An electron gun is a device that uses an electric or magnetic field to accelerate electrons along a conductive path and produce a beam of high-energy electrons. The most common type of electron gun is the cathode ray tube (CRT), which is used in televisions and computer monitors.
The first electron gun was built in 1897 by J.J. Thomson, who discovered the electron. He used it to study the properties of electricity and magnetism, and to investigate the structure of atoms. In his experiment, he placed an electrode inside a sealed evacuated glass tube and applied a high voltage between the electrode and the walls of the tube. This created an electric field that accelerated electrons from the electrode towards the walls of the tube. When these electrons hit the walls, they emitted a bright light, which allowed Thomson to observe their trajectory and measure their energy.
Today, electron guns are used in many different applications, including particle accelerators, X-ray tubes, lasers, and microscopes. They are also used in industry for welding, coating materials with thin films, and producing X-rays for nondestructive testing (NDT). Electron guns can be either DC (direct current) or RF (radio frequency). DC guns are typically used for low-energy applications such as CRTs while RF guns are used for high-energy applications such as particle accelerators.