Editing Neutron (section)

== Applications ==
{{Science with neutrons}}

===Nuclear energy===
Because of the strength of the nuclear force at short distances, the nuclear [[binding energy|energy binding]] nucleons is many orders of magnitude greater than the electromagnetic energy binding electrons in atoms.<ref name="ENW"/>{{rp|4}} In [[nuclear fission]], the absorption of a neutron by some heavy nuclides (such as [[uranium-235]]) can cause the nuclide to become unstable and break into lighter nuclides and additional neutrons.<ref name="ENW"/> The positively charged light nuclides, or "fission fragments", then repel, releasing electromagnetic [[potential energy]].<ref name="Nuclear Energy">{{cite web |last1= |title=Nuclear Energy |url=http://electron6.phys.utk.edu/phys250/modules/module%205/nuclear_energy.htm |website=Physics 250: Modern Physics |publisher=The University of Tennessee Department of Physics and Astronomy |access-date=1 May 2024 |archive-date=20 February 2020 |archive-url=https://web.archive.org/web/20200220205637/http://electron6.phys.utk.edu/phys250/modules/module%205/nuclear_energy.htm |url-status=live }}</ref> If this reaction occurs within a mass of [[fissile material]], the additional neutrons cause additional fission events, inducing a cascade known as a [[nuclear chain reaction]].<ref name="ENW"/>{{rp|12–13}}  For a given mass of fissile material, such [[nuclear reaction]]s release energy that is approximately ten million times that from an equivalent mass of a conventional chemical [[explosive]].<ref name="ENW"/>{{rp|13}}<ref>A 0.57 kg mass of fissionable material, such as uranium-235, can release an amount of energy equivalent to 10 metric kilotons of TNT. Fissionable material therefore has an energy density approximately 10<sup>7</sup> greater than this conventional explosive.</ref> Ultimately, the ability of the nuclear force to store energy arising from the electromagnetic repulsion of nuclear components is the basis for most of the energy that makes nuclear reactors or bombs possible; most of the energy released from fission is the kinetic energy of the fission fragments.<ref name="Nuclear Energy"/><ref name="ENW"/>{{rp|12}}

The neutron plays an important role in many nuclear reactions. For example, neutron capture often results in [[neutron activation]], inducing [[radioactivity]]. In particular, knowledge of neutrons and their behavior has been important in the development of [[nuclear reactor]]s and [[nuclear weapon]]s. The [[nuclear fission|fissioning]] of elements like [[uranium-235]] and [[plutonium-239]] is caused by their absorption of neutrons.

=== Other uses ===

[[Neutron temperature|''Cold'', ''thermal'', and ''hot'']] [[neutron radiation]] is commonly employed in [[neutron scattering]] facilities for [[neutron diffraction]], [[small-angle neutron scattering]], and [[neutron reflectometry]]. Slow neutron [[matter waves]] exhibit properties similar to geometrical and wave optics of light, including reflection, refraction, diffraction, and interference.<ref name="Klein Werner 1983 pp. 259–335">{{cite journal | last1=Klein | first1=A G | last2=Werner | first2=S A | title=Neutron optics | journal=Reports on Progress in Physics | publisher=IOP Publishing | volume=46 | issue=3 | date=1983-03-01 | issn=0034-4885 | doi=10.1088/0034-4885/46/3/001 | pages=259–335 | s2cid=250903152 | url=https://www.researchgate.net/publication/231072989 | access-date=2023-07-06 | archive-date=2024-05-12 | archive-url=https://web.archive.org/web/20240512232101/https://www.researchgate.net/publication/231072989_4_Neutron_Optics | url-status=live }}</ref> Neutrons are complementary to [[X-ray]]s in terms of atomic contrasts by different scattering [[cross section (physics)|cross sections]]; sensitivity to magnetism; energy range for inelastic neutron spectroscopy; and deep penetration into matter.

The development of "neutron lenses" based on total internal reflection within hollow glass capillary tubes or by reflection from dimpled aluminum plates has driven ongoing research into neutron microscopy and neutron/[[gamma ray tomography]].<ref>{{cite journal |last=Kumakhov |first=M.A. |author2=Sharov, V.A. |year=1992 |title=A neutron lens |journal=[[Nature (journal)|Nature]] |volume=357 |issue= 6377|pages=390–391 |doi=10.1038/357390a0 |bibcode= 1992Natur.357..390K|s2cid=37062511 }}</ref><ref>[http://www.physorg.com/news599.html Physorg.com, "New Way of 'Seeing': A 'Neutron Microscope'"] {{Webarchive|url=https://web.archive.org/web/20120124122838/http://www.physorg.com/news599.html |date=2012-01-24 }}. Physorg.com (2004-07-30). Retrieved on 2012-08-16.</ref><ref>[http://www.nasa.gov/vision/earth/technologies/nuggets.html "NASA Develops a Nugget to Search for Life in Space"] {{Webarchive|url=https://web.archive.org/web/20140308200231/http://www.nasa.gov/vision/earth/technologies/nuggets.html |date=2014-03-08 }}. NASA.gov (2007-11-30). Retrieved on 2012-08-16.</ref><ref>{{Cite journal|last1=Ioffe|first1=A.|last2=Dabagov|first2=S.|last3=Kumakhov|first3=M.|date=1995-01-01|title=Effective neutron bending at large angles|url=https://doi.org/10.1080/10448639508217696|journal=Neutron News|volume=6|issue=3|pages=20–21|doi=10.1080/10448639508217696|issn=1044-8632}}</ref>

A major use of neutrons is to excite delayed and prompt [[gamma ray]]s from elements in materials. This forms the basis of [[neutron activation analysis]] (NAA) and [[prompt gamma neutron activation analysis]] (PGNAA). NAA is most often used to analyze small samples of materials in a [[nuclear reactor]] whilst PGNAA is most often used to analyze subterranean rocks around [[bore hole]]s and industrial bulk materials on conveyor belts.

Another use of neutron emitters is the detection of light nuclei, in particular the hydrogen found in water molecules. When a fast neutron collides with a light nucleus, it loses a large fraction of its energy. By measuring the rate at which slow neutrons return to the probe after reflecting off of hydrogen nuclei, a [[neutron probe]] may determine the water content in soil.