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 degrees to the 2 theta axis and form a multiple-detector system. Five scintillation counters coupled with flat Ge(lll) crystal analyzers on the respective arms can simultaneously record the whole powder pattern divided into five segments, each with an equal 2 theta span. The optics design is based on flat-specimen reflection geometry using a parallel beam. The intensity data are collected using a 2 theta 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 flat 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 degrees and a peak maximum intensity of more than 40 000 counts s(-1) for the (111) reflection from Si powder. The whole powder pattern of Mg2SiO2 over a 2 theta range of 130 degrees could be step-scanned at a step interval of 0.004 degrees (2 theta) in just 4 h. Results of whole-powder-pattern decomposition and Rietveld refinement of the Mg2SiO4 pattern are given.