Problem 406

Simulated configuration where the problem arose: we defined a monodirectional
and monochromatic photon beam (100 keV) with normal incidence on an iron plate.
We were interested in verifying the spatial distribution (behind the plate) of
singularly Rayleigh-scattered photons.  We observed that the photons that
undergo Rayleigh effect in the plate and are afterwards counted behind the plate
don't fit the shape of the theoretical Rayleigh differential-in-angle cross
section. The number of Rayleigh-scattered photons is too high at small angle
values. The problem could come from the value of the form factor used when the
momentum transfer parameter x is below 1e5 cm-1 (the first non-zero value in the
tabulated data). There seems to be a discontinuity in the obtained photon flux
profile corresponding to x=1e5 cm-1. The problem has been observed for other
energies (for example 1 MeV).
We are a research team at INSA-Lyon scientific and technical university and we
develop a simulation code devoted to x-ray imaging techniques. We use GEANT4 to
verify our results and to assess the role of scattering in the x-ray image
formation process.
If you consider that you will need all the information concerning our
simulation, please tell us and we will provide all the details. Thank you very
much.
 Nicolas Freud and Simona Pistrui