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Electron gun from an oscilloscope CRT Setup of an electron gun. 1. Hot cathode.2. Wehnelt cylinder.3. Anode. A direct current, electrostatic thermionic electron gun is formed from several parts: a hot cathode, which is heated to create a stream of electrons via thermionic emission; electrodes generating an electric field to focus the electron beam (such as a Wehnelt cylinder); and one or more ...
The basic components of a typical electron-beam processing device include: [1] an electron gun (consisting of a cathode, grid, and anode), used to generate and accelerate the primary beam; and, a magnetic optical (focusing and deflection) system, used for controlling the way in which the electron beam impinges on the material being processed ...
A cross-section view, showing how a Wehnelt localizes emissions at the filament tip and serves as a convergent electrostatic lens. A Wehnelt cylinder (also known as Wehnelt cap, grid cap or simply Wehnelt) is an electrode in the electron gun assembly of some thermionic devices, used for focusing and control of the electron beam.
The electron gun contains a heater, which heats a cathode, which generates electrons that, using grids, are focused and ultimately accelerated into the screen of the CRT. The acceleration occurs in conjunction with the inner aluminum or aquadag coating of the CRT. The electron gun is positioned so that it aims at the center of the screen. [190]
Schottky-emitter electron source of an Electron microscope. A field emission gun (FEG) is a type of electron gun in which a sharply pointed Müller-type [clarification needed] emitter [1]: 87–128 is held at several kilovolts negative potential relative to a nearby electrode, so that there is sufficient potential gradient at the emitter surface to cause field electron emission.
In electron emission devices, especially electron guns, the thermionic electron emitter will be biased negative relative to its surroundings. This creates an electric field of magnitude E at the emitter surface. Without the field, the surface barrier seen by an escaping Fermi-level electron has height W equal to the
This is a list of vacuum tubes or thermionic valves, and low-pressure gas-filled tubes, or discharge tubes.Before the advent of semiconductor devices, thousands of tube types were used in consumer electronics.
The latter two contained an electron gun with deflecting plates. The beams can be bent by applying voltages to various electrodes in the tube or by holding a magnet close by. The electron beams are visible as fine bluish lines. This is accomplished by filling the tube with low-pressure helium (He) or Hydrogen (H 2) gas.