Abstract
Pulse height distributions of the output of a secondary electron multiplier for various kinds of ions in the keV region were measured and analyzed to determine the true detection efficiencies for these ions. A high sensitivity mass spectrometer was used for the measurement at residual gas pressures around 10-9 Torr. An Allen-type secondary electron multiplier of 12-stage Cu-Be dynodes connected to a low-noise charge-sensitive preamplifier was used for detecting keV ions. It is assumed in the analysis that the pulse height distribution can be obtained from Polya statistics. The pulse height distributions for the ions of which secondary electron yields were markedly different made it possible to estimate the pulse height distribution for the single electron emitted from the conversion dynode. It was made clear that the statistics of the secondary electron emission by the light ions, e. g. H+, H2+ and He+, was different from that by the heavy ions, e. g. Ar+, CO+ and CO2+.
