Gamma geometry dependency of efficiency functions in the 4πß-γ coincidence measurements of complex decaying nuclides.

ABSTRACT

In order to clarify the γ-efficiency dependency of 4πß-γ efficiency functions, a series of 4πß-γ efficiency extrapolation measurements of a (134)Cs source were carried out for a wide variety of γ-geometries using a 4πß(PS)-4πγ detector configuration. As the source is situated in the plastic scintillator (PS) ß-detector, the γ-efficiency of the system can be readily changed by extracting the ß-detector from the well-hole in a series of stages. For data acquisition and analyses, a list-mode two-parameter data acquisition system was employed. The forms of the extrapolation curves were monitored with decreasing γ-geometry, eventually exhibiting a similar behavior to those obtained in a usual 4πß-γ coincidence counting system. The experimental results and considerations suggested that the γ-geometry dependency of the efficiency functions were due to summing effects in the γ-channel, and some qualitative remarks on the form of the extrapolation functions are given.