John Ray Dunning was an American physicist, who recorded a historic measurement of energy released from the fission of natural uranium. He played key role in the Manhattan Project to build the atomic bomb.
Background
John Ray Dunning was born on September 24, 1907, in Shelby, Nebraska. He was the son of Josephine Thelen and Albert Chester Dunning, a grain merchant and amateur radio engineer. Encouraged by his family to enter the ministry or the law, Dunning was more interested in scientific endeavors and built his first radio set, reportedly the first in his part of the country, when he was twelve years old.
Education
In 1925, Dunning graduated from Shelby High School and enrolled in Nebraska Wesleyan University, where he received a B. A. degree with highest honors in 1929. From 1929 to 1933, Dunning was a graduate student in physics at Columbia University.
Career
Dunning's entire academic career was spent at Columbia University, where he was appointed to the physics faculty as an instructor in 1933. His principal subject of research was the neutron. His collaboration with George B. Pegram produced twenty-four papers on neutrons between 1933 and 1936 and formed the basis for his Ph. D. dissertation (1935) on the emission and scattering of neutrons.
In 1935, he was promoted to assistant professor, and in the 1935-1936 academic year was granted a Cutting Traveling Fellowship, which gave him the opportunity to meet many of the great nuclear physicists of his time, including Enrico Fermi in Rome, Ernest Rutherford and James Chadwick at Cambridge, Werner Heisenberg at the University of Leipzig, and Niels Bohr at the University of Copenhagen.
Upon his return to Columbia, Dunning brought his considerable talents, energy, and enthusiasm to developing a leading laboratory for neutron research. He had followed the development of the cyclotron at Berkeley and was determined, despite a lack of government funding, to build a cyclotron at Columbia. Foundation and industry gifts helped Dunning and his colleagues establish, in the basement of Pupin, Columbia University's first cyclotron, which is now part of the permanent collection of the Smithsonian Institution.
In 1938, Dunning was promoted to associate professor of physics. At this time startling developments were being announced from the laboratories of Enrico Fermi, who first fired neutron bullets into uranium, and Otto Hahn, who announced that uranium, when bombarded by neutrons, splits into elements weighing about half as much, implying the release of large amounts of energy.
Dunning was working with his colleague and long-time collaborator, Eugene T. Booth, when on the evening of January 25, 1939, he recorded a historic measurement of energy released from the fission of natural uranium, a moment of great importance. It was engagingly reported in the New Yorker (August 19, 1945) and more formally in "The Fission of Uranium" (Physical Review, March 1, 1939).
Dunning initiated and directed the original experiments at Columbia on the separation of uranium 235 from other isotopes by the gaseous diffusion method. During the Manhattan Project to build the atomic bomb, Dunning was the director of research for Division I SAM (Substitute Alloy Materials) Laboratories, the code name for the nuclear laboratory at Columbia University where the development of the gaseous diffusion process was carried out. After World War II, Dunning served as scientific director for the construction of the 385 MEV synchrocyclotron at the Nevis Laboratories, a joint project of the Atomic Energy Commission, the Office of Naval Research, and Columbia University, located at Irvington-on-the-Hudson, New York.
Dunning was promoted to full professor in 1946 and was appointed Thayer Lindsley professor of applied science. From 1950 to 1969, he served as dean of the School of Engineering and Applied Science at Columbia. Throughout his career he remained committed to informing and educating not only his colleagues and students, but the general public as well, about the nature and challenges of atomic energy. In 1941, he published, with Hugh Campbell Paxton, Matter, Energy, and Radiation. He delivered the Sigma Xi National Lectures in 1948: "The Future of Atomic Energy" and "Atomic Structure and Energy. " These lectures were published in American Scientist (October 1949 and December 1950). He retired to Florida in 1969 and died in Key Biscayne.