The geometrical diffraction model was used to simulate super-screw dislocation images in both characteristic radiation and synchrotron radiation topographs. It was revealed that, due to the finite spectrum width, characteristic radiation diffraction which occurred in the deformed lattice of a dislocation also constituted polychromatic diffraction. The contrast formation mechanisms of characteristic radiation topography were therefore almost identical to those of synchrotron white-beam topography. In general, the dimensions of the dislocation images increased sharply with increasing sample-to-film distance, thus making the characteristic radiation images which were recorded at small sample-to-film distances much smaller than the synchrotron radiation images which were recorded at large distances.

Dependence of the Direct Dislocation Image on Sample-to-Film Distance in X-Ray Topography. X.R.Huang, M.Dudley, J.Y.Zhao, B.Raghothamachar: Philosophical Transactions of the Royal Society, 1999, 357, 2659-70