An optimized scheme for measurement of the concentrations of the decay products of radon and thoron.

Radon daughter measurement methods have not previously been fully optimized in the presence of thoron daughters, the presence of which leads to an increase in the total potential alpha energy. Taking into account the fluctuations associated with flow rate and concentration as well as the statistics of decay, optimized counting schemes were determined for the daughters of radon and thoron for different sampling times over a wide range of counting intervals. The counting schemes examined were optimized for maximum precision. Counting schemes corresponding to impractically long counting intervals, and counting times which required measurements beyond an 8 hr working shift were rejected. Under these constraints the most appropriate sampling time was found to be 10 min.