Wehnelt cylinder

The Wehnelt cylinder is a cylinder- shaped control electrode for controlling the brightness in cathode ray tubes and the focusing of electron beams. It was developed in the years 1902/ 03 by Arthur Whenelt.

The Wehnelt is placed in the vicinity of a hot cathode and towards her with a negative electrical potential. By adjusting this voltage, the number of electrons that can overcome the potential, and thus the intensity of the electron beam varied.

Furthermore, electrons having far different from the direction of flight of the beam axis, uniformly repelled by the negative potential of the cylindrical wall of the latter and thus directed back to the beam axis. The electron beam is converged and it is now easier to carry out tests with it, for example, in the thread -ray tube.

• Electrode
• Electron tube