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COLLECTION Identifier: HUGFP 152

Papers of Kenneth T. Bainbridge, 1873, 1923-1996


Kenneth T. Bainbridge (1904-1996), the first George Vasmer Leverett Professor of Physics at Harvard University (1934-1975), was recognized as a scientific leader in the field of physics for his design and application of mass spectrographs as research tools for mass measurements. He designed and built the first cyclotron at Harvard University, participated in the development of radar during World War II, and oversaw the test explosion of the first nuclear bomb at Alamogordo, New Mexico in July 1945.


  • Creation: 1873, 1923-1996


Conditions on Use and Access

Permission of the University Archives is required for access to the Papers of Kenneth Tompkins Bainbridge. Please consult the reference staff for further details. Additional restrictions may apply to some material.


41 cubic feet (92 document boxes, 1 folio box, 10 portfolio folders)

The Papers of Kenneth Tompkins Bainbridge document his professional activities for the length of his career, including his contributions to the field of nuclear physics. The research materials, writings, and lectures contained in this collection describe his work with mass spectrographs and cyclotrons. These materials also document his thoughts as an experimenter and the details of his experiments. This collection also explains the role he played in the development of radar during World War II and outlines his supervision of the first nuclear explosion in 1945. The correspondence in these papers documents Bainbridge's interaction and collaboration with some of the leading physicists of his time and reveals how his ideas and concepts developed. Bainbridge's class notes, lecture materials, syllabi, reading lists, and other instructional materials illustrate his teaching methodology and teaching career. Moreover, this collection includes materials that describe his involvement in the development of the Harvard physics program. The biographical and social activist materials in this collection document both Bainbridge's personal and professional life and include correspondence with family members and non-scientists.



Kenneth T. Bainbridge (1904-1996), the first George Vasmer Leverett Professor of Physics at Harvard University (1934-1975), was one of the leading scientists of his generation. He was a noted authority in the field of mass spectroscopy and the application of mass spectrographs as research tools. He designed and built the first cyclotron at Harvard University, participated in the development of radar at the Massachusetts Institute of Technology Radiation Laboratory during World War II, and oversaw the test explosion of the first atomic bomb at Alamogordo, New Mexico in July, 1945. During his tenure at Harvard University, he helped attract brilliant faculty members and students to the physics department, actively worked to improve the physics department's laboratory courses, and assisted in the design and creation of an advanced nuclear physics laboratory for graduate students.

Early Life and Education

Bainbridge was born on July 27, 1904 to William Warin Bainbridge and Mae (Tompkins) Bainbridge in Cooperstown, New York; he was the second of three brothers. Growing up in New York, Bainbridge attended the Horace Mann School (1910-1915) and the Horace Mann High School (1915-1921) where he received a solid preparation in mathematics, physics, chemistry, and biology. He also developed an interest in radio and became a "ham" operator with his own call letters 2WN. His interaction with other radio operators stimulated his interest in electrical engineering, science, and technology.

College Days

Bainbridge entered the Massachusetts Institute of Technology (MIT) (1921-1925) to study electrical engineering and enrolled in the General Electric Company cooperative engineering program. He worked at the General Electric plants in Lynn, Massachusetts and Schenectady, New York. It was his work at General Electric that laid the foundation for his future research. As an apprentice and budding scientist, Bainbridge learned the use of different types of machine tools including shapers, lathes, drill presses and grinders. He studied drafting and worked in the General Electric Company engineering department developing various relay devices. Spending time in the Street Lighting Department and Meter Departments, Bainbridge tested street light transformers and calibrated meters. Moreover, he became familiar with large machines and oscillographs testing the limits of equipment destruction in the Switch Gear Testing Department. Bainbridge's studies and work at MIT and General Electric led to several patented inventions. He built several photoelectric devices that advanced the development of television and talking movies and his improvement of electro-magnetic pumps for liquids, used for refrigeration purposes in household refrigerators, found application in the circulating pumps of reactors.

After graduating from MIT, Bainbridge decided that he was more interested in working in a research laboratory than in an engineering department. He consequently enrolled at Princeton University (1926-1929) to pursue his strong interest in physics. His attraction to mass spectroscopy began at Princeton University as a result of his desire to search for the then undetected element 87 of the periodic table. During his years at Princeton, Bainbridge designed his first mass spectrograph, developed methods for identifying rare elements, and began the study of nuclei. He also developed contacts with students from various fields that he maintained over his lifetime and that benefited him in his future endeavors.

Years before World War II

Following his PhD from Princeton University, Bainbridge spent the next four years at the Bartol Research Foundation at the Franklin Institute in Pennsylvania (1929-1933). This was a successful period of time for Bainbridge in which he learned the art as well as the science of subtle and difficult mass measurements. At the Bartol laboratories, Bainbridge built a mass spectrometer for studying the relative abundance of isotopes and a spectrograph for the accurate determination of the masses of nuclei. In 1933, he reported the first accurate experimental check of Albert Einstein's theory of the equivalence of mass and energy. As a result of his efforts at Bartol, Bainbridge was awarded the Louis Edward Levy Medal.

Traveling abroad, Bainbridge continued his studies of mass spectroscopy at the Cavendish Laboratory in Cambridge, England from July 1933 to September 1934. Here, Bainbridge designed a new and better mass spectrograph and started his first work with nuclear chain reactions. At Cavendish, Bainbridge interacted with some of the most significant nuclear physicists of his time, sharpened his research skills, and prepared himself to teach physics at a university.

By 1934, after developing some of the most advanced mass spectrographs of his era, Bainbridge had established himself as a leader in mass spectroscopy.

Early Years at Harvard University

Bainbridge joined the Harvard faculty in September 1934. His appointment, as well as that of his colleague Jabez Curry Street, introduced nuclear physics to Harvard and led to a reinvigorated physics program.

From 1934 to 1937, Bainbridge constructed a mass spectrograph and continued his studies of atomic masses. He also began to focus his work on the structure of nuclear isotopes. In 1937 he began work on the building of a Cyclotron, a powerful tool used for the production of artificial substances possessing properties identical to radium. Bainbridge designed and personally drafted plans of the magnet, coils, acceleration chamber, and other accessories for this new apparatus. By 1940, the Cyclotron was complete and was being used to aid the physics staff in their studies of atomic nuclei and other subatomic particles.

In addition to his work on the Cyclotron, Bainbridge developed a method of isotope separation using a Holweck pump. Isotope separation is an important process for the preparation of fuel for nuclear fission devices such as atomic reactors or atomic weapons. When Bainbridge brought his Holweck pump to the attention of the authorities in Washington D.C., he was told that classified work was already being done on this process by government scientists and that he should abandon his own work.

World War II War Work

In September 1940, Bainbridge became the first physicist recruited to work for the Massachusetts Institute of Technology Radiation Laboratory in Cambridge, Massachusetts. This facility became the largest wartime laboratory devoted to radar development in the United States. It was charged with the task of developing microwave air-interception radars, night-fighter radars for airplanes, gun direction radars for anti-aircraft systems, and long-range navigation radar systems. Bainbridge, on a leave of absence from Harvard University, spent the next two and a-half years working here.

Bainbridge began work at the radiation laboratory as head of the Modulator Group between November 1940 and March 1941. From March 1941 to May 1941 he served on a technical mission in England in order to exchange information about radar development with the British. He visited various radar installations in England, saw British radar equipment under actual combat conditions, and studied radar development. Moreover, he met with a group of British scientists and learned first hand about British efforts to develop an atomic weapon. Upon returning to the United States, Bainbridge reported orally on both British radar and atomic weapons development.

Bainbridge's technical work at the radiation laboratory concerned the development of radars of increasing power for the United States Navy. He became head of a division responsible for ship-borne interception control radar, ground systems search and warning class radar, ground-based fire control radar, microwave early-warning radar, search and fighter-control radar, and fire-control radar. Many of these systems eventually defended aircraft carriers in the Pacific war.

In September 1943, Bainbridge was recruited for the Manhattan Project, a United States government research project (1942-1945) that produced the first atomic bombs. His initial task involved work on the design specifications for the Hiroshima and Nagasaki type bombs. Furthermore, he helped develop methods by which bomb trajectories could be determined.

In early 1944, Bainbridge was asked to undertake the oversight of the design of high explosive assemblies and prepare a full-scale test of an atomic bomb. In March 1945, Bainbridge was appointed director of the division responsible for this atomic test, code named Trinity. As director, Bainbridge was responsible for selecting a test site and building a base camp that eventually would contain guards and soldiers, houses, shelters, and site roads. Bainbridge was also involved in developing bomb detonator equipment, planning yield measuring devices, and solving any ballistic design problems. The test was successfully carried out on July 16, 1945. After the test, Bainbridge helped write an official account of the Trinity Project for the government.

Later Years at Harvard University

Shortly after his return to Harvard University in 1946, Bainbridge began the construction of a larger mass spectrograph. Using this new device, Bainbridge established the existence of a fundamental part of matter that had eluded his contemporaries, the neutrino. During his remaining years at Harvard, Bainbridge continued to seek techniques and mechanisms by which the precise yields of atomics masses could be obtained.

During the 1950's, Bainbridge began work on a new and larger cyclotron, the synchrocyclotron. Harvard University's pre-war cyclotron had been requisitioned by the United States Army during World War II and ended up at Los Alamos, never to return. Although the responsibility for the final completion of this new machine was turned over to others, Bainbridge helped design the magnet for this larger device. Using this new machine, Bainbridge continued to perform research on isotopes and radioactivity until his retirement.

Much of Bainbridge's time at Harvard University from the 1950's through the 1970's was spent improving the physics program. Bainbridge devoted a great deal of energy to improving both the graduate and under-graduate advanced physics laboratories. As a lecturer, he introduced many graduate students to experimental nuclear physics and developed many new and innovative physics laboratory experiments for study. As chairman of the physics department, Bainbridge oversaw the rehabilitation of the Jefferson Laboratory, the introduction of the Morris Loeb Lectureship, and an increase in the number of physics courses offered to students.

Bainbridge retired from active teaching in 1975.


Kenneth Bainbridge married Margaret (Peg) Pitkin in September, 1931. They had three children: Martin Keeler Bainbridge, Joan (Bainbridge) Safford, and Margaret Tompkins (Bainbridge) Robinson. In January 1967, Margaret died. In October, 1969 Kenneth married Helen Brinkley King. Helen died in 1989.

Kenneth T. Bainbridge died on July 14, 1996.


Motivated to find the truth and to reveal the unknown, Kenneth Bainbridge made early and lasting contributions to the field of physics. He won a reputation for his precise data collection methods and for his use of clever experiments to test both well-founded and tenuous scientific hypotheses. As a master builder of apparatus, his mass spectrographs and early cyclotrons helped advance the study of atomic masses and other chemical properties. He worked and talked with some of the most distinguished scientists of his era and became one of the leading scientists of his generation.

In World War II, he supported America's scientific war effort helping to develop radar and the atomic bomb. This last experience made him acutely aware of the dangers, as well as the promise, of nuclear power. Following the war he became dedicated to ending nuclear weapons testing and a life-long advocate of the civilian control of developments in the nuclear field.

During his long career, Bainbridge maintained a high standard of scholarship, a willingness to shoulder administrative responsibilities, and a deep concern and enjoyment for teaching. He made an early impact in physics and continued to pioneer in the development of this science for many years.

References used for this biography were:

  1. Bainbridge, Kenneth T. Electrical Engineer, transcript of an oral history interview conducted by John Bryant, IEEE History Center, Rutgers University (New Brunswick : New Jersey, 1991).
  1. Bainbridge, Kenneth T. The Reminiscences of Kenneth T. Bainbridge, transcript of an oral history interview conducted by Joan Safford, Columbia University Oral History Research Office (New York, New York : 1964).
  1. Bainbridge, Kenneth T. The Harvard Cyclotron. Harvard Alumni Bulletin, 17 May 1940, 1010-1015.
  1. Bainbridge, Kenneth T. Prelude to Trinity. The Bulletin of Atomic Scientists 31 (April 1975) : 42-46.
  1. Bainbridge, Kenneth T. A Foul and Awesome Display. The Bulletin of Atomic Scientists 31 (May 1975) : 40-46.
  1. Pound, Robert V. Kenneth Tompkins Bainbridge. Physics Today 50 (1997) : 80-82.
  1. Pound, Robert V. and Norman F. Ramsey. Kenneth Tompkins Bainbridge, July 27, 1904 - July 14, 1996. Biographical Memoirs, vol. 76. Washington, D.C.: National Academy Press, 1999.
  1. Pound, Robert, Richard Wilson, Norman Ramsey. Memorial Minute: Kenneth Tompkins Bainbridge. Harvard University Gazette (May 7, 1998) : 8.
  1. Roth, Frederick A. Kenneth Bainbridge. In The Yearbook of Harvard and Radcliffe, 28-29. Cambridge, Massachusetts : Harvard Yearbook Publications, Inc., 1967.
  1. Sopka, Katherine R. Physics at Harvard During the Past Half-Century: A Brief Departmental History. Harvard University, Department of Physics, 1978.

Series and Sub-series in the Collection

  1. Biographical Materials
  2. Correspondence
  3. ___Alphabetically arranged correspondence
  4. ___Chronologically and alphabetically arranged correspondence
  5. ___Chronologically arranged correspondence
  6. ___Harvard University correspondence
  7. ___Evaluations and Recommendations
  8. Research Materials
  9. ___MIT/General Electric Research Laboratory
  10. ___Bartol Research Foundation
  11. ___Cavendish Laboratory
  12. ___MIT Radiation Laboratory
  13. ___Trinity Project
  14. ___Brookhaven National Laboratory
  15. ___Harvard University
  16. Teaching Materials
  17. ___Course Instruction
  18. ___Course Notes
  19. Consultant Services
  20. Talks and Lectures
  21. Writings
  22. Committees and Boards
  23. Social Activism

Acquisition Information

  1. Accession number: 13283; 1996 March 29.
  2. Accession number: 13512; 1997 March 10.

Related Material

  1. Records of the Harvard University Department of Physics, 1879-1983.
  2. American Institute of Physics. Center for History of Physics. Niels Bohr Library. Emilio Segrè Visual Archives. One Physics Ellipse, College, Park, MD 20740. Bainbridge gave the AIP photographs of himself and other scientists.
  3. Churchill College, University of Cambridge, Cambridge, England. Crockcroft Letters.
  4. Columbia University. Oral History Research Office, Butler Library, New York, New York, 10027. The Oral History Research Office has a transcript of an oral history titled: The Reminiscences of Kenneth T. Bainbridge.

General note

This document last updated 2018 October 26.

Processing Information

Processed February 2004 by Dominic P. Grandinetti.

Processing included re-housing materials in the appropriate containers, establishment of series and sub-series hierarchy, and the creation of this finding aid. The archivist placed the documents into acid-free folders, re-housed the materials into archival document boxes, and examined the folder contents to establish the date of the material. In all respects, the archivist attempted to retain and preserve the original arrangement and existing relationships of the documents as established by Bainbridge. Details about the processing and arrangement of each series are noted at the series level.

Bainbridge, Kenneth T. (Kenneth Tompkins), 1904-1996. Papers of Kenneth Tompkins Bainbridge : an inventory
Language of description

Repository Details

Part of the Harvard University Archives Repository

Holding nearly four centuries of materials, the Harvard University Archives is the principal repository for the institutional records of Harvard University and the personal archives of Harvard faculty, as well as collections related to students, alumni, Harvard-affiliates and other associated topics. The collections document the intellectual, cultural, administrative and social life of Harvard and the influence of the University as it emerged across the globe.

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