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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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- Fall '08