Neutron flux 1131721 220634419 2008-06-20T20:27:07Z Superm401 35752 since it says area, I'm changing this to square cm. Already says cm&sup2; '''Neutron flux''' is a term referring to the number of [[neutron]]s passing through an [[area]] over a span of [[time]]. It is most commonly measured in neutrons/([[square centimeter|cm&sup2;]]·[[second|s]]).<ref name=NRC> [http://www.nrc.gov/reading-rm/basic-ref/glossary/neutron-flux.html Neutron flux] from the United States [[Nuclear Regulatory Commission]], retrieved 05/30/2008</ref> This is drawn from the [[mathematics|mathematical]] definition of [[flux]]. The ''neutron fluence'' is defined as the neutron flux integrated over a certain time period and represents the number of neutrons per unit area that passed during this time. Both within natural processes and in the experimental laboratory, neutron flux may be applied to [[atomic nuclei]], in which nuclei are bombarded with neutrons at a steady rate. This can be used to produce different [[isotope]]s, including unstable, [[radioactive]] ones, of a given [[chemical element]]. ==Natural neutron flux== {{Original research|date=May 2008}} Neutron flux in [[Asymptotic Giant Branch]] [[star]]s and in [[supernova]]e is responsible for most of the natural [[nucleosynthesis]] producing [[Chemical element|element]]s heavier than [[iron]]. In stars there is a relatively low neutron flux on the order of 10<font size= "-1"><sup>5</sup></font> to 10<font size= "-1"><sup>11</sup></font> neutrons per cm<font size= "-1"><sup>2</sup></font> per second, resulting in nucleosynthesis by the [[s-process]] ([[Neutron temperature|slow-neutron]]-capture-process). By contrast, after a core-collapse supernova, there is an extremely high neutron flux, on the order of 10<font size= "-1"><sup>22</sup></font> neutrons per cm<font size= "-1">²</font> per second, resulting in nucleosynthesis by the [[r-process]] ([[Neutron temperature|rapid-neutron]]-capture-process). ==Artificial neutron flux== {{Original research|date=May 2008}} [[Artificial]] neutron flux refers to neutron flux which is man-made, as by weapons or nuclear energy production. A flow of neutrons is often used to initiate the [[nuclear fission|fission]] of unstable large nuclei. The extra neutron(s) pushes the [[nuclide]] over the edge, causing it to split to form more stable products. This effect is essential in [[fission reactor]]s and [[nuclear weapon]]s. Neutrons are produced during [[nuclear fusion]]. While this effect is used in most modern nuclear weapons in various ways to achieve sometimes dramatic increases of yield, it is a major drawback for proposed applications of nuclear fusion as an energy source: As the particles do not carry a [[electric charge|charge]], they cannot be deflected by [[electric field|electric]] or [[magnetic field]]s but inevitably collide with the containment vessel, leaving it [[radioactive]]. As this is one of the main obstacles to fusion power generation, the [[International Fusion Materials Irradiation Facility]] has been founded as an initiative to invent a suitable containment vessel. Within a nuclear reactor the neutron flux is primarily the form of measurement used to control the reaction inside. The flux shape is the term applied to the density or relative strength of the flux as it moves around the reactor. Typically the strongest neutron flux occurs in the middle of the reactor core, becoming lower as you approach the edges. The higher the neutron flux the greater the chance of a nuclear reaction occurring as there are more neutrons going through an area. ==References== {{reflist}} ==See also== *[[Free neutron]] *[[Neutron radiation]] *[[Neutron transport]] {{Fusion power}} [[Category:Neutron|Flux]]