High resolution TOF neutron powder diffractometer with supermirror guide

A new time-of-flight (TOF) neutron powder diffractometer, Sirius, installed at Neutron Science Laboratory (KENS) of High Energy Accelerator Research Organization (KEK), has realized both the high resolution (Delta d/d = 9 x 10(-4) at its best) and the high intensity. Sirius is situated 38 m apart from a solid-methane moderator at ca. 20 K. A long flight path, required from the above resolution, demands the use of a neutron guide tube to avoid the loss of intensities. In order to intensify short-wavelength neutrons, we use 28.5 m supermirror guide tubes which enable high intensity even below lambda = 1 Angstrom A backward bank has a detective area as large as 4 m(2) To cover this area, arrays of one-dimensional He-3 position-sensitive detectors (PSD's) has been used. This new geometry also makes it possible to increase the efficiency of data collection and to improve resolution. Several examples, including Rietveld analysis of LiMn2O4, are given. High intensity at large Q has been achieved by the use of the supermirror guide. With this feature, the high-resolution total scattering by Sirius give us more detailed local structure which is indistinct by lower resolution diffractometers. Preliminary results on pair distribution function (PDF) of CeO2 are presented.