Editing Neutron scattering (section)

== Scattering of fast neutrons ==
{{See also|Neutron temperature|neutron moderator}}

"Fast neutrons" (see [[neutron temperature]]) have a kinetic energy above 1&nbsp;[[Electronvolt|MeV]]. They can be scattered by condensed matter—nuclei having kinetic energies far below 1&nbsp;eV—as a valid experimental approximation of an [[elastic collision]] with a particle at rest. With each collision, the fast neutron transfers a significant part of its kinetic energy to the scattering nucleus (condensed matter), the more so the lighter the nucleus. And with each collision, the "fast" neutron is slowed  until it reaches thermal equilibrium with the material in which it is scattered.

[[Neutron moderator]]s are used to produce [[thermal neutrons]], which have kinetic energies below 1&nbsp;eV (T < 500K).<ref name=ibach>
{{cite book
|last=Lüth
|first=Harald Ibach, Hans
|title=Solid-state physics : an introduction to principles of materials science
|year=2009
|publisher=Springer
|location=Berlin
|isbn=978-3-540-93803-3
|edition=4th extensively updated and enlarged
}}
</ref> Thermal neutrons are used to maintain a nuclear chain reaction in a [[nuclear reactor]], and as a research tool in neutron scattering experiments and other applications of neutron science (see below). The remainder of this article concentrates on the scattering of thermal neutrons.