Cambridge Encyclopedia » Cambridge Encyclopedia Vol. 23

electron gun - Ionisation

tubes cathode electrons beam

A device for producing electron beams. A heated cathode produces electrons by thermionic emission. These are attracted away by a nearby positively-charged grid, which regulates the number of electrons and hence beam brightness. Electric fields then accelerate and focus the beam. It is an essential component of television tubes, electron microscopes, and cathode ray tubes.

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