Metrology of very weak activities

In the determination of low level activities, the necessary techniques do not differ fundamentally from those used for higher activities but they require the devising of appropriate measurement and calibration systems. They mandatorily require detectors with the smallest possible inherent movement. The laboratory, of which the fundamental characteristics are given, is therefore so designed, to wit, to enable the three causes of inherent movement to be reduced: cosmic radiation, contamination of materials and the ambient radiation of the laboratory. A description is also given of a number of measuring systems: alpha determination apparatus, beta determination apparatus and Ge-Li gamma spectrometry apparatus