Teller's "Super" was for many years the chief force lobbying for research into developing fusion weapons. The idea of using the energy from a fission device to begin a fusion reaction was first proposed by the Italian physicist
Enrico Fermi to his colleague
Edward Teller in late 1941 during what would soon become the
Manhattan Project, the
World War II effort by the United States and United Kingdom to develop the first
nuclear weapons. Teller soon was a participant at
Robert Oppenheimer's 1942 conference on the development of a fission bomb held at the
University of California, Berkeley, where he guided discussion towards the idea of creating his "Super" bomb, which would hypothetically be many times more powerful than the yet-undeveloped fission weapon. Teller assumed creating the fission bomb would be nothing more than an engineering problem, and that the "Super" provided a much more interesting theoretical challenge. For the remainder of the war the effort was focused on first developing fission weapons. Nevertheless, Teller continued to pursue the "Super", to the point of neglecting work assigned to him for the fission weapon at the secret
Los Alamos lab where he worked. (Much of the work Teller declined to do was given instead to
Klaus Fuchs, who was later discovered to be a spy for the
Soviet Union. , the largest pure
fission bomb tested by the US, yielding 500 kt (November 16, 1952) Even though they had witnessed the
Trinity test, after the
atomic bombings of Japan scientists at Los Alamos were surprised by how devastating the effects of the weapon had been. by Teller and Ulam on March 9, 1951. The exact amount of contribution provided respectively from Ulam and Teller to what became known as the "
Teller–Ulam design" is not definitively known in the public domain—the degree of credit assigned to Teller by his contemporaries is almost exactly commensurate with how well they thought of Teller in general. In an interview with
Scientific American from 1999, Teller told the reporter: I contributed; Ulam did not. I'm sorry I had to answer it in this abrupt way. Ulam was rightly dissatisfied with an old approach. He came to me with a part of an idea which I already had worked out and difficulty getting people to listen to. He was willing to sign a paper. When it then came to defending that paper and really putting work into it, he refused. He said, "I don't believe in it." At the Oppenheimer hearing, in 1954, Bethe spoke of Teller's “stroke of genius” in the invention of the H-bomb. And finally in 1997 Bethe stated that “the crucial invention was made in 1951, by Teller.” Other scientists (antagonistic to Teller, such as
J. Carson Mark) have claimed that Teller would have never gotten any closer without the idea of Ulam. The nuclear weapons designer
Ted Taylor was clear about assigning credit for the basic staging and compression ideas to Ulam, while giving Teller the credit for recognizing the critical role of radiation as opposed to hydrodynamic pressure.
Priscilla Johnson McMillan in her book
The Ruin of J. Robert Oppenheimer: And the Birth of the Modern Arms Race, writes that Teller sought to "conceal the role" of Ulam, and that only "radiation implosion" was Teller's idea. Teller went as far as refusing to sign the patent application because it would need Ulam's signature.
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". Teller became known in the press as the "father of the hydrogen bomb", a title which he did not seek to discourage. 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). 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. As for me, I guess I am the midwife." it generated severe
nuclear fallout, which caused one of the worst nuclear accidents in US history after unforeseen weather patterns blew it over populated areas of the atoll and Japanese fishermen on board the
Daigo Fukuryu Maru. After an initial period focused on making multi-megaton hydrogen bombs, efforts in the United States shifted towards developing miniaturized Teller–Ulam weapons which could outfit
intercontinental ballistic missiles and
submarine launched ballistic missiles. The last major design breakthrough in this respect was accomplished by the mid-1970s, when versions of the Teller–Ulam design were created which could fit on the end of a small
MIRVed missile.
Soviet research In the
Soviet Union, the scientists working on their own
hydrogen bomb project also ran into difficulties in developing a megaton-range fusion weapon. 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"). Though nuclear fusion was technically achieved, it did not have the scaling property of a staged weapon, and their first hydrogen bomb test,
Joe 4, is considered a hybrid fission/fusion device more similar to a large
boosted fission weapon than a Teller–Ulam weapon (though using an order of magnitude more fusion fuel than a boosted weapon). Detonated in 1953 with a yield equivalent to (only – from fusion), the
Sloika device did, however, have the advantage of being a weapon which could actually be delivered to a military target, unlike the "Ivy Mike" device, though it was never widely deployed. 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. The Soviet physicists calculated that at best the design might yield a single megaton of energy if it was pushed to its limits. 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. One of the key Soviet bomb designers,
Yuli Khariton, later said: At that time, Soviet research was not organized on a sufficiently high level, and useful results were not obtained, although radiochemical analyses of samples of fallout could have provided some useful information about the materials used to produce the explosion. The relationship between certain short-lived isotopes formed in the course of thermonuclear reactions could have made it possible to judge the degree of compression of the thermonuclear fuel, but knowing the degree of compression would not have allowed Soviet scientists to conclude exactly how the exploded device had been made, and it would not have revealed its design. 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. Sakharov stated in his memoirs that though he and Davidenko had fallout dust in cardboard boxes several days after the "Mike" test with the hope of analyzing it for information, a chemist at
Arzamas-16 (the Soviet weapons laboratory) had mistakenly poured the concentrate down the drain before it could be analyzed. Only in late 1952 did the Soviet Union set up an organized system for monitoring fallout data. 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. He then turned his focus to finding a way for an explosion to one side to be used to compress the ball of fusion fuel within of symmetry, which he realised could be achieved by focusing the X-rays. The Soviet Union demonstrated the power of the "staging" concept in October 1961 when they detonated the massive and unwieldy
Tsar Bomba, a hydrogen bomb which derived almost 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. Had it been fired in its "full" form, it would have yielded at around . The weapon was technically deployable (it was tested by dropping it from a specially modified bomber), but militarily impractical, and was developed and tested primarily as a show of Soviet strength. It is the largest nuclear weapon developed and tested by any country. ==Other countries==