Editing Ion source (section)

===Particle accelerators===
{{Main|Particle accelerator}}
[[File:CARIBU at ATLAS.jpg|thumb|300px|Surface ionization source at the [[Argonne Tandem Linear Accelerator System]] (ATLAS)]]
[[File:Ion source at used in the Cockcroft-Walton accelerators at Fermilab.jpg|thumb|Ion source used in the [[Cockcroft-Walton generator|Cockcroft-Walton]] pre-accelerator at [[Fermilab]]<ref>{{cite book|title=35 years of H- ions at Fermilab|publisher=Fermilab|pages=12|url=http://www-ad.fnal.gov/proton/PIP/Communicate/Calendar/Repository/2014/35%20years%20of%20H-%20ions%20at%20Fermilab.pdf|access-date=12 August 2015}}</ref>]]
In particle accelerators an ion source creates a [[particle beam]] at the beginning of the machine, the ''source''. The technology to create ion sources for particle accelerators depends strongly on the type of particle that needs to be generated: [[electron]]s, [[proton]]s, [[Hydride|H<sup>−</sup> ion]] or a [[Heavy ions]].

Electrons are generated with an [[electron gun]], of which there are many varieties.

Protons are generated with a [[plasma (physics)|plasma]]-based device, like a [[duoplasmatron]] or a [[magnetron]].

[[hydride|H<sup>−</sup>]] ions are generated with a [[magnetron]] or a [[Penning ionization|Penning]] source.  A magnetron consists of a central cylindrical cathode surrounded by an anode. The discharge voltage is typically greater than 150 V and the current drain is around 40 A. A [[magnetic field]] of about 0.2 [[tesla (unit)|tesla]] is parallel to the [[cathode]] axis.  Hydrogen gas is introduced by a pulsed gas valve.  [[Caesium]] is often used to lower the [[work function]] of the cathode, enhancing the amount of ions that are produced. Large caesiated sources are also used for [[neutral beam injection|plasma heating]] in nuclear fusion devices.

For a  [[Penning ionization|Penning source]], a strong magnetic field parallel to the electric field of the sheath guides electrons and ions on cyclotron spirals from cathode to cathode. Fast H-minus ions are generated at the cathodes as in the magnetron. They are slowed down due to the charge exchange reaction as they migrate to the plasma aperture. This makes for a beam of ions that is colder than the ions obtained from a magnetron.

Heavy ions can be generated with an [[electron cyclotron resonance]] ion source.  The use of electron cyclotron resonance (ECR) ion sources for the production of intense beams of highly charged ions has immensely grown over the last decade. ECR ion sources are used as injectors into linear accelerators, Van-de-Graaff generators or cyclotrons in nuclear and elementary particle physics. In atomic and surface physics ECR ion sources deliver intense beams of highly charged ions for collision experiments or for the investigation of surfaces. For the highest charge states, however, [[Electron beam ion source]]s (EBIS) are needed. They can generate even bare ions of mid-heavy elements. The [[Electron beam ion trap]] (EBIT), based on the same principle, can produce up to bare uranium ions and can be used as an ion source as well.

Heavy ions can also be generated with an [[ion gun]] which typically uses the thermionic emission of electrons to ionize a substance in its gaseous state. Such instruments are typically used for surface analysis.[[File:Ion implanter schematic.svg|thumb|300px|Ion beam deposition system with mass separator]]

Gas flows through the ion source between the anode and the cathode.  A positive [[voltage]] is applied to the anode.  This voltage, combined with the high magnetic field between the tips of the internal and external cathodes allow a plasma to start. Ions from the plasma are repelled by the anode's electric field.  This creates an ion beam.<ref>{{Cite journal|url=http://www.advanced-energy.com/en/upload/File/Sources/SL-ION-230-02.pdf |title=Ion Beam Sources |journal=Science |volume=311 |issue=5767 |pages=1566–70 |access-date=2006-12-14 |archive-url=https://web.archive.org/web/20061018152802/http://www.advanced-energy.com/en/upload/File/Sources/SL-ION-230-02.pdf |archive-date=2006-10-18 |bibcode=2006Sci...311.1566C |url-status=dead |doi = 10.1126/science.1119426 |pmid=16543450 |year=2006 |last1=Cooks |first1=R. G |last2=Ouyang |first2=Z |last3=Takats |first3=Z |last4=Wiseman |first4=J. M |s2cid=98131681 }}</ref>