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Generation of Electron Beams

There are two different ways to produce electron beams:
Thermoionic gun: Electron emission through heating (W or LaB6).
Field emission gun (FEG): Electron emission through applying an extraction voltage.

Some typical values for the different guns are given in the table:
Properties
Tungsten
LaB6
FEG
Work function / eV
4.5
2.4
4.5
Temperature / K
2700
2000
1800
Energy spread / eV
3-4
1.5-3
0.4-1.5
Source size / nm
30000
5000
3-20
Maximum current / nA
1000
500
300
Brightness / A/m2sr
109
5x1010
1013
Lifetime / h
100
500
> 1000
 
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modified: 5 November, 2021 by F. Krumeich | © ETH Zürich and the authors