Draft method of measuring surface density of foils of various materials

The origin of characteristic radiation and the process of backscattering are briefly described. The principle is given of the method for measuring the surface density of Cu, Fe, Ni etc. foils using either characteristic radiation or backscattered gamma radiation. Several variants are shown of the configuration of the detection unit and of the measured material which makes it possible to limit the effects of the radiation flux backscattered by the measured material, on the output signal course in dependence on the surface density of the measured material. In determining the optimal measurement conditions, the instability was considered of the output signal caused either by an absolute or a relative instrument error or by the statistical fluctuations of the output signal caused by decay or ionization processes. Optimal measurement conditions are given and values of surface density are presented for Al, Fe, Cu and Pb corresponding to optimal conditions in case 241Am is used as the radiation source. The described method permits the appropriately accurate measurement of surface density of foils mainly in the region of low surface densities and makes possible the attainment of favourable measuring conditions by a mere exchange of the adjustable backing without necessitating the change of the applied radionuclide. In measurements of surface density outside the interval of the applicability of the suggested method it is possible to change the geometry of measurement and to measure the material using routine scattering techniques. (J.P.)