Volume 1, Issue 7
Berkeley's Scientific Legacy
1940: Edwin M. McMillan and the transuranium triumph
For many years, scientists believed that Uranium, with its atomic weight of 92, was the upper limit of the periodic table. But in 1940, more than a century and a half after Uranium was first discovered, UC Berkeley physicist Edwin M. McMillan, working with Philip Abelson at Lawrence Radiation Laboratory, boosted the number of known elements to 93. Neptunium led the way for the discovery of many other elements heavier than Uranium, and the development of various nuclear fuels.
Nobel Laureate Edwin M. McMillan
During those early days at the Lawrence Radiation Laboratory, Ernest O. Lawrence ran a tight ship with a limited budget. "You had to be a theorist, experimentalist, and an engineer," McMillan once said. Still, Lawrence's newly-invented cyclotron enabled the researchers to conduct groundbreaking experiments with huge scientific pay-offs.
In some ways, McMillan and Abelson succeeded where famed Italian physicist Enrico Fermi fell short. In 1934, Fermi claimed that by bombarding uranium with neutrons, he had converted it into a new element, number 93 on the periodic table. It was later found that Fermi had actually split the uranium atom, demonstrating nuclear fission, but not another element.
With the aid of the cyclotron though, McMillan and Abelson conducted their own fission experiments and eventually produced a true sample of element 93. Following the naming of uranium, the new element was dubbed neptunium for the next planet out in our solar system.
Edwin McMillan the year he discovered neptunium
McMillan and his collaborators went on to find early evidence of element 94. However it was during those experiments that he was called to MIT to conduct research for the war effort. There, he helped develop radar and sonar and, later at Los Alamos, worked on the atomic bomb. Back at the Berkeley Lab, Glenn Seaborg and his colleagues continued McMillan's experiments and eventually confirmed the discovery of plutonium. That line of research made headlines when the atomic bomb was dropped on Nagasaki, ending the war.
In 1951, McMillan and Seaborg shared the Nobel Prize in Chemistry for their "discoveries in the chemistry of transuranium elements."
After the death of Lawrence in 1958, McMillan was appointed director of the Lawrence Radiation Laboratory at Berkeley and Livermore. Shortly after, he discovered "phase stability," a principle that massively increased the energy of particle accelerators. The findings led to McMillan's invention of the synchrotron, still a key instrument in nuclear physics research. He and Russian physicist VI Veksler shared a 1963 Atoms for Peace Award for their independent work in this area.
In 1971, the Lawrence Berkeley Laboratory and the Lawrence Livermore Laboratory split into two entities as they exist today. McMillan directed the former until his retirement in 1973. He died in 1991.