New neutron scattering instruments at Risoe National Laboratory: A multipurpose spectrometer and the SANS facility

Two neutron scattering instruments recently installed at the DR3 reactor at Risoe National Laboratory are described and examples of experimental results are given. One instrument is a multipurpose instrument TAS3 which can be operated in three different modes: 1) TAS-MODE: In this mode the detector system consists of a complete analyser-detector system, and the instrument is a conventional neutron triple-axis-spectrometer used for inelastic neutron scattering. 2) DAS-MODE: In this mode the detector system consists of a detector system, which can be rotated around the vertical sample axis and in addition by means of an automated mechanical tilt can be tilted from 5 deg. below to 25 deg. above the horizontal plane. The spectrometer is used for elastic neutron scattering. 3) DPS-MODE: In this mode the detector system is a linear position sensitive detector which is mounted vertically in the mechanical tilt device used in the DAS-mode. The DPS-mode supplements the DAS-mode and has proven to be useful in single crystal structural studies when searching for satellite Bragg peaks in odd directions of reciprocal space. 4) TEX-MODE: This mode is used for measuring texture of polycrystalline materials, both statistical and dynamical. An Eulereian craddle is mounted on the sample table, and the detector system consists of a linear position sensitive detector mounted as in the DPS-mode. The other facility to be described is the six meter Small Angle Neutron Scattering facility SANS. It is situated at a cold source beam outside the DR3 reactor confinement at the end of a 20 m long neutron guide. A mechanical velocity selector with variable tilt provides the monochromatization with Δγ/γ in the range 0.05 to 0.20. As a novel feature the sample is placed in high vacuum, (< 10-6 mbar), without windows between the entrance slit and the 40cmx40cm area-sensitive detector. The sample can be rotated and translated automatically in the vacuum, which allows the use of cryostats, cryomagnets and furnaces without introduction of extra windows