High-Resolution Structure Analysis Using Synchrotron Radiation with a Multiple-Detector System

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A new powder diffractometer for synchrotron radiation with six detector arms has been constructed. Five detector arms, which are attached radially at intervals of 25ﾟ to the 2rheta-axis, compose a multiple-detector system. Five scintillation counters coupled with a flat Ge (111) crystal analyzer on respective arms can record simultaneously the whole powder pattern divided into five segments with an equal 2rheta span. The optics design is based on the flat-specimen-reflection geometry using parallel-beam. The intensity data are collected by using a 2rheta-step-scan technique in the asymmetric diffraction at a fixed incident angle. A sixth detector arm can be used for multi-purpose in the conventional single-arm-scan mode. It can equip various kinds of analyzers such as long horizontal parallel slits, a flat or channel-cut crystal analyzer, a receiving slit, a solid state detector. The diffractometer was installed at the beam-line BL-4B at the Photon Factory in Tsukuba in April, 1995, and test operations had been conducted since then. From the April of 1996, the whole system has been used by general users for high-resolution powder diffraction experiments. It recorded the fullwidth at half-maximum of 0.022ﾟ and the peak maximum intensity of more than 40,000 counts per second for the (111) reflection from Si powder. By the use of a focusing mirror, the maximum peak intensity was increased to more then 100,000 counts per second. The whole powder pattern in the 2rheta-range of 130ﾟ could be step-scanned at a step interval of 0.004ﾟ (2rheta) in just 4 hours. Results of structure refinements will be published elsewhere.