A New Powder Diffractometer for Synchrotron Radiation with a Multiple-Detector System

A new powder diffractometer for synchrotron radiation with six detector arms has been constructed. Five detector arms are attached radially at intervals of 25° to the 2θ axis and form a multiple-detector system. Five scintillation counters coupled with flat Ge(111) crystal analyzers on the respective arms can simultaneously record the whole powder pattern divided into five segments, each with an equal 2θ span. The optics design is based on flat-specimen reflection geometry using a parallel beam. The intensity data are collected using a 2θ step-scan technique in asymmetric diffraction at a fixed incident angle. A sixth multi-purpose detector arm can be used in the conventional single-arm scan mode. It can be equipped with various kinds of analyzers such as long horizontal parallel slits, a fiat or channel-cut crystal analyzer, a receiving slit and a solid-state detector. Test operations of the multiple-detector system, conducted at the Photon Factory in Tsukuba, recorded a full width at half maximum of 0.022° and a peak maximum intensity of more than 40000 counts s⁻¹ for the (111) reflection from Si powder. The whole powder pattern of Mg₂SiO₄ over a 2θ range of 130° could be step-scanned at a step interval of 0.004° (2θ) in just 4 h. Results of whole-powder-pattern decomposition and Rietveld refinement of the Mg₂SiO₄ pattern are given.