On the Minimum Detectable Activity of β Spectrometers and Selective Radiometers

摘要

A method of P-ray spectrometry is described that consists in measuring the activity of a particular radionuclide in a mixture of a few P-emitting nuclides. The activity of radionuclides simultaneously emitting β and γ rays is determined with a y spectrometer, and their contribution to the total β spectrum is calculated. Formulas for finding the minimum detectable activity and the error of these measurements are derived. A frequently occurring specific case is considered in which the activity of 90{sup left}Sr radionuclide in equilibrium with 90{sup left}Y is measured against the background of 137{sup left}Cs and 40{sup left}K. The minimum activities that can be measured by the phoswich detector and a detector based on a plastic scintillator are compared. The main sources of errors inherent in this measuring technique are analyzed.