  The hard x-ray gamma-ray absorption by cylindrically symmetric U-238 test
objects is studied by means of gamma-ray transmission measurements. To make a
precise comparison between the theoretically modelled values and the absorption
coefficients calculated from the experimental data, we have developed a highly
accurate numerical code based on a new solution of Abel's integral equation. It
is shown that progressive filtering, surface reflections by Compton scattering,
and the enhanced backscattering due to impurities can explain much of the
observed discrepancy. We also discuss optimal experimental conditions with
regard to the feasibility of quantitative radiography for gamma-ray
diagnostics.
