Definition of electron-gun system

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Photonics Dictionary

electron-gun system: An electron-gun system is an assembly used to generate and control a focused beam of electrons. Electron guns find applications in various fields, including cathode ray tubes (CRTs), electron microscopes, electron-beam lithography systems, and particle accelerators.

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Key components and features of an electron gun system typically include:

Cathode: The cathode is the source of electrons in the electron gun. It emits electrons when heated or when a voltage is applied to it. The cathode material is typically chosen for its ability to emit electrons efficiently, such as tungsten, lanthanum hexaboride (LaB₆), or field-emission cathodes in modern systems.

Electron emission mechanism: The electron emission mechanism determines how electrons are generated from the cathode. This could involve thermionic emission, where electrons are emitted due to heating of the cathode, or field emission, where electrons are extracted from the cathode by a strong electric field.

Anode: The anode is a positively charged electrode that accelerates the emitted electrons towards a target. It creates an electric field that accelerates the electrons towards the desired direction.

Wehnelt cylinder or control grid: This electrode, located between the cathode and the anode, controls the flow of electrons. By adjusting the voltage applied to the Wehnelt cylinder or control grid, the intensity and focus of the electron beam can be controlled.

Focus and deflection coils: These electromagnetic coils are used to control and manipulate the trajectory of the electron beam. By varying the currents through these coils, the electron beam can be focused to a fine spot and directed to specific areas of a target.

Beam aperture: The beam aperture is an opening in the system that determines the size and shape of the electron beam. It helps to define the spatial resolution of the system.

Vacuum system: Electron gun systems operate under high vacuum conditions to prevent electron scattering and interactions with gas molecules, ensuring the accuracy and stability of the electron beam.

Electron-gun systems are used in a wide range of applications. In CRTs, electron guns are used to generate beams that scan across a phosphorescent screen, producing images in televisions, computer monitors, and oscilloscopes. In electron microscopes, electron guns generate highly focused beams used to image samples at extremely high resolution. In electron-beam lithography systems, electron guns are used to write patterns onto substrates with high precision. And in particle accelerators, electron guns are used to generate beams of high-energy electrons for various research and industrial applications.