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Half buried under a thick shell of earth and concrete in Cambridge, Mass., a great ring-shaped machine went into operation last week, humming softly while green lines measuring its power drifted across the face of an oscilloscope. Called the Cambridge Electron Accelerator, the machine cost $12 million (paid by the Atomic Energy Commission), is 236 ft. in diameter, and consumes enough electricity at full power to operate 40 medium-sized TV stations. Its practical use is nil. It will never freshen sea water, cure cancer, or solve any other specific problem of applied science. But in the hands...
Scientists have long used high-energy protons (fundamental particles that form the nuclei of hydrogen atoms) as tools to explore the secret innards of matter. Two enormous accelerators, one at Brookhaven National Laboratory, Long Island, the other near Geneva, Switzerland, spew out protons with 30 billion electron-volts of energy. Yet in some ways protons are clumsy tools for basic research; for many subtle experiments, electrons (much lighter negative particles of electricity) are better. But electrons are so much more difficult to handle that scientists have never been able to give them really high energy. The Cambridge accelerator is designed...
Growing these fattened electrons is no easy job. They are shot into the accelerator's vacuum-ring in bunches of about 100 billion, already moving at close to the speed of light and carrying 25 million electron-volts of energy. If left to their own devices, they would move in straight lines, soon hitting the ring's outside wall. But the ring is surrounded by magnets whose power can be varied accurately. When each bunch of electrons enters, the magnetism is just strong enough to make them move in a circle, keeping away from the ring...
Another difficulty is the electrons' habit of losing much of the energy that is stuffed into them. When electrons move in a magnetic field, they turn some of their energy into "synchrotron radiation" that shoots off like mud slinging off a wheel. The more energy they have, the more they radiate away. When they have been fattened to about 1 billion electron-volts (or 1 BEV, as physicists call it), they begin to radiate visible light. At 2 BEV, they radiate the more powerful ultraviolet rays. At 4 BEV, they radiate X rays, losing several million electron-volts...
Begun at Harvard's biological laboratories last September, Porter's current research uses a new $40,000 electron microscope. The shadow picture produced by introducing the cell specimen into a beam of electrons has a resolution of one fifty-millionth of an inch. Porter in 1945 made the first electron microscope photograph of a cell...