Some Remarks as to Dark Current and Pulse-Height Distribution in E.M.I. 6260 Photomultipliers

Bias curves measured with an E.M.I. 6260 photomultiplier tube for dark current, and single photo-electrons emitted from the cathode under light stimulation, are discussed. It is shown that the dark current has a multi-electron emission component, the major part of which can be attributed to the K40 content of the glass. Pulse-height distributions are shown to be dependent on focusing characteristics of the multiplier and to broaden when space-charge limitation occurs.