Gain Fatigue Mechanism in Channel Electron Multipliers

Abstract
A study of the instability in surface composition of reduced lead oxide glass surfaces is described which suggests a possible mechanism for the observed gain degradation of channel electron multipliers in high vacuum environments. In particular, the depletion of surface oxygen from initial levels which were up to 10 times the stoichiometric concentration was observed, using the method of Auger electron spectroscopy. A model incorporating surface oxygen as a possible donor species in the secondary emission process is discussed, which qualitatively predicts the observed pressure dependence of multiplier gain and the onset of fatigue at about 10−7 Torr.

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