A Wien Filter for Use as an Energy Analyzer with an Electron Microscope

Abstract

An electron optical system is described which is suitable for energy loss analysis in an electron microscope. A focusing spectrometer of the Wien type has been added underneath the column of a Hitachi HU11A electron microscope. After passing through the microscope, the electrons are slowed down before entering the spectrometer and reaccelerated to the detection point. Appropriate control of the electron trajectories into the Wien analyzer is achieved with a quadrupole field lens which makes it possible to use a long entrance slit. The energy resolution of the analyzer is limited by the width of the entrance slit which is adjusted to match the beam spread (1.5 eV). It can be made large (250 μ) compared with that of the Möllenstedt analyzer (5 μ), thereby passing much higher intensity through the analyzer and increasing the system flexibility.