We describe a multipurpose neutron powder diffractometer for high-efficiency and high-resolution measurements, HERMES, which has been installed at the JRR-3M reactor in Japan Atomic Energy Research Institute. To obtain high-quality data for a short counting time, or with a small sample amount, HERMES has a multi-detector system which consists of 150 3He neutron detectors and simple window type collimation. The best resolution is Δ2θ of 18' and Δd/d of 3 ×10-3, where 2θ and d are scattering-angle and d-spacing, respectively. The duration of an ordinary powder diffraction experiment is 1–5 h under the present conditions in JRR-3M. Some typical results of powder diffraction experiments and performance are given in this paper. We also show a result of 2D intensity mapping of magnetic diffuse scattering from a single crystal of a spin glass material.

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A renewed Ge-crystal monochromator was installed in a neutron spectrometer at JRR-3. The beam size at the sample position is vertically about 1.5 times as large as before, while the neutron luminosity is unchanged. Wellcollimated, monochromatic beams with quite different incident energy (E i ) are available through a slight rotation in the monochromator-crystal angle by making use of discrete Bragg reflections of Ge. The ability of inelastic-neutronscattering measurements is examined through observation of magnetic Brillouin scattering with extremely high resolution and with a supplementary use of two E i s.