Gain Variations in Channel Electron Multipliers

Abstract

Using measurements of pulse height distributions of four channel electron multipliers, the individual multiplier gains have been followed throughout an operating history of 2×1011 counts. These multipliers all exhibit an initial gain decrease occurring over the first 109 counts followed by a slight gain increase and stabilization at approximately 1010 counts. An intentional increase in anode voltage after an accumulated exposure of 2×1010 counts resulted in a gain increase which was reasonably maintained for the remainder of the testing period. Additional operational tests in which chemical additives were introduced into the vacuum environment have isolated at least one chemical (lauric acid) which appears to offer a technique for producing gain recovery in a degrading multiplier.