When the United States entered World War II in December 1941, nuclear research was consolidated to some degree. Fermi had built a series of “piles,” as he called them, at Columbia. Now he moved to the University of Chicago, where he continued to construct piles in a space under the stands of the football field. The final structure, a flattened sphere about 7.5 metres (25 feet) in diameter, contained 380 tons of graphite blocks as the moderator and 6 tons of uranium metal and 40 tons of uranium oxide as the fuel, distributed in a careful pattern. The pile went “critical” on December 2, 1942, proving that a nuclear reaction could be initiated, controlled, and stopped. Chicago Pile-1, as it was called, was the first prototype for several large nuclear reactors constructed at Hanford, Washington, where plutonium, a man-made element heavier than uranium, was produced. Plutonium also could fission and thus was another route to the atomic bomb.
In 1944 Fermi became an American citizen and moved to Los Alamos, New Mexico, where physicist J. Robert Oppenheimerled the Manhattan Project’s laboratory, whose mission was to fashion weapons out of the rare uranium-235 isotope and plutonium. Fermi was an associate director of the lab and headed one of its divisions. When the first plutonium bomb was tested on July 16, 1945, near Alamogordo, New Mexico, Fermi ingeniously made a rough calculation of its explosive energy by noting how far slips of paper were blown from the vertical.
After the war ended, Fermi accepted a permanent position at the University of Chicago, where he influenced another distinguished group of physicists, including Harold Agnew, Owen Chamberlin, Geoffrey Chew, James Cronin, Jerome Friedman, Richard Garwin, Murray Gell-Mann, Marvin Goldberger, Tsung-Dao Lee, Jack Steinberger, and Chen Ning Yang. As in Rome, Fermi recognized that his current pursuits, now in nuclear physics, were approaching a condition of maturity. He thus redirected his sights on reactions at higher energies, a field called elementary particle physics, or high-energy physics.
Credit : Britannica
Picture Credit : Google