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electron gun
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Diagram of a color television picture tube using the shadow-mask technique, showing red, green, and blue electron beams from electron guns passing through an aperture grille to strike phosphor-coated glass, with labeled parts and a close-up of the grille structure. Cutaway diagram of a gyrotron showing labeled components including the electron gun, resonant cavity, magnetic field coils, vessel, and beam collector, with arrows indicating electron and microwave beam paths. Labeled diagram of an iconoscope television camera tube showing internal components including the electron gun, deflecting coils, anode, mosaic, signal plate, and scanning beam path. Diagram of a traveling-wave tube showing labeled components including the electron-emitting cathode, electron gun, focus electrode, anode, electron beam, RF input and output, helix, magnetic field, and multistage depressed collector.
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Diagram of a color television picture tube using the shadow-mask technique, showing red, green, and blue electron beams from electron guns passing through an aperture grille to strike phosphor-coated glass, with labeled parts and a close-up of the grille structure.
In a colour-television tube, three electron guns (one each for red, green, and blue) fire electrons toward the phosphor-coated screen. The electrons are directed to a specific spot (pixel) on the screen by magnetic fields, induced by the deflection coils. To prevent “spillage” to adjacent pixels, a grille or shadow mask is used. When the electrons strike the phosphor screen, the pixel glows. Every pixel is scanned about 30 times per second.

electron gun

electronics
Also known as: electron gun tube
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History

electron gun, electrode structure that produces and may control, focus, and deflect a beam of electrons, as in a television picture tube (see figure), where the beam produces a visual pattern on the tube’s screen. The source of the electron beam is the cathode, a flat metal support covered with oxides of barium and strontium. When heated by a coil behind the support, these oxides emit electrons, which are drawn toward a positively charged sleeve (first anode) that is contoured to allow the electron beam to flow within the inside diameter. The beam is then electrostatically constricted and collimated by a metal disk with a hole (the control electrode) before it is directed to strike a phosphor-coated screen.

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