Soviet Atomic Test Accelerates U.S. Efforts

The first Soviet atomic bomb test in 1949 put pressure on the Americans to accelerate work on its nuclear arsenal. On January 31, 1950, President Harry Truman issued a proclamation directing the Atomic Energy Commission to "continue its work on all forms of atomic weapons, including the so-called hydrogen or superbomb." At this point, however, the exact mechanism was still not known: the "classical" hydrogen bomb, whereby the heat of the fission bomb would be used to ignite the fusion material, seemed highly unworkable. However, an insight by Los Alamos mathematician Stanislaw Ulam showed that the radiation of the fission bomb could first work in a way to compress the fusion material before igniting it.

Ulam conceived the idea of using a stream of neutrons generated from a primary atomic bomb's explosion to compress a separate fusion core containing thermonuclear fuel. Compression would be accomplished via special hydrodynamic lenses. He also proposed a configuration based on a train of thermonuclear units designed to operate on the same principle and detonate sequentially. Ulam presented these ideas to Edward Teller at the end of January 1951, and after hesitating, Teller embraced them with enthusiasm. However, he soon proposed his own parallel version that modified Ulam's concept and made it, according to Ulam, "perhaps more convenient and general." Rather than a stream of neutrons, Teller suggested that radiation from the primary atomic bomb be utilized to generate a shock wave that would compress the secondary thermonuclear core in Ulam's configuration.

Teller Ulam device diagram

Teller-Ulam device cutaway

On March 9, 1951, Ulam and Teller published a joint report, "On Heterocatalytic Detonations I: Hydrodynamic Lenses and Radiation Mirrors." The report described their new concept for the construction of a thermonuclear weapon. The new superbomb design was named the Teller-Ulam configuration. Far from creating an amicable partnership, the new configuration led to many years of disagreement in the scientific community over which of the two scientists deserved more credit. Prior to releasing their report on the configuration, Teller had suggested a series of geometrical equations that would make Ulam's concept feasible, and Ulam, Max Goldstein and Arnold Kramish-independent of Teller-worked through the night to come up with an approximate solution. However, Herbert York contended that Ulam's concept was a general idea, which Teller had converted into a sketch for a superbomb that would work. Teller worked for decades to play down Ulam's contributions, and Ulam later denied the invention's originality.

In April 1951, Teller presented the results of additional analytical and theoretical justification of the new superbomb by Frederic de Hoffmann and proposed an initiator of active fissionable material situated in the secondary core inside the thermonuclear fuel. The initiator was meant to trigger an atomic detonation inside the fuel.

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