Fringing field correction for 127 degrees and 180 degrees electron spectrometers

The entrance and exit regions of 127 degrees cylindrical or 180 degrees spherical electron spectrometers with real apertures are approximated by a shielded parallel plate capacitor. By employing a resistor network, the fringing field resulting from a new arrangement of shielding electrodes is measured. It is shown that the adverse influence of fringing fields on the beam trajectories can be reduced, while retaining narrow apertures at the entrance and exit planes of the deflector and without changing the deflection angle, as would be required by the Herzog correction.