Simple and efficient monoenergetic electron source

A source of monoenergetic electrons giving a high electron current (3×10−8 A) simultaneously with a good energy resolution (30 meV) is described. It has been ascertained that the emitted electron beam is not superimposed on a background which normally appears when an electron beam is scattered on deflecting electrodes within the instrument. This double 127° cylindrical selector is especially suitable for experiments where relatively high intensities in conjunction with high quality beams are essential and where stable electron currents over periods of several days or weeks are required. Such a stability is observed in the case where the gas pressure inside the selectors is as high as 10−5 Torr.