Sensitive and descript β and β-γ counting assemblies

In this paper are described recent advances that have been made in the authors' laboratory towards 'high-sensitivity' and 'descript' measurement of trace quantities of radioactivity due to β and β-γ emitters in solid sources of relatively high specific activity. The β-detection assembly provides accurate information on the characteristic energy of the radiation permitting its identification at low levels. The detection system is relatively inexpensive and simple as Geiger counters are used as detectors. The information on the energy of the β radiation is obtained while measuring the total disintegration rate; thus the system has the versatility of detectors capable of providing information on the energy of individual β particles, e. g. solid state detectors and scintillators. The observed counting efficiencies and background rates of a few β and β-γ systems constructed are discussed. The figure of merit of these detectors can be considerably enhanced by certain modifications which are in progress. The techniques discussed above have been developed to meet specific requirements encountered in the study of certain problems in nuclear physics and geocosmophysics. The β-γ system has been employed to measure the half-life of 48Ca for single β decay: the measurements to date have yielded a lower limit of 1019 yr for its half-life. (author)