Bevatron at Work

On Charter Hill above Berkeley, Calif, a strange and monstrous machine, the AEC's bevatron,* was slowly coming to life last week. Housed in a circular building 75 feet high is a steel doughnut 135 feet in diameter and weighing 10,000 tons. This is the world's greatest magnet, energized by current flowing through 26.5 miles of copper cable two inches thick. When its current was first turned on, a crashing clatter shook the bevatron building as iron objects on the floor rearranged themselves violently to fit the invisible pattern of its magnetic field.

Now the magnet is quiet, snoring softly, but in a ring-shaped vacuum chamber running around inside it, a dangerous, man-made genie throbs and thrashes. Out of an electric arc springs a swarm of protons (hydrogen nuclei). Powerful forces grab them and speed them down a channel toward the great machine. They sail into the chamber, and the magnet steers them in a circular orbit.

1.25 Times to the Moon. The protons keep together like a swarm of bees, and each time they circle the track, they get a boost of electrical energy that increases their speed. Round and round they go, 4,000,000 times in 1.85 seconds. After they have traveled 300,000 miles (1.25 times the distance to the moon), they are moving at almost the speed of light, and each proton carries an explosive cargo of energy.

The University of California scientists who designed and built the bevatron are gradually stepping up its energy, starting only small groups of protons around the magnetic race track, but already their energy at the end of their run is 4.7 billion electron-volts. This is twice the energy of the second largest accelerator, the cosmotron at Brookhaven National Laboratory, Long Island. It is the energy of middle sized cosmic-ray particles, which have been accelerated, perhaps for billions of years, by unknown forces in space. Each proton at the end of its journey has a mass six times as great as when it started.*

Shields Needed. When the bevatron is finally operating at its design energy, 6.25 bev, 20 swarms of 100 million protons each will burst from its chamber every minute. No one knows exactly how dangerous they will be. The scientists are gingerly observing the first small pulses to see how they should place their thick concrete shields.

The ancestors of the bevatron, accelerators with less than a thousandth of its power, extracted from nature the information that told man how to build uranium and hydrogen bombs. The bevatron will strike far deeper into the atomic nucleus, where matter and energy lie closely twined together.

* From bev, scientists' shorthand for billion electron-volts. * By the Einstein principle that mass increases with speed.

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