Edwin Mattison McMillan (September 18, 1907 – September 7, 1991) was an American physicist and Nobel laureate credited with being the first ever to produce a transuranium element. He received the Nobel Prize in Chemistry in 1951.
He then took his Doctor of Philosophy from Princeton University in 1932 for the thesis: "Deflection of a Beam of HCI Molecules in a Non-Homogeneous Electric Field" under the supervision of Edward Condon.
In 1940 he and Philip Abelson created neptunium, while conducting a fission experiment of uranium-239 with neutrons, using the cyclotron at Berkeley. The newly found isotope of neptunium was created by absorption of neutron into the uranium-239 and a subsequent beta decay. McMillan understood the underlying principle of the reaction and started to bombard the uranium-239 with deuterium to create the element 94. He moved to the radar research at the Massachusetts Institute of Technology and Glenn T. Seaborg finished the work.
In World War II, he was involved in research on radar at MIT in Cambridge, Massachusetts, sonar near San Diego, and nuclear weapons at the Los Alamos Laboratory. After this unsteady time during the World War II, he joined the Berkeley Radiation Laboratory again and became head of the institute after the death of Ernest Lawrence in 1958.
In 1945 he developed ideas for the improvement of the cyclotron, leading to the development of the synchrotron. The synchrotron was used to create new elements at Berkeley Radiation Laboratory extending the periodic system of elements far beyond the 92 elements known before 1940.
With Glenn T. Seaborg, he shared the Nobel Prize in Chemistry in 1951 for the creation of the first transuranium elements. This medal is currently held at the National Museum of American History, a division of The Smithsonian.
In 1946, he became a full professor at Berkeley, and in 1954 he was appointed associate director of the Lawrence Radiation Laboratory, being promoted to director in 1958, where he stayed until his retirement in 1973.
He was elected to the National Academy of Sciences in 1947, serving as its chairman from 1968 to 1971.