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. 2017 Jul 17;4(5):054303. doi: 10.1063/1.4994004

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© 2017 Author(s).

2329-7778/2017/4(5)/054303/18

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FIG. 7. — Electron positions after 1300 ps flight time for a 2000 electron bunch photo-emitted from (a) a guard ring cathode (750 μm gap) and (b) a truncated tip cathode (650 μm gap). For the truncated tip cathode, only electron emission from the flat central truncated area was considered (shank-emitted electrons were omitted). The figure shows the influence of the Wehnelt bias on the dispersion of the electron bunch. The inset show the initial lateral distribution of the photoelectrons on the central flat surface of the cathode (in the relevant color-code).