Design of energy filters for electron microscopes

Software for simulating 3D electric and magnetic fields followed by the direct ray tracing in individual field and combined fields (E031). MO3D and CO3D) are well applied to the design of energy filters attached to electron microscopes.When we had designed a high resolution EELS instrument, we had no 3D software, and encountered problems in designing a retarding Wien filter used as the monochromator and analyzer. At that time, electric field homogeneity inside the gap of magnet and the deflection of beam at the fringing region due to the deviation of the Wien condition were unsolved problems. When we designed a low energy reflection electron microscope (LEEM). we had 3D software, and some of the above problems were solved. We used an arc shaped electrode for the beam separator and an eight-pole filter fur the analyzer. The __________________________________________ coincidence of the magnetic and electric fringing field distributions at the fringing regions (Wien condition) was not perti.ct but was improved. We have designed an omega filter fur in-column energy filtered transmission electron microscope (EF1'EM). The omega filter consists of four sector magnets. Optical behavior of the system is very complicated. First, we designed the filter by 21) approximation and then checked by electron trajectories by the 31) software. [he designed omega filter works successfully.