An
electron gun (also called
electron emitter) is an electrical component in some
vacuum tubes that produces a narrow,
collimated electron beam that has a precise
kinetic energy. The largest use is in
cathode ray tubes (CRTs), used in nearly all
television sets,
computer displays and
oscilloscopes that are not flat-panel displays. They are also used in FED displays, which are essentially flat-panel displays made out of rows extremely small cathode ray tubes. They are also used in microwave linear beam
vacuum tubes such as
klystrons,
inductive output tubes,
travelling wave tubes, and
gyrotrons, as well as in scientific instruments such as
electron microscopes and
particle accelerators. Electron guns may be classified by the type of electric field generation (DC or RF), by emission mechanism (
thermionic,
photocathode,
cold emission,
plasmas source), by focusing (pure electrostatic or with magnetic fields), or by the number of electrodes.