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Electric Field in Electron Source/Gun
- Practical Electron Microscopy and Database -
- An Online Book -
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https://www.globalsino.com/EM/
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This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers. You can click How to Cite This Book to cite this book. Please let Dr. Liao know once you have cited this book so that the brief information of your publication can appear on the “Times Cited” page. This appearance can also help advertise your publication.
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Table 4270. Operating parameters and characteristics of electron sources
Type of source |
Tungsten
thermionic |
LaB6
thermionic |
Schottky
emission |
Cold field
emission |
|
Material |
W |
LaB6 |
ZrO/W |
W |
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ds (µm) |
≈40 |
≈10 |
≈0.02 |
≈0.01 |
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ΔE (eV) |
1.5 |
1.0 |
0.5 |
0.3 |
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φ (eV) |
4.5 |
2.7 |
2.8 |
4.5 |
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T (K) |
2700 |
1800 |
1800 |
300 |
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E (V/m) |
Low |
Low |
≈108 |
>109 |
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Je (A/m2) |
≈104 |
≈106 |
≈107 |
≈109 |
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β (Am-2/sr-1) |
≈109 |
≈1010 |
≈1011 |
≈1012 |
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Vacuum (Pa) |
<10-2 |
<10-4 |
<10-7 |
≈10-8 |
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Lifetime (hours) |
100 |
1000 |
104 |
104 |
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** ds -- Effective (or virtual) source
diameter; ΔE -- Energy spread of the electron beam; φ -- Work function; T -- Operating temperature; E -- Electric field; Je -- current density of electron beam; β -- Electron-optical brightness at the cathode.
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