On the Measurement of Transit Time Dispersion in Multiplier Phototubes

In the use of a multiplier phototube to measure short time intervals, the accuracy of the measurement is limited by the statistical deviations in the output pulse from the phototube. These deviations arise from variations in the electron transit time in the phototube. This paper reports a technique by which the transit time dispersion in the tube structure can be measured. A beam of electrons is deflected through an aperture onto the first dynode of the photomultiplier by an rf sweep voltage. The output pulse resulting is examined using the sweep voltage as a time base. Values of the order of 1 m¿sec were obtained using three commercial type photomultiplier tubes.