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Fermi, Enrico

nuclear bomb neutrons italian

[fair mee] (1901–54) Italian–US nuclear physicist: built first atomic reactor.

Enrico Fermi was the greatest Italian scientist of modern times and was highly creative both as a theoretical and experimental physicist. The son of a railway official, he showed ability from an early age and earned his PhD at Pisa, researching on X-rays. Fermi then worked with at Göttingen and with P Ehrenfest (1880–1933) at Leiden, before returning to a professorship at Rome in 1927. He had already published over 30 papers, including some on quantum statistics (Fermi–Dirac statistics) followed by work on spin½ particles (now called fermions) such as the electron.

Fermi worked hard to build up Italian physics, but the circle of talent around him was dispersed by the growth of Fascism, and Fermi and his wife, who was Jewish, left for Columbia University, New York in 1938. While in Rome, Fermi worked on the effect, hyperfine structure, cosmic rays and virtual quanta. In 1933 he produced the theory of radioactive beta-decay, whereby a neutron emits an electron (beta-particle) and an anti-neutrino and becomes a proton. The following year he showed that, rather as the had used helium nuclei (alpha-particles) to induce nuclear transmutations, neutrons were even more effective. This led to his rapid discovery of over 40 new radioactive isotopes. He then, by chance, discovered that paraffin wax could be used to slow down the neutrons and make them more effective, by a factor of hundreds, in causing transmutations of nuclei (they remain close to the target nucleus longer and are thus more likely to be absorbed). For all this work he received the 1938 Nobel Prize for physics.

Fermi had misinterpreted the transmutation of uranium with neutrons, but the ideas of in 1938 corrected this, and proposed that nuclear fission with production of additional neutrons was occurring and F Strassmann (1902–80) in Berlin also obtained these results, and both parties realized that vast amounts of energy could be released in such a chain reaction. Fermi, moved quickly to warn Roosevelt and urge him to develop a nuclear weapon before Germany did so. The Manhattan project was set up (at a final cost of $2 billion) and Fermi’s group at Chicago obtained the first controlled self-sustaining nuclear reaction (in a graphite-moderated reactor or ‘pile’ at Stagg Field stadium) on 2 December 1942. A historic telephone call was made by COMPTON to the managing committee at Harvard stating that ‘the Italian navigator has just landed in the New World’.

Fermi continued to work on the project and attended the first test explosion of the fission bomb (A-bomb) in the New Mexico desert. While approving of its use against Japan, he, like , opposed the development of the fusion bomb (H-bomb). He defended Oppenheimer, the director of Los Alamos Laboratory, where the work was done, against charges of disloyalty and of being a security risk.

Fermi took a professorship at Chicago after the war, but died young of cancer. He was much liked as an inspiring teacher and warm and vivacious character, enjoying sports and displaying clarity as a lecturer and research leader. Element number 100 was named fermium after him.

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