Optimum Deflection Angle for Cylindrical and Spherical Electrostatic Spectrometer

The electron-energy distribution for the idealized cylindrical (127°) and spherical (180°) electrostatic electron spectrometer have been computed in second-order approximation. It is shown that one can improve these spectrometers by injecting at the entrance slit of the spectrometer only that fraction of incident electrons that have positive radial velocity components and at the same time setting the angle between entrance and exit slit plane to a proper smaller value. A method to build an electron spectrometer operating this way is suggested.