Hiroshima_ The World's Bomb - Andrew J. Rotter [64]
On 2 December 1942, the first day of Chanukah and also a day of mourning for Jews, an estimated two million of whom had already been murdered by the Nazis, Fermi was ready to test his strange machine. Over forty people squeezed onto the balcony of the squash court, among them the head of research for the Du Pont Company, whom Leslie Groves was hoping to attract to the bomb-building project. The pile was punctured at various points by control rods made with cadmium, an absorber of neutrons. A young physicist named George Weil, the only person on the floor next to the pile, was responsible for manipulating these. Three young men stood atop the pile wielding buckets of cadmium salts; the physicist Norman Hilberg held an axe that could cut a rope holding a master safety rod should it be necessary to halt a runaway reaction. Just after 10.30 a.m., on Fermi’s order, Weil pulled the last safety rod, 13 feet in height, out 1 foot. Radiation-measuring instruments clicked audibly. A graph confirmed the presence of radiation. Fermi checked his calculations against the readings and told Weil to withdraw the rod another 6 inches. As if alarmed by the subsequent rise in neutron activity, the safety rod, on its own volition, slammed down into place. ‘I’m hungry,’ Fermi said. ‘Let’s go to lunch.’
The experiment resumed at 2.00 p.m. The last control rod was withdrawn another 6 inches and the meters showed another jump in activity. ‘The clicks came more and more rapidly,’ wrote Fermi’s colleague Herbert Anderson, ‘and after a while they began to merge into a roar; the counter couldn’t follow anymore.’ Technicians changed the scale of the recording devices, trying to keep up with the pile’s intensity. Fermi proclaimed that the pile had gone critical. He let it run for twenty-eight minutes altogether as the neutron counter continued to click and the stylus on the chart recorder swung upward. ‘When do we become scared?’ the physicist Leona Woods asked Fermi. Finally, as the instruments showed that radiation levels in the balcony were becoming worrisome, Fermi ordered that the safety rods be dropped into place. The reactor had performed as expected and produced atomic power. Eugene Wigner passed around a bottle of Chianti, and everyone drank a bit from paper cups. Compton, who had won a cigar from Lawrence, phoned Conant in Washington, and neither man concealed his excitement. But, as people left the cold squash court, Leo Szilard approached Fermi, shook his hand, and told him gloomily that this was ‘a black day in the history of mankind’.18
Not every top American physicist moved to Chicago in 1942. Coming out of the September 1941 meeting with Compton and Conant and especially the 6 December meeting in Washington, wherein Bush charged him with producing U-235 for the bomb, Ernest Lawrence, while staying in close touch with the Met Lab, was more determined than ever to maintain Berkeley as a center for nuclear research. Since the late 1920s, Lawrence had been interested in smashing atoms, exploring their intricacies and unleashing their energy, and he had built larger and larger machines to help him do this. These were his cyclotrons, circular structures that allowed him to fire atomic particles around magnetized racetracks at tremendous speed; his latest, the frame of which he had showed Marcus Oliphant the previous summer, might (he hoped) accelerate particles to an energy of 100 million volts, if it did not first spring a leak, blow a tube, or cause a blackout on campus and in nearby neighborhoods of Berkeley. The atom-smashing all but accidentally produced radiation, unknown to Lawrence and unmeasured because of his impatience to increase