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Electron optical design of a compact LEEM
Adamec, P. ; Bauer, E. ; Lencová, Bohumila
Pavel Adamec spent most of his Ph.D. study in Clausthal and later in ASU Tempe. The aim of his Ph.D. project was to design a small compact LEEM that could be fitted to an UHV system, i.e. the sample must be on ground potential and the optics should fit to a standard UHV flange. The design has to use "floating" electrostatic lenses and it must be of compact size and low weight.
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Computations of Wien Filter Properties and Aberrations
Lencová, Bohumila ; Vlček, Ivan
Wien filter is studied in electron optics as a separator in a LEEM or as a separator of primary and secondary beams in a low voltage SEM. The advantage of the Wien filter is that one beam is only slightly influenced by the filter and the second beam can easily be handled, the required separation angle for this is about 10-20 degrees. The computation of aberrations of the Wien filter needs to take into account field shapes of both strong dipole fields and the additional quadrupole, the action of the filter is then that of a weak lens and the aberation structure is more complicated than that of a rotationally symmetric lens. The determination of aberation coefficients from direct ray tracing for this optical element is often preferred to aberration theory.
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