An Extension of the 4πβ–γ Coincidence Technique: Two Dimensional Extrapolation

As an extension of the 4 πβ - γ coincidence technique, it is shown that for some radionuclides, the β count rate should be expressed as a function of at least two observed β efficiencies, and that the absolute disintegration rate can be obtained by a simultaneous extrapolation to 100% efficiency in the two or more dimensions. Measurements on 57 Co and 134 Cs are described as examples. For these nuclides, the separated efficiency functions are shown to be linear in theory as well as in practice. Thus a major source of systematic uncertainty in efficiency extrapolation, that due to the unknown form of the extrapolation function, is greatly reduced.