TRAVERSE PATTERN OF DEFECTS IN THE BRAGG CASE. T.S. Uragami, H. Kobayashi and D. Orii, Faculty of Engineering, Okayama University of Science, Okayama, 700 Japan

On the camera with traverse mechanism for X-ray diffraction with an incident wave of finite width, the defects in a Silicon single crystal was observed in the Bragg case by using the diffracted wave which comes out from the inner part of a crystal. The diffracted wave can be observed without disturbance from the directy reflected wave when the width of the incident wave is adjusted as to eliminate the overlapping of the directly reflected wave and the image-forming one at the exit point. The Pendelloesung fringes in the Bragg case are strong in the inner part of the specimen, but fade out on approaching the entrance surface except at the incident point and around its neighbourhood. A strong wave is produced by a defect in a region where the Pendelloesung fringes are intense, and a faint wave is produced in a region where those are weak.

The experiment was done with an X-ray source, entrance slit, specimen crystal, receiving slit and plate. The leaf of one side of the receiving slit was used to stop the beam of direct reflection by 220 and 440 net planes in a Silicon single crystal. The plate receives the crystal wave coming out from the surface except the incident point since the beam of direct reflection is stopped by the receiving slit. As the entrance slit is narrow, the width of transmitted wave traveling in the crystal is not wide. The non-diffracted component of the diffracted wave may have the same width as the entrance slit. The kinematical images of defects are produced from the transmitted wave in the region where the non-diffracted component flows.

The background is mainly increased by the crystal misorientation during the traverse motion and by the Compton inelastic scattering. The Compton scattering may be reduced by making a non-diffracted component narrower. The entrance slit of 10É[[opthyphen]]m width and the narrower turned out to h ave been effective for this purpose.