RaMonA system for radon and thoron measurement

Summary. — RaMonA is a homemade system for the measurements in air of the specific activity of 222Rn (radon) and 220Rn (thoron) based on the electrostatic collection of the alpha emissions of the ionized descendants of the two radioisotopes. The use of a semiconductor detector and of an appropriate signal processing apparatus allows to obtain alpha spectra with excellent energy resolution. The system has been used for many years for the continuous monitoring of the gas indoors, outdoors and in soil air. For several purposes, different geometries of the measurement chamber are realized and suitably calibrated, even in mixed atmospheres of 222Rn and 220Rn. In this paper, the different measurement systems and their potentialities are presented and the collection efficiencies of the different polonium isotopes are compared.