From Wikipedia, the free encyclopedia
A
thermonuclear weapon is a
nuclear weapon design that uses the
heat generated by a fission bomb to compress a nuclear
fusion stage which indirectly results in greatly increased energy yield (i.e.,
bomb "power"). It is colloquially referred to as a
hydrogen bomb or H-bomb
because it employs
hydrogen fusion, though in most applications the majority of its
destructive energy comes from
uranium fission, not hydrogen fusion by itself. The fusion
stage in such weapons is required to efficiently cause the large quantities of
fission characteristic of most thermonuclear weapons.
[1]
The concept of the thermonuclear weapon was first developed and used by
the
United States and has since been used in most of the
world's nuclear weapons.
[2] The modern design of all thermonuclear
weapons in the United States is known as the
Teller-Ulam design for its
two chief contributors,
Edward Teller and
Stanisław Ulam, who developed it in 1951 for the U.S.,
with certain concepts developed with the contribution of
John von Neumann. The first test of this principle was
the "
Ivy Mike"
nuclear test in 1952, conducted by the United States.
In the
Soviet Union, the design was independently developed
and known as
Andrei Sakharov's "Third Idea", first tested in 1955.
Similar devices were developed by the United Kingdom, China, and France, though
no specific code names are known for their designs.
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 exploiting the temperature difference
between the secondary'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—and it usually is—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.
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