Measurement of nuclear radiation bursts with detector having finite response time

Pile-up phenomena arising in radiation burst measurements have been studied. These phenomena are treated as a non-stationary stochastic process, and the following results have been derived. (1) if the single radiation response of the detector is exponential with time constant τ, the height of the resultant pulse due to the pile-up process satisfies the Kolmogorov-Feller equation. If the response exhibits finite rise time, the piled-up pulse height expressed by the sum of many single radiation responses satisfies the non-stationary shot noise process. (2) The expected value of piled-up pulse, when treated as a noise in energy spectral measurement, is proportional to the total energy of a burst. The expected value of piled-up pulse is also directly related to the single radiation response of the detector, so that the pile-up phenomena can be used to measure the radiation field quantities and to determine the single radiation response. (3) The distribution of piled-up pulse height approaches the special Gaussian distribution as λ (a mean value of arriving particles in unit time) increases, and the deviation of the piled-up pulse heights from their expected values becomes negligible, independently of the energy spectrum of incident radiation particles. (author)