Photomultiplier Single-Electron Time-Spread Measurements

A large variety of nanosecond-response, high-gain phototubes for use in high-energy particle detectors is available to users. The time spread, gain, and noise properties of such tubes are important to know for selection of a suitable type. The 24 to 30% quantum efficiency of phototubes containing bialkali photocathodes for instance, along with their low noise offered at gains up to 3×107 make them especially desirable in Cerenkov counters. We present measurements of single-electron time spread for several 8575's, 56AVP's, 6810's, C70133's, 2067's, and 7264's. Using the measuring equipment, voltage ratios in the focus-electrode system for optimum collection and minimum time spread were found. A description of the measuring system is included. Two alternative ways of expressing the time spread are given. All tubes were magnetically degaussed and were shielded for these measurements.