Ouen Chemberlen
USABiography of Owen Chamberlain
Owen Chamberlain, an American physicist, was born in San Francisco, California, to Edward Chamberlain and Genevieve Lucinda (Owen) Chamberlain. At the age of 10, his family moved to Philadelphia, where he received his secondary education. He obtained a Bachelor's degree from Dartmouth College in 1941 and enrolled in the graduate program at the University of California, Berkeley. However, after the United States entered World War II, he interrupted his studies to participate in the Manhattan Project, a secret program to develop atomic bombs. Chamberlain conducted research on uranium isotopes in Berkeley under the guidance of Ernest O. Lawrence, the inventor of the cyclotron, and in 1943, he was sent to Los Alamos, where he continued his work and witnessed the first test of the bomb in 1945.
After the war, Chamberlain specialized in particle physics at the Argonne National Laboratory in Chicago, focusing on the diffusion of slow neutrons in liquids. At the same time, he resumed his graduate studies at the University of Chicago under the supervision of Enrico Fermi and obtained his Ph.D. in 1948. In the same year, he accepted an invitation to return to Berkeley as a physics professor, becoming an assistant professor in 1950, an associate professor in 1954, and a full professor in 1958. At Berkeley, Chamberlain utilized the university's cyclotron, a new high-energy particle accelerator, to study the scattering of fast protons and neutrons.
In the early 1950s, Chamberlain began collaborating with Emilio Segrè, his colleague at Berkeley whom he had met during their time at Los Alamos, and a research group that included Clyde Wiegand and Thomas Ipsilantis. Segrè represented the renowned Italian physics school established by Fermi at the University of Rome in the 1930s. Their joint work led to the discovery of the antiproton, the theoretical counterpart of a proton but with opposite electrical charge and some other inverse properties. In 1928, the English physicist P.A.M. Dirac predicted the existence of antiparticles based on equations he derived by combining Albert Einstein's theory of relativity with quantum theory. However, the existence of antiparticles was not universally accepted without experimental confirmation. Trust in Dirac's theory grew when, four years later, Carl D. Anderson discovered the positron, the counterpart of the negatively charged electron but with a positive charge (i.e., the antielectron). Positrons were observed in cosmic rays, high-energy radiation bombarding the Earth from space. This discovery stimulated the search for other antiparticles using newly constructed particle accelerators. Since antiparticles are produced in the destructive collision of an accelerated particle and a target, obtaining such particles requires high energy. To obtain a heavy particle like the antiproton, more energy was needed than the accelerators available at that time could provide. The situation changed with the construction of the bevatron in Berkeley, the most powerful particle accelerator at that time, capable of accelerating particles to energies reaching billions of electron volts. Using this facility, Chamberlain, Segrè, and their colleagues accelerated protons to an energy of 6.2 billion electron volts and bombarded copper atoms with them. Although theoretically this energy was sufficient to produce antiprotons, their quantity was expected to be small, their lifetime short, and they were extremely difficult to detect among the debris left after collisions, which included a large number of other subatomic particles. Solving the problem of detection and identification was Chamberlain's and Segrè's major achievement, along with their research group. They developed a complex and ingenious system consisting of magnets and magnetic focusing devices that isolated particles possessing the mass, charge, and velocity of the antiproton from all others. Electron counters and timers measured the speed of the particles as they passed through a predetermined path; proton-antiproton annihilation was detected using photographic emulsion (which served as definitive confirmation of other measurements); and other means were used to eliminate possible errors. The emulsion recorded the track of the incoming antiproton, which ended in annihilation, resembling a star, with the tracks of the annihilation products serving as rays. It was discovered that mesons, approximately five of them per annihilation event, were the annihilation products.
In 1955, when a convincing number (40) of detections had accumulated (only one of approximately 30,000 particles was an antiproton, and one antiproton was observed approximately every 15 minutes), the scientists announced the discovery of the antiproton. "The bevatron is the only energy source large enough to produce antiprotons," Chamberlain later said. "Even stars are a million times colder than needed, whereas a hydrogen bomb, which is essentially a star, belongs to a different category." This experiment also revealed that antiprotons do not exist by themselves but always appear in pairs: proton-antiproton, just as positrons appear only in electron-positron pairs. This observation confirmed Dirac's theory and convinced scientists that other antiparticles exist, regardless of whether they can be observed. In the months following the main experiments, Chamberlain and his colleagues conducted related research using various photographic techniques to obtain more images of proton-antiproton annihilation. A Guggenheim Fellowship allowed him to spend 1957 at the University of Rome's physics department, where he continued his research on the antiproton, partially in collaboration with Edoardo Amaldi, another physicist from Fermi's original group in the 1930s. Upon his return to Berkeley, Chamberlain received the title of full professor of physics, and the following year, he was invited to Harvard for a semester as a physics lecturer.
Chamberlain and Segrè received the Nobel Prize in Physics in 1959 for the discovery of the antiproton. In his speech, Erik Hultén of the Royal Swedish Academy of Sciences acknowledged Chamberlain and his "ingenious methods of recognition and analysis of the new particle." In his Nobel lecture, Chamberlain summarized the results of his work with colleagues. "Since the proton and neutron are close relatives," he said, "it was expected that the discovery of the antineutron would quickly follow the discovery of the antiproton. It would be natural to assume that antiparticles exist for all charged particles." While remaining at Berkeley, Chamberlain continued to work in the field of particle physics, researching the interaction of antiprotons with hydrogen and deuterium, pion scattering, and the possibility of obtaining antineutrons from antiprotons.
In 1943, Chamberlain married Beatrice Babette Cooper, and they had three daughters and a son. The marriage was dissolved in 1978. Chamberlain was a member of the American Physical Society, the National Academy of Sciences, the American Association for the Advancement of Science, and the American Academy of Arts and Sciences.
