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Enrico Fermi: Atomic Energy, 9147


Investigations continued and in October 1934, erratic results were noticed during irradiation experiments on silver. The resulting radioactivity of the metal depended on its placement inside the protective lead container. So experiments were set up to compare the radioactivity produced when various materials were inserted between the radon source and the silver target. On October 22, as an alternative to the heavy metal lead which showed slight activity increase, Fermi suggested a light material: paraffin wax. His accidental choice worked well. The Geiger counter showed the artificial radioactivity of this silver sample to increase by up to a hundred times—the excitement grew. Fermi's explanation was that the multiple hydrogen atoms in the paraffin effectively "slowed" the neutrons to a state that permitted many more collisions with the atoms of silver. The next amazing possibility of controlled or "harnessed" radiation exposure by neutron bombardment was near.

Foreseeing the ramifications of this discovery, Corbino insisted that a patent be applied for immediately. The application was filed on October 26, 1934.

Further work followed this momentous discovery but the group of scientists gradually dispersed as the pace of experimentation slowed; most traveled to North America. The uncertain political climate in Italy and the likelihood of war weighed on the Fermis. With the Rome-Berlin Axis in place, a crusade of anti-Semitism began in 1938. Laura Fermi was Jewish.