Realization and characterization of a 220Rn source for calibration purposes

The recent interest for measuring 220Rn activity in air and the following development of the corresponding measurement techniques require the improvement of standards for the calibration and characterization of the measurement devices. Due to the short half-life of the 220Rn, the adopted techniques for the production of 222Rn sources are not always reliable. In this paper a methodology for realizing a thoron known activity starting from a 232Th source will be presented and discussed.