Kenneth Tompkins Bainbridge (July 27, 1904 – July 14, 1996) was an American physicist at Harvard University who worked on cyclotron research. His accurate measurements of mass differences between nuclear isotopes allowed him to confirm Albert Einstein's mass–energy equivalence concept. He was the Director of the Manhattan Project's Trinity nuclear test, which took place July 16, 1945. Bainbridge described the Trinity explosion as a "foul and awesome display". He was educated at Horace Mann School in New York. While at high school he developed an interest in ham radio which inspired him to enter Massachusetts Institute of Technology (MIT) in 1921 to study electrical engineering. In five years he earned both Bachelor of Science (S.B.) and Master of Science (S.M.) degrees. During the summer breaks he worked at General Electric's laboratories in Lynn, Massachusetts and Schenectady, New York. While there he obtained three patents related to photoelectric tubes.

Bainbridge's work at General Electric made him aware of how interested he was in physics. Upon graduating from MIT in 1926, he enrolled at Princeton University, where Karl T. Compton, a consultant to General Electric, was on the faculty. While at Princeton, Bainbridge created his first mass spectrograph, came up with methods for identifying elements, and started studying nuclei.

Early career

Bainbridge enjoyed a series of prestigious fellowships after graduation. He was awarded a National Research Council, and then a Bartol Research Foundation fellowship. At the time the Franklin Institute's Bartol Research Foundation was located on the Swarthmore College campus in Pennsylvania, and was directed by W. F. G. Swann, an English physicist with an interest in nuclear physics. Bainbridge spent four years (1929-1933) at the Franklin Institute’s Bartol laboratories and during his time there Bainbridge learned how to take subtle and difficult mass measurements. He used this instrument to verify Albert Einstein's mass–energy equivalence, E = mc<sup>2</sup>. Since Bainbridge was the first to successfully test Einstein’s theory of the equivalence of mass and energy, he was awarded the Louis Edward Levy Medal.

One of the cyclotron's most notable experiments was in nuclear transmutation, specifically the synthesis of precious metals including gold, which Bainbridge and his collaborators Rubby Sherr and Herbert H. Anderson announced in 1941.

Bainbridge was elected a Fellow of the American Academy of Arts and Sciences in 1937. His interest in mass spectroscopy led naturally to an interest in the relative abundance of isotopes. The discovery of nuclear fission in uranium-235 led to an interest in separating this isotope. He proposed using a Holweck pump to produce the vacuum necessary for this work, and enlisted George B. Kistiakowsky and E. Bright Wilson to help. There was little interest in their work because research was being carried out elsewhere. Bainbridge ended up bringing his Holweck pump to government authorities in Washington D.C., however the government authorities claimed that scientists working for the government were already working on a process of isotope separation and that he should discontinue his work using the Holweck pump for isotope separation. Bainbridge ended up finding a site that was approximately 200 miles away from Los Alamos, located in the Alamogordo Gunnery Range. Bainbridge along with his assistant director, John Williams who was also a physicist planned and oversaw the construction of the needed facilities at the test site. The facilities consisted of observation bunkers, hundreds of miles of wiring, miles of paved roads, as well as housing. Additionally, Bainbridge played a role in the development of bomb detonator equipment and setting up equipment for measuring the yield of the explosion. He turned to Oppenheimer and said, "Now we are all sons of bitches."

For his work on the Manhattan Project, Bainbridge received two letters of commendation from the project's director, Major General Leslie R. Groves, Jr. He also received a Presidential Certificate of Merit for his work at the MIT Radiation Laboratory.

Postwar

Bainbridge returned to Harvard after the war, and initiated the construction of a synchro-cyclotron, which has since been dismantled. Also, upon arriving back at Harvard, Bainbridge created a larger mass spectrograph. Utilizing his new device, Bainbridge was able to establish the existence of the neutrino, which is a basic component of matter that had eluded scientists for some time. He died at his home in Lexington, Massachusetts, on July 14, 1996. He was survived by his daughters from his first marriage, Joan Bainbridge Safford and Margaret Bainbridge Robinson. He was buried in the Abel's Hill Cemetery on Martha's Vineyard, in a plot with his first wife Margaret and his son Martin. His papers are in the Harvard University Archives.

In the 2023 film Oppenheimer, he is portrayed by Josh Peck.

See also

  • Bainbridge mass spectrometer

Notes

References

  • Oral History interview transcript for Kenneth Bainbridge on 16 March 1977, American Institute of Physics, Niels Bohr Library and Archives - Session I
  • Oral History interview transcript for Kenneth Bainbridge on 23 March 1977, American Institute of Physics, Niels Bohr Library and Archives - Session II