DETECTION OF DISLOCATIONS IN STRONGLY ABSORBING CRYSTALS BY PROJECTION X-RAY TOPOGRAPHY IN BACK REFLECTION

X-ray projection reflection topography has been applied to a number of strongly absorbing crystals in order to find general rules for render ing dislocations visible. Single- and double-crystal schemes have been utilized. Considering direct images of dislocations and calculating t he ratio of extinction to the absorption depth, we have established a quantitative criterion for detecting individual dislocations. It is sh own that ordered dislocation arrangements are less sensitive to the re striction due to the absorption.