Lawrence's 60 inch cyclotron, with magnet poles 60 inches in diameter, at the UC Lawrence Radiation Laboratory, Berkeley, August 1939, the most powerful accelerator in the world at the time. Seaborg and McMillan (right) used it to discover plutonium, neptunium and many other transuranic elements and isotopes, for which they received the 1941 Nobel Prize in physics. The cyclotron magnet is at left, the beamline which analyzed the particles is at right.