High Resolution Neutron Powder Diffractometer with a Solid Methane Moderator at Pulsed Spallation Neutron Source

Abstract

A high-resolution neutron powder diffractometer has been constructed at the pulsed spallation neutron facility KENS. The instrument utilizes a narrow pulsed beam of thermal and epithermal neutrons from a solid methane moderator. A high resolution of Δ d / d ∼3×10 -3 has been realized over a wide d range with a good data accumulation rate and with an excellent signal-to-background ratio. An off-line time-focussing method is introduced in order to obtain better statistics. A Rietveld refinement technique with a new profile shape function is briefly described. Some examples of measurements using a unique capability of this instrument are also presented.