Nuclear weapon design

context: en: A spherical secondary can achieve higher implosion densities than a cylindrical secondary, because spherical implosion pushes in from all directions toward the same spot. However, in warheads yielding more than one megaton, the diameter of a spherical secondary would be too large for most applications. A cylindrical secondary is necessary in such cases. The small, cone-shaped re-entry vehicles in multiple-warhead ballistic missiles after 1970 tended to have warheads with spherical secondaries, and yields of a few hundred kilotons.
qas: question: zh_tw: 必須使用什麼形狀？
answers: en: text: cylindrical

context: en: After the war, interest in the hollow pit design was revived. Its obvious advantage is that a hollow shell of plutonium, shock-deformed and driven inward toward its empty center, would carry momentum into its violent assembly as a solid sphere. It would be self-tamping, requiring a smaller U-238 tamper, no aluminium pusher and less high explosive.
qas: question: zh_tw: 需要什麼樣的小填充物？
answers: en: text: U-238

context: en: An important tool for test analysis was the diagnostic light pipe. A probe inside a test device could transmit information by heating a plate of metal to incandescence, an event that could be recorded by instruments located at the far end of a long, very straight pipe.
qas: question: zh_tw: 什麼是測試分析的重要工具？
answers: en: text: the diagnostic light pipe

context: en: Because even low-yield nuclear warheads have astounding destructive power, weapon designers have always recognised the need to incorporate mechanisms and associated procedures intended to prevent accidental detonation.
qas: question: zh_tw: 武器設計人員在整合機制和相關流程時的意圖是什麼？
answers: en: text: to prevent accidental detonation

context: en: ERWs were two-stage thermonuclears with all non-essential uranium removed to minimize fission yield. Fusion provided the neutrons. Developed in the 1950s, they were first deployed in the 1970s, by U.S. forces in Europe. The last ones were retired in the 1990s.
qas: question: zh_tw: 什麼是中子彈？
answers: en: text: two-stage thermonuclears

context: en: Equally important, the active ingredients in the Flute probably cost no more than those in the Swan. Most of the fission came from cheap U-238, and the tritium was manufactured in place during the explosion. Only the spark plug at the axis of the secondary needed to be fissile.
qas: question: zh_tw: 必須裂變的唯一部分是什麼？
answers: en: text: axis of the secondary

context: en: Finally, the heat for fusion ignition comes not from the primary but from a second fission bomb called the spark plug, embedded in the heart of the secondary. The implosion of the secondary implodes this spark plug, detonating it and igniting fusion in the material around it, but the spark plug then continues to fission in the neutron-rich environment until it is fully consumed, adding significantly to the yield.The initial impetus behind the two-stage weapon was President Truman's 1950 promise to build a 10-megaton hydrogen superbomb as the U.S. response to the 1949 test of the first Soviet fission bomb. But the resulting invention turned out to be the cheapest and most compact way to build small nuclear bombs as well as large ones, erasing any meaningful distinction between A-bombs and H-bombs, and between boosters and supers. All preferred techniques for fission and fusion explosions are incorporated into one all-encompassing, fully scalable design principle. Even 6-inch (150 mm) diameter nuclear artillery shells can be two-stage thermonuclears.In the ensuing fifty years, nobody has come up with a more efficient way to build a nuclear bomb. It is the design of choice for the United States, Russia, the United Kingdom, China, and France, the five thermonuclear powers. On 3 September 2017 North Korea carried out what it reported as its first "two-stage thermo-nuclear weapon" test. According to Dr. Theodore Taylor, after reviewing leaked photographs of disassembled weapons components taken before 1986, Israel possessed boosted weapons and would require supercomputers of that era to advance further toward full two-stage weapons in the megaton range without nuclear test detonations. The other nuclear-armed nations, India and Pakistan, probably have single-stage weapons, possibly boosted.
qas: question: zh_tw: 印度和巴基斯坦可能擁有哪些型別的核武器？
answers: en: text: single-stage weapons, possibly boosted

context: en: Initially, gamma radiation from the fission products of an equivalent size fission-fusion-fission bomb are much more intense than Co-60: 15,000 times more intense at 1 hour; 35 times more intense at 1 week; 5 times more intense at 1 month; and about equal at 6 months. Thereafter fission drops off rapidly so that Co-60 fallout is 8 times more intense than fission at 1 year and 150 times more intense at 5 years. The very long-lived isotopes produced by fission would overtake the 60Co again after about 75 years.The triple "taiga" nuclear salvo test, as part of the preliminary March 1971 Pechora–Kama Canal project, produced a small amount of fission products and therefore a comparatively large amount of case material activated products are responsible for most of the residual activity at the site today, namely Co-60. With this fusion generated neutron activation product being responsible for about half of the gamma dose now(2011) at the test site, albeit with that dose being too small to cause deleterious effects, normal green vegetation exists all around the lake that was formed.
qas: question: zh_tw: 鈷 - 60 γ 射線釋放的裂變強度有多大？
answers: en: text: 8 times more intense than fission at 1 year and 150 times more intense at 5 years

context: en: It was much more difficult to understand how it worked or why it failed. Designers gathered as much data as possible during the explosion, before the device destroyed itself, and used the data to calibrate their models, often by inserting fudge factors into equations to make the simulations match experimental results. They also analyzed the weapon debris in fallout to see how much of a potential nuclear reaction had taken place.
qas: question: zh_tw: 他們分析了什麼？
answers: en: text: weapon debris

context: en: Nuclear fission separates or splits heavier atoms to form lighter atoms. Nuclear fusion combines together lighter atoms to form heavier atoms. Both reactions generate roughly a million times more energy than comparable chemical reactions, making nuclear bombs a million times more powerful than non-nuclear bombs, which a French patent claimed in May 1939.In some ways, fission and fusion are opposite and complementary reactions, but the particulars are unique for each. To understand how nuclear weapons are designed, it is useful to know the important similarities and differences between fission and fusion. The following explanation uses rounded numbers and approximations.
qas: question: zh_tw: 那解釋使用了什麼型別的數字？
answers: en: text: rounded

context: en: Once the critical mass is assembled, at maximum density, a burst of neutrons is supplied to start as many chain reactions as possible. Early weapons used a modulated neutron generator codenamed "Urchin" inside the pit containing polonium-210 and beryllium separated by a thin barrier. Implosion of the pit crushed the neutron generator, mixing the two metals, thereby allowing alpha particles from the polonium to interact with beryllium to produce free neutrons. In modern weapons, the neutron generator is a high-voltage vacuum tube containing a particle accelerator which bombards a deuterium/tritium-metal hydride target with deuterium and tritium ions. The resulting small-scale fusion produces neutrons at a protected location outside the physics package, from which they penetrate the pit. This method allows better control of the timing of chain reaction initiation.
qas: question: zh_tw: 調製中子發生器的代號是什麼？
answers: en: text: Urchin

context: en: The first effort to exploit the symbiotic relationship between fission and fusion was a 1940s design that mixed fission and fusion fuel in alternating thin layers. As a single-stage device, it would have been a cumbersome application of boosted fission. It first became practical when incorporated into the secondary of a two-stage thermonuclear weapon.The U.S. name, Alarm Clock, came from Teller: he called it that because it might "wake up the world" to the possibility of the potential of the Super. The Russian name for the same design was more descriptive: Sloika (Russian: Слойка), a layered pastry cake. A single-stage Soviet Sloika was tested on August 12, 1953. No single-stage U.S. version was tested, but the Union shot of Operation Castle, April 26, 1954, was a two-stage thermonuclear device code-named Alarm Clock. Its yield, at Bikini, was 6.9 megatons.
qas: question: zh_tw: “鬧鐘” 炸彈有多大？
answers: en: text: 6.9 megatons

context: en: The only practical way to capture most of the fusion energy is to trap the neutrons inside a massive bottle of heavy material such as lead, uranium, or plutonium. If the 14 MeV neutron is captured by uranium (of either isotope; 14 MeV is high enough to fission both 235U and 238U) or plutonium, the result is fission and the release of 180 MeV of fission energy, multiplying the energy output tenfold.
qas: question: zh_tw: 當中子被鈾原子核捕獲時，會發生什麼？
answers: en: text: fission

context: en: The picture below shows the Shrimp device, detonated on March 1, 1954 at Bikini, as the Castle Bravo test. Its 15-megaton explosion was the largest ever by the United States. The silhouette of a man is shown for scale. The device is supported from below, at the ends. The pipes going into the shot cab ceiling, which appear to be supports, are actually diagnostic light pipes. The eight pipes at the right end (1) sent information about the detonation of the primary. Two in the middle (2) marked the time when x-radiation from the primary reached the radiation channel around the secondary. The last two pipes (3) noted the time radiation reached the far end of the radiation channel, the difference between (2) and (3) being the radiation transit time for the channel.
qas: question: zh_tw: 哪一個國家執行城堡 Bravo 試驗？
answers: en: text: United States

context: en: The public records for devices that produced the highest proportion of their yield via fusion reactions are the peaceful nuclear explosions of the 1970s, with the 3 detonations that excavated part of Pechora–Kama Canal being cited as 98% fusion each in the Taiga test's 15 kiloton explosive yield devices; that is, a total fission fraction of 0.3 kilotons in a 15 kt device. Others include the 50 megaton Tsar Bomba at 97% fusion, the 9.3 megaton Hardtack Poplar test at 95.2%, and the 4.5 megaton Redwing Navajo test at 95% fusion.On July 19, 1956, AEC Chairman Lewis Strauss said that the Redwing Zuni shot clean bomb test "produced much of importance ... from a humanitarian aspect." However, less than two days after this announcement, the dirty version of Bassoon, called Bassoon Prime, with a uranium-238 tamper in place, was tested on a barge off the coast of Bikini Atoll as the Redwing Tewa shot. The Bassoon Prime produced a 5-megaton yield, of which 87% came from fission. Data obtained from this test, and others, culminated in the eventual deployment of the highest yielding US nuclear weapon known, and the highest yield-to-weight weapon ever made, a three-stage thermonuclear weapon with a maximum "dirty" yield of 25 megatons, designated as the B41 nuclear bomb, which was to be carried by U.S. Air Force bombers until it was decommissioned; this weapon was never fully tested.
qas: question: zh_tw: 同度巴松管的輸出量是多少？
answers: en: text: 5-megaton yield

question: zh_tw: 花了幾天才完成測試？
answers: en: text: two days

context: en: The secondary is located in the wide end of the re-entry cone, where it can be larger, and thus more powerful. The usual arrangement is to put the heavier, denser secondary in the narrow end for greater aerodynamic stability during re-entry from outer space, and to allow more room for a bulky primary in the wider part of the cone. (The W87 warhead drawing in the W87 article shows the usual arrangement.) Because of this new geometry, the W88 primary uses compact conventional high explosives (CHE) to save space, rather than the more usual, and bulky but safer, insensitive high explosives (IHE). The re-entry cone probably has ballast in the nose for aerodynamic stability.The alternating layers of fission and fusion material in the secondary are an application of the Alarm Clock/Sloika principle.
qas: question: zh_tw: 工程師們把較重的次級火箭放在太空梭的哪一端？
answers: en: text: narrow end

context: en: While x-rays would normally travel at the speed of light through a low-density material like the plastic foam channel filler between (2) and (3), the intensity of radiation from the exploding primary creates a relatively opaque radiation front in the channel filler, which acts like a slow-moving logjam to retard the passage of radiant energy. While the secondary is being compressed via radiation-induced ablation, neutrons from the primary catch up with the x-rays, penetrate into the secondary, and start breeding tritium via the third reaction noted in the first section above. This Li-6 + n reaction is exothermic, producing 5 MeV per event. The spark plug has not yet been compressed, and, thus, remains subcritical, so no significant fission or fusion takes place as a result. If enough neutrons arrive before implosion of the secondary is complete, though, the crucial temperature differential between the outer and inner parts of the secondary can be degraded, potentially causing the secondary to fail to ignite. The first Livermore-designed thermonuclear weapon, the Morgenstern device, failed in this manner when it was tested as Castle Koon on April 7, 1954. The primary ignited, but the secondary, preheated by the primary's neutron wave, suffered what was termed as an inefficient detonation; thus, a weapon with a predicted one-megaton yield produced only 110 kilotons, of which merely 10 kt were attributed to fusion.These timing effects, and any problems they cause, are measured by light-pipe data. The mathematical simulations which they calibrate are called radiation flow hydrodynamics codes, or channel codes. They are used to predict the effect of future design modifications.
qas: question: zh_tw: Livermore 的第一個熱核武器的名稱是什麼？
answers: en: text: the Morgenstern device

question: zh_tw: 如果溫度不對，可能會損壞什麼？
answers: en: text: outer and inner parts of the secondary