Edwin Mattison McMillan Biography (1907-1991)


McMillan was born in Redondo Beach, California, on September 18, 1907. He earned his bachelor's degree (1928) and master's degree (1929) at the CaliforniaInstitute of Technology and his doctorate in physics at Princeton in 1932. After a two-year stint with Ernest Orlando Lawrence at the University of California Radiation Laboratory in Berkeley, he joined the faculty at Berkeley in1935. He became full professor of physics in 1946, associate director of theRadiation Laboratory in 1954, and director in 1958. He remained at the post until his retirement in 1973.

During World War II, McMillan played an important role in the development ofmicrowave radar, sonar, and the atomic bomb. McMillan is best known for two accomplishments, one in the field of chemistry and one in the field of physics. In 1940, while working with Philip Abelson, McMillan discovered the first transuranium element, neptunium. For this discovery, he shared the 1951 NobelPrize for chemistry with Glenn Seaborg. McMillan's second important achievement involved the improvement of particle accelerators. Lawrence's invention ofthe cyclotron in 1932 provided physicists with a powerful new tool for the study of matter.

For a decade, larger and larger cyclotrons--"atom-smashers"--were designed, built, and utilized to probe ever deeper into the atomic nucleus. Hopes for continued progress were dampened, however, as a fundamental limitation of cyclotrons became more obvious. As particles are accelerated, they become more massive. At relatively low energies, this "relativistic mass increase" is not very important. In larger cyclotrons, however, with the ability to generate very high energy particles, the problem can become severe. As particles gain mass, they tend to slow down and fall out of step with the AC electrical fieldsthat accelerate them. They become lost within the machine. A solution to thisproblem was devised independently in the mid-1940s by V. I. Veksler in the Soviet Union and Edwin McMillan in the United States. Veksler and McMillan realized that the electrical field or the magnetic field--or both--could be modified to stay in step with the slow-downed particles in a machine. For example, if the electrical field is made to change direction a bit more slowly during each revolution of the particles, it can be made to stay in phase with those particles. This theory of phase stability was soon used in the design of larger, more powerful accelerators, for which McMillan suggested the name synchrotron. For their invention of this modification of the cyclotron, Veksler and McMillan shared the 1963 Atoms for Peace Award.

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