Electron gun

An electron gun generates electrons and accelerates them into a beam. Its design controls the beam’s energy, current, shape, and focus.

Thermionic emission: Electron emission from a heated material, driven by thermal energy overcoming the material’s work function. Heated cathodes use this process to supply electrons.
Cathode: An electrode from which electrons are emitted into a vacuum or other medium. It is the electron source at the heart of most guns.
Electron microscope: A microscope that forms images using a focused beam of electrons rather than visible light. Its illumination system uses an electron gun to create the probe beam.
Ion source: A device that creates and extracts a beam of ions, which are charged atoms or molecules. It produces positive or negative ions rather than a beam of free electrons.
Field emission: Electron emission caused by quantum tunneling through a material’s surface barrier under a strong electric field. It provides an alternative to heating the cathode.
Work function: The minimum energy needed to remove an electron from a material’s surface. It helps determine how readily a cathode can emit electrons.
Cathode-ray tube: A vacuum display or imaging tube that directs an electron beam onto a phosphor-coated screen. Its gun produces the beam that draws images on the screen.
Electron multiplier: A detector that amplifies a small electron signal through secondary electron emission. It multiplies detected electrons instead of primarily generating an output beam.
Electron optics: The control of electron trajectories using electric and magnetic fields. It describes the broader framework for shaping and focusing the beam.
Vacuum tube: An electronic device that controls electric current through electrodes in an evacuated enclosure. Many electron guns are built as vacuum-tube structures.

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