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Microdefects in striated (swirl defects) and nonstriated distribution (D-defects) have been observed in float-zoned crystals doped with various impurities by x-ray topography following copper decoration. A new type of defects were found to be present in swirl-free and D-defect-free regions and to become invisible by doping gallium. This gallium effect led to the conclusion that they are microprecipitates produced from residual oxygen impurity in FZ crystals. Effects of various impurities on defect formation indicate that D-defects are of vacancy agglomerates. It was observed that swirl defects are formed when the temperature gradient near the interface is high, and that their formation is suppressed by doping nitrogen. Formation processes of microprecipitates, swirls, and D-defects are discussed on the basis of observation of their mutual interaction and the impurity effects.

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Reproduction of x-ray diffraction topographic images has been made at about 25 diameters enlargement by a closed-circuit television camera system with an x-ray sensing Vidicon tube which utilizes a beryllium window and PbO photoconductive target. The height of video signals is exactly proportional to x-ray intensity, and intensity distribution can be observed as a video waveform. It is shown that the television image system can be used for rapid observations of topographic images such as Pendellösung fringes and imperfections in crystals, although its resolution (about 30 μ) is inferior to that of the photographic method.

The radial and angular contributions to the pair term of the correlation function relevant to collision-induced light scattering are analysed. The dynamic features of the relative motion of the pair are shown to be more and more affected by orientational effects as the density increases.