We continue examination of the photon correlation properties of silicon avalanche photodiodes operated in photon-counting mode by extending their operation from that of passive quenching(1) to active quenching, yielding shorter dead time and higher frequency operation.

A number of photomultiplier tubes have been assessed for application in experiments where the counting of individual photoelectrons from the photocathode is necessary or advantageous. Pulse height distributions, signal-to-noise-in-signal ratios, over-all quantum-counting efficiencies, time dependent statistical correlations, and dark current properties have been investigated and compared with theoretical expectations. Amajor finding has been the general low value of over-all quantum-counting efficiency. Direct measurements of this figure have not, to our knowledge, been published previously. A second conclusion has been that, although there seems to be no reason why high performance with respect to each of the features considered should not be achieved in a single tube, we have not yet found one in which this is so.

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The effect of gain variation on the integrated output-charge distribution of a photomultiplier tube is investigated experimentally and shown to be a predictable function of the multiplier single-electron response. Standardized or nonstandardized pulses recorded using either capacitive or digital storage are considered. Theoretical values for the moment-generating functions and variances (noise powers) of the charge distributions obtained in these four cases are given, and the role of these various distributions in determining the length of time required to achieve a given accuracy in a light-flux measurement is discussed. The experimental measurements adequately confirm the theoretical predictions. The work includes a critical discussion of the field of theoretical and experimental noise investigations in photomultiplier tubes with regard to their relevance in the present state of technology.

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