Edwin Mattison McMillan
Edwin Mattison McMillan was an influential American physicist known for his pioneering work in nuclear science and particle physics. Born to a physician and a homemaker, McMillan developed an early interest in science, eventually pursuing a degree in physics at the California Institute of Technology (Caltech) and later earning a PhD from Princeton University. He became a key figure at the University of California, Berkeley, where he worked alongside notable scientists like Ernest Orlando Lawrence.
McMillan's most significant contributions include the discovery of neptunium and plutonium, elements critical to the development of nuclear weapons and energy. His innovative research led to the advancement of the cyclotron, a particle accelerator, and the introduction of the principle of phase stability, which greatly enhanced the energy output of these machines. His work was instrumental during World War II, particularly in relation to the Manhattan Project.
In recognition of his contributions, McMillan received the Nobel Prize in Chemistry in 1951, shared the Atoms for Peace Award in 1963, and was awarded the National Medal of Science in 1990. He served as director of the Lawrence Berkeley Laboratory until his retirement in 1973, leaving a lasting impact on both nuclear physics and the scientific community. McMillan's legacy continues to influence modern scientific research and technology.
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Edwin Mattison McMillan
Nuclear Physicist
- Born: September 18, 1907
- Birthplace: Redondo Beach, California
- Died: September 7, 1991
- Place of death: El Cerrito, California
American physicist
Twentieth-century American physicist and chemist Edwin McMillan discovered the radioactive metal neptunium and codiscovered plutonium, which is fundamental to nuclear power and nuclear weapons. He also discovered the important principle of phase stability, which made possible the high-energy accelerators of the late twentieth century and allowed for fundamental advances in the understanding of the nature of matter.
Born: September 18, 1907; Redondo Beach, California
Died: September 7, 1991; El Cerrito, California
Primary fields: Physics; chemistry
Specialties: Atomic and molecular physics; nuclear physics; statistical mechanics
Early Life
Edwin Mattison McMillan was the only child born to Edwin McMillan, a physician, and Anne Marie Mattison McMillan, a housewife. As a teenager, McMillan spent considerable time attending public lectures and finding reasons to visit the laboratories at the California Institute of Technology (Caltech), which was only about a mile from his home. It was in this environment that he developed his powers of observation, attention to detail, and a sense of self-reliance.
Following high school, McMillan majored in physics at Caltech and received his bachelor’s of science degree in 1928 and a master’s degree one year later. He then transferred to Princeton University for his doctoral work, receiving his PhD in 1932. McMillan was awarded a two-year National Research Fellowship for postdoctoral study, which he elected to pursue at the University of California, Berkeley.
Following his fellowship, McMillan was awarded a research assistantship with Ernest Orlando Lawrence at the Berkeley Radiation Laboratory on the UC campus working with Lawrence’s invention, the cyclotron, a machine that uses a circular motion to accelerate charged particles to high energies. McMillan was appointed an instructor in the Physics Department at Berkeley in 1935. He became an assistant professor in 1936, an associate professor in 1941, and a full professor of physics in 1946.
Life’s Work
Shortly after joining Lawrence’s staff, McMillan helped to advance the effectiveness of the cyclotron by improving magnetic field shaping, particle beam extraction, and power and control systems. He was also active in the laboratory’s experimental program. With M. Stanley Livingston, he discovered the isotope oxygen-15, which is now used in medical physics to diagnose disease. With Samuel Ruben, he discovered a long-lived isotope of beryllium, beryllium-10, which now has important applications in the dating of geological and archaeological materials.
After the discovery of fission in Germany in 1939, McMillan quickly began to investigate this new phenomenon; specifically, he and other researchers began to recreate the experiments Enrico Fermi conducted with uranium in the mid-1930s. Using uranium oxide, stacks of cigarette paper, and a neutron beam formed by the cyclotron, the men were able to produce fissions in the uranium. McMillan also noticed, however, that after the neutron bombardment, the original uranium oxide had a new radioactivity. In 1940, after a year of exhaustive chemical tests that both confirmed and invalidated current chemical theories, McMillan and his colleague Philip Abelson realized they had discovered element 93 and had opened a new field of transuranic elements (elements that have an atomic number higher than 92, the atomic weight of uranium). McMillan named the new element neptunium after the planet Neptune, which is the next planet in the solar system after Uranus, after which uranium was named.
McMillan immediately started experiments directed at finding element 94, but before he could complete the work he was called to the Massachusetts Institute of Technology to do radar research for the US government. With McMillan’s permission and notes, Glenn Theodore Seaborg and coworkers Arthur C. Wahl and Joseph W. Kennedy continued McMillan’s work, eventually finding element 94, which McMillan named plutonium, for the planet Pluto, the next planet in the solar system after Neptune. For his work in discovering transuranic elements, McMillan (jointly with Seaborg) received the Nobel Prize in Chemistry in 1951.
McMillan’s and Seaborg’s research on plutonium was of crucial importance to the Manhattan Project (the US research and development program that produced the first atomic bomb), because plutonium is a fissionable material suitable for the fabrication of a nuclear bomb. In fact, the bomb used at Nagasaki, Japan, in the final days of World War II was made of plutonium. In the early work on the Manhattan Project, the plutonium that was produced in the cyclotron was of critical importance in establishing design criteria for the bomb and for the reactors that would produce the plutonium in the quantities needed.
McMillan continued his research for the war effort by investigating sonar at the US Navy’s Radio and Sound Laboratory in San Diego, California. He finished his war work with the Manhattan Project at the Los Alamos National Laboratory in New Mexico, and it was there at the conclusion of the war that his thoughts turned to the problem of the energy limitation for particles produced by prewar cyclotrons. This limitation was a result of the special theory of relativity, which requires that as a particle increases its velocity, it also increases its mass. Therefore, during the particle’s acceleration in the cyclotron, it fell out of synchronism with the radio frequency field and eventually failed to gain energy from it. McMillan was able to show theoretically that if one used a new principle of phase stability, the relativistic limitation could be overcome.
McMillan’s concept of phase stability was immediately put to the test in an electron synchrotron, as he named it, which was constructed at the Berkeley laboratory, and the principle of phase stability was soon applied to dramatically increase the energy available from cyclotrons, which amounted to more than twice the energy achieved with a conventional design. Soon a number of synchrocyclotrons, as they came to be called, were built at nuclear laboratories throughout the world.
The phase stability concept was also discovered by a Russian scientist, Vladimir I. Veksler, who was working independently and in isolation in the Soviet Union during World War II. For their joint discovery, McMillan and Veksler shared the prestigious Atoms for Peace Award for 1963, which had a prize of seventy-five thousand dollars.
In July of 1958, Ernest Lawrence, who was in declining health, appointed McMillan deputy director of the Berkeley Radiation Laboratory, and after Lawrence died in 1959, McMillan was named director of the laboratory, which was renamed the Ernest O. Lawrence Berkeley Laboratory and is commonly known today as Berkeley Lab. McMillan would remain director of the laboratory until his retirement in 1973.
McMillan has been recognized in many ways for his service to science and his country. From 1954 to 1958 he served on the General Advisory Committee of the Atomic Energy Commission, and from 1960 to 1966 on the Commission on High Energy Physics of the International Union of Pure and Applied Physics. He served in 1972 as vice president of the American Association for the Advancement of Science and was a member of the National Academy of Sciences, having achieved this honor at the early age of thirty-nine. He was also a member of the American Philosophical Society and a fellow of both the American Physical Society and the American Academy of Arts and Sciences. McMillan received the National Medal of Science in 1990.
In 1941, McMillan married Elsie Walford Blumer, daughter of Dr. George Blumer, dean of Yale Medical School. Together, they had three children. In 1984, McMillan suffered the first of several strokes and died in 1991.
Impact
McMillan’s discovery of neptunium opened the field of the transuranic elements. The element plutonium, which he codiscovered, is of profound importance to the nuclear fuel cycle and is, along with uranium-235, the fissionable material that makes nuclear weaponry possible. Furthermore, one of the isotopes of plutonium, Pu-238, was found to emit alpha particles over a fairly long half-life, making it useful as a power source in thermal electric generators, which are used for research in space.
The principle of phase stability led to a new generation of accelerators and is still a fundamental element in the design of “atom-smashers” such as the Superconducting Super Collider, which was designed to produce twenty-trillion-electronvolt protons.
Bibliography
Bernstein, Jeremy. Plutonium:A History of the World’s Most Dangerous Element. Washington, DC: National Academies Press, 2007. Print. Provides a history of plutonium and includes information about its discovery and use in the creation of nuclear weapons.
Kelly, Cynthia C. The Manhattan Project: The Birth of the Atomic Bomb in the Words of Its Creators, Eyewitnesses, and Historians. New York: Black Dog, 2009. Print. Examines the history of the development of the first nuclear weapons from the perspectives of first-person accounts and primary documents.
Livingood, John J. Principles of Cyclic Particle Accelerators. Princeton, NJ: Van Nostrand, 1961. Print. A chapter of this book is devoted to the idea of phase stability and the associated betatron oscillations of the particle beam. Applications to electron synchrotrons, fixed frequency cyclotrons, and alternating gradient accelerators are given.