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COCKROFT-WALTON MACHINES
Science > Particle Accelerators and Other Technologies
A Cockroft-Walton machine is a type of particle accelerator used to produce highly energetic beams of charged particles. This device accelerates particles by ratcheting up the voltage applied to a beam of particles traveling down a straight tube. As the particles pass through the tube they are kicked up to higher and higher energies in the cascade, even with relatively small voltage inputs. Today this technique can achieve energies of a mega electron volt (MeV). 
Physicists John Douglas Cockroft and Ernest Thomas Sinton Walton working at the Cavendish Laboratory in Cambridge, England, developed this technology in the late 1920s and improved on the design to yield higher and higher energies in subsequent years. By 1932 they accelerated protons to sufficient energies to conduct the first experiments with induced nuclear reactions. By bombarding lithium with a beam of accelerated protons, they found that the atomic nucleus would disintegrate into two alpha particles. This work provided support for behavior predicted by quantum theory. Through this work Cockroft and Walton earned the 1951 Nobel Prize in physics "for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles." During the Manhattan Project, scientists employed Cockroft-Walton machines at Los Alamos in the P-Division (physics) for study of neutron scattering and later by the reorganized R-Division (research) for studying neutron behavior in subcritical uranium masses.
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The text for this page is original to the Department of Energy's Office of History and Heritage Resources. Major sources consulted include the following. Two useful sources for understanding the Cockroft-Walton machine in its historical context is, Helge Kragh, Quantum Generations: a History of Physics in the Twentieth Century (Princeton: Princeton University Press, 1999); and a wonderful online History Web Exhibit from the American Institute of Physics called, "Ernest Lawrence and the Cyclotron" at https://history.aip.org/exhibits/lawrence/index.htm. For biographical information about physicists John Douglas Cockroft and Ernest Thomas Sinton Walton see their Nobel Prize website at, http://nobelprize.org/nobel_prizes/physics/laureates/1951/index.html. For more information of Cockroft-Walton machines in wartime operation see Lillian Hoddeson, et. al., Critical Assembly: a Technical History of Los Alamos During the Oppenheimer Years, 1943-1945 (Cambridge: Cambridge University Press, 1993), page 193. The image of the Cockroft-Walton machine is courtesy the Los Alamos National Laboratory. The image of Walton, Rutherford, and Cockroft is courtesy the U.S. Department of Energy.