Calculations of a CHA transmission function for quantitative analysis in the constant pass energy mode. I. Point sources for AES

The analyser transmission function T of a concentric hemispherical analyser (CHA) with an input lens system has been studied, and the behaviour of T under suitable operation conditions for a point source has been determined by means of numerical calculations. One of the significant factors controlling T was found to be the aberrations of the input lens, which have a strong dependence on the retardation ration γ and the angular magnification M α of the lens. The M α also determines the entering angles of electrons to the CHA, and thus this should be kept sufficiently small as far as the aberrations in the CHA are concerned. The calculated results showed, however, that for each γ there exists an optimum M α , which corresponds to a compromise point between the aberrations of the input lens and those of the CHA. If M α is kept constant, T varies according to the increase or decrease in the lens aberrations as functions of γ. Lineshapes calculated for a monochromatic point source were also shown. These were found to be asymmetrical and have tailings on the low‐energy side due to the aberrations of the CHA.