Charged particle source with integrated electrostatic energy filter

摘要

The invention relates to a charged particle filter with an integrated energy filter. Where most filters used have a highly curved optical axis, and thus use parts with forms that are difficult to manufacture, the source according the invention uses electrodes surrounding a straight optical axis. Surprisingly the inventor found that it is well possible to deflect a beam of charged particles 106a quite far from the axis 104 showing respectable energy dispersion at an energy selecting slit 108 without introducing coma or astigmatism that cannot be corrected, provided that some of the electrodes (114, 116, 120, 122) are formed as 120°/60°/120°/60°. Such electrodes can be attached to each other by gluing or brazing of ceramic, and then series of a highly concentric bores can be formed by e.g. spark erosion.