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A thermonuclear weapon is a nuclear weapon that uses the energy from a primary nuclear fission reaction to compress and ignite a secondary nuclear fusion reaction. The result is greatly increased explosive power when compared to single-stage fission weapons. It is colloquially referred to as a hydrogen bomb or H-bomb because it employs hydrogen fusion. The fission stage in such weapons is required to cause the fusion that occurs in thermonuclear weapons.〔The misleading term "hydrogen bomb" was already in wide public use before fission product fallout from the Castle Bravo test in 1954 revealed the extent to which the design relies on fission.〕 The concept of the thermonuclear weapon was first developed and used in 1952 and has since been employed by most of the world's nuclear weapons.〔From National Public Radio Talk of the Nation, November 8, 2005, Siegfried Hecker of Los Alamos, "the hydrogen bomb – that is, a two-stage thermonuclear device, as we referred to it – is indeed the principal part of the U.S. arsenal, as it is of the Russian arsenal."〕 The modern design of all thermonuclear weapons in the United States is known as the ''Teller-Ulam configuration'' for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951〔 on the ( Nuclear Non-Proliferation Institute ) website. This is the original classified paper by Teller and Ulam proposing staged implosion. This declassified version is heavily redacted, leaving only a few paragraphs.〕 for the United States, with certain concepts developed with the contribution of John von Neumann. The first test of a hydrogen bomb prototype was the "Ivy Mike" nuclear test in 1952, conducted by the United States. The first ready-to-use thermonuclear bomb "RDS-6s" ("Joe 4") was tested on August 12, 1953, in the Soviet Union. Similar devices were developed by the United Kingdom, China, and France. As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above 50 kilotons, virtually all the nuclear weapons deployed by the five nuclear-weapon states under the NPT today are thermonuclear weapons using the Teller–Ulam design.〔 "So far as is known all high yield nuclear weapons today (>50 kt or so) use this design."〕 The essential features of the mature thermonuclear weapon design, which officially remained secret for nearly three decades, are: 1) separation of stages into a triggering "primary" explosive and a much more powerful "secondary" explosive, 2) compression of the secondary by X-rays coming from nuclear fission in the primary, a process called the "radiation implosion" of the secondary, and 3) heating of the secondary, after cold compression, by a second fission explosion inside the secondary. The radiation implosion mechanism is a heat engine that exploits the temperature difference between the secondary stage's hot, surrounding radiation channel and its relatively cool interior. This temperature difference is briefly maintained by a massive heat barrier called the "pusher", which also serves as an implosion tamper, increasing and prolonging the compression of the secondary. If made of uranium, as is almost always the case, it can capture neutrons produced by the fusion reaction and undergo fission itself, increasing the overall explosive yield. In many Teller–Ulam weapons, fission of the pusher dominates the explosion and produces radioactive fission product fallout. ==Public knowledge concerning nuclear weapon design== Detailed knowledge of fission and fusion weapons is classified to some degree in virtually every industrialized nation. 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 the doctrine has been at times called into question; see ''United States v. The Progressive''). Born secret is rarely invoked for cases of private speculation. The official policy of the United States Department of Energy has been to not acknowledge the leaking of design information, as such acknowledgment would potentially validate the information as accurate. In a small number of prior cases, 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 Ford defied government orders to remove classified information from his new book, ''Building the H Bomb: A Personal History''. Ford claims he only used pre-existing information and even submitted a manuscript to the government who wanted to remove entire sections of the book for concern that foreign nations 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 is the primary example). Such processes have resulted in a body of unclassified knowledge about nuclear bombs which is generally consistent with official unclassified information releases, related physics, and is thought to be internally consistent, though there are some points of interpretation which are still considered open. The state of public knowledge about the Teller–Ulam design has been mostly shaped from a few specific incidents outlined in a section below. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thermonuclear weapon」の詳細全文を読む スポンサード リンク
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