Distribution of light pulse sizes from single cathode electrons in an image intensifier

The size distribution of light pulses from the anode of a transmission secondary electron image intensifier tube has been measured for single photoelectrons emitted from the cathode. The distribution deviates from a simple exponential, but does not approach a Poisson distribution. The noise distribution has also been studied and several different components distinguished. The effect on these components of cooling the cathode has been investigated. By virtue of absolute calibrations, a measurement of the photon gain of the intensifier can be calculated from the observed single electron pulse height distribution. A comparison of this gain with that determined by a direct measurement indicates that a significant fraction of the electrons emitted from the cathode are lost in the dynode structure, even under conditions of good electron optics.