Calibration method of a Na I (Tl) detector - application to γ emitter dosimetry in gaseous phase

In the first section, the present paper gives a general method for calculating (1) (2) the absolute total efficiency of a cylindrical Na-I crystal, for few geometries: point source, line source, line source, disk source, cylindrical source. In the second section, we determined experimentally the photo-fraction of this crystal. The product of the absolute total efficiency into the photo-fraction, yields the absolute peak efficiency R, of the crystal for those geometries. We plotted R, versus E_γ, the energy of the incident photon on the crystal. Those curves are usually used to determine the quantity of radionuclides contained in a source of a given geometry when the corresponding reference source is unknown. This case is usual with cylindrical gaseous sources, reference source of which are practically impossible to be found. (author)