Wehnelt cylinder
The Wehnelt cylinder is a cylinder-shaped control electrode to the rules of brightness in cathode ray tubes and the focusing of electron beams . It was developed by Arthur Wehnelt in 1902/03 .
The Wehnelt cylinder is attached in the immediate vicinity of a hot cathode and provided opposite it with a negative electrical potential . Adjusting this voltage changes the number of electrons that can overcome the potential and thus the intensity of the electron beam.
Furthermore, electrons whose flight direction deviates very far from the beam axis are evenly repelled by the negative potential of the cylinder wall and thus directed back towards the beam axis. The electron beam is focused and it is now easier to carry out experiments with it, e.g. B. in the fine line tube .
Thanks to the Wehnelt cylinder, the previously required very high anode voltage could be significantly reduced.
literature
- Thomas Fauster, Lutz Hammer, Klaus Heinz, Alexander Schneider: Surface physics. Basics and methods . Oldenbourg Wissenschaftsverlag, Munich 2013, ISBN 978-3-486-72135-5 , p. 92-95 .