Enrico Fermi. Joshua Wells. ELEC 424: Solid State Devices. Dr. Dunlop

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1 Enrico Fermi Joshua Wells ELEC 424: Solid State Devices Dr. Dunlop March 4, 2003

2 Wells 2 If the 19th century was the century of chemistry, the 20th was the century of physics (Rhodes 1). So begins Time Magazine s article on Enrico Fermi in their Top 100 Scientists and Thinkers of the 20 th century. With the multitude of developments during the 20 th century, including medical imaging, the computer, transistors and television, one stands out as the most advanced technical feat of them all: the development of nuclear energy. Enrico Fermi, with his theories on neutrons, high-energy physics and other areas, is considered one of the fathers of atomic energy. His life and career would take him on a journey from helping to develop the principles on how our universe interacts, to unlocking the secret to the most caustic weapon known to man ( Enrico Fermi 1-2). Enrico Fermi was born on the 29 th of September, 1901 in Rome, Italy. His father was Alberto Fermi, one of the Chief Inspectors at the Ministry of Communications, working with the Italian railroad ( Enrico Fermi 1). His mother went by the name of Ida De Gattis, an elementary school teacher. Enrico had two older siblings: a sister named Maria and a brother named Giulio. An incident in 1915 involving Giulio would begin to lead Enrico down his future path. Giulio developed a throat abscess and was taken to the local hospital in Rome for a routine surgery operation. Before he was able to be fully anesthetized, however, Giulio passed away. Enrico dealt with his grief by losing himself in books (Fermi 16-18). On one particular afternoon, he was able to procure a two-volume treatise on mathematical physics. Over the next few days, he became completely enthralled with the concepts contained within the work. On some occasions, he would even correct the mathematical formulas in the treatise. When he had completed both volumes, he told his older sister Maria that he had not even noticed they were written in Latin (Rhodes 1-2). At the age of eighteen, Enrico left home for Pisa to study physics at the Reale Scuola Normale of Pisa, a school established by Napolean Bonaparte in 1810 to attract the top students of the time (Fermi 22-23). Although he did spend much time in the laboratories and classrooms, he was equally well-known for his pranks and mischievousness. One such incident involved locking his classmate Franco Rasetti in his own home. The two eventually became inseparable friends and worked on a number of physics projects together under the direction of their professor, Dr. Luigi Puccianti. At

3 Wells 3 the age of 21, in 1922, Enrico received his degree of Doctor of Physics from the University. At his dissertation, his explanation of Roengten rays (X-rays) was so above the evaluators comprehension, he was granted his degree but the university refused to publish his work (Fermi 23-26). In the years that would follow, Enrico Fermi would work with distinguished professors, scientists, and physicists of the times. In 1923, he spent several months working with Professor Max Born, a noted physicist in the area of crystal lattices, followed by a stint with P. Ehrenfest, who worked in the field of quantum statistics, which would greatly influence Fermi s later work ( Enrico Fermi 1) ( Max Born 1). In 1926, working as a professor at the University of Rome, Fermi developed his theories on statistical laws, known today as Fermi Statistics. The principle behind Fermi Statistics is the study of large numbers of particles, which is important when looking at semiconductors or other materials. In dealing with large numbers of particles, we are interested only in the statistical behavior of the group as a whole rather than in the behavior of each individual particle. Fermi, along with Paul Dirac, created a probability distribution function that gives the probability that a quantum state at the energy E will be occupied by an electron (Neamen 88-91). This equation, known as the Fermi-Dirac distribution function, is shown below: 1 f F E 1 exp E E f kt Fermi s next great accomplishment came in the form of an accident in the summer of 1934 while working at the University of Rome on neutron bombardment. During an experiment with several of his colleagues, Fermi and the others noticed a change in the behavior of silver during a radioactivity test based on the location of the silver in the test set-up. They began to move the silver around the laboratory and found that the silver, when tested for radioactivity, was affected by any objects within its vicinity. Eventually, they found that if the silver was surrounded by a high concentration of hydrogen atoms, the artificially induced radioactivity of silver could be increased several hundred times by slowing down the incoming neutron irradiation. With further experimentation, the theory of slow-neutrons was created (Fermi ). This

4 Wells 4 process essentially allowed Fermi and his colleagues to create artificially radioactive substances in large quantities at very small expense of resources or funds. These radioactive transformations would eventually become the founding theories in the development of nuclear energy, although they did not realize it at the time. It was a blessing in disguise. If fission had come to light in the mid-1930s, while democracies still slept, Nazi Germany would have won a long lead toward building an atom bomb (Rhodes 1-2). The work Fermi did on slow-neutrons and radioactivity earned him the Nobel Prize in Physics in Immediately following his reception of the award, he fled to America with his wife Laura and children, Giulio and Nella, to escape Mussolini s fascist dictatorship in Italy. Upon arrival in the United States, Fermi took up refuge at Columbia University. In the year that would follow, Fermi worked at the University further developing the Slow-Neutron theory to the point of discovering nuclear fission. In 1939, Fermi and Szilard, a fellow physicist, co-invented the first nuclear reactor at Columbia University (Rhodes 2). This led to the first demonstration of a controlled nuclear reaction in 1942 at the University of Chicago. Fermi was working at the University on the recently established Manhattan project, and on a cold December morning, he demonstrated his discovery on a volleyball field ( Enrico Fermi 1). One of Fermi s colleagues described the moment: For some time we had known that we were about to unlock a giant Still, we would not escape an eerie feeling when we knew we had actually done it (Rhodes 2). This discovery would earn Fermi the name Architect of the Atomic Age (Atoms for the World 44). Even though Fermi had helped to invent the technology that eventually would be used to build the first atomic bombs, in 1949 he would enter the debate to fight against the development of the hydrogen bomb. This type of device could yield much more firepower than the original atomic bombs dropped on Nagasaki and Hiroshima. He called it a weapon which in practical effect is almost one of genocide (Rhodes 2). His advice was ignored. Fermi spent the rest of his life working as a researcher at the University of Chicago. He occupied himself with the mysterious origin of cosmic rays, thereby developing a theory, according to which a universal magnetic field acting as a giant

5 Wells 5 accelerator would account for the fantastic energies present in the cosmic ray particles. ( Enrico Fermi 1-2). In 1954, Fermi died prematurely of stomach cancer, having lived out the last few years of his life in Chicago. He is most remembered for his development of Slow- Neutron Theory, which would eventually lead him to the discovery of nuclear fission. His theories and developments in the field of artificial radioactivity would also allow future scientists to create elements above Uranium, number 92. Uranium was thought to be the heaviest of all elements in the periodic table. In 1960, however, element 99 was developed by Russian and American scientists, and named fermium in honor of Enrico Fermi (Atoms for the World 123).

6 Wells 6 Works Cited Enrico Fermi Biography. Noble Lectures: Physics Fermi, Laura. Atoms for the World. Chicago: University of Chicago Press, Fermi, Laura. Atoms in the Family: My Live with Enrico Fermi. Chicago: University of Chicago Press, Max Born Biography. Noble Lectures: Physics Neamen, Donald A. Semiconductor Physics and Devices. New York: McGraw- Hill, Rhodes, Richard. Atomic Physcist: Enrico Fermi TIME 100: Scientists and Thinkers.

One nucleus splits into two smaller nuclei and typically a few neutrons by the bombardment of a neutron. U-235 is the only naturally occurring

One nucleus splits into two smaller nuclei and typically a few neutrons by the bombardment of a neutron. U-235 is the only naturally occurring nuclide that fissions However, both U-238 and Th-232 can be