| ABSTRACT: | RECENT IMPROVEMENTS FOR SCATTER SIMULATION IN SINDBAD, A COUPLED
PHOTON MONTE CARLO AND CAD SOFTWARE
J. Tabary, R. Guillemaud, P. Hugonnard, F. and Mathy
LETI-CEA Recherche Technologique, CEA GRENOBLE, Grenoble, France
In X-ray radiography, scattering of photons from the inspected object, as well as backscattering or scattering
from the environment, may have significant deleterious effects on image quality, reducing the relative
contrast of the flaw indication. Therefore, development of computational models simulating scattering in
radiographic studies is of primary interest, to correctly evaluate flaw detectability. The X-ray radiographic
simulation software, Sindbad, developed for Non-Destructive Evaluation applications, models the whole
radiographic set-up, with the X-ray source, the beam interaction inside the object represented by its CAD
model and the imaging process in the detector. An analytical computation is used for the uncollided image
whereas the scatter flux is computed with a Monte Carlo approach. Two major evolutions in Sindbad have
been recently developed to provide realistic scatter images in reasonable computing time.
Up to now, because of a geometrical restriction of the coupling of EGS4 Nova and BRL CAD, we couldn’t
simulate detectors inside the object. An algorithm has been recently modified to consider the whole
radiographic set-up, including the environment and all the parts of the object and detector which are behind
the sensitive detector layer. Therefore, both backscattering and scattering from the environment are
computed. Examples of simulations on industrial parts under experimental conditions show that contribution
of backscattering can exceed half of the overall scattering flux. Moreover, as scattering is not sensitive to
sharp structures of the inspected items, an object simplification algorithm has been developed to speed up
the Monte Carlo computation without modifying the scatter image. This simplification is automatic and
takes into account the spectrum energy, the materials and the set-up geometry. On complex industrial
objects, the computations can be twenty times faster.
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