A Cool New Atom Smasher

In their efforts to probe more deeply into the mysterious subatomic world and its host of recently discovered particles, scientists are rapidly refining and adding to the spectacular tools of high-energy physics: the massive and powerful bevatrons, cyclotrons, synchrotrons and linear accelerators. The latter are designed to fire beams of particles, usually high-speed electrons, down a long copper tube at experimental targets. Stanford University, for example, now has a two-mile-long atom-smashing model called SLAC (TIME, July 22). SLAC, which stands for Stanford Linear Accelerator, is just beginning its experimental program. Yet last week Stanford Physicist Alan Schwettman reported in Washington that a prototype of an improved and more advanced linear accelerator had been successfully tested on the Palo Alto campus.

The new device differs from SLAC and the others in its ability to fire electrons continuously. In previous linear accelerators, the high-frequency radio waves used to accelerate electrons through the copper tube could quickly produce high temperatures by generating electric currents in the walls of the tube. To prevent serious heat damage, the electrons were fired in very short bursts. Stanford's SLAC is designed to fire electrons in millionth-of-a-second bursts separated by intervals of a thousandth of a second.

To enable their experimental instrument to accelerate a continuous stream of electrons, Schwettman, Physicist William Fairbank and their associates lined the inner walls of their 5-ft. prototype with lead and surrounded the tube with an aluminum cylinder containing liquid helium cooled to --457DEG F.--about two degrees above absolute zero. At this temperature, the lead lining becomes a superconductor, losing practically afl of its heat-causing electrical resistance and allowing the continuous flow of high-energy electrons without overheating.

The superconducting accelerator has already set Physicist Wolfgang Panofsky, director of Stanford's SLAC, to thinking ahead. The new accelerator does not actually make SLAC obsolete, he says, but it "might be wise," as early as 1970, to examine the possibility of converting the big machine to a superconducting accelerator.

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