The multiple emission of electrons in a secondary-electron particle counter

The statistical distribution of multiple emission of secondary electrons has been studied when He 0 atoms in the energy range 1-5 kev impinge on pure aluminium in a secondary-electron scintillation detector. The results show that the distribution function is Poisson type, and by analysis of only two peaks on the pulse-height spectrum the fraction of incident He 0 atoms which fail to cause the emission of an electron can be estimated. Secondary-electron coefficients γ have been obtained from the experimental distribution functions for He 0 and Ar 0 incident on Al. For He 0 , γ varied smoothly from 1·3 to 2·4 in the energy range 1-5 kev. The effect of argon ion-cleaning of the cathode has also been studied.