely violent: its field of 100,000 gauss will exert a force of six tons per sq. in. at the end of the coil. Another difficulty is that the coil will have to be kept near absolute zero, presumably by bathing it in liquid helium, whose high volatility makes it a nightmare to handle.

Bell scientists are sure that they can overcome these difficulties, see endless jobs for superconducting magnets in many fast-advancing fields of science. Strong magnetic fields are needed for masers, bubble chambers and other important instruments with which scientists probe the secrets of nature. Industrial applications, especially in radio and radar, should also prove numerous. Perhaps the most exciting potential is in research for extracting peaceful energy from the nuclear fusion of hydrogen. This fierce H-bomb reaction can be contained only by powerful and precisely controlled magnetic fields. The superconducting magnet may be the key device that worldwide fusion research has been waiting for.

* Drs. John E. Kunzler, Ernest Buehler, Francis S. Hsu, Jack H. Wernick.

/- On the Kelvin scale, zero is absolute zero, --273DEG C. or --460DEGF.

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