Vi . Noise in Electron Devices

We report experimentally observed higher order moments of the photoelectron counts in a photomultiplier illuminated by a maser operating below but near threshold. The results are compared with theory. The photoelectron counts occurring in a set of predetermined intervals of length T were recorded on tape and then fed to a computer. The second, third, and fourth order moments of the photoelectron counts as functions of the observation interval, T, were evaluated. The higher order moments contain information about the higher order correlation functions of the power P(t) incident upon the photomultiplier. The probability w(K) of receiving exactly K photoelectrons within a time interval extending from t = 0 to t = T is'