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188-403: The Partial Test Ban Treaty of 1963 banned atmospheric nuclear testing. This led to a requirement for an underground test area that could accommodate higher yield tests than Yucca Flat . Pahute Mesa was seen as ideal due to its geology and distance of over 160 kilometers (99 mi) from Las Vegas. Holes can be drilled to a depth of more than 1,370 meters (4,490 ft). This allows tests in

376-410: A hohlraum or radiation case. The "George" shot of Operation Greenhouse of 9 May 1951 tested the basic concept for the first time on a very small scale. As the first successful (uncontrolled) release of nuclear fusion energy, which made up a small fraction of the 225  kt (940  TJ ) total yield, it raised expectations to a near certainty that the concept would work. On 1 November 1952,

564-730: A secondary section that consists of fusion fuel . The energy released by the primary compresses the secondary through the process of radiation implosion , at which point it is heated and undergoes nuclear fusion . This process could be continued, with energy from the secondary igniting a third fusion stage; the Soviet Union's AN602 " Tsar Bomba " is thought to have been a three-stage fission-fusion-fusion device. Theoretically by continuing this process thermonuclear weapons with arbitrarily high yield could be constructed. This contrasts with fission weapons, which are limited in yield because only so much fission fuel can be amassed in one place before

752-450: A "cut-off" of fissionable-material production in a "partial" disarmament plan. The British government, then led by Macmillan, had yet to fully endorse a test ban. Accordingly, it pushed the US to demand that the production cut-off be closely timed with the testing moratorium, betting that the Soviet Union would reject this. London also encouraged the US to delay its disarmament plan, in part by moving

940-588: A "standstill agreement" on nuclear testing. Nehru viewed a testing moratorium as a crucial first step toward broader and more comprehensive arms control agreements, reflecting his commitment to nuclear disarmament and global peace. In the same year, the British Labour Party , then led by Clement Attlee , called on the UN to ban testing of thermonuclear weapons. 1955 marks the beginning of test-ban negotiations, as Soviet leader Nikita Khrushchev first proposed talks on

1128-410: A Soviet intelligence officer to settle on 15 inspections per year. This was rejected by Khrushchev. Thermonuclear weapons A thermonuclear weapon , fusion weapon or hydrogen bomb ( H bomb ) is a second-generation nuclear weapon design . Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs , a more compact size, a lower mass, or

1316-534: A ban), became convinced that the Geneva findings were too optimistic regarding detection of underground tests, though Macmillan warned that using the data to block progress on a test ban might be perceived in the public as a political ploy. In early 1959, Wadsworth told Tsarapkin of new US skepticism towards the Geneva System. While the Geneva experts believed the system could detect underground tests down to five kilotons,

1504-462: A belief that dominance in the nuclear arena, particularly given the size of Soviet conventional forces, was critical to US security. Interest in nuclear control and efforts to stall proliferation of weapons to other states grew as the Soviet Union's nuclear capabilities increased. In 1954, just weeks after the Castle Bravo test, Indian Prime Minister Jawaharlal Nehru made the first public call for

1692-467: A clear nuclear advantage via regular testing and that the negative environmental impacts of such tests were overstated. Furthermore, Strauss repeatedly emphasized the risk of the Soviet Union violating a ban, a fear Eisenhower shared. On 7 November 1957, after Sputnik and under pressure to bring on a dedicated science advisor, Eisenhower created the President's Science Advisory Committee (PSAC), which had

1880-561: A cohesive test ban policy, noting his ability to "believe in two mutually contradictory and inconsistent propositions at the same time." Upon assuming the presidency in January 1961, John F. Kennedy was committed to advancing a comprehensive test ban on nuclear weapons. He quickly ordered a review of the U.S. negotiating position to revitalize stalled talks, as he believed Eisenhower 's previous approach had been "insufficient" in achieving meaningful progress toward nuclear disarmament. Kennedy saw

2068-467: A combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 ( U ) or plutonium-239 ( Pu ). The first full-scale thermonuclear test ( Ivy Mike ) was carried out by the United States in 1952, and

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2256-589: A cutoff in nuclear production should precede a test ban. In the summer of 1957, Khrushchev was at acute risk of losing power, as the Anti-Party Group composed of former Stalin allies Lazar Kaganovich , Georgy Malenkov , and Vyacheslav Molotov launched an attempt to replace Khrushchev as General Secretary of the Communist Party (effectively the leader of the Soviet Union) with Nikolai Bulganin , then

2444-430: A design could not produce thermonuclear weapons whose explosive yields could be made arbitrarily large (unlike U.S. designs at that time). The fusion layer wrapped around the fission core could only moderately multiply the fission energy (modern Teller–Ulam designs can multiply it 30-fold). Additionally, the whole fusion stage had to be imploded by conventional explosives, along with the fission core, substantially increasing

2632-487: A dozen megatons, which was generally considered enough to destroy even the most hardened practical targets (for example, a control facility such as the Cheyenne Mountain Complex ). Even such large bombs have been replaced by smaller yield nuclear bunker buster bombs. For destruction of cities and non-hardened targets, breaking the mass of a single missile payload down into smaller MIRV bombs in order to spread

2820-456: A few specific incidents outlined in a section below. The basic principle of the Teller–Ulam configuration is the idea that different parts of a thermonuclear weapon can be chained together in stages, with the detonation of each stage providing the energy to ignite the next stage. At a minimum, this implies a primary section that consists of an implosion-type fission bomb (a "trigger"), and

3008-413: A halt to nuclear weapons production (the one-time US demand). In explaining the policy shift, Eisenhower privately said that continued resistance to a test ban would leave the US in a state of "moral isolation." On 8 April 1958, still resisting Khrushchev's call for a moratorium, Eisenhower invited the Soviet Union to join these technical negotiations in the form of a conference on the technical aspects of

3196-453: A high-yield explosion. A W88 warhead manages to yield up to 475 kilotonnes of TNT (1,990 TJ) with a physics package 68.9 inches (1,750 mm) long, with a maximum diameter of 21.8 inches (550 mm), and by different estimates weighing in a range from 175 to 360 kilograms (386 to 794 lb). The smaller warhead allows more of them to fit onto a single missile and improves basic flight properties such as speed and range. The idea of

3384-477: A highly efficient detonation fallout was relatively limited. Between 1951 and 1958, the US conducted 166 atmospheric tests, the Soviet Union conducted 82, and Britain conducted 21; only 22 underground tests were conducted in this period (all by the US). In 1945, Britain and Canada made an early call for international discussions on the control of atomic power, anticipating the global implications of nuclear technology. At

3572-435: A lead US envoy, offered a new proposal in an attempt to bridge the gap between the two sides. The early Kennedy proposal largely grew out of later Eisenhower efforts, with a ban on all tests but low-yield underground ones (below magnitude 4.75), which would be subject to a three-year moratorium. The US and UK proposed 20 on-site inspections per annum, while the Soviet Union proposed three. The verification procedures included in

3760-516: A limit Eisenhower would revise upward in May 1959—would be banned first, with negotiations on underground and outer-space tests continuing. This proposal was turned down on 23 April 1959 by Khrushchev, calling it a "dishonest deal." On 26 August 1959, the US announced it would extend its year-long testing moratorium to the end of 1959, and would not conduct tests after that point without prior warning. The Soviet Union reaffirmed that it would not conduct tests if

3948-483: A massive effort was mounted to re-invent the process. An impurity crucial to the properties of the old Fogbank was omitted during the new process. Only close analysis of new and old batches revealed the nature of that impurity. The manufacturing process used acetonitrile as a solvent , which led to at least three evacuations of the Fogbank plant in 2006. Widely used in the petroleum and pharmaceutical industries, acetonitrile

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4136-528: A new US proposal by which only tests deemed verifiable by the Geneva System would be banned, including all atmospheric, underwater, and outer-space tests within detection range. Underground tests measuring more than 4.75 on the Richter scale would also be barred, subject to revision as research on detection continued. Adopting Macmillan's quota compromise, the US proposed each nuclear state be subject to roughly 20 on-site inspections per year (the precise figure based on

4324-428: A pair of widely circulated academic papers challenging the claim of Teller and others that a clean, fallout-free nuclear bomb could be developed, due to the formation of carbon-14 when nuclear devices are detonated in the air. A one-megaton clean bomb, Sakharov estimated, would cause 6,600 deaths over 8,000 years, figures derived largely from estimates on the quantity of carbon-14 generated from atmospheric nitrogen and

4512-564: A possibility. It was first used in thermonuclear weapons with the W76 thermonuclear warhead and produced at a plant in the Y-12 Complex at Oak Ridge, Tennessee , for use in the W76. Production of Fogbank lapsed after the W76 production run ended. The W76 Life Extension Program required more Fogbank to be made. This was complicated by the fact that the original Fogbank's properties were not fully documented, so

4700-575: A precursor to a test ban. On 1 July 1958, responding to Eisenhower's call, the nuclear powers convened the Conference of Experts in Geneva , aimed at studying means of detecting nuclear tests. The conference included scientists from the US, Britain, the Soviet Union, Canada, Czechoslovakia, France, Poland, and Romania. The US delegation was led by James Fisk, a member of PSAC, the Soviets by Evgenii Fedorov, and

4888-501: A roadblock to an agreement was removed as Macmillan and Eisenhower, over opposition from the Department of Defense, agreed to consider a test ban separately from broader disarmament endeavors. On 13 April 1959, facing Soviet opposition to on-site detection systems for underground tests, Eisenhower proposed moving from a single, comprehensive test ban to a graduated agreement where atmospheric tests—those up to 50 km (31 mi) high,

5076-473: A scheme would be able to detect 90% of underground detonations, accurate to 5 kilotons, and atmospheric tests with a minimum yield of 1 kiloton. The US had initially advocated for 650 posts, versus a Soviet proposal of 100–110. The final recommendation was a compromise forged by the British delegation. In a widely publicized and well-received communiqué dated 21 August 1958, the conference declared that it "reached

5264-407: A significant build-up of strontium-90 in bones of babies and helped galvanise public support for a ban on atmospheric nuclear testing in the US. Lewis Strauss and Edward Teller , dubbed the "father of the hydrogen bomb," both sought to tamp down on these fears, arguing that fallout [at the dose levels of US exposure] were fairly harmless and that a test ban would enable the Soviet Union to surpass

5452-550: A significant increase in U.S. defense spending, a move that was soon mirrored by the Soviet Union . This escalation intensified the arms race and placed the test-ban negotiations within a broader context of heightened military competition. Despite these growing tensions, Kennedy( JFK ) remained committed to pursuing a comprehensive test ban, recognizing it as a crucial step toward curbing the nuclear arms race. On 21 March 1961, test-ban negotiations resumed in Geneva and Arthur Dean ,

5640-545: A temporary basis (a duration of roughly 1 year, versus the Soviet proposal of 4–5 years), but this could only happen after verifiable tests had been banned and a seismic research group (the Seismic Research Program Advisory Group) convened. The Soviet Union responded positively to the counterproposal and the research group convened on 11 May 1960. The Soviet Union also offered to keep an underground ban out of

5828-531: A test ban before its own testing program was completed. Following the Soviet declaration, Eisenhower called for an international meeting of experts to determine proper control and verification measures—an idea first proposed by British Foreign Secretary Selwyn Lloyd . The advocacy of PSAC, including that of its chairmen James Rhyne Killian and George Kistiakowsky , was a key factor in Eisenhower's eventual decision to initiate test-ban negotiations in 1958. In

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6016-478: A test ban in 1958. There was also increased environmental concern in the Soviet Union. In the mid-1950s, Soviet scientists began taking regular radiation readings near Leningrad , Moscow , and Odessa and collected data on the prevalence of strontium-90, which indicated that strontium-90 levels in western Russia approximately matched those in the eastern US. Rising Soviet concern was punctuated in September 1957 by

6204-519: A test ban in the late 1950s. The proliferation of thermonuclear weapons coincided with a rise in public concern about nuclear fallout debris contaminating food sources, particularly the threat of high levels of strontium-90 in milk (see the Baby Tooth Survey ). This survey was a scientist and citizen led campaign which used "modern media advocacy techniques to communicate complex issues" to inform public discourse. Its research findings confirmed

6392-553: A test ban. The British governments of 1954–58 (under Conservatives Winston Churchill , Anthony Eden , and Harold Macmillan ) also quietly resisted a test ban, despite the British public favoring a deal, until the US Congress approved expanded nuclear collaboration in 1958 and until after Britain had tested its first hydrogen bombs . In their view, testing was necessary if the UK nuclear program were to continue to develop. This opposition

6580-442: A test-ban, specifically the technical details of ensuring compliance with a ban. The proposal was, to a degree, a concession to the Soviet Union, as a test ban would be explored independent of the previously demanded cutoff in fissionable-material production. Khrushchev initially declined the invitation, but eventually agreed "in spite of the serious doubts" he had after Eisenhower suggested a technical agreement on verification would be

6768-468: A testing series and the US was about to begin Operation Hardtack I , a series of atmospheric, surface-level, and underwater nuclear tests. Eisenhower instead insisted that any moratorium be linked to reduced production of nuclear weapons. In April 1958, the US began Operation Hardtack I as planned. The Soviet declaration concerned the British government, which feared that the moratorium might lead to

6956-485: A thermal barrier to keep the fusion fuel filler from becoming too hot, which would spoil the compression. If made of uranium , enriched uranium or plutonium, the tamper captures fast fusion neutrons and undergoes fission itself, increasing the overall explosive yield . Additionally, in most designs the radiation case is also constructed of a material that undergoes fission driven by fast thermonuclear neutrons. Such bombs are classified as two stage weapons. Fast fission of

7144-529: A thermonuclear fusion bomb ignited by a smaller fission bomb was first proposed by Enrico Fermi to his colleague Edward Teller when they were talking at Columbia University in September 1941, at the start of what would become the Manhattan Project . Teller spent much of the Manhattan Project attempting to figure out how to make the design work, preferring it over work on the atomic bomb, and over

7332-617: A yield of over one megaton. Three tests were conducted as part of operation Plowshare and one as part of Vela Uniform . In 1988, as a prelude to the signing of the protocols to the Threshold Test Ban Treaty and the Peaceful Nuclear Explosions Treaty , the United States and the Soviet Union conducted two joint tests employing proposed treaty verification techniques. The first was Kearsarge , conducted in Area 19 of

7520-457: Is flammable and toxic. Y-12 is the sole producer of Fogbank. A simplified summary of the above explanation is: How exactly the energy is "transported" from the primary to the secondary has been the subject of some disagreement in the open press but is thought to be transmitted through the X-rays and gamma rays that are emitted from the fissioning primary . This energy is then used to compress

7708-487: Is omitted, by replacing the uranium tamper with one made of lead , for example, the overall explosive force is reduced by approximately half but the amount of fallout is relatively low. The neutron bomb is a hydrogen bomb with an intentionally thin tamper, allowing as many of the fast fusion neutrons as possible to escape. Current technical criticisms of the idea of "foam plasma pressure" focus on unclassified analysis from similar high energy physics fields that indicate that

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7896-529: Is one order of magnitude greater than the higher proposed plasma pressures and nearly two orders of magnitude greater than calculated radiation pressure. No mechanism to avoid the absorption of energy into the radiation case wall and the secondary tamper has been suggested, making ablation apparently unavoidable. The other mechanisms appear to be unneeded. United States Department of Defense official declassification reports indicate that foamed plastic materials are or may be used in radiation case liners, and despite

8084-462: Is the Soviet early Sloika design. In essence, the Teller–Ulam configuration relies on at least two instances of implosion occurring: first, the conventional (chemical) explosives in the primary would compress the fissile core, resulting in a fission explosion many times more powerful than that which chemical explosives could achieve alone (first stage). Second, the radiation from the fissioning of

8272-426: Is the fusion fuel, usually a form of lithium deuteride , which is used because it is easier to weaponize than liquefied tritium/deuterium gas. This dry fuel, when bombarded by neutrons, produces tritium, a heavy isotope of hydrogen that can undergo nuclear fusion, along with the deuterium present in the mixture. (See the article on nuclear fusion for a more detailed technical discussion of fusion reactions.) Inside

8460-446: Is the medium by which the outside pressure (force acting on the surface area of the secondary) is transferred to the mass of fusion fuel. The proposed tamper-pusher ablation mechanism posits that the outer layers of the thermonuclear secondary's tamper-pusher are heated so extremely by the primary's X-ray flux that they expand violently and ablate away (fly off). Because total momentum is conserved, this mass of high velocity ejecta impels

8648-416: Is the primary example). Such processes have resulted in a body of unclassified knowledge about nuclear bombs that is generally consistent with official unclassified information releases and related physics and is thought to be internally consistent, though there are some points of interpretation that are still considered open. The state of public knowledge about the Teller–Ulam design has been mostly shaped from

8836-549: Is thought to be a standard implosion method fission bomb, though likely with a core boosted by small amounts of fusion fuel (usually 1:1 deuterium : tritium gas) for extra efficiency; the fusion fuel releases excess neutrons when heated and compressed, inducing additional fission. When fired, the Pu or U core would be compressed to a smaller sphere by special layers of conventional high explosives arranged around it in an explosive lens pattern, initiating

9024-489: Is thought to have used multiple stages (including more than one tertiary fusion stage) in their 50 Mt (210 PJ) (100 Mt (420 PJ) in intended use) Tsar Bomba. The fissionable jacket could be replaced with lead, as was done with the Tsar Bomba. If any hydrogen bombs have been made from configurations other than those based on the Teller–Ulam design, the fact of it is not publicly known. A possible exception to this

9212-409: Is widely assumed to be beryllium , which fits that description and would also moderate the neutron flux from the primary. Some material to absorb and re-radiate the X-rays in a particular manner may also be used. Candidates for the "special material" are polystyrene and a substance called " Fogbank ", an unclassified codename. Fogbank's composition is classified, though aerogel has been suggested as

9400-546: The Lucky Dragon upon whom "ashes of death" had rained. In the same year, a Soviet test sent radioactive particles over Japan. Around the same time, victims of the atomic bombing of Hiroshima visited the US for medical care, which attracted significant public attention. In 1961, the Soviet Union tested the Tsar Bomba , which had a yield of 50 megatons and remains the most powerful man-made explosion in history, though due to

9588-677: The Artemis program . The Pahute Control Point is located in Area 18, south of Pahute Mesa. It was used until 1971 to monitor tests in Pahute Mesa. The Pahute Mesa Airstrip , also in Area 18, was used to ship supplies and equipment to Pahute Mesa. [REDACTED]  This article incorporates public domain material from websites or documents of the United States Department of Energy . Partial Test Ban Treaty The Partial Test Ban Treaty ( PTBT ), formally known as

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9776-526: The Kyshtym disaster , which forced the evacuation of 10,000 people after an explosion at a nuclear plant. Around the same time, 219 Soviet scientists signed Pauling's antinuclear petition. Soviet political elites did not share the concerns of others in the Soviet Union. However; Kurchatov unsuccessfully called on Khrushchev to halt testing in 1958. On 14 June 1957, following Eisenhower's suggestion that existing detection measures were inadequate to ensure compliance,

9964-623: The Premier of the Soviet Union . The attempted ouster, which was foiled in June, was followed by a series of actions by Khrushchev to consolidate power. In October 1957, still feeling vulnerable from Anti-Party Group's ploy, Khrushchev forced out defense minister Georgy Zhukov , cited as "the nation's most powerful military man." On 27 March 1958, Khrushchev forced Bulganin to resign and succeeded him as Premier. Between 1957 and 1960, Khrushchev had his firmest grip on power, with little real opposition. Khrushchev

10152-463: The Supreme Soviet of the Soviet Union approved a decision to halt nuclear testing, conditional on other nuclear powers doing the same. Khrushchev then called on Eisenhower and Macmillan to join the moratorium. Despite the action being met with widespread praise and an argument from Dulles that the US should reciprocate, Eisenhower dismissed the plan as a "gimmick"; the Soviet Union had just completed

10340-559: The Trident II SLBM, had a prolate primary (code-named Komodo ) and a spherical secondary (code-named Cursa ) inside a specially shaped radiation case (known as the "peanut" for its shape). The value of an egg-shaped primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary: if an egg-shaped primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver

10528-542: The United States in Moscow on 5 August 1963 before it was opened for signature by other countries. The treaty formally went into effect on 10 October 1963. Since then, 123 other states have become party to the treaty. Ten states have signed but not ratified the treaty. The primary motivation for the treaty stemmed from growing public concern over radioactive fallout from above-ground and underwater nuclear testing, especially as

10716-599: The W-80 the gas expansion velocity is roughly 410 km/s (41 cm/μs) and the implosion velocity 570 km/s (57 cm/μs). The pressure due to the ablating material is calculated to be 5.3  billion bars (530  trillion pascals ) in the Ivy Mike device and 64 billion bars (6.4 quadrillion pascals) in the W-80 device. Comparing the three mechanisms proposed, it can be seen that: The calculated ablation pressure

10904-544: The W47 warhead deployed on Polaris ballistic missile submarines , megaton-class warheads were as small as 18 inches (0.46 m) in diameter and 720 pounds (330 kg) in weight. Further innovation in miniaturizing warheads was accomplished by the mid-1970s, when versions of the Teller–Ulam design were created that could fit ten or more warheads on the end of a small MIRVed missile. The first Soviet fusion design, developed by Andrei Sakharov and Vitaly Ginzburg in 1949 (before

11092-552: The neutron flux from the primary to prematurely begin heating the secondary, weakening the compression enough to prevent any fusion. There is very little detailed information in the open literature about the mechanism of the interstage. One of the best sources is a simplified diagram of a British thermonuclear weapon similar to the American W80 warhead. It was released by Greenpeace in a report titled "Dual Use Nuclear Technology" . The major components and their arrangement are in

11280-408: The nuclear chain reaction that powers the conventional "atomic bomb". The secondary is usually shown as a column of fusion fuel and other components wrapped in many layers. Around the column is first a "pusher- tamper ", a heavy layer of uranium-238 ( U ) or lead that helps compress the fusion fuel (and, in the case of uranium, may eventually undergo fission itself). Inside this

11468-460: The secondary . The crucial detail of how the X-rays create the pressure is the main remaining disputed point in the unclassified press. There are three proposed theories: The radiation pressure exerted by the large quantity of X-ray photons inside the closed casing might be enough to compress the secondary. Electromagnetic radiation such as X-rays or light carries momentum and exerts a force on any surface it strikes. The pressure of radiation at

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11656-466: The 1950s as "an embarrassing series of American reversals," suggesting a lack of real US commitment to arms control efforts. The historian Robert Divine also attributed the failure to achieve a deal to Eisenhower's "lack of leadership," evidenced by his inability to overcome paralyzing differences among US diplomats, military leaders, national security experts, and scientists on the subject. Paul Nitze would similarly suggest that Eisenhower never formulated

11844-654: The 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water , prohibited all test detonations of nuclear weapons except for those conducted underground . It is also abbreviated as the Limited Test Ban Treaty ( LTBT ) and Nuclear Test Ban Treaty ( NTBT ), though the latter may also refer to the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which succeeded

12032-461: The 21 August communiqué. Nevertheless, pleased by the findings, the Eisenhower administration proposed negotiations on a permanent test ban and announced it would self-impose a year-long testing moratorium if Britain and the Soviet Union did the same. This decision amounted to a victory for John Foster Dulles, Allen Dulles (then the Director of Central Intelligence ), and PSAC, who had argued within

12220-642: The Anglo-American plan were unacceptable to Tsarapkin, who responded with separate proposals rejected by the Western powers. Specifically, the Soviet Union proposed a "troika" mechanism: a monitoring board composed of representatives of the West, the Soviet Union, and nonaligned states that would require unanimity before acting (effectively giving the Soviet Union veto authority). In May 1961, Kennedy attempted via secret contact between Attorney General Robert F. Kennedy and

12408-561: The Baruch Plan as a US attempt to secure its nuclear dominance, and called for the US to halt weapons production and release technical information on its program. The Acheson–Lilienthal paper and Baruch Plan would serve as the basis for US policy into the 1950s. Between 1947 and 1954, the US and Soviet Union discussed their demands within the United Nations Commission for Conventional Disarmament. A series of events in 1954, including

12596-434: The British delegation by William Penney , who had led the British delegation to the Manhattan Project. Whereas the US approached the conference solely from a technical perspective, Penney was specifically instructed by Macmillan to attempt to achieve a political agreement. This difference in approach was reflected in the broader composition of the US and UK teams. US experts were primarily drawn from academia and industry. Fisk

12784-513: The British fusion bomb, with Sir William Penney in charge of the project. British knowledge on how to make a thermonuclear fusion bomb was rudimentary, and at the time the United States was not exchanging any nuclear knowledge because of the Atomic Energy Act of 1946 . The United Kingdom had worked closely with the Americans on the Manhattan Project. British access to nuclear weapons information

12972-514: The Castle Bravo test and spread of fallout from a Soviet test over Japan, redirected the international discussion on nuclear policy. Additionally, by 1954, both US and Soviet Union had assembled large nuclear stockpiles, reducing hopes of complete disarmament. In the early years of the Cold War , the US approach to nuclear control reflected a strain between an interest in controlling nuclear weapons and

13160-474: The Discontinuance of Nuclear Tests) and agreed to a temporary moratorium (the Soviet Union joined the moratorium shortly after this date). The moratorium would last for close to three years. The Conference on the Discontinuance of Nuclear Tests convened in Geneva at Moscow's request (the Western participants had proposed New York City ). The US delegation was led by James Jeremiah Wadsworth , an envoy to

13348-499: The Eisenhower administration for separating a test ban from larger disarmament efforts, and a defeat for the Department of Defense and AEC, which had argued to the contrary. In May 1958, Britain had informed the US that it would be willing to join a testing moratorium on 31 October 1958, by which point it would have finished its hydrogen-bomb testing, conditional on the US providing Britain with nuclear information following amendment of

13536-572: The Joint Committee on Atomic Energy, argued that the Soviet system would be unable to prevent secret tests. That year, the AEC published a report arguing that the continuing testing moratorium risked "free world supremacy in nuclear weapons," and that renewed testing was critical for further weapons development. The joint committee also held hearings in April which cast doubt on the technical feasibility and cost of

13724-565: The Macmillan–Eisenhower proposal. But US-Soviet relations soured after an American U-2 spy plane was shot down in Soviet airspace in May 1960. The Paris summit was abruptly cancelled and the Soviet Union withdrew from the seismic research group, which subsequently dissolved. Meetings of the Geneva Conference continued until December, but little progress was made as Western-Soviet relations continued to grow more antagonistic through

13912-754: The Manhattan Project, who was skeptical of Warren's then-theoretical claims. Warren's arguments were lent credence in the scientific community and public by the Castle Bravo test of 1954. Eisenhower, as president, first explicitly expressed interest in a comprehensive test ban that year, arguing before the National Security Council , "We could put [the Russians] on the spot if we accepted a moratorium ... Everybody seems to think that we're skunks, saber-rattlers and warmongers. We ought not miss any chance to make clear our peaceful objectives." Then-Secretary of State John Foster Dulles had responded skeptically to

14100-474: The McMahon Act. The US Congress approved amendments permitting greater collaboration in late June. Following Soviet assent on 30 August 1958 to the one-year moratorium, the three countries conducted a series of tests in September and October. At least 54 tests were conducted by the US and 14 by the Soviet Union in this period. On 31 October 1958 the three countries initiated test-ban negotiations (the Conference on

14288-615: The NNSS, the second Shagan , conducted at the Semipalatinsk Test Site . The following tests resulted in a release of radioactivity that was detected outside of the NNSS. The Schooner plume spread plutonium and other radionuclides across Area 20 and northward into Nellis Air Force Range . According to measurements taken in 2001, the Schooner crater has the highest annual mean concentration of radioactive tritiated water of any area of

14476-494: The NNSS. The Schooner crater area resembles the lunar landscape. It was used along with other areas of the NNSS to train some of the astronauts of the Apollo program , among them Neil Armstrong , Dick Gordon , Buzz Aldrin , Dave Scott and Rusty Schweickart . In 1970, the Apollo 16 team of John Young and Charlie Duke trained at Schooner in the lunar rover . In May 2023, NASA returned to Schooner to test lunar equipment for

14664-489: The PTBT for ratifying parties. Negotiations initially focused on a comprehensive ban, but that was abandoned because of technical questions surrounding the detection of underground tests and Soviet concerns over the intrusiveness of proposed verification methods. The impetus for the test ban was provided by rising public anxiety over the magnitude of nuclear tests, particularly tests of new thermonuclear weapons (hydrogen bombs), and

14852-455: The Soviet Union allowed in late November 1958 for explicit control measures to be included in the text of the drafted treaty. By March 1959, the negotiators had agreed upon seven treaty articles, but they primarily concerned uncontroversial issues and a number of disputes over verification persisted. First, the Soviet verification proposal was deemed by the West to be too reliant on self-inspection, with control posts primarily staffed by citizens of

15040-429: The Soviet Union as "both powerful and responsible." At the 20th Communist Party Congress in 1956, Khrushchev declared that nuclear war should no longer be seen as "fatalistically inevitable." Simultaneously, however, Khrushchev expanded and advanced the Soviet nuclear arsenal at a cost to conventional Soviet forces (e.g., in early 1960, Khrushchev announced demobilization of 1.2 million troops). On 31 March 1958,

15228-472: The Soviet Union insisted that the inspection quota be determined on a political basis, not a scientific one. The Soviet offer faced a mixed reception. In the US, Senator Hubert Humphrey and the Federation of American Scientists (which was typically seen as supportive of a test ban) saw it as a clear step towards an agreement. Conversely, AEC chairman John A. McCone and Senator Clinton Presba Anderson , chair of

15416-449: The Soviet Union privately suggested it would accept a quota of three inspections per year. The US argued that the quota should be set according to scientific necessity (i.e., be set according to the frequency of seismic events). In June 1959, a report of a panel headed by Lloyd Berkner , a physicist, was introduced into discussions by Wadsworth. The report specifically concerned whether the Geneva System could be improved without increasing

15604-427: The Soviet Union put forth a plan for a two-to-three-year testing moratorium. The moratorium would be overseen by an international commission reliant on national monitoring stations, but, importantly, would involve no on-the-ground inspections. Eisenhower initially saw the deal as favorable, but eventually came to see otherwise. In particular, Strauss and Teller, as well as Ernest Lawrence and Mark Muir Mills , protested

15792-440: The Soviet Union the ability to conduct secret tests and move ahead in the arms race. The degree of Eisenhower's interest in a test ban is a matter of some historical dispute. Stephen E. Ambrose writes that by early 1960, a test ban had become "the major goal of his Presidency, indeed of his entire career," and would be "his final and most lasting gift to his country." Conversely, John Lewis Gaddis characterizes negotiations of

15980-516: The Soviet Union, United Kingdom, France, China and India. The thermonuclear Tsar Bomba was the most powerful bomb ever detonated. As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above 50 kilotons of TNT (210 TJ), virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using

16168-471: The Soviets had a working fission bomb), was dubbed the Sloika , after a Russian layer cake , and was not of the Teller–Ulam configuration. It 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 might have been technically achievable, it did not have the scaling property of a "staged" weapon. Thus, such

16356-493: The Soviets searched for an alternative design. 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, in the course of being bombarded by neutrons, produce tritium and free deuterium. In late 1953 physicist Viktor Davidenko achieved the first breakthrough of staging the reactions. The next breakthrough of radiation implosion

16544-661: The Teller–Ulam configuration was tested at full scale in the "Ivy Mike" shot at an island in the Enewetak Atoll , with a yield of 10.4  Mt (44  PJ ) (over 450 times more powerful than the bomb dropped on Nagasaki during World War II ). The device, dubbed the Sausage , used an extra-large fission bomb as a "trigger" and liquid deuterium—kept in its liquid state by 20 short tons (18  t ) of cryogenic equipment—as its fusion fuel, and weighed around 80 short tons (73  t ) altogether. The liquid deuterium fuel of Ivy Mike

16732-429: The Teller–Ulam design. Detailed knowledge of fission and fusion weapons is classified to some degree in virtually every industrialized country . In the United States, such knowledge can by default be classified as " Restricted Data ", even if it is created by persons who are not government employees or associated with weapons programs, in a legal doctrine known as " born secret " (though the constitutional standing of

16920-435: The U.S. and Soviets, achieving only approximately 300 kt (1,300 TJ). The second test Orange Herald was the modified fission bomb and produced 720 kt (3,000 TJ)—making it the largest fission explosion ever. At the time almost everyone (including the pilots of the plane that dropped it) thought that this was a fusion bomb. This bomb was put into service in 1958. A second prototype fusion bomb, Purple Granite ,

17108-590: The U.S. conducted the Castle Bravo test at Bikini Atoll as part of Operation Castle , which resulted in a yield of 15 megatons of TNT , more than double the expected yield. This unexpectedly high yield caused widespread radioactive fallout, leading to severe environmental and human consequences. The Castle Bravo test resulted in the worst radiological event in US history as radioactive particles spread over more than 11,000 square kilometers (4,200 sq mi), affected inhabited areas (including Rongelap Atoll and Utirik Atoll ), and sickened Japanese fishermen aboard

17296-486: The U.S. government has attempted to censor weapons information in the public press , with limited success. According to the New York Times , physicist Kenneth W. Ford defied government orders to remove classified information from his book Building the H Bomb: A Personal History . Ford claims he used only pre-existing information and even submitted a manuscript to the government, which wanted to remove entire sections of

17484-535: The UN, the British by David Ormsby-Gore , the Minister of State for Foreign Affairs , and the Soviets by Semyon K. Tsarapkin , a disarmament expert with experience dating back to the 1946 Baruch Plan. The Geneva Conference began with a Soviet draft treaty grounded in the Geneva System. The three nuclear weapons states (the "original parties") would abide by a test ban, verified by the Geneva System, and work to prevent testing by potential nuclear states (such as France). This

17672-562: The US While the test ban was not a focus on conversations, a positive meeting with Eisenhower at Camp David eventually led Tsarapkin to propose a technical working group in November 1959 that would consider the issues of on-site inspections and seismic decoupling in the "spirit of Camp David." Within the working group, Soviet delegates allowed for the timing of on-site inspections to be grounded in seismic data, but insisted on conditions that were seen as excessively strict. The Soviets also recognized

17860-631: The US and UK continued to observe a moratorium. To break the deadlock over verification, Macmillan proposed a compromise in February 1959 whereby each of the original parties would be subject to a set number of on-site inspections each year. In May 1959, Khrushchev and Eisenhower agreed to explore Macmillan's quota proposal, though Eisenhower made further test-ban negotiations conditional on the Soviet Union dropping its Control Commission veto demand and participating in technical discussions on identification of high-altitude nuclear explosions . Khrushchev agreed to

18048-429: The US assented to a two-year testing moratorium proposed by the Soviet Union, but required that it be linked to restrictions on the production of fissionable material with military uses, a condition that the Soviet Union rejected. While Eisenhower insisted on linking a test ban to a broader disarmament effort (e.g., the production cut-off), Moscow insisted on independent consideration of a test ban. On 19 September 1957,

18236-500: The US conducted the first contained underground test at the Nevada Test Site , codenamed Rainier . The Rainier shot complicated the push for a comprehensive test ban, as underground tests could not be as easily identified as atmospheric tests. Despite Eisenhower's interest in a deal, his administration was hamstrung by discord among US scientists, technicians, and politicians. At one point, Eisenhower complained that "statecraft

18424-431: The US in nuclear capabilities. Teller also suggested that testing was necessary to develop nuclear weapons that produced less fallout. Support in the US public for a test ban to continue to grow from 20% in 1954 to 63% by 1957. Moreover, widespread antinuclear protests were organized and led by theologian and Nobel Peace Prize laureate Albert Schweitzer , whose appeals were endorsed by Pope Pius XII , and Linus Pauling ,

18612-555: The US now believed that it could only detect tests down to 20 kilotons (in comparison, the Little Boy bomb dropped on Hiroshima had an official yield of 13 kilotons). As a result, the Geneva detection regime and the number of control posts would have to be significantly expanded, including new posts within the Soviet Union. The Soviets dismissed the US argument as a ruse, suggesting that the Hardtack data had been falsified. In early 1959,

18800-438: The US pursue a test ban agreement with the Soviet Union before testing its first thermonuclear weapon, but his interest in international controls was echoed in the 1946 Acheson–Lilienthal Report , which had been commissioned by President Harry S. Truman to help construct US nuclear weapons policy. J. Robert Oppenheimer , who had led Los Alamos National Laboratory during the Manhattan Project, exerted significant influence over

18988-425: The US would not be held to its testing moratorium when it expired on 31 December 1959, though pledged to not test if Geneva talks progressed. The Soviet Union followed by reiterating its decision to not test as long as Western states did not test. In early 1960, Eisenhower indicated his support for a comprehensive test ban conditional on proper monitoring of underground tests. On 11 February 1960, Wadsworth announced

19176-399: The West. The proposal would serve as the basis of the Soviet negotiating position through 1957. Eisenhower had supported nuclear testing after World War II . In 1947, he rejected arguments by Stafford L. Warren , the Manhattan Project's chief physician, concerning the detrimental health effects of atmospheric testing, agreeing instead with James Bryant Conant , a chemist and participant in

19364-490: The X-ray energy impinging on its pusher/ tamper. This compresses the entire secondary stage and drives up the density of the plutonium spark plug. The density of the plutonium fuel rises to such an extent that the spark plug is driven into a supercritical state, and it begins a nuclear fission chain reaction . The fission products of this chain reaction heat the highly compressed (and thus super dense) thermonuclear fuel surrounding

19552-411: The amount of chemical explosives needed. The first Sloika design test, RDS-6s , was detonated in 1953 with a yield equivalent to 400 kt (1,700 TJ) ( 15%- 20% from fusion). Attempts to use a Sloika design to achieve megaton-range results proved unfeasible. After the United States tested the "Ivy Mike" thermonuclear device in November 1952, proving that a multimegaton bomb could be created,

19740-446: The book for concern that foreign states could use the information. Though large quantities of vague data have been officially released—and larger quantities of vague data have been unofficially leaked by former bomb designers—most public descriptions of nuclear weapon design details rely to some degree on speculation, reverse engineering from known information, or comparison with similar fields of physics ( inertial confinement fusion

19928-472: The casing to a plasma, which then re-radiated radiation into the secondary's pusher, causing its surface to ablate and driving it inwards, compressing the secondary, igniting the sparkplug, and causing the fusion reaction. The general applicability of this principle is unclear. In 1999 a reporter for the San Jose Mercury News reported that the U.S. W88 nuclear warhead, a small MIRVed warhead used on

20116-440: The casing's circumference. The neutron guns are tilted so the neutron emitting end of each gun end is pointed towards the central axis of the bomb. Neutrons from each neutron gun pass through and are focused by the neutron focus lens towards the centre of primary in order to boost the initial fissioning of the plutonium. A " polystyrene Polarizer/Plasma Source" is also shown (see below). The first U.S. government document to mention

20304-451: The closeness of the Soviet proposal to earlier Western proposals, the US reversed its position on the provisions and rejected the Soviet offer "in the absence of more general control agreements," including limits on the production of fissionable material and protections against a surprise nuclear strike . The May 1955 proposal is now seen as evidence of Khrushchev's "new approach" to foreign policy, as Khrushchev sought to mend relations with

20492-576: The commission's proceedings. Finally, the Soviet Union preferred temporary inspection teams drawn from citizens of the country under inspection, while the West insisted on permanent teams composed of inspectors from the Control Commission. Additionally, despite the initial positive response to the Geneva experts' report, data gathered from Hardtack operations of 1958 (namely the underground Rainier shot) would further complication verification provisions as US scientists, including Hans Bethe (who backed

20680-436: The complex technical questions of a test ban, driven in part by a strong interest among American experts to lower the error rate of seismic test detection technology. Some, including Kistiakowsky, would eventually raise concerns about the ability of inspections and monitors to successfully detect tests. The primary product of negotiations under Eisenhower was the testing moratorium without any enforcement mechanism. Ultimately,

20868-401: The concept has since been employed by most of the world's nuclear powers in the design of their weapons. Modern fusion weapons essentially consist of two main components: a nuclear fission primary stage (fueled by U or Pu ) and a separate nuclear fusion secondary stage containing thermonuclear fuel: heavy isotopes of hydrogen ( deuterium and tritium ) as

21056-455: The conclusion that it is technically feasible to set up ... a workable and effective control system for the detection of violations of a possible agreement on the worldwide cessation of nuclear weapons tests." The technical findings, released on 30 August 1958 in a report drafted by the Soviet delegation, were endorsed by the US and UK, which proposed that they serve as the basis for test-ban and international-control negotiations. However,

21244-412: The conditions needed for fusion, and the idea of staging or placing a separate thermonuclear component outside a fission primary component, and somehow using the primary to compress the secondary. Teller then realized that the gamma and X-ray radiation produced in the primary could transfer enough energy into the secondary to create a successful implosion and fusion burn, if the whole assembly was wrapped in

21432-443: The conference. At particular issue was the ability of sensors to differentiate an underground test from an earthquake. There were four techniques examined: measurement of acoustic waves , seismic signals, radio waves , and inspection of radioactive debris. The Soviet delegation expressed confidence in each method, while Western experts argued that a more comprehensive compliance system would be necessary. The Conference of Experts

21620-500: The contemporary risk models at the time, along with the assumption that the world population is "thirty billion persons" in a few thousand years. In 1961, Sakharov was part of the design team for a 50 megaton "clean bomb", which has become known as the Tsar Bomba , detonated over the island of Novaya Zemlya . In the spring of 1957, the US National Security Council had explored including a one-year test moratorium and

21808-410: The country housing the posts and a minimal role for officials from the international supervisory body. The West insisted that half of a control post staff be drawn from another nuclear state and half from neutral parties. Second, the Soviet Union required that the international supervisory body, the Control Commission, require unanimity before acting; the West rejected the idea of giving Moscow a veto over

21996-523: The danger of its accidentally becoming supercritical becomes too great. Surrounding the other components is a hohlraum or radiation case , a container that traps the first stage or primary's energy inside temporarily. The outside of this radiation case, which is also normally the outside casing of the bomb, is the only direct visual evidence publicly available of any thermonuclear bomb component's configuration. Numerous photographs of various thermonuclear bomb exteriors have been declassified. The primary

22184-416: The decision to go forward with the development of the new weapon. Teller and other U.S. physicists struggled to find a workable design. Stanislaw Ulam , a co-worker of Teller, made the first key conceptual leaps towards a workable fusion design. Ulam's two innovations that rendered the fusion bomb practical were that compression of the thermonuclear fuel before extreme heating was a practical path towards

22372-424: The diagram, though details are almost absent; what scattered details it does include likely have intentional omissions or inaccuracies. They are labeled "End-cap and Neutron Focus Lens" and "Reflector Wrap"; the former channels neutrons to the U / Pu Spark Plug while the latter refers to an X-ray reflector; typically a cylinder made of an X-ray opaque material such as uranium with

22560-532: The discord within American circles, particularly among scientists, was made clear in hearings before the Senate Subcommittee on Nuclear Disarmament, chaired by Senator Hubert Humphrey . The hearings featured conflicting testimony from the likes of Teller and Linus Pauling, as well as from Harold Stassen, who argued that a test ban could safely be separated from broader disarmament, and AEC members, who argued that

22748-403: The doctrine has been at times called into question; see United States v. Progressive, Inc. ). Born secret is rarely invoked for cases of private speculation. The official policy of the United States Department of Energy has been not to acknowledge the leaking of design information, as such acknowledgment would potentially validate the information as accurate. In a small number of prior cases,

22936-415: The effect of eroding the AEC's monopoly over scientific advice. In stark contrast to the AEC, PSAC promoted a test ban and argued against Strauss's claims concerning its strategic implications and technical feasibility. In late 1957, the Soviet Union made a second offer of a three-year moratorium without inspections, but lacking any consensus within his administration, Eisenhower rejected it. In early 1958,

23124-414: The effects of that absorbed energy led to the third mechanism: ablation . The outer casing of the secondary assembly is called the "tamper-pusher". The purpose of a tamper in an implosion bomb is to delay the expansion of the reacting fuel supply (which is very hot dense plasma) until the fuel is fully consumed and the explosion runs to completion. The same tamper material serves also as a pusher in that it

23312-505: The energy of the explosions into a "pancake" area is far more efficient in terms of area-destruction per unit of bomb energy. This also applies to single bombs deliverable by cruise missile or other system, such as a bomber, resulting in most operational warheads in the U.S. program having yields of less than 500 kt (2,100 TJ). In his 1995 book Dark Sun: The Making of the Hydrogen Bomb , author Richard Rhodes describes in detail

23500-520: The experts' report failed to address precisely who would do the monitoring and when on-site inspections—a US demand and Soviet concern—would be permitted. The experts also deemed detection of outer-space tests (tests more than 50 kilometers (31 mi) above the earth's surface) to be impractical. Additionally, the size of the Geneva System may have rendered it too expensive to be put into effect. The 30 August report, which contained details on these limitations, received significantly less public attention than

23688-508: The far more powerful Super. The debate covered matters that were alternatively strategic, pragmatic, and moral. In their Report of the General Advisory Committee, Robert Oppenheimer and colleagues concluded that "[t]he extreme danger to mankind inherent in the proposal [to develop thermonuclear weapons] wholly outweighs any military advantage." Despite the objections raised, on 31 January 1950, President Harry S. Truman made

23876-436: The fissioning of the final natural uranium tamper, something that could not normally be achieved without the neutron flux provided by the fusion reactions in secondary or tertiary stages. Such designs are suggested to be capable of being scaled up to an arbitrary large yield (with apparently as many fusion stages as desired), potentially to the level of a " doomsday device ." However, usually such weapons were not more than

24064-539: The frequency of seismic events). Tsarapkin responded positively to the US proposal, though was wary of the prospect of allowing underground tests registering below magnitude 4.75. In its own proposal offered 19 March 1960 the Soviet Union accepted most US provisions, with certain amendments. First, the Soviet Union asked that underground tests under magnitude 4.75 be banned for a period of four-to-five years, subject to extension. Second, it sought to prohibit all outer-space tests, whether within detection range or not. Finally,

24252-496: The gap between the Neutron Focus Lens (in the center) and the outer casing near the primary. It separates the primary from the secondary and performs the same function as the previous reflector. There are about six neutron guns (seen here from Sandia National Laboratories ) each protruding through the outer edge of the reflector with one end in each section; all are clamped to the carriage and arranged more or less evenly around

24440-426: The goal of a comprehensive test ban would be abandoned in favor of a partial ban due to questions over seismic detection of underground tests. Political scientist Robert Gilpin later argued that Eisenhower faced three camps in the push for a test ban. The first was the "control" camp, led by figures like Linus Pauling and astronomer Harlow Shapley , which believed that both testing and possession of nuclear weapons

24628-458: The intensities seen in everyday life, such as sunlight striking a surface, is usually imperceptible, but at the extreme intensities found in a thermonuclear bomb the pressure is enormous. For two thermonuclear bombs for which the general size and primary characteristics are well understood, the Ivy Mike test bomb and the modern W-80 cruise missile warhead variant of the W-61 design, the radiation pressure

24816-420: The internal components of the "Ivy Mike" Sausage device, based on information obtained from extensive interviews with the scientists and engineers who assembled it. According to Rhodes, the actual mechanism for the compression of the secondary was a combination of the radiation pressure, foam plasma pressure, and tamper-pusher ablation theories; the radiation from the primary heated the polyethylene foam lining of

25004-492: The interstage was only recently released to the public promoting the 2004 initiation of the Reliable Replacement Warhead (RRW) Program. A graphic includes blurbs describing the potential advantage of a RRW on a part-by-part level, with the interstage blurb saying a new design would replace "toxic, brittle material" and "expensive 'special' material... [that require] unique facilities". The "toxic, brittle material"

25192-573: The last year of the project he was assigned exclusively to the task. However once World War II ended, there was little impetus to devote many resources to the Super , as it was then known. The first atomic bomb test by the Soviet Union in August 1949 came earlier than expected by Americans, and over the next several months there was an intense debate within the U.S. government, military, and scientific communities regarding whether to proceed with development of

25380-460: The latter and was noncommittal on the former. A working group in Geneva would eventually devise a costly system of 5–6 satellites orbiting at least 18,000 miles (29,000 km) above the earth, though it could not say with certainty that such a system would be able to determine the origin of a high-altitude test. US negotiators also questioned whether high-altitude tests could evade detection via radiation shielding . Concerning Macmillan's compromise,

25568-420: The latter of whom organized an anti-test petition signed by more than 9,000 scientists across 43 countries (including the infirm and elderly Albert Einstein ). The AEC would eventually concede, as well, that even low levels of radiation were harmful. It was a combination of rising public support for a test ban and the shock of the 1957 Soviet Sputnik launch that encouraged Eisenhower to take steps towards

25756-415: The layer of fuel is the " spark plug ", a hollow column of fissile material ( Pu or U ) often boosted by deuterium gas. The spark plug, when compressed, can undergo nuclear fission (because of the shape, it is not a critical mass without compression). The tertiary, if one is present, would be set below the secondary and probably be made of the same materials. Separating

25944-492: The limited arms-control suggestion of Nehru, whose proposal for a test ban was discarded by the National Security Council for being "not practical." Harold Stassen , Eisenhower's special assistant for disarmament, argued that the US should prioritize a test ban as a first step towards comprehensive arms control, conditional on the Soviet Union accepting on-site inspections, over full disarmament. Stassen's suggestion

26132-432: The low direct plasma pressure they may be of use in delaying the ablation until energy has distributed evenly and a sufficient fraction has reached the secondary's tamper/pusher. Richard Rhodes ' book Dark Sun stated that a 1-inch-thick (25 mm) layer of plastic foam was fixed to the lead liner of the inside of the Ivy Mike steel casing using copper nails. Rhodes quotes several designers of that bomb explaining that

26320-930: The megaton range to be fully contained with minimal ground motion being felt in Las Vegas. Pahute Mesa was thus incorporated into the boundary of the NNSS in late 1963 under an agreement between the United States Atomic Energy Commission and the U.S. Air Force . Pahute Mesa is part of the Tonopah Basin and includes the Silent Canyon caldera complex of the Southwest Nevada volcanic field. Rugged terrain features and harsh winter conditions make year-round operations difficult. A total of 85 nuclear tests were conducted in Pahute Mesa between 1965 and 1992. Three of them— Boxcar , Benham and Handley —had

26508-529: The number of control posts. Berkner's proposed measures were seen as highly costly and the technical findings themselves were accompanied by a caveat about the panel's high degree of uncertainty given limited data. Around the same time, analysis conducted by the Livermore National Laboratory and RAND Corporation at Teller's instruction found that the seismic effect of an underground test could be artificially dampened (referred to as "decoupling") to

26696-494: The offer. At a meeting with Eisenhower in the White House, the group argued that testing was necessary for the US to eventually develop bombs that produced no fallout ("clean bombs"). The group repeated the oft-cited fact, which was supported by Freeman Dyson , that the Soviet Union could conduct secret nuclear tests. In 1958, at the request of Igor Kurchatov, Soviet nuclear physicist and weapons designer Andrei Sakharov published

26884-424: The outer radiation case, with the components coming to a thermal equilibrium , and the effects of that thermal energy are then analyzed. The energy is mostly deposited within about one X-ray optical thickness of the tamper/pusher outer surface, and the temperature of that layer can then be calculated. The velocity at which the surface then expands outwards is calculated and, from a basic Newtonian momentum balance,

27072-438: The plastic foam layer inside the outer case is to delay ablation and thus recoil of the outer case: if the foam were not there, metal would ablate from the inside of the outer case with a large impulse, causing the casing to recoil outwards rapidly. The purpose of the casing is to contain the explosion for as long as possible, allowing as much X-ray ablation of the metallic surface of the secondary stage as possible, so it compresses

27260-449: The point that a 300-kiloton detonation would appear in seismic readings as a one-kiloton detonation. These findings were largely affirmed by pro-ban scientists, including Bethe. The third blow to the verification negotiations was provided by a panel chaired by Robert Bacher, which found that even on-site inspections would have serious difficulty determining whether an underground test had been conducted. In September 1959, Khrushchev visited

27448-474: The power of nuclear devices continued to increase. Additionally, there was widespread apprehension about the broader environmental damage caused by such testing. In 1952–53, both the United States and the Soviet Union detonated their first thermonuclear weapons (hydrogen bombs), which were significantly more powerful than the atomic bombs that had been tested and deployed since the Trinity test in 1945. In 1954,

27636-413: The pressure produced by such a plasma would only be a small multiplier of the basic photon pressure within the radiation case, and also that the known foam materials intrinsically have a very low absorption efficiency of the gamma ray and X-ray radiation from the primary. Most of the energy produced would be absorbed by either the walls of the radiation case or the tamper around the secondary. Analyzing

27824-519: The primary and secondary assemblies placed within an enclosure called a radiation case, which confines the X-ray energy and resists its outward pressure. The distance separating the two assemblies ensures that debris fragments from the fission primary (which move much more slowly than X-ray photons ) cannot disassemble the secondary before the fusion explosion runs to completion. The secondary fusion stage—consisting of outer pusher/ tamper , fusion fuel filler and central plutonium spark plug—is imploded by

28012-442: The primary and secondary at either end. It does not reflect like a mirror; instead, it gets heated to a high temperature by the X-ray flux from the primary, then it emits more evenly spread X-rays that travel to the secondary, causing what is known as radiation implosion . In Ivy Mike , gold was used as a coating over the uranium to enhance the blackbody effect. Next comes the "Reflector/Neutron Gun Carriage". The reflector seals

28200-425: The primary would be used to compress and ignite the secondary fusion stage, resulting in a fusion explosion many times more powerful than the fission explosion alone. This chain of compression could conceivably be continued with an arbitrary number of tertiary fusion stages, each igniting more fusion fuel in the next stage although this is debated. Finally, efficient bombs (but not so-called neutron bombs ) end with

28388-605: The production of atomic energy. Though Dwight D. Eisenhower , then the Chief of Staff of the United States Army , was not a significant figure in the Truman administration on nuclear questions, he did support Truman's nuclear control policy, including the Baruch Plan's provision for an international control agency, provided that the control system was accompanied by "a system of free and complete inspection." The Soviet Union dismissed

28576-508: The proposed verification measures. Additionally, Teller continued to warn of the dangerous consequences of a test ban and the Department of Defense (including Neil H. McElroy and Donald A. Quarles , until recently its top two officials) pushed to continue testing and expand missile stockpiles. Shortly after the Soviet proposal, Macmillan met with Eisenhower at Camp David to devise a response. The Anglo-American counterproposal agreed to ban small underground tests (those under magnitude 4.75) on

28764-448: The pure element or in modern weapons lithium deuteride . For this reason, thermonuclear weapons are often colloquially called hydrogen bombs or H-bombs . A fusion explosion begins with the detonation of the fission primary stage. Its temperature soars past 100 million kelvin , causing it to glow intensely with thermal ("soft") X-rays . These X-rays flood the void (the "radiation channel" often filled with polystyrene foam ) between

28952-654: The report, particularly in its recommendation of an international body that would control production of and research on the world's supply of uranium and thorium . A version of the Acheson-Lilienthal plan was presented to the United Nations Atomic Energy Commission (UNAEC) as the Baruch Plan in June 1946. The Baruch Plan proposed that an International Atomic Development Authority would control all research on and material and equipment involved in

29140-418: The rest of the tamper-pusher to recoil inwards with tremendous force, crushing the fusion fuel and the spark plug. The tamper-pusher is built robustly enough to insulate the fusion fuel from the extreme heat outside; otherwise, the compression would be spoiled. Rough calculations for the basic ablation effect are relatively simple: the energy from the primary is distributed evenly onto all of the surfaces within

29328-458: The resulting nuclear fallout . A test ban was also seen as a means of slowing nuclear proliferation and the nuclear arms race . Though the PTBT did not halt proliferation or the arms race, its enactment did coincide with a substantial decline in the concentration of radioactive particles in the atmosphere. The PTBT was signed by the governments of the Soviet Union , the United Kingdom , and

29516-450: The secondary efficiently, maximizing the fusion yield. Plastic foam has a low density, so causes a smaller impulse when it ablates than metal does. Possible variations to the weapon design have been proposed: Most bombs do not apparently have tertiary "stages"—that is, third compression stage(s), which are additional fusion stages compressed by a previous fusion stage. The fissioning of the last blanket of uranium, which provides about half

29704-422: The secondary from the primary is the interstage . The fissioning primary produces four types of energy: 1) expanding hot gases from high explosive charges that implode the primary; 2) superheated plasma that was originally the bomb's fissile material and its tamper; 3) the electromagnetic radiation ; and 4) the neutrons from the primary's nuclear detonation. The interstage is responsible for accurately modulating

29892-580: The secondary stages by radiation implosion. Because of these difficulties, in 1955 Prime Minister Anthony Eden agreed to a secret plan, whereby if the Aldermaston scientists failed or were greatly delayed in developing the fusion bomb, it would be replaced by an extremely large fission bomb. In 1957 the Operation Grapple tests were carried out. The first test, Green Granite, was a prototype fusion bomb that failed to produce equivalent yields compared to

30080-497: The security of both Russians and Americans is dangerously weakened." He had also claimed that renewed testing would be "damaging to the American image" and might threaten the "existence of human life." On the campaign trail, Kennedy's test-ban proposal consisted of a continued US testing moratorium, expanded efforts to reach a comprehensive agreement, limit any future tests to those minimizing fallout, and expand research on fallout. Notably, early in his presidency, Kennedy also oversaw

30268-418: The spark plug to around 300 million kelvin, igniting fusion reactions between fusion fuel nuclei. In modern weapons fueled by lithium deuteride, the fissioning plutonium spark plug also emits free neutrons that collide with lithium nuclei and supply the tritium component of the thermonuclear fuel. The secondary's relatively massive tamper (which resists outward expansion as the explosion proceeds) also serves as

30456-512: The spring of 1958, chairman Killian and the PSAC staff (namely Hans Bethe and Isidor Isaac Rabi ) undertook a review of US test-ban policy, determining that a successful system for detecting underground tests could be created. At the recommendation of Dulles (who had recently come to support a test ban), the review prompted Eisenhower to propose technical negotiations with the Soviet Union, effectively detaching test-ban negotiations from negotiations over

30644-522: The start of the moratorium back to November 1958. At the same time, Macmillan linked British support for a test ban to a revision of the Atomic Energy Act of 1946 (McMahon Act), which prohibited sharing of nuclear information with foreign governments. Eisenhower, eager to mend ties with Britain following the Suez Crisis of 1956, was receptive to Macmillan's conditions, but the AEC and the congressional Joint Committee on Atomic Energy were firmly opposed. It

30832-481: The subject in February 1955. On 10 May 1955, the Soviet Union proposed a test ban before the UN Disarmament Commission's "Committee of Five" (Britain, Canada , France , the Soviet Union, and the US). This proposal, which closely reflected a prior Anglo-French proposal, was initially part of a comprehensive disarmament proposal meant to reduce conventional arms levels and eliminate nuclear weapons. Despite

31020-589: The summer, punctuated by the Congo Crisis in July and angry exchanges at the UN in September. Macmillan would later claim to President John F. Kennedy that the failure to achieve a test ban in 1960 "was all the fault of the American 'big hole' obsession and the consequent insistence on a wantonly large number of on-site inspections." Eisenhower would leave office with an agreement out of reach, as Eisenhower's technical advisors, upon whom he relied heavily, became mired in

31208-407: The tamper and radiation case is the main contribution to the total yield and is the dominant process that produces radioactive fission product fallout . Before Ivy Mike, Operation Greenhouse in 1951 was the first American nuclear test series to test principles that led to the development of thermonuclear weapons. Sufficient fission was achieved to boost the associated fusion device, and enough

31396-403: The test ban as a critical step toward reducing nuclear proliferation and easing Cold War tensions. In making his case for a test ban, Kennedy drew a direct link between continued testing and nuclear proliferation, calling it the "'Nth-country' problem." While a candidate, Kennedy had argued, "For once China , or France, or Sweden , or half a dozen other nations successfully test an atomic bomb,

31584-486: The theory behind decoupling, but dismissed its practical applications. The working group closed in December with no progress and significant hostility. Eisenhower issued a statement blaming "the recent unwillingness of the politically guided Soviet experts to give serious scientific consideration to the effectiveness of seismic techniques for the detection of underground nuclear explosions." Eisenhower simultaneously declared that

31772-485: The time, the U.S. had not yet developed a cohesive policy or strategy regarding nuclear weapons. Vannevar Bush , who had been instrumental in initiating and overseeing the Manhattan Project , sought to leverage this moment to advance his long-term goal of banning nuclear weapons production, despite the project's role in developing them. As a first step in this direction, Bush proposed an international agency dedicated to nuclear control. Bush unsuccessfully argued in 1952 that

31960-404: The transfer of energy from the primary to the secondary. It must direct the hot gases, plasma, electromagnetic radiation and neutrons toward the right place at the right time. Less than optimal interstage designs have resulted in the secondary failing to work entirely on multiple shots, known as a " fissile fizzle ". The Castle Koon shot of Operation Castle is a good example; a small flaw allowed

32148-506: The treaty under negotiation. In May 1960, there were high hopes that an agreement would be reached at an upcoming summit of Eisenhower, Khrushchev, Macmillan, and Charles de Gaulle of France in Paris. A test ban seemed particularly close in 1960, with Britain and France in accord with the US (though France conducted its first nuclear test in February) and the Soviet Union having largely accepted

32336-412: The velocity at which the rest of the tamper implodes inwards. Applying the more detailed form of those calculations to the Ivy Mike device yields vaporized pusher gas expansion velocity of 290 kilometres per second (29 cm/μs) and an implosion velocity of perhaps 400 km/s (40 cm/μs) if + 3 ⁄ 4 of the total tamper/pusher mass is ablated off, the most energy efficient proportion. For

32524-404: The weapon (with the foam) would be as follows: This would complete the fission-fusion-fission sequence. Fusion, unlike fission, is relatively "clean"—it releases energy but no harmful radioactive products or large amounts of nuclear fallout . The fission reactions though, especially the last fission reactions, release a tremendous amount of fission products and fallout. If the last fission stage

32712-500: The yield in large bombs, does not count as a "stage" in this terminology. The U.S. tested three-stage bombs in several explosions during Operation Redwing but is thought to have fielded only one such tertiary model, i.e., a bomb in which a fission stage, followed by a fusion stage, finally compresses yet another fusion stage. This U.S. design was the heavy but highly efficient (i.e., nuclear weapon yield per unit bomb weight) 25 Mt (100 PJ) B41 nuclear bomb . The Soviet Union

32900-424: Was a vice president at Bell Telephone Laboratories and was joined by Robert Bacher and Ernest Lawrence, both physicists who had worked on the Manhattan Project. Conversely, British delegates largely held government positions. The Soviet delegation was composed primarily of academics, though virtually all of them had some link to the Soviet government. The Soviets shared the British goal of achieving an agreement at

33088-405: Was becoming a prisoner of scientists." Until 1957, Strauss's AEC (including its Los Alamos and Livermore laboratories) was the dominant voice in the administration on nuclear affairs, with Teller's concerns over detection mechanisms also influencing Eisenhower. Unlike some others within the US scientific community, Strauss fervently advocated against a test ban, arguing that the US must maintain

33276-480: Was calculated to be 73 × 10 ^   bar (7.3  TPa ) for the Ivy Mike design and 1,400 × 10 ^   bar (140  TPa ) for the W-80. Foam plasma pressure is the concept that Chuck Hansen introduced during the Progressive case, based on research that located declassified documents listing special foams as liner components within the radiation case of thermonuclear weapons. The sequence of firing

33464-436: Was characterized as "highly professional" and productive. By the end of August 1958, the experts devised an extensive control program, known as the "Geneva System," involving 160–170 land-based monitoring posts, plus 10 additional sea-based monitors and occasional flights over land following a suspicious event (with the inspection plane being provided and controlled by the state under inspection). The experts determined that such

33652-415: Was cut off by the United States at one point due to concerns about Soviet espionage. Full cooperation was not reestablished until an agreement governing the handling of secret information and other issues was signed. However, the British were allowed to observe the U.S. Castle tests and used sampling aircraft in the mushroom clouds , providing them with clear, direct evidence of the compression produced in

33840-405: Was dangerous. Second, there was the "finite containment" camp, populated by scientists like Hans Bethe, which was concerned by perceived Soviet aggression but still believed that a test ban would be workable with adequate verification measures. Third, the "infinite containment" camp, of which Strauss, Teller, and members of the defense establishment were members, believed that any test ban would grant

34028-595: Was discovered and developed by Sakharov and Yakov Zel'dovich in early 1954. Sakharov's "Third Idea", as the Teller–Ulam design was known in the USSR, was tested in the shot " RDS-37 " in November 1955 with a yield of 1.6 Mt (6.7 PJ). The Soviets demonstrated the power of the staging concept in October 1961, when they detonated the massive and unwieldy Tsar Bomba. It was the largest nuclear weapon developed and tested by any country. In 1954 work began at Aldermaston to develop

34216-535: Was dismissed by others in the administration over fears that the Soviet Union would be able to conduct secret tests. On the advice of Dulles, Atomic Energy Commission (AEC) chairman Lewis Strauss , and Secretary of Defense Charles Erwin Wilson , Eisenhower rejected the idea of considering a test ban outside general disarmament efforts. During the 1952 and 1956 presidential elections, Eisenhower fended off challenger Adlai Stevenson , who ran in large part on support for

34404-509: Was impractical for a deployable weapon, and the next advance was to use a solid lithium deuteride fusion fuel instead. In 1954 this was tested in the " Castle Bravo " shot (the device was code-named Shrimp ), which had a yield of 15  Mt (63  PJ ) (2.5 times expected) and is the largest U.S. bomb ever tested. Efforts shifted towards developing miniaturized Teller–Ulam weapons that could fit into intercontinental ballistic missiles and submarine-launched ballistic missiles . By 1960, with

34592-463: Was learned to achieve a full-scale device within a year. The design of all modern thermonuclear weapons in the United States is known as the Teller–Ulam configuration for its two chief contributors, Edward Teller and Stanisław Ulam , who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist John von Neumann . Similar devices were developed by

34780-427: Was not until after Sputnik in late 1957 that Eisenhower quickly moved to expand nuclear collaboration with the UK via presidential directives and the establishment of bilateral committees on nuclear matters. In early 1958, Eisenhower publicly stated that amendments to the McMahon Act were a necessary condition of a test ban, framing the policy shift in the context of US commitment to its NATO allies. In August 1957,

34968-431: Was personally troubled by the power of nuclear weapons and would later recount that he believed the weapons could never be used. In the mid-1950s, Khrushchev took a keen interest in defense policy and sought to inaugurate an era of détente with the West. Initial efforts to reach accords, such as on disarmament at the 1955 Geneva Summit , proved fruitless, and Khrushchev saw test-ban negotiations as an opportunity to present

35156-499: Was rejected by Anglo-American negotiators due to fears that the verification provisions were too vague and the Geneva System too weak. Shortly after the Geneva Conference began in the fall of 1958, Eisenhower faced renewed domestic opposition to a comprehensive test ban as Senator Albert Gore Sr. argued in a widely circulated letter that a partial ban would be preferable due to Soviet opposition to strong verification measures. The Gore letter did spur some progress in negotiations, as

35344-419: Was tempered by concern that resistance to a test ban might lead the US and Soviet Union to pursue an agreement without Britain having any say in the matter. Members of the Soviet military–industrial complex also opposed a test ban, though some scientists, including Igor Kurchatov , were supportive of antinuclear efforts. France, which was in the midst of developing its own nuclear weapon, also firmly opposed

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