Preparation and standardization of large-area sources for calibration of alpha-particle contamination monitors

Large-area sources of 241Am for calibration of surface-contamination monitors have been produced by incorporating the radionuclide into a thin layer of anodized Al. A measurement chamber has been developed which allows the standardization of alpha-particle emitting sources with active areas up to 12 × 17 cm2. The counter can be operated as an ionization chamber or in the proportional region. The sources can be standardized in terms of alpha-particle emission rate or activity with uncertainties in the order of 1%.