History of the Teller–Ulam design

Many scientists, such as Teller's colleague Hans Bethe (who had discovered stellar nucleosynthesis, the nuclear fusion that takes place in stars), urged that the United States should not develop such weapons and set an example towards the Soviet Union.

[3] In any case, work slowed greatly at Los Alamos, as some 5,500 of the 7,100 scientists and related staff who had been there at the conclusion of the war left to go back to their previous positions at universities and laboratories.

[2]: 91 When the Soviet Union exploded their own atomic bomb (dubbed "Joe 1" by the US) in August 1949, it caught Western analysts off guard, and over the next several months there was an intense debate within the US government, military, and scientific communities on whether to proceed with the far-more-powerful Super.

[2]: 91 The exact history of the Teller–Ulam breakthrough is not completely known, partly because of numerous conflicting personal accounts and also by the continued classification of documents that would reveal which was closer to the truth.

In 1951, after many years of fruitless labor on the "Super", a breakthrough idea from the Polish émigré mathematician Stanislaw Ulam was seized upon by Teller and developed into the first workable design for a megaton-range hydrogen bomb.

This concept, now called "staged implosion" was first proposed in a classified scientific paper, On Heterocatalytic Detonations I. Hydrodynamic Lenses and Radiation Mirrors[note 1][4] by Teller and Ulam on March 9, 1951.

Thomas Powers writes that "of course the bomb designers all knew the truth, and many considered Teller the lowest, most contemptible kind of offender in the world of science, a stealer of credit".

Many of Teller's colleagues were irritated that he seemed to enjoy taking full credit for something he had only a part in, and in response, with encouragement from Enrico Fermi, Teller authored an article titled "The Work of Many People", which appeared in Science magazine in February 1955, emphasizing that he was not alone in the weapon's development (he would later write in his memoirs that he had told a "white lie" in the 1955 article, and would imply that he should receive full credit for the weapon's invention).

[11] Hans Bethe, who also participated in the hydrogen bomb project, once said, "For the sake of history, I think it is more precise to say that Ulam is the father, because he provided the seed, and Teller is the mother, because he remained with the child.

The elegance of the design impressed many scientists, to the point that some who previously wondered if it were feasible suddenly believed it was inevitable and that it would be created by both the US and the Soviet Union.

On November 1, 1952, the Teller–Ulam configuration was tested in the "Ivy Mike" shot at an island in the Enewetak atoll, with a yield of 10.4 megatons of TNT (44 PJ) (over 450 times more powerful than the bomb dropped on Nagasaki during World War II).

The elaborate refrigeration plant necessary to keep its fusion fuel in a liquid state meant that the "Ivy Mike" device was too heavy and too complex to be of practical use.

Because Klaus Fuchs had only been at Los Alamos at a very early stage of the hydrogen bomb design (before the Teller–Ulam configuration had been completed), none of his espionage information was of much use, and the Soviet physicists working on the project had to develop their weapon independently.

The first Soviet fusion design, developed by Andrei Sakharov and Vitaly Ginzburg in 1949 (before the Soviet Union had a working fission bomb), was dubbed the Sloika, after a Russian layered puff pastry, and was not of the Teller–Ulam configuration, but rather used alternating layers of fissile material and lithium deuteride fusion fuel spiked with tritium (this was later dubbed Sakharov's "First Idea").

Teller had proposed a similar design as early as 1946, dubbed the "Alarm Clock" (meant to "wake up" research into the "Super"), though it was calculated to be ultimately not worth the effort and no prototype was ever developed or tested.

Attempts to use a Sloika design to achieve megaton-range results proved unfeasible in the Soviet Union as it had in the calculations done in the US, but its value as a practical weapon since it was 20 times more powerful than their first fission bomb, should not be underestimated.

After the US tested the "Ivy Mike" device in 1952, proving that a multimegaton bomb could be created, the Soviet Union searched for an additional design and continued to work on improving the Sloika (the "First Idea").

The "Second Idea", as Sakharov referred to it in his memoirs, was a previous proposal by Ginzburg in November 1948 to use lithium deuteride in the bomb, which would, by the bombardment by neutrons, produce tritium.

[14]: 299, 314  In late 1953, physicist Viktor Davidenko achieved the first breakthrough, that of keeping the primary and secondary parts of the bombs in separate pieces ("staging").

The next breakthrough was discovered and developed by Sakharov and Yakov Zeldovich, that of using the X-rays from the fission bomb to compress the secondary before fusion ("radiation implosion"), in early 1954.

Nonetheless, the memoirs also say that the yield from one of the American tests, which became an international incident involving Japan, told Sakharov that the US design was much better than theirs, and he decided that they must have exploded a separate fission bomb and somehow used its energy to compress the lithium deuteride.

[14] The Soviet Union demonstrated the power of the "staging" concept in October 1961 when they detonated the massive and unwieldy Tsar Bomba, a 50 Mt (210 PJ) hydrogen bomb which derived almost 97% of its energy from fusion rather than fission—its uranium tamper was replaced with one of lead for the test, in an effort to prevent excessive nuclear fallout.

Dr. Harold M. Agnew, former director of the Los Alamos National Laboratory, said that India's assertion of having detonated a staged thermonuclear bomb was believable.

[22] Professor Jack Evernden, a US seismologist, has always maintained that for correct estimation of yields, one should "account properly for geological and seismological differences between test sites."

Aside from images of the warhead casing but never of the "physics package" itself, most information in the public domain about the design is relegated to a few terse statements and the work of a few individual investigators.

In 1998, the DOE declassified the statement that "The fact that materials may be present in channels and the term 'channel filler,' with no elaboration," which may refer to the polystyrene foam (or an analogous substance).

)[clarification needed] Whether the statements vindicate some or all of the models presented above is up for interpretation, and official US government releases about the technical details of nuclear weapons have been purposely equivocating in the past (such as the Smyth Report).

Most of the current ideas of the Teller–Ulam design[clarification needed] came into public awareness after the DOE attempted to censor a magazine article by the anti-weapons activist Howard Morland in 1979 on the "secret of the hydrogen bomb."

Through a variety of more complicated circumstances,[clarification needed] the DOE case began to wane, as it became clear that some of the data it attempted to claim as "secret" had been published in a students' encyclopedia a few years earlier.

Ivy Mike , the first full test of the Teller–Ulam design (a staged fusion bomb), with a yield of 10.4 megatons (November 1, 1952)
Physicist Edward Teller was for many years the chief force lobbying for research into developing fusion weapons.
Ivy King , the largest pure fission bomb tested by the US, yielding 500 kt (November 16, 1952)
A view of the "Sausage" device casing, with its instrumentation and cryogenic equipment attached. The long pipes were for measurement purposes; their function was to transmit the first radiation from the "primary" and "secondary" stages (known as "Teller light") to instruments just as the device was detonated, before being destroyed in the explosion. The man seated lower right shows scale.
The dry-fuel device detonated in the " Castle Bravo " shot demonstrated that the Teller–Ulam design could be made deployable, but also that the final fission stage created large amounts of nuclear fallout .
Like the Bravo test, Castle Romeo " ran away ," producing a much higher yield than originally estimated (11 megatons instead of 4), making it the third largest test ever conducted by the US. The Romeo "shrimp" device derived its lithium deuteride from natural instead of "enriched" lithium .
Fireball of the Tsar Bomba (RDS-220), the largest weapon ever detonated (1961). Dropped from over 10 km and detonated at 4 km high, its fireball would have touched the ground were it not for the shock wave from the explosion reflecting off the ground and striking the bottom of the fireball, [ 17 ] and nearly reached as high as the altitude of the deploying Tu-95 bomber. The RDS-220 test demonstrated how "staging" could be used to develop arbitrarily powerful weapons.
Photographs of warhead casings, such as this one of the W80 nuclear warhead, allow for some speculation as to the relative size and shapes of the primaries and secondaries in US thermonuclear weapons.