BORRMANN IMAGE OF DISLOCATION IN THE CRYSTAL OF THALLIUM ACID PHTHALATE
邻苯二甲酸氢铊单晶位错的Borrmann象衬度

The crystal of thallium acid phthalate (TAP) is a newly developed X-rays analyzing ele-ment with higher diffraction power. The Bormann image of the spiral dislocations has been observed and studied by means of X-ray topography. It is shown that the image contrast with fine structure nearly in the core of dislocation is decreasing not only with decreasing the crystal thickness, but also with decreasing the Borrmann coefficient s so greatly as to blur or even to make the fine contrast information loss completely when the images are inversed from "white" to "black" in the contrast.