A new dedicated high-resolution high-throughput powder diffraction beamline has been built, fully commissioned, and opened to general users at the Advanced Photon Source. The optical design and commissioning results are presented. Beamline performance was examined using a mixture of the NIST Si and Al(2)O(3) standard reference materials, as well as the LaB6 line-shape standard. Instrumental resolution as high as 1.7 x 10(-4) (DeltaQQ) was observed.

A dedicated high-resolution high-throughput X-ray powder diffraction beamline has been constructed at the Advanced Photon Source (APS). In order to achieve the goals of both high resolution and high throughput in a powder instrument, a multi-analyzer detector system is required. The design and performance of the 12-analyzer detector system installed on the powder diffractometer at the 11-BM beamline of APS are presented.

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We have determined the crystal structure of the single-phase stoichiometric high-temperature superconductor in the Y-Ba-Cu-O system using high-resolution neutron powder diffraction. This compound has an orthorhombic structure with space group Pmmm and lattice constants a = 3.8231 A, b = 3.8864 A, and c = 11.6807 A. The structure consists of "dimpled" Cn0 2 layers in the a-b planes loosely bonded by one-dimensional fenceIike square-planar cun, chains in the b-c planes. Recently, superconductivity above 90 K was reported by Wu et at. l in a multiphase sample with a nominal composition of V!.2 B8.,,).8 0.1 2 0 4 _ b' Subsequent studies by several groups2-S identified the superconducting compound as VEa 2 Cu} Oy. Although the metal-ion stoichiometry is wen established the structure is still in question. One of the simplest ordered perovskite structures with a YBa 2 CU3 Oy stoichiometry consists of 1: l:n stacking of cubic perovskite building blocks with Cu atoms on the cube corners, Y or Ba atoms in the center of the cube, and 0 atoms on the cube edges. From powder x-ray diffraction data Cava et al. 3 pro

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