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Electron gun
From Wikipedia, the free encyclopedia
An electron gun is a component that produces an electron beam that has a precise kinetic energy, being used in all TVs and monitors which use cathode ray tube technology, and in other instruments, eg. electron microscopes and at the beginning of linear particle accelerators.
It is formed of several parts: a hot cathode, which is heated to create a stream of electrons via thermionic emission, electrodes generating an electric field which focus the beam (eg. a Wehnelt cylinder), and one or more anode electrodes which accelerate and further focus the electrons.
Most colour CRTs (such as is used in a colour television set) are made up of three electron guns, each one producing a different stream of electrons. Each stream travels through a shadow mask where the electrons will impinge upon either a red, green or blue phosphor to light up a colour dot of a pixel of the screen, the resultant colour being a combination of these three primary colours (including white).
An electron gun can be used to ionize particles by adding or removing electrons from the atom. This technology is used in the mass spectrometer to ionise vaporized particles. This is used to deflect the ions by their different masses and thus helps to identify the compound. Once again an electron gun is used in this technology, which is vital to modern chemistry.