Editing Neutron generator (section)

{{Short description|Source of neutrons from linear particle accelerators}}
{{About|generators employing accelerators|more general sources|Neutron source}}
{{Use American English|date = March 2019}}
{{more citations needed|date=July 2016}}
{{Nuclear physics}}
[[File:Experiment using an electronic neutron generator.jpg|thumb|Nuclear physicist at the [[Idaho National Laboratory]] sets up an experiment using an electronic neutron generator.]]
'''Neutron generators''' are [[neutron source]] devices which contain compact [[linear particle accelerator]]s and that produce [[neutron]]s by fusing [[isotopes of hydrogen]] together. The [[nuclear fusion|fusion]] reactions take place in these devices by accelerating either [[deuterium]], [[tritium]], or a mixture of these two isotopes into a metal [[hydride]] target which also contains deuterium, tritium or a mixture of these [[isotopes]]. Fusion of deuterium atoms (D + D) results in the formation of a [[helium-3]] ion and a neutron with a kinetic energy of approximately 2.5&nbsp;[[MeV]]. Fusion of a deuterium and a tritium atom (D + T) results in the formation of a [[helium-4]] ion and a neutron with a kinetic energy of approximately 14.1&nbsp;MeV. Neutron generators have applications in medicine, security, and materials analysis.<ref>{{cite journal|last=Reijonen|first=J|title=Compact Neutron Generators for Medical, Homeland Security, and Planetary Exploration|journal=Proceedings of 2005 Particle Accelerator Conference, Knoxville, Tennessee|pages=49–53|url=https://accelconf.web.cern.ch/AccelConf/p05/papers/foab001.pdf}}</ref>

The basic concept was first developed by [[Ernest Rutherford]]'s team in the [[Cavendish Laboratory]] in the early 1930s. Using a linear accelerator driven by a [[Cockcroft–Walton generator]], [[Mark Oliphant]] led an experiment that fired deuterium ions into a deuterium-infused metal foil and noticed that a small number of these particles gave off [[alpha particle]]s. This was the first demonstration of nuclear fusion, as well as the first discovery of Helium-3 and tritium, created in these reactions. The introduction of new power sources has continually shrunk the size of these machines, from Oliphant's that filled the corner of the lab, to modern machines that are highly portable. Thousands of such small, relatively inexpensive systems have been built since the 1960s.

While neutron generators do produce fusion reactions, the number of accelerated ions that cause these reactions is very low. It can be easily demonstrated that the energy released by these reactions is many times lower than the energy needed to accelerate the ions, so there is no possibility of these machines being used to produce net [[fusion power]]. A related concept, [[colliding beam fusion]], attempts to address this issue by using two accelerators firing toward one another.

[[File:Neutristor test sample.jpg|thumb|[[Neutristor]] in its simplest form as tested by the inventor at Sandia National Laboratories]]