A selective and versatile low level beta-, X-, and gamma-ray detector assembly

Abstract

By incorporating various features of the well known Geiger, proportional and scintillation counting in a single system, a low level detector for measurement of β ^±-, X- and γ-radiation has been developed. The system can be operated in five different modes to suit the decay scheme of the radionuclide under study. It is specially suited for an unambiguous identification of radionuclides which emit β /χ rays in coincidence with γ radiation where a background of the order of 10^-3 cpm has been achieved. To illustrate the merit of this system the case of radioactives in meteorites is considered where, when coincidence measurements are possible, the sample requirement reduces significantly over the counting devices now in practice. Specific cases are discussed which show that about a dozen useful radionuclides can be measured in a stone meteorite sample of less than 30 g including ²²Na and ²⁶Al in 5 g, and ⁵³Mn in mg quantities. The limited data available so far permit us to evaluate the contribution some of the sources to the residual background of the detector.