Single-Electron Response of a Porous KCl Transmission Dynode and Application of Polya Statistics to Particle Counting in an Electron Multiplier

Abstract

The single electron statistics of a porous KCl transmission dynode are studied experimentally. Pulse amplification for subsequent analysis in a multichannel analyzer is obtained by coupling the output of the transmission dynode to a 14 stage electron multiplier. The observed pulse height distribution is quasiexponential. Single primary electrons, emitted thermionically from a hairpin filament and accelerated to 8–9 kV impact energy, produce stable secondary electron yields of 30–40 electrons at pulse counting rates up to 2×106 cps. In a second experiment, the KCl transmission dynode is preceded by an Al2O3 target surface, which is bombarded by single ions and produces a peaked secondary electron distribution from this surface. In this case, the anode pulse height distribution of the electron multiplier also is peaked, but has a relative variance greater than that expected from Poisson statistics. The two physical arrangements cover a wide range of shapes of pulse height distributions, and the resulting compound distributions are in good agreement with theoretical shapes calculated from a Polya statistical model, which includes Poisson and exponential distributions as limiting cases.