The Discovery of Spontaneous Fission in Plutonium

It was the spring of 1944. In a secluded canyon in New Mexico, 14 miles from the bustling technical area of the wartime Los Alamos Laboratory, three physics graduate students were working inside a Forest Service log cabin filled with electronics. For the past eight months, they had been driving there each day by jeep to search for evidence of “spontaneous fission,” a naturally occurring process in which certain heavy atomic nuclei split of their own accord, emitting neutrons. Anxiously, they puzzled over a startling oscilloscope trace produced by a sample of plutonium. Why were these students studying the phenomenon of spontaneous fission in this canyon? What caused their concern?

The professor in charge of the work, nuclear physicist Emilio Segrè, had fled Italy in 1938 and joined Ernest Lawrence's nuclear physics laboratory in Berkeley, California. In 1943, at the request of theoretical physicist J. Robert Oppenheimer, Segré had moved several of his Berkeley experiments to Los Alamos to be part of Project Y – the secret project to build the first atomic bombs. Jointly directed by Oppenheimer and military engineer Gen. Leslie R. Groves, Project Y was a part of the Manhattan Project (the Manhattan Engineer District). Before World War II, Los Alamos, a small New Mexico town on a high mesa, had been the site of a ranch school for boys.