Simultaneous measurements of the brightness and the energy distribution of electrons emitted from a triode gun

Abstract

The energy distribution of electrons in a part of the electron beam selected by two apertures situated on the axis was measured using a wienfilter-type energy analyser. These measurements gave brightness values for electrons in specific energy intervals of the distribution which fitted the theory extremely well. The influence of the measuring system on the energy distribution was also demonstrated and it indicated that the discrepancy between experiment and theory observed by Nottingham and Hutson was due to a crude approximation in the electron optics of the theory rather than a large electron reflection effect. The anomalous broadening of the energy distribution (Boersch effect) was found to be independent of the measuring system and had no influence on the brightness. Energy gains were also observed in the broadening process.