Practical application of oow energy gamma rays and X-rays in I.N.A.A. was restricted because of the complexity of the X-ray
spectrum and sample self-absorption. This paper describes a method for the calculation of sample self-absorption on the basis
of the actual sample spectra only, as measured with a high resolution semiconductor X-ray detector. In the 20–400 keV energy
range, the attenuation coefficient can be represented by a three parameter function of photon energy. This was verified by
measuring the transmission of photons of different energies through a range of materials. Experiments with neutron irradiated
U.S.G.S. standard reference materials with known major oxide composition showed that self-absorption thus calculated from
the observed spectra is in good agreement with the results of theoretical calculations based on known attenuation coefficients.