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| Fig. 1: Lawrence and colleague in the Radiation Lab with 60-inch cyclotron. (Courtesy of NARA. Source: Wikimedia Commons_) |
Ernest Orlando Lawrence Berkeley National Laboratory, formerly known as the "Radiation Laboratory", is the oldest of the laboratories making up our national laboratory system. Its beginnings stem back to 1919, when English scientist Ernest Rutherford bombarded nuclei with alpha particles to induce transformations, but found that he could not penetrate the nuclei of heavier elements without faster alpha particles. [1] For a decade after his discovery, no technology emerged to accelerate particles to the necessary speeds to study these transformations, leading to stagnation in the field of nuclear physics. This changed in 1929 when scientist Ernest O. Lawrence, a new faculty member at the University of California, Berkeley, realized how to engineer a particle accelerating machine, ushering physics into a new age.
Lawrence designed a machine that gradually increased the speed of the moving particles with each cycle, much like pushing a child on a swing. By leveraging the ability of a magnetic field to bend charged particles, he enabled particles to make repeated passes through the same accelerating field, gaining energy on each cycle. [2] In January 1931, he designed the first successful cyclotron. By August of that year, he founded the University of California Radiation Laboratory in a neglected campus lab. As 2ft, 3ft, and 5ft accelerators were developed, this old wooden building became the Mecca of cyclotroneers (Fig. 1). In 1939, three years after Lawrence was named director of the laboratory, he was awarded the Nobel Prize in physics for his development of the cyclotron. It was the first of 13 Nobel Prizes awarded to Berkeley Lab scientists.
However, war was on the horizon. In this era of nuclear research and worldwide catastrophe, Albert Einstein warned President Franklin D. Roosevelt that Germany might be developing atomic explosives. Roosevelt immediately declared a program to build a bomb powered by nuclear fission. Enormous funds flowed into the Berkeley lab, bringing unprecedented changes in its size and scope. Large teams of engineers and scientists spanning a spectrum of backgrounds were created, their efforts aimed toward the singular goal of bomb development. Thus began what historians call the beginning of "big science". [3]
Lawrence developed a plan to separate the fissile (explosive) part of naturally occurring uranium, U-235, from its more abundant isotope U-238. Though most physicists doubted that his separation process would work, there was no time to build a pilot project to test the design. [4] In February 1943, a production plant underwent construction in Oak Ridge, Tennessee for the electromagnetic complex, and in August, the operation began. Edwin McMillan, Glenn Seaborg and their colleagues at the Lawrence Radiation Laboratory pioneered a separate frontier toward nuclear arms. Screening through the myriad of radioactive species that fission produced, McMillan discovered an undocumented substance that behaved much like uranium, but was different. He identified it as a new element, the 93rd in the periodic table - the radioactive neptunium. Shortly after, Seaborg and colleagues discovered the 94th element, plutonium. Within a month of their discovery, it became clear that plutonium was fissionable and may sustain an explosive chain reaction. Years later, in 1951, McMillan and Seaborg were awarded the Nobel Prize in chemistry for their discovery of these first transuranic elements.
In a frenzy to stay ahead of Germany, a production plant was built for plutonium in Hanford, Washington. Like the U-235 plant in Tennessee, by June, 1945 it had produced enough fissile material for a nuclear bomb. At this point, America had two designs to choose from: Lawrence's U-235 or Seaborg's plutonium. Because most of the scientists had higher confidence that the U-235 would detonate, it was decided that the plutonium bomb would be used for a test while the U-235 saved for the war. On July 16, 1945, the desert test, codenamed Trinity, showed scientists the devastating power of the plutonium-powered nuclear bomb. Lawrence, horrified by the test results, urged to demonstrate the destructive power of the bomb to the Japanese army rather than use it on civilians. [4] However, heated discussion persuaded him that a demonstration alone would not sway the Japanese. A mere month later, the history of war changed forever - the U-235 fueled bomb had demolished Hiroshima; the plutonium- fueled bomb had eradicated Nagasaki. Japan gave in to unconditional surrender, and the war in the Pacific came to a close.
After World War II, Berkeley Lab moved toward a broader set of fundamental scientific research. A majority of its contracted research became for nonmilitary purposes. Keeping up its legacy, accelerator design was at the head of the labs research. In 1954, the Bevatron, a proton synchrotron of 6.2 GeV, was completed, and would be used in the coming decades to research elementary particle physics. [5]
Currently, Berkeley Lab is home nearly 4,000 employees in interdisciplinary groups working in divisions that include chemical, material, earth, and life sciences; human genome; structural biology; energy and environment; accelerator and fusion research; artificial photosynthesis, and of course, nuclear science. The spirit of Big Science laid down by Lawrence continues to propel Berkeley Lab to new heights in scientific research.
© Matthew Liu. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. L. Heilbron, Ernest Rutherford: And the Explosion of Atoms (Oxford Portraits in Science) (Oxford University Press, 2003).
[2] M. S. Livingston, "The Cyclotron," The Scientific Monthly 46, 198 (1938).
[3] M. Hiltzik, Big Science: Ernest Lawrence and the Invention that Launched the Military-Industrial Complex (Simon & Schuster, 2016).
[4] H. Childs, An American Genius: The Life of Ernest Orlando Lawrence, Father of the Cyclotron (Plunkett Lake Press, 2018).
[5] H. A. Grunder et al., "Acceleration of Heavy Ions at the Bevatron," Science 174, 1128 (1971).
