Lect05_notes

20 cold field emission gun instability cbems

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Unformatted text preview: ure 05 ! 18 LaB6 Filaments! !  LaB6 – Crystal, ground to point, resistively heated! ! ! CBEMS 164 – XRD, SEM & Microanalysis: Lecture 05 ! 19 Field Emission Gun! !  Emitter (tip) is tungsten wire fashioned to a sharp point! <013> oriented single crystal! Coated with ZrO2 to reduce work function! ! !  Typically still thermionic emission (requires heating) but a strong electric field draws electrons from the tip (cathode) which are then accelerated towards the anode! !  Field 10V/nm! ! Ultra-high vacuum r...
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