page_title: Ion source
section_title: Particle accelerators
hierarchical_section_title: Ion source / Applications / Particle accelerators
caption_attribution_description: English: Schematics of an mass separating implantation/deposition setup. Ion energy at the substrate is determined by the difference of Uaccell and Udecell. Image created using Tgif.
context_page_description: An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.
context_section_description: 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: electrons, protons, H⁻ ion or a Heavy ions.
  Electrons are generated with an electron gun, of which there are many varieties.
  Protons are generated with a plasma-based device, like a duoplasmatron or a magnetron.
  H⁻ ions are generated with a magnetron or a 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 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 H⁻ sources are also used for plasma heating in nuclear fusion devices.
  For a  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 sources (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.
  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 electric field.  This creates an ion beam.
caption: Ion beam deposition system with mass separator
exif: {}