karotrons

Karotrons are a type of electron tube developed in the 1920s for use in television display systems. They were designed to simplify the process of electron beam deflection, which is a critical component in the production of cathode ray tubes.

Karotrons consist of a tube containing an electron gun, an accelerating anode, and a pumping port for evacuation. The interior is evacuated to a high vacuum using a mechanical pump, and the electron gun is typically a thermionic triode design. The accelerating anode is usually a metal disk with a rectangular aperture, allowing the electron beam to pass through and be focused onto a phosphorescent screen.

The innovative aspect of karotrons is the system used to control electron beam deflection. A magnetic field is applied perpendicular to the electron beam path by coiling a wire around a metal rod, often referred to as the "deflection rod". Pairs of coils are placed around the rod in a Helmholtz configuration to achieve a linear magnetic field. The position of the electron beam is then accessed by controlling the current through the coils.

Karotrons were not widely adopted for their intended use, as they were ultimately not as efficient as direct electrostatic deflection schemes. However, their design laid the groundwork for the technological developments that led to the creation of modern television display systems. Karotrons have largely been replaced by solid-state technologies, but their significance in the history of television technology remains notable.