Electron Beam Technology in Vacuum Tubes

The Cathode and Electron Emission

A heated cathode, typically made of a metal with a low work function, emits electrons through thermionic emission. The intensity of electron emission is controlled by adjusting the cathode's temperature.

Electron Acceleration and Focusing

A high voltage applied between the cathode and anode accelerates the emitted electrons, forming a beam. Focusing elements, such as electrostatic or electromagnetic lenses, shape and concentrate the electron beam, ensuring it remains narrow and focused on the intended target.

Deflection System

Electromagnetic or electrostatic fields deflect the electron beam, allowing for controlled manipulation of its position on a screen. Horizontal and vertical deflection coils or plates are used to scan the beam across the screen in a raster pattern.

Phosphor Screen and Luminescence

The electron beam strikes a phosphor-coated screen. Upon impact, the phosphor material emits light, creating the visible image. Different phosphors offer varying colors and persistence (how long the light emission lasts).

Vacuum Environment

The entire process takes place within a high-vacuum environment. This prevents scattering of electrons by air molecules and ensures a clear, focused beam. The vacuum also protects the internal components from oxidation and other degradation processes.

High Voltage Power Supply

A high-voltage power supply is essential to generate the accelerating potential required for the electron beam. The precise voltage requirements depend on the tube's design and intended application.

Applications

Historically, this technology found widespread use in televisions, oscilloscopes, computer monitors, and radar systems. Though largely superseded by newer technologies in most display applications, specialized uses still exist in niche areas.