An electron gun creates, accelerates and shapes a directed electron beam. A source such as a heated cathode supplies electrons, an applied electric potential difference accelerates them toward an anode, and electrodes control the emitted current and beam geometry.
For an electron accelerated from rest through potential difference , the ideal gained kinetic energy is , with the voltage sign chosen to accelerate it. Focusing optics then control beam position and convergence. Source size, energy spread and space charge affect the useful beam; increasing accelerating voltage alone does not guarantee a smaller probe or higher image resolution.
A cold cathode supplies electrons without relying on deliberate heating for thermionic emission. The term describes that operating distinction rather than one universal microscopic emission mechanism.
A strong surface electric field can produce field emission; in a gas discharge, particle impact and secondary electron emission can sustain the supply. A cathode may still warm during operation, so cold does not guarantee room temperature. Comparing emitted current as a function of field, illumination or discharge conditions helps distinguish mechanisms. The source's energy spread, stability and emitting geometry matter when it is used in an electron gun.
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An electron gun is a device that generates and emits a stream of electrons, typically in a vacuum environment. It consists of several key components that work together to produce and control a focused electron beam. Electron guns are commonly used in various applications, including: 1. **Cathode Ray Tubes (CRTs)**: In traditional television sets and computer monitors, electron guns are used to direct beams of electrons onto a phosphorescent screen, creating images.