The American physicist Ernest Orlando Lawrence (1901-1958), by inventing and successively improving the cyclotron, pioneered in the development of particle accelerators.
Ernest Orlando Lawrence
Ernest O. Lawrence was born on Aug. 8, 1901, in Canton, South Dakota. By age 9 he had become interested in simple electrical devices and by age 13 had constructed wireless equipment. Nevertheless he decided to study medicine after completing his high school education.
Lawrence pursued this goal for a year (1918-1919) at St. Olaf's College in Northfield, Minn., and briefly, beginning the following year, at the University of South Dakota in Vermillion. At the latter institution, he came under the influence of Lewis Akeley, the dean of the College of Electrical Engineering, who acquainted him with the intellectual challenge and rewards of physics. As a result, he abandoned his plans for a medical career, mastered course after course of physics, and completed his bachelor's degree in physics with high honors in 1922. It took him only one academic year to complete his master's degree under W. F. G. Swann. When Swann moved first to the University of Chicago (1923-1924) and then to Yale University, Lawrence accompanied him in both moves. Simultaneously, Lawrence made remarkably rapid progress toward his doctoral degree, which he received at Yale in 1925.
Lawrence's exceptional talents as an experimental physicist earned him a National Research Council fellowship for further study at Yale during 1925-1927. He explored a variety of problems related to his thesis research, which was on the photoelectric effect in potassium vapor. His achievements clearly indicated that Lawrence was one of the most talented experimentalists in the country.
After a year (1927-1928) as assistant professor of physics at Yale, Lawrence accepted a position as associate professor of physics at the University of California at Berkeley. Two years later he became the youngest full professor in Berkeley history. He remained at Berkeley for the rest of his life. In 1932 he married Mary Kimberly Blumer. They had two sons and four daughters.
Within a very short time Lawrence established a thriving school of research at Berkeley and became completely engrossed in his work. Very deliberately, he decided to abandon his past line of research and embark on a new one: nuclear physics. Theoretical considerations indicated, however, that to cultivate this field of research one required nuclear probes, for example, charged particles, of large energy.
To accomplish this, Lawrence designed a machine that would accelerate ions in a spiral path between two D-shaped electrodes. This was the "magnetic resonance accelerator"—the cyclotron. By the early 1930s a small model was made to work by M. Stanley Livingston, then a graduate student working under Lawrence's close supervision. By early 1932 a new 10-inch model was producing protons of energy in excess of 1 million electron volts—an event that precipitated a great deal of excitement and celebration in the laboratory. Since doubling the diameter of a cyclotron theoretically quadruples the energy of the particles it accelerates, and since larger particle energies meant deeper insight into the structure of the nucleus, Lawrence repeatedly pushed for the construction of larger and larger machines in the 1930s. He began with a 27-inch machine and eventually constructed a 184-inch machine, which, although funded in 1940, had to await the end of the war and crucial technical breakthroughs for completion. Meanwhile, many cyclotrons of different sizes had been constructed with Lawrence's help and encouragement in many laboratories throughout the world.
For his invention and development of the cyclotron, Lawrence was elected to membership in the National Academy of Sciences, in 1934, and in many other scientific societies; in addition, he received many medals, honorary degrees, and other distinctions, the highest of which was the Nobel Prize of 1939.
In 1940-1941 a select group of American physicists began laying plans to beat the Germans in the construction of the atomic bomb. Knowing that A. O. C. Nier at Minnesota had used mass-spectroscopic techniques to separate the fissionable isotope of uranium, U235, from its much more abundant companion, U238, Lawrence proposed this method of isotope separation as a concrete plan for obtaining a supply of fissionable material. He argued that if the method was made into a large-scale enterprise it could relatively quickly yield a sufficient supply of U235 for a bomb. In early 1941 he turned his convictions into actions by beginning to convert his 37-inch cyclotron into a huge mass spectrograph.
But at that time three other isotope-separation techniques were also known: a gaseous centrifuge technique, a liquid thermal diffusion technique, and a gaseous diffusion technique. As it turned out, the history of the development of the atomic bomb in the United States involved a race for supremacy among the various isotope-separation techniques. Early in the war Lawrence's electromagnetic separation technique seemed to offer the most promise of success, and as a result it was heavily funded. By early 1945, however, the problems in the gaseous diffusion technique had been solved, and by May this technique began yielding U235 in quantity. Moreover, at about the same time, an entirely independent project, the production of Pu239(the fissionable isotope of plutonium) in the Hanford, Wash., atomic piles proved to be extremely successful. The net result was that Lawrence's electromagnetic separation technique, which had made huge demands on him personally, became obsolete in a very short time.
Even before the war had ended, Lawrence was planning future accelerator projects for Berkeley. The first that he pushed through to completion was the 184-inch cyclotron. By 1946 it was operative, and soon thereafter experiments with it began yielding results of great importance for particle physics. A few years later Lawrence, after securing funds from the Atomic Energy Commission, began supervising the construction of a huge new accelerator, the electron synchrotron, or "bevatron," based on E. M. McMillan's wartime discovery of "phase stability."
In the midst of these successes, Lawrence experienced a severe setback: the failure in 1950 of the so-called Materials Testing Accelerator (MTA), a machine designed to produce Pu239 by proton bombardment of U238. Its failure represented a turning point in Lawrence's life: his health, owing to an intestinal ulcer, began to progressively deteriorate, and his personal relationships with his colleagues took a definite turn for the worse.
Lawrence's life was not without its controversial aspects. Nevertheless, few would deny that he was an extraordinarily gifted human being. One of his associates remarked that his genius lay in being able to precisely estimate what was humanly possible for a man or research group to accomplish. Physics was his life, and for his accomplishments he received, in addition to the Nobel Prize, many other honors, including the Medal of Merit in 1946 and the Fermi Award in 1957. The laboratory at Berkeley, which he directed for so many years, is now called the Lawrence Radiation Laboratory, and when, in 1961, a new transuranic element was discovered there, it was named lawrencium (Lw).
Lawrence was serving as a representative of the United States to the International Conference on Scientific Detection of Nuclear Explosions, which took place in Geneva, Switzerland, when he became critically ill and was rushed back to the United States for surgery. Shortly after the operation, he died in Palo Alto, Calif., on Aug. 27, 1958.
Further Reading on Ernest Orlando Lawrence
Lawrence discussed his discovery of the cyclotron in his Nobel lecture, reprinted in Nobel Foundation, Nobel Lectures in Physics, vol. 2 (1965). A full-length biography of him is Herbert Childs, An American Genius: The Life of Ernest Orlando Lawrence (1968). For insight into Lawrence the man see Nuel Pharr Davis, Lawrence and Oppenheimer (1968). See also M. Stanley Livingston, ed., The Development of High-energy Accelerators (1966).