Word: cadmium
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Then the scientist nodded to TIME's correspondent. "Turn the switch." The switch looked like a valve on a gas stove, it turned easily. Control rods (probably of cadmium) clanged into place. They soaked up the vital neutrons faster than they were produced from the uranium. The pile stopped...
...about 3⅓ Ibs.). Theoretically, a pile might heat up to the temperature of the sun (over 6,000°), but no known container can withstand more than 1,500°. The physicists discovered that the simplest way to throttle down a pile was to thrust into it a cadmium bar, which stops neutrons cold...
This stunt was no mere atomic doodle. It promised the ideal measuring stick for which scientists have been crying. Since 1893, they had used as their primary standard the wavelength of a narrow band of red light in the spectrum of cadmium. Theoretically, a band of green light in the mercury spectrum would be even better: 1) the mercury atom, heavier than cadmium, gives light with a more sharply defined wavelength; 2) mercury vapor glows at low temperatures, while cadmium must be heated very...
...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...
...below the "critical size" of the theory, instruments gave the alarm. The reaction was starting to cook. Luckily, the cadmium strips had been inserted at "retard" position. Slowed down by their influence, the reaction was easily stopped. "This," commented Dr. Smyth dryly, "was fortunate...