Energy analysis of electron beams from perforated-mesh hollow-cathode gas discharge guns

Abstract

The operating characteristics of perforated-mesh hollow-cathode gas discharge electron guns (hc guns) have been investigated paying particular attention to the energy spectrum of the electrons forming the beam. While it was found impractical to attempt a complete systematic study, sufficient quantitative data was obtained to apparently confirm certain findings made by Boring and Stauffer in 1963 relating to the potential of the plasma within the cathode. Further observations made visually help towards a more complete understanding of the operation of the gun.There are similarities between the spectra produced by this gun and those produced by the hollow-anode (ha) gun. The most obvious difference is that electrons from the hc gun lie within one of two distinct energy ranges, both of which are often present, while in the case of the two-electrode ha gun only one range is present. Of these two energy groups one is associated with the full cathode to anode potential difference while the other seems to be the result of acceleration from the internal cathode plasma potential to anode potential.It has been found that similar, but not identical, spectra can be obtained from an ha gun modified to include a third electrode at a potential near that of the cathode. This also indicates that the electrons from the hc gun are produced at two different sites and that the mechanism which is necessary for the production of electrons in the ha gun also operates in the hc gun.