American physicist Owen Chamberlain (born 1920) won a share of the 1959 Nobel Prize in Physics for proving the existence of the antiproton. Previously, the subatomic particle existed only in theory, and scientists had been frustrated in their attempts to prove it was indeed real. Discovery of its existence led to further discoveries about many more antiparticles. Chamberlain went on to discover the antineutron.
Despite having only the most modest aspirations when he was a young boy, Owen Chamberlain grew up to become a pioneer in the field of physics. His work lead to the discovery of the antiproton, which proved to be a major advancement in the field of anti–matter research.
Owen Chamberlain was born in San Francisco, California, on July 10, 1920, to W. Edward and Genevieve Lucinda (Owen) Chamberlain. His father was a prominent radiologist at Stanford University Hospital. He also had an interest in physics. Discussing his childhood, Chamberlain recalled that when he entered first grade, he was the only student who could not write his own name. He also recalled that he was a poor reader and, ironically, he had no real interest in science. "Mostly, we constructed forts and made cigarettes out of eucalyptus root," he related to an interviewer at the University of California in Berkeley, where he would later become professor emeritus of physics. "I don't think I can really recall any ambitions. I think I wanted to be maybe a streetcar motorman."
When Chamberlain was ten years old, he moved with his family to Philadelphia, Pennsylvania, where he entered the Germantown Friends School. He studied physics and received his bachelor's of science degree at Dartmouth College in New Hampshire in 1941. When he was 21 years old, he entered the graduate school in physics at the University of California at Berkeley, where he began a long–standing association with renowned physicist Emilio Segrè. It was Segrè who inspired Chamberlain to think more critically and scientifically. In the speech he gave on the occasion of winning the Nobel Prize in 1959, he recalled, "Within a short time I found myself working under Professor Emilio Segrè. Whenever there was a pause in the routine parts of our work, his agile mind produced intriguing questions and scientific puzzles to tease my intellect." Unfortunately, his studies were interrupted when the United States entered World War II in 1942.
Involved in the Manhattan Project
That year, Chamberlain joined the Manhattan Project, the United States' secret program to build an atom bomb. The U.S. government began the project in 1942 in response to the growing concern that the Axis powers were close to developing atomic weaponry. The project, operated by the Army Corps of Engineers, was designed to develop an atomic bomb before Germany or Japan did. Noted physicist J. Robert Oppenheimer (1904–1967) directed the construction and test of the first A–bomb at the Los Alamos laboratory. Some of the greatest names in the physics field were involved in the project, including Enrico Fermi, Neils Bohr, James Chadwick, Isidor Rabi, and Richard Tolman.
As part of the project, Chamberlain was able to continue working with Segrè, first in Berkeley, California, and then in Los Alamos, New Mexico. With Segrè, he investigated nuclear cross sections for intermediate–energy neutrons and the spontaneous fission of heavy elements. In addition, he researched uranium isotopes with Ernest O. Lawrence, inventor of the cyclotron, the first particle accelerator.
In 1943, Chamberlain was sent to Los Alamos, where he witnessed the testing of the first atom bomb. Recalling this first test, Chamberlain later told the Berkeley interviewer, "I thought the weapon then ought to be somehow demonstrated for the Japanese rather than used on a city. In retrospect, a demonstration of the nuclear weapon over some lightly populated or unpopulated area would have failed in its purpose. It wasn't that impressive until you gave it the real city to work on."
Continued Graduate Work with Fermi
After the war, in 1946, Chamberlain returned to his graduate studies. However, he continued these studies at the University of Chicago and not at Berkeley, where he did his pre–war graduate work. In Chicago, he studied at the Argonne National Laboratory, where his doctoral research was sponsored by Professor Fermi, who had also been involved in the Manhattan Project. Now, in his capacity as a sponsor, Fermi proved to be an important guide and mentor to Chamberlain. As Chamberlain had demonstrated a strong aptitude for experimental physics, Fermi encouraged his student to move away from theoretical physics, even though that field was more prestigious.
During his Nobel speech, Chamberlain recalled the legendary physicist: "[Fermi] was, I believe, the most intelligent man I have ever met. For a considerable period he devoted several hours per week to helping me with my research toward the doctor's degree. When I faltered, he found a method of circumventing the difficulty. Professor Segrè has taught me the value of asking the right question, for by asking the right question one may find a key to new knowledge. From Professor Fermi, I have learned that even the simplest methods may give answers to difficult questions."
In 1948, Chamberlain received his Ph.D. from the University of Chicago after he had completed his experimental work on the diffraction of slow neutrons in liquids. That same year, he returned to the University of California at Berkeley, to accept a teaching position. That began a long involvement with the institution. Chamberlain would remain at Berkeley for his entire career, except for a brief period in the late 1950s when he took leave to complete a Guggenheim fellowship in Rome and to serve as Loeb lecturer at Harvard University. In 1958, he became a full professor. He eventually became a professor emeritus in 1989.
Found the Elusive Antiproton
Upon his return to Berkeley, Chamberlain conducted research on alpha particle decay, neutron diffraction in liquids, and high–energy nuclear particle reactions. In addition, his research work included extensive studies of proton–proton scattering. This he did with Segrè and Dr. Clyde Wiegand. He also worked on a series of experiments on polarization effects in proton scattering. These experiments later led to triple–scattering experiments with Segrè, Wiegand, Dr. Thomas Ypsilantis, and Dr. Robert D. Tripp. In 1955, his proton scattering experiments with Segrè, Wiegand, and Ypsilantis led to the discovery of the antiproton. The work involved the use of a bevatron, which is a powerful particle accelerator or atom smasher.
According to theory, an antiproton was a mirror image of the proton, a particle found in the nucleus of atoms. That is, the antiproton is a particle exactly like a proton except that it is negatively charged. But the actual existence of the antiproton still eluded scientists by the 1950s. Its existence would prove nature's symmetry. The existence of such antiparticles had been predicated as far back as 1928. The idea was first advanced by Paul Dirac, who theorized that mirror images of known particles, such as the electron and the proton, had to exist. Still, he could not offer any proof. The theory was given a boost in the early 1930s when Carl D. Anderson discovered the positron, a particle with a positive electrical charge and a twin of the negative electron. This discovery greatly excited particle physicists and it led to further research, including Chamberlain's work with the cyclotron at Berkeley. In turn, that research placed the groundwork for later attempts to produce and detect antiprotons. In the speech at the Nobel banquet that he delivered when he won the Nobel Prize, Chamberlain said, "The development of physics, like the development of any science, is a continuous one. Each new idea is dependent upon the ideas of the past. The whole structure of science gradually grows, but only as it is built upon a firm foundation of past research. Each generation of scientists stands upon the shoulders of those who have gone before. In a different way, each generation of scientists depends upon the previous generation for instruction and training."
By the early 1950s, the bevatron accelerator had been constructed at Berkeley. The device could fire protons of 6.2 billion electron volts, a nuclear force far stronger than the energy generated by the hydrogen bomb or even by stars. It would provide the key to the antiproton's discovery, as its ability to propel particles to such high energy levels enabled the researchers to produce these antiprotons.
But one of the hurdles that needed to be surmounted was finding the short–lived antiprotons in the collision debris left in the aftermath of the atom smashing process. Chamberlain and colleagues accomplished this by developing a series of focusing and measuring devices that could isolate the antiprotons. Further, they developed a photographic process to document protons and antiprotons colliding and destroying each other. In 1955, after the researchers recorded forty antiproton sightings, they felt confident enough to announce the results of their experiments. The scientific world was amazed at the finding. The discovery of antiprotons was a giant step forward in the study of matter and anti–matter, as well as a major breakthrough for particle physicists in their study of anti–matter.
Because of the magnitude of importance of this discovery, in 1959 Chamberlain was given the Nobel Prize in Physics for proving the existence of the antiproton. Appropriately, he shared the honor with Segrè his friend and long–time colleague. In his Nobel address, Chamberlain envisioned potential discoveries that could come in the wake of his successful work on the antiproton: "Since the proton and neutron are close sisters, it was expected that the discovery of the antineutron [would] quickly follow that of the antiproton. In fact, it is natural to infer that antiparticles of all charged particles exist."
After discovery of the antiproton, Chamberlain became involved in experiments that were designed to determine the interactions of antiprotons with hydrogen and deuterium, the production of antineutrons from antiprotons, and the scattering of p mesons. His later research also included the Time Projection Chamber and work at the Stanford Linear Accelerator. Eventually, his work did indeed prove the existence of the antineutron.
Chamberlain has authored many scientific papers regarding his discoveries. His work has been published in journals in America and overseas. His professional affiliations include a fellowship in the American Physical Society, membership in the National Academy of Sciences, and membership in the American Association for the Advancement of Science. He has also been a Fellow of the American Academy of Arts and Sciences. He was awarded a Guggenheim Fellowship in 1957 to conduct studies in the physics of antinucleons at the University of Rome.
Later in his career, Chamberlain was politically active in issues involving peace and social justice, and he often spoke out against the Vietnam War. He was a member of Scientists for Sakharov, Orlov, and Shcharansky, who were three physicists of the Soviet Union who were imprisoned for their political beliefs. In the 1980s, he was one of the founders of the nuclear freeze movement.
His prestige as a Nobel Prize–winner no doubt enhanced his influence in these matters. But of the prize itself, he once remarked, "I think that no doubt, I'm listened to much more as a Nobel Prize winner. I often think that people in the public domain pay too much attention to winners and not enough to other scientists who are also very well qualified to speak up on similar issues." In 1943, Chamberlain married Beatrice Babette Cooper. They had three daughters and a son before they were divorced in 1978. He married June Steingart in 1980. In 1985, Chamberlain was diagnosed with Parkinson's disease. In 1989, he retired from teaching, although his legacy continues on.
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