Everything about Electron Gun totally explained
An
electron gun is a component that produces an
electron beam that has a precise
kinetic energy, being used in
televisions and
monitors which use
cathode ray tube technology, and in other instruments, as
electron microscopes and
particle accelerators.
Electron guns can be classified in several ways: by the type of electric field generation (DC or RF), by emission mechanism (thermionic, photocathode, cold emission, plasma source), by focusing (pure electrostatic or with magnetic fields), and by a number of electrodes.
A DC, electrostatic thermionic electron gun 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—such as a
Wehnelt cylinder—and one or more
anode electrodes which accelerate and further focus the electrons. A large voltage between cathode and anode accelerates the electrons. A repulsive ring placed between them focuses the electrons onto a small spot on the anode on the expense of a lower extraction field strength on the cathode surface. Often at this spot is a hole, so that the electrons pass through the anode forming a collimated beam and finally reach a second anode called a collector. This arrangement is similar to a
Einzel lens.
Likewise one type of an
ion gun consists of a cylinder, where gas enters from one end face, electron bombardment from the side walls, and an extraction voltage from the other end face. The cage has the role of the cathode, an extractor has the role of the anode, and an unnamed ring as the role of the Wehnelt cylinder.
Most colour
cathode ray tubes—as those used in colour television - 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.
An
electron gun can be used to
ionise particles by adding or removing electrons from the
atom. This technology is sometimes used in
mass spectrometry in a process called
electron ionisation to ionise
vaporised or
gaseous particles.
Further Information
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