Geometrical factor of measuring systems with cylindrical symmetry

Solution of the problem of determining geometrical factor (G) of the plant, equal to the ratio of number of particles, entering detector during one time unit, to the value of source activity, is presented. Such solution is required for measuring radionuclide source activity by the method of limited solid angle. Exact analytical expression for G was determined. Methods for G calculation for the following sources were considered: planar, circular, with thin protective coated with self-absorption, cylindrical without self-absorption. The suggested method can be used for more complicated calculations and for estimation of other values as well. 5 refs