BAINBRIDGE, KENNETH (KEN) TOMPKINS

(b. Cooperstown, New York, 27 July 1904;d. Lexington, Massachusetts, 14 July 1996)

experimental physics, mass spectography, microwave radar.

Many people remember Bainbridge for his famous remark to J. Robert Oppenheimer on the morning of 16 July 1945, immediately after the first atomic bomb test at Alamogordo, New Mexico: “Now we are all sons of bitches.” This contrasted with Oppenheimer’s sophisticated reference to the line from the Bhagavad Gita: “I have become Death; the Destroyer of Worlds.” But Bainbridge, an outstanding experimenter, was always more direct in his approach. Bainbridge was recognized early in his scientific career for his precise measurements of mass differences between nuclear isotopes, using the mass spectrograph he had designed. When compared to the energies of decay radiations, these confirmed Albert Einstein’s mass-energy equivalency. In collaboration with the late Jabez Curry Street, he designed and built a small cyclotron at Harvard University that was later sent to Los Alamos National Laboratory in New Mexico. Even before the United States entered World War II Bainbridge joined the Radiation Laboratory at the Massachusetts Institute of Technology (MIT) spending 2 1/2 years there developing microwave radar, particularly high-powered systems. In the spring of 1943 he transferred to the nuclear weapons project at Los Alamos. Starting in 1945, he built a new, more precise mass spectrograph, began the construction of a new cyclotron, and was able to measure changes in the decay rates of some radioactive nuclei resulting from differing molecular bonding and from physical compression.

Early Years 1904–1929. Bainbridge was born on 27 July 1904, in Cooperstown, New York. He grew up in New York City, attending the Horace Mann School and the Horace Mann High School. The Bainbridge family lived on Riverside Drive near 158th Street and the Hudson River, where just after World War I returning naval vessels docked. Bainbridge, interested in radio in high school, put an antenna on the family’s rooftop. Ship radio operators would knock on his door to investigate. Ken bought 5-watt vacuum tubes from his callers for a couple of dollars. Thereby he set up a radiotelephone, obtained a radio amateur license, and operated a “ham” station with the call letters 2WN.

In 1921 Ken entered MIT to study electrical engineering in a five-year cooperative program with the General Electric Company (GE). In the summers he worked at one of the General Electric facilities, first in Lynn, Massachusetts, and then mostly at the Research Laboratories in Schenectady, New York. As an outgrowth of his work there, Ken obtained a couple of patents on photo-cells. After completion, with both an MS and a BS degree, he changed his direction to physics. Karl T. Compton, a consultant to GE, recognized Bainbridge’s quality, and recruited him for graduate work at Princeton, where he was head of the physics department. Bainbridge remembered, with pleasant amusement, his interview with Dean Andrew Fleming West and quoted him as saying, “You're nice boys, but it’s too bad you never went to college.”

It was at Princeton that Bainbridge began his lifelong interest in mass spectroscopy. He first searched for the then undetected element 87 of the periodic table, an element that should behave chemically as a heavy alkali. But his search was unfruitful and it was left to Marguerite Perey at the Radium Institute of Paris to find element 87 and call it “francium.” This disappointment discouraged Bainbridge but did not stop him.

Postdoctoral Appointments, 1929–1934. After completing his PhD program at Princeton, Bainbridge spent four years at the Franklin Institute’s Bartol Research Foundation, first as a National Research Council fellow and then as a Bartol Research Foundation fellow. The “Bartol” was directed by William Francis Gray Swann, who was especially interested in research on cosmic rays and nuclear physics. Bainbridge continued to develop his mass spectrographs at Bartol and undertook precise nuclear mass measurements to confirm the mass-energy equivalence, E = Mc². While at Bartol, in September 1931 Bainbridge married Margaret (“Peg”) Pitkin, then a member of the Swarthmore teaching faculty.

In the summer of 1933 Bainbridge joined the Cavendish Laboratory of Lord Ernest Rutherford, a world leader in experimental nuclear physics. In a later year Bainbridge described how Rutherford stopped him in passing in a corridor to ridicule as obviously impractical a suggestion just made to him by a visitor, Leo Szilard, for a nuclear chain reaction based on protons. Szilard went on to envisage a much more practical process involving neutrons, which, of course, only became reality after neutron-induced uranium fission was discovered. Bainbridge began a continuing close friendship with John D. Cock-roft (later Sir John) at Cambridge, which became important later. Peg had also traveled to Cambridge, and their first child, Martin K. Bainbridge, was born there in 1933.

Prewar Academia, 1934–1939. In September of 1934 Bainbridge returned to the United States and joined the faculty of the physics department at Harvard University, where he later became the first George Vasmer Leverett Professor of Physics. He built and employed an improved mass spectrograph that he had designed during his sojourn at the Cavendish Laboratory and proposed a method of modifying isotopic abundance using gaseous counterflow in a Holweck molecular vacuum pump. In 1935 Bainbridge led the construction of a cyclotron as a joint project between the Harvard Graduate School of Engineering, represented by Professor Harry Mimno, and the physics department, represented by with Bainbridge and Street. Bainbridge and Street were the primary workers. The cyclotron was complete in 1938, and the report of the physics department in 1939 states that radioactive materials were supplied to Harvard Medical School, Massachusetts General Hospital, and Memorial Hospital in New York, and in addition to uses for physics at Woods Hole Meteorological Station, MIT physics department, and members of Williams College and Purdue University.

It supported the work of fourteen researchers in Harvard departments. According to the late Roger Hickman, who as a graduate student assisted in the construction, the cost was about $40,000, of which about $20,000 came from the Rockefeller Foundation, which then funded medical research. The Bainbridge’s two daughters Joan Bainbridge Safford and Margaret Tomkins (Bainbridge) Robinson were born in Cambridge, Massachusetts.

The War Years, 1939–1945. In 1939 Bainbridge became concerned about the rise of Nazism in 1939 as Europe became embroiled in World War II. When Britain sent the Tizard Mission in September of 1940, sharing their military secrets, Bainbridge took a leave of absence from Harvard and joined Ernest Orlando Lawrence in the newly formed Radiation Laboratory at MIT to develop microwave “radar.” While there Bainbridge interacted with the local Raytheon company. Bainbridge’s friendship with British physicists, especially with Cockroft, who had been a scientist member of the Tizard Mission, became an invaluable asset. In 1941 he was selected to go on a visit to England in 1941 to gain information about the radar program, but he also learned of British progress toward releasing nuclear energy while attending a meeting of the Maud Committee, which was overseeing that effort in Britain. Bainbridge’s particular project at the Radiation Laboratory was the push toward higher-powered radars, especially for the navy. He found the navy at that time the most technically oriented of the U.S. military services and the least handicapped by protocols related to military rank. This experience was reflected in his concern about the organization of Los Alamos, where he was recruited in May of 1943, which operated under the Manhattan District of the U.S. Army and General Leslie R. Groves.

At Los Alamos it became clear that a cyclotron was needed to measure various nuclear reaction cross sections of interest, and to supplement the work already being ably carried out at the Princeton cyclotron. Bainbridge knew where one was to be found—at Harvard. Discussions began at a high administrative and top secret level, between Harvard president James B. Conant (then away from Cambridge) and Groves, and it was agreed that Harvard would sell the cyclotron to the U.S. government for $1 with an informal promise of a cyclotron to replace it when the war was over. Because the atomic bomb project was top secret, the purpose of the purchase had to be disguised from those not cleared for secret information. A medical physicist, Dr. Hymer Friedell, and a nuclear physics expert Robert Wilson accompanied the cyclotron. The “cover story” was that the cyclotron was needed for medical treatment of military personnel, and it was sent to St. Louis to be forwarded to an “unknown destination.”

At Los Alamos early in 1944, at the request of George Kistiakowsky and Oppenheimer, who had been named director of the National Laboratory in 1942, Bainbridge undertook the oversight of the design of high explosive assemblies and the preparations for a full-scale test of a nuclear bomb. In articles in the Bulletin of the Atomic Scientists in 1975, Bainbridge lucidly described the search for an appropriate site, the preparations, and the successful carrying out of the test early in the morning of 16 July 1945. The second of those stories was entitled: “A Foul and Awesome Display.” His immediate thought on witnessing the first explosion was relief that the test was successful; for if not, he would have had to find out what had gone wrong. His famous remark, noted in the introduction above, marked the beginning of his dedication to ending the testing of nuclear weapons and to maintaining civilian control of future developments in that field.

Return to Academic Life, 1945–1969. In the fall of 1945 Bainbridge returned to academic science at Harvard. He undertook construction of a large mass spectrograph, designed for high resolution of masses. The prewar cyclotron was replaced by a much more powerful one utilizing the then newly invented concept of synchronous acceleration. He handed over the task first to Wilson, who had joined the physics department at Harvard after the end of the war, and then to Norman F. Ramsey, who joined Harvard in 1947. Unfortunately, the cyclotron design had been completed before discovery of the pi meson, and the energy of the new synchrocyclotron turned out to be just less than that required for pion production. For about a dozen years the new Harvard cyclotron was employed for many scattering experiments and other studies of nucleon-nucleon forces and of nuclear structure. During construction, Bainbridge insisted to his students that it was for nuclear research and not for medical work. One of the students, David Bodansky, recalls his saying, “There will be no rats running around this cyclotron.” He was shortly contradicted when one of the first experiments was, in fact, irradiation of animals! The operating life of the cyclotron was greatly extended when it became a facility for research on the use and clinical applications of the highly focused proton beam in collaborative projects with staff members from the Massachusetts General Hospital. It was shut down finally on 2 June 2002, when its role was taken over by an even more powerful and flexible dedicated machine at the hospital, enabling further expansion of the important clinical applications developed using the physics cyclotron.

Bainbridge devoted much of his energy just after the war to designing for the Harvard physics department an advanced laboratory in nuclear physics intended as a course of study for graduate students. Because of the many new students underwritten by the GI Bill, the number of graduate students in physics was far greater than had been the norm before the war. Nuclear physics had gained new visibility and popularity from its contributions to winning the war. Students gained their first experience in activities preparing them for research in experimental physics in Bainbridge’s meticulously designed and documented laboratory. The experiments ranged from a replication of Joseph John Thompson’s positive ray apparatus (a precursor of mass spectrographs) to a bent crystal x-ray spectrograph, a 180-degree beta-ray spectrograph using the then new technique of nuclear magnetic resonance (NMR) for field calibration, and an analysis of tracks in photographic emulsions to identify muons. Demonstrating his dislike of the development and testing of nuclear weapons, he also set up an associated facility to collect and measure radioactive fallout. It is noteworthy that he measured fallout from the first Chinese bomb test as soon as the radioactive particles arrived in Massachusetts, two weeks after the explosion. In his fundamental research he built balanced ionization chambers with which he was able to determine changes in lifetimes of several long-lived isomers, which decay by internal electron conversion when their atoms are differently bonded chemically or are subjected to physical compression. In addition to constructing his large mass spectrograph to make precise measurements of mass differences among pairs, he built an elegant double-focusing electron spectrograph. In the years before his retirement in 1975, Bainbridge devoted much of his time to improving the facilities in his graduate student advanced laboratory, which was later integrated with the laboratory for advanced undergraduates.

From 1950 to 1954 Bainbridge served as chairman of the physics department at Harvard. This was a time marked by the vicious attacks on certain members of academia, and especially at Harvard, by the House Un-American Activities Committee and a committee of the Senate dominated by Senator Joseph McCarthy. Bainbridge gave generously of his time and energy overseeing the relationship between the university administration and one of his colleagues, who became a prime target of these attacks. In this he had the unanimous support of the department. Bainbridge was as precise in his administrative dealings as in his physics. In January 1955, he wrote to this author (RW) that the department, the dean, and the president had voted to appoint me as assistant professor, but the appointment still had to be approved by the Harvard Corporation. But, he added, “the last time the Corporation rejected such a recommendation was in 1847” (or some similar date). Such careful precision, which included the details of possible promotion to tenure, was most helpful to young faculty.

Later Years and Retirement. In the late 1950s Bainbridge was one of the first members of the Harvard faculty to participate in a new academic exchange program with the Soviet Union. The University of Leningrad was designated as Harvard’s sister university. In June 1975 in his last year before his retirement, Bainbridge was enlisted to serve on a joint Iran-Harvard planning commission to design Reza Shah Kabir University for Iran. Bainbridge and his Harvard colleagues made several visits to Iran; however, this project was short-lived because of the political upheaval and expulsion of the shah from Iran.

Bainbridge never forgot the awful problems that the world faces because of the knowledge of how to make an atomic bomb. He constantly discussed them, stimulated no doubt by his wife, Peg, who was a member of the Society of Friends (Quakers) and an antiwar activist. He was most proud of his articles in the Bulletin of the Atomic Scientists, one on the use of the bomb; and another on the importance of civilian control of atomic energy. He opposed the May-Johnson bill, which kept military control, whereas the MacMahon bill set up the Atomic Energy Commission of five civilian commissioners. He was proud of his membership in the Federation of Atomic Scientists. He would discuss some of the major actors: Compton, Henry D. Smyth, Szilard, Oppenheimer, and somewhat reluctantly, Edward Teller.

In 1966 Bainbridge and his family finished a summer house in Chilmark, Martha’s Vineyard, designed and constructed with the same careful attention to detail that exemplified all of Bainbridge’s activities. Then in January 1967 Bainbridge suffered a tragic loss when his wife Margaret (Pitkin) Bainbridge, the mother of his three children, died suddenly at their home in Watertown, Massachusetts, from a blood clot associated with a recently fractured wrist. In October 1969 Bainbridge married Helen Brinkley King, an old friend then serving as an editor for the William Morrow publishing house in New York City. She, as well as his son, Martin, predeceased him. His two daughters, Joan and Margaret, led successful professional lives.

Bainbridge was awarded the Levy Medal of the Franklin Institute in 1934. He was elected a fellow of the American Academy of Arts and Sciences in 1937 and a member of the National Academy of Sciences in 1946. He was the recipient of two letters of commendation from General Groves for his work on the Manhattan Project and the Presidential Certificate of Merit for his services as staff member of the MIT Radiation Laboratory.

BIBLIOGRAPHY

The primary source for this memoir is the memoir for the National Academy of Sciences by Robert V. Pound and Norman F. Ramsey, both colleagues of Bainbridge and colleagues and close friends of this author. With their permission, I quote and paraphrase liberally excerpts from their fine memoir.

WORKS BY BAINBRIDGE

“The Harvard Cyclotron.” Harvard Alumni Bulletin 17 (May 1940): 1010–1015.

“The Reminiscences of Kenneth T. Bainbridge.” Transcript of an oral history interview conducted by Joan Safford. Columbia University Oral History Research Office, New York, 1964.

“Prelude to Trinity.” The Bulletin of Atomic Scientists 31 (April 1975): 42–46.

“A Foul and Awesome Display.” The Bulletin of Atomic Scientists31 (May 1975): 40–46.

“Electrical Engineer.” Transcript of an oral history interview conducted by John Bryant. IEEE History Center, Rutgers University, New Brunswick, NJ, 1991.

OTHER SOURCES

Pound, Robert V., and Norman F. Ramsey. “Kenneth Tompkins Bainbridge, July 27, 1904–July 14, 1996.” In Biographical Memoirs, Vol. 76. Washington, DC: National Academy Press, 1999.

Pound, Robert, Richard Wilson, and Norman Ramsey. “Memorial Minute: Kenneth Tompkins Bainbridge.” Harvard University Gazette (7 May 1998): 8.

Sopka, Katherine R. “Physics at Harvard during the Past Half-Century: A Brief Departmental History.” Harvard University, Department of Physics, 1978.

Wilson, Richard. A Brief History of the Harvard University Cyclotrons. Cambridge, MA: Harvard University Press, 2004.

Richard Wilson