Nuclear physics research efforts in the United States were not entirely asleep before 1939. Although research expenditures for fundamental sci­ence were chronically short by today’s standards, there was never a short­age of curiosity and a need to push physics into unknown territory. An

area where the United States made bold progress during the Great Depres­sion years was in particle acceleration. Charged subatomic particles, such as protons or electrons, can be accelerated electrically from rest energy up to great speeds, simulating radioactive decay products blasting free of nuclei but on a larger scale. The availability of a large flux of energetic charged particles made it possible to do element transmutation or nuclear disintegration on a scale order of magnitude bigger than had been accom­plished using radioactive sources. Using a large enough accelerator, mea­surable quantities of isotopes could be manufactured in a laboratory, or enhanced resolution in nuclear probing was available. This class of machine came to be known as the atom smasher. The master of atom smasher design was Ernest Lawrence, of the University of California.

Ernest Lawrence (1901-58) was unique in the field of Nobel Prize­winning physics, in that his entire education was in the United States, without the degree from Europe that was considered necessary at the time. He started his college work at the University of South Dakota, transferred to the University of Minnesota, and received his bachelor’s degree in 1922. He earned a master’s in physics in 1923 and went to Yale University in Connecticut for a Ph. D. in physics in 1925. His most important contribu­tions to nuclear research and development were two-fold. He invented the cyclotron atom smasher and the calutron large-scale isotope separator. He won the Nobel Prize in physics in 1939 for his work with the cyclotron.

Lawrence built his first cyclotron in 1929 at the University of Califor­nia, Berkeley, using available materials. He called it his “proton merry — go-round” because it constrained charged particles to spin around in a tight spiral under a magnetic field as they gained power. The machine cost about $25 to build, the equivalent of about $313 today, and it was only five inches (13 cm) around, but it proved his point. Although the concept of the cyclotron probably occurred several places at about the same time, Lawrence dug in and built one. Leo Szilard patented a cyclo­tron in Europe, but it takes more than a patent to break up nuclei. In 1934, Lawrence obtained a patent for the cyclotron, and by 1936 he had taken over the Civil Engineering Testing Laboratory, renamed it the Radiation Laboratory, and filled it with a 37-inch (94-cm) cyclotron capable of accel­erating alpha particles to 16 MeV. He used it to create the first artificial element, technetium, a substance that is in the middle of the periodic table but does not exist in the crust of the Earth.

In 1939, Lawrence completed his 60-inch (150-cm) cyclotron, just in time to participate in the pivotal year in nuclear physics. It was a colossal

Ernest Lawrence’s 60-inch (152-cm) cyclotron at the University of California, Berkeley. Lawrence was awarded a Nobel Prize for his work with cyclotrons and later developed a magnetic isotope separator used in the atomic bomb project. (Lawrence Berkeley National Laboratory)

machine, with a magnet weighing 220 tons (200 metric tons), and it would be used to discover carbon-14, neptunium, and plutonium. Lawrences calutron was an industrial version of the magnetic mass spectrometer invented at the Cavendish Lab in Great Britain in 1918. It would be a criti­cal component of the atomic bomb development project that would soon consume the United States.

When World War II started in Europe, the United States had all it needed to develop nuclear weapons and power systems. Available were many of the best scientists of Europe, an amazing array of homegrown physicists graduating from or teaching in universities, an industrial infra­structure capable of building anything that could be assembled by man­kind, and a warehouse in New York filled with uranium ore. All that was needed was the spark to start the fire. In the next chapter, the spark and the beginning of the resulting conflagration are revealed.