ELECTRON-OPTICAL ANALYSIS OF A HIGH-RESOLUTION ELECTRON-ENERGY LOSS SPECTROMETER WITH A RETARDING WIEN FILTER

The transfer matrix up to the second-order aberrations has been formulated for an electron optical systems of a monochromator and an energy analyzer. Both of these instruments have two magnetic round lenses and a retarding Wien filter. The filter consists of a deceleration lens, a Wien filter, and an acceleration lens. The optimum excitation of the round lens is found to be that which provides parallel exit of electrons from the acceleration lens. The excitation of the Wien filter must be adjusted to focus the beam on the slit. The computed results are useful for finding the optimum operating conditions and for explaining experimental results of the high-resolution electron energy loss spectrometer.