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- Author or Editor: G. Sibbens x
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Some modifications are presented to Sima’s simple analytical model for the calculation of the total detection efficiency of a well-type γ-ray detector, aiming at improving its accuracy and broadening its applicability. The modifications pertain to some general improvements in the photon transmission probabilities through absorbing materials and implementation of specific equations for solid angle and mean path length through materials that describe the case of eccentrically positioned sources as well as volume sources. In particular, some improvement is achieved by implementing a contribution from elastic scattering effects.
High-resolution alpha-particle spectrometry was performed on three uranium materials enriched in 235U. Besides the 235U peaks, separate peaks belonging to impurity traces of 234U could be quantified. Relying on the isotopic composition of the uranium, as determined by mass spectrometry, the ratio of the half-lives of 238U and 235U was determined via the activity ratio of 234U and 235U in the materials. As an intermediate link, the 234U/238U half-life ratio was taken from published mass spectrometric analyses of ‘secular equilibrium’ uranium material. The resulting half-life ratio T 1/2(238U)/T 1/2(235U) = 6.351±0.031 is in agreement with the commonly adopted half-life values determined by Jaffey et al.