Science: 100 Million Volts

The huge, super-secret “betatron”—which generates an X ray so powerful and dangerous that the entire apparatus must be enclosed in three-foot concrete walls—was completed a couple of years ago. Wartime security kept it hidden until last week. Even then, General Electric Co. did not tell quite all. But G.E. did give a fair description of how the great gadget works, and some broad hints about a few of the things that it will do.

The betatron, a close relative of the ordinary transformer which raises or lowers the voltage of an alternating current, is an electron accelerator. A whopping electromagnet (130 tons) is energized by a heavy current flowing through two coils made of one-inch copper rods.

Between the poles of the magnet is a doughnut-shaped glass vacuum tube, 74 inches across. A heated filament sprays electrons (particles of negative electricity) into the tube. The intense electric field stirred up by the magnetism between the poles makes the electrons whirl round & round the tube in a circular orbit. In 1 240th of a second they make 250,000 complete circuits. The enormous velocity of all this whirling, measured in electrical terms, is equivalent to 100 million volts.

Then the current in the coils begins to fall. A secondary magnetic field deflects the electrons from their circular course. They spiral inward and hit a tungsten “target.” Out bursts the X ray.

The X ray shines through thick steel castings as if they were made of ice. But it will do other, even more interesting things. A silver half-dollar, for instance, held briefly in its beam, becomes dangerously radioactive. The rays knock neutrons out of silver atoms, turning them into an unstable silver isotope, which breaks down into cadmium, giving off powerful streams of electrons. Some silver, too, is turned into palladium, while some of the copper in the coin’s alloy is turned into atoms of nickel.* The betatron is controlled from a neighboring room.

After giving such fascinating hints about the talents of its betatron, G.E. retreated again into silence. Obviously, a gadget which transmutes elements so handily has more than a nodding acquaintance with nuclear fission, science’s most secluded subject.

* These transmutations are not profitable commercially because they require far more energy than the products are worth.