Distribution of the 222Rn decay products from a 226Ra solution in a PTB ampoule - Implications for calibration

The spatial distribution of the activity in a flame-sealed PTB ampoule containing 226Ra solution, incompletely filling the ampoule, was studied by autoradiography and by taking well-collimated gamma-ray spectra in 23 sections of the ampoule. A complex activity profile was observed and used for the Monte Carlo simulation of the ampoule by the GESPECOR code. The computed values of the efficiency transfer factors are in agreement with the experimental data. As a byproduct, the radon partition ratio in the solution-air phases was obtained.