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prompt neutrons

The neutrons emitted during a nuclear fission process within less than a microsecond of fission. Compare delayed neutrons.

prompt neutrons

prompt neutrons   Quick reference

A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
20 words

...prompt neutrons The neutrons emitted during a nuclear fission process within less than a microsecond of fission. Compare delayed neutrons...

prompt neutrons

prompt neutrons  

The neutrons emitted during a nuclear fission process within less than a microsecond of fission. Compare delayed neutrons.
delayed neutrons

delayed neutrons  

The small proportion of neutrons that are emitted with a measurable time delay in a nuclear fission process. Compare prompt neutrons.
prompt radiation

prompt radiation  

The gamma rays produced in fission and as a result of other neutron reactions and nuclear excitation of the weapon materials appearing within a second or less after a nuclear explosion.[...]
delayed neutrons

delayed neutrons   Quick reference

A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
23 words

...delayed neutrons The small proportion of neutrons that are emitted with a measurable time delay in a nuclear fission process. Compare prompt neutrons...

prompt radiation

prompt radiation   Reference library

The Oxford Essential Dictionary of the U.S. Military

Reference type:
Subject Reference
Current Version:
2002

... radiation the gamma rays produced in fission and as a result of other neutron reactions and nuclear excitation of the weapon materials appearing within a second or less after a nuclear...

unified atomic mass unit

unified atomic mass unit   Quick reference

A Dictionary of Weights, Measures, and Units

Reference type:
Subject Reference
Current Version:
2004

... Rev. Mod. Phys. 72:351–495 (2000) Mohr P. Phys. Today 53:7, 11–16 (2000) For latest recommended values, see http://physics.nist.gov/cuu/Constants/index.html Its frequent use in the burgeoning world of molecular biology has prompted the use of the handier name dalton . History Imprecisely the mass of a proton else neutron, the unit began as the atomic mass unit or amu , defined as the mass of the hydrogen atom, then, in 1885 , as 1 / 16 the mass of an atom of oxygen. However, chemists came to see this as the naturally occurring mixture of oxygen...

radioactivity

radioactivity   Reference library

The Oxford Companion to the History of Modern Science

Reference type:
Subject Reference
Subject:
Science and technology, History of Science
Length:
1,730 words

...in 1933 that Pauli's little “neutron” be renamed the “neutrino” following James Chadwick's identification of the proton-sized neutral neutron in 1932 . Fermi's theory was adopted, although the neutrino eluded detection until 1956 . Rays from naturally occurring sources continued to serve nuclear physicists and chemists even in the era of the cyclotron. Fermi and his collaborators irradiated every element they could find with neutrons derived from a radon-beryllium source, discovered the efficacy of slow neutrons in inducing nuclear reactions, and,...

atomic bomb

atomic bomb   Reference library

R. V. Jones and Martin J. Sherwin

The Oxford Companion to World War II

Reference type:
Subject Reference
Current Version:
2003
Subject:
History, Military History, Social sciences, Warfare and Defence
Length:
4,698 words
Illustration(s):
1

...together by attractive forces between the protons and neutrons of which it was composed, against the electric forces of repulsion between its protons. In the common isotope of uranium, U238, there were 92 protons and 146 neutrons. This nucleus was hard to split by bombarding it with a further neutron; but the rarer isotope, U235, with 92 protons and 143 neutrons was less stable, particularly to ‘slow’ neutrons. One possible route to a bomb might therefore depend on the fission of U235 by slow neutrons, but these would take so long (a millisecond or so) to...

cold fusion

cold fusion   Reference library

The Oxford Companion to the History of Modern Science

Reference type:
Subject Reference
Subject:
Science and technology, History of Science
Length:
518 words

...of the experimental apparatus and methods that produced their astonishing result and persistently ducked requests from scientists for more information. Some scientists wryly observed that fusion cells running as hot as Pons and Fleischmann's should have been producing enough neutron radiation to kill them. Laboratories in the United States, Europe, and Japan geared up to witness the miracle firsthand or debunk it. Theoretical calculations demonstrated that the fusion of deuterium was impossible with Pons and Fleischman's apparatus, and experimental tests in...

nuclear power

nuclear power   Reference library

The Oxford Companion to the History of Modern Science

Reference type:
Subject Reference
Subject:
Science and technology, History of Science
Length:
1,168 words

...power as “moonshine.” However, nuclear power suddenly became a realistic possibility when Otto Hahn and his collaborators in Berlin in 1938 discovered that uranium is capable of fission upon bombardment with neutrons. Physicists soon learned that in the process of fission, a large quantity of energy is released along with more neutrons, possibly enough to make a chain reaction. While an uncontrolled chain reaction would make a nuclear explosion, a controlled one in a nulear reactor would provide a source of energy that could be transformed into...

Particle families

Particle families   Reference library

Magic Universe: A Grand Tour of Modern Science

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, History of Science
Length:
2,958 words

...towards the words.’ What troubled Yukawa that night, and not for the first time, was the discovery of the neutron by James Chadwick in Cambridge in 1932 . This uncharged particle had about the same mass as the positively charged proton, which was already well known as the nucleus of the hydrogen atom. Thenceforward, the nuclei of all heavier atoms could be easily understood as collections of so many protons and so many neutrons. After the neutron discovery, physicists were puzzled to know how atoms heavier than hydrogen survived at all. Why did the...

Gamma-ray bursts

Gamma-ray bursts  

Magic Universe: A Grand Tour of Modern Science

...produced. So the source of the gamma-ray burst is a supernova and not a neutron-star collision.’ The continuing watch That did not mean that the neutron-star theory was wrong. The events vary greatly in their behaviour. All of those examined in detail up to 2002 had gamma-ray bursts persisting for a minute or more. Some that last for only a few seconds may also be supernovae. But other bursts last less than a second and may well involve a different mechanism. Systems with a pair of neutron stars rotating around each other are known to exist, and eventually...

accelerator

accelerator   Reference library

The Oxford Companion to the History of Modern Science

Reference type:
Subject Reference
Subject:
Science and technology, History of Science
Length:
995 words

...and linear accelerators were used at many universities and research institutes in the 1930s to explore the new field of nuclear physics. Financial support for the development of particle accelerators came largely from medical philanthropies. They hoped their high-voltage X rays, neutrons, and other particles as well as the artificially radioactive products of their interactions with other substances would be more effective against cancer and other diseases than the natural radiations from radium and other substances. Lawrence was especially successful in...

geiger and electronic counters

geiger and electronic counters   Reference library

The Oxford Companion to the History of Modern Science

Reference type:
Subject Reference
Subject:
Science and technology, History of Science
Length:
747 words

...States in World War II developed new amplifiers, pulse-height analyzers, and other electronic devices that would find use in electronic detectors. Rossi worked at Los Alamos on fast timing circuits to measure nuclear processes, such as the time between the emission of prompt and delayed neutrons from nuclear fission. Nuclear energy also provided a market for Geiger counters as radiation detectors. Following the development of vacuum tube amplifiers by the radio industry, Geiger counters were connected to audio speakers to register particle counts as clicks. A...

Gravitational waves

Gravitational waves  

Magic Universe: A Grand Tour of Modern Science

...probably limits ground antennas to wavelengths of 300 to 30,000 kilometres, which roughly corresponds to the frequencies in cycles per second of sounds audible to the human ear. The bang of a star exploding, in the Milky Way or in a nearby galaxy, or the crash of two very dense neutron stars colliding, are likely sources of strong gravitational waves accessible on the Earth's surface, but such events are rare. ‘Our detectors on the ground should register short- wavelength gravitational waves,’ said Karsten Danzmann from the German–UK GEO600 project located...

nuclear weapons

nuclear weapons   Reference library

The Oxford Companion to Military History

Reference type:
Subject Reference
Current Version:
2004
Subject:
History, Military History, Social sciences, Warfare and Defence
Length:
2,143 words
Illustration(s):
1

...This vision led western powers, whose territory was likely to be the scene for such vast zones of destruction, to try to refine the effects of nuclear weapons. In an enhanced radiation/reduced blast weapon, such as the US W-79 8 inch artillery round, the burst of prompt nuclear radiation (neutrons and gamma rays) is enhanced by minimizing the fission yield relative to the fusion yield. Small enhanced radiation weapons can kill by radiation well outside the range of the blast: with ordinary nuclear weapons, the blast and heat usually kill first. Because there...

science fiction

science fiction   Reference library

The Oxford Companion to the History of Modern Science

Reference type:
Subject Reference
Subject:
Science and technology, History of Science
Length:
1,452 words

...students analyzing the concept determined that such a structure would not be mechanically stable, which prompted Niven to add “stabilizing rockets” to the construct in Ringworld Engineers ( 1979 ). Other provocative subjects for informed scrutiny surfaced in Hoyle's The Black Cloud ( 1957 ), featuring an intelligent cloud traveling through space, and Robert F. Forward 's Dragon's Egg ( 1980 ), describing the evolution of life on the surface of a neutron star. Science fiction might also be lauded for sustaining interest in the possibility of time travel...

Nuclear Power

Nuclear Power   Reference library

The Oxford Encyclopedia of Economic History

Reference type:
Subject Reference
Current Version:
2005
Subject:
Social sciences, Economics
Length:
2,397 words
Illustration(s):
2

...nuclear power plants (NPPs) and nuclear fuel. Nuclear Fuel Cycle Figure 1 shows the Nuclear Fuel Cycle. Uranium (U) is 99.3 percent U-238 and 0.7 percent U-235. With fission, U-235 releases energy and neutrons, which either are captured by U-238 to become plutonium (e.g., Pu-239), or “split” (fission) U-235 atoms, releasing more energy and neutrons in a chain reaction. Nuclear weapons require nearly pure U-235 or plutonium. To produce electricity, NPPs use natural or enriched uranium, a mix of uranium and plutonium (mixed oxide, MOX), or plutonium. In...

Nuclear weapons

Nuclear weapons   Reference library

Magic Universe: A Grand Tour of Modern Science

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, History of Science
Length:
2,510 words

...fuel of choice was lithium-6 deuteride. This is a compound of heavy hydrogen—deuterium or hydrogen-2—with a selected form of the lightest metal. Lithium-6 breaks up in the nuclear reaction to make tritium or hydrogen-3, which then reacts very vigorously with deuterium. A lot of neutrons, neutral nuclear particles, fly around, but the net result is that lithium-6 plus hydrogen-2 makes two nuclei of helium-4, with the release of energy on a huge scale. Spies had kept the Soviet Union well informed about the wartime Manhattan Project, and the post-war nuclear arms...

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