New imaging bandpass electron energy analyzer

Abstract
An electron energy analyzer which acts as a bandpass filter while maintaining the spatial integrity of an electron image in a uniform magnetic field is described. It embodies some new electron-optical properties. Image electrons injected parallel to the magnetic field are guided, using crossed electrostatic and magnetic fields, to a low-pass electron mirror and then through a high-pass retardation filter. Nonuniform electrostatic deflection fields are used to compensate for the energy-dependent dispersion of the crossed fields. A simple computer modeling method used to design the electrostatic fields is described. A test analyzer was constructed to operate in a 0.0125-T (125 G) uniform magnetic field to investigate its properties. Bandpass filtered images of an 18-eV electron source demonstrating the removal of energy-dependent dispersion and the narrowing of the bandwidth to 100 meV are presented. Another application of the analyzer, to obtain an energy spectrum from a spatially extended electron source, is demonstrated.

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