Wehnelt Unit in Electron Source
- Practical Electron Microscopy and Database -
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Figure 3608 shows schematic diagram of a thermionic electron gun. A high voltage is placed between the cathode and the anode, modified by a potential on the Wehnelt which acts as the grid in a triode system. The electric field from the Wehnelt focuses the electrons into a crossover. In other words, the Wehnelt cylinder has a small negative bias to confine the beam and enable it to pass through the anode into the column.

Wehnelt Unit in Electron Source

Figure 3608. Schematic diagram of tungsten (W) electron source.

 

 

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