Measurement of the average path length of photons in samples by self-attenuation of X-rays

For homogeneous samples a relation between the average path length of photons detected in full-energy peaks in the spectra of X- and gamma-rays and the counting efficiency is derived for an arbitrary sample-detector geometry. An experimental method of measuring the average path length in the samples is presented. The results of such measurements are compared to the calculated average path lengths and discussed in terms of self-attenuation factors.