Four-circle diffractometer with three-axis energy analysis
Guide hall n 1, thermal guide H24
Divergence - supermirror (m=2)
6.9 mrad Å
Vertically focussing and continuously variable
1.8 < λ < 6 Å
1.1 < λ < 3 Å
incident energy range
2.5 < Eo< 68 meV
relative energy resolution δE/E
5 x 10-3
absolute energy resolution δE
0.02 THz at ki = 1.55 Å-1
< 2 x 10-4 at 1.26 Å with Cu monochromator and no analyser
10 x 8 mm2
≥5 x 106 cm-2s-1
vertically focussing pyrolytic graphite
94x94 mm2 area detector, or single 3He detector
spacial resolution 1.5 * 1.5 mm2 high counting rate
< 3 cpm (without analyser)
Due to its good momentum resolution with relatively high flux and its low intrinsic background, D10 can be used for all kinds of conventional crystallographic studies of nuclear and magnetic structures. In addition the optional energy analysis allows a restricted energy window to be set to lower the background so that delicate problems, such as Huang scattering, weak diffuse scattering, magnetic multilayers and commensurate-incommensurate phase transitions, can be studied. Inelastic scattering studies, for example of phonon dispersion, may be performed on large samples in both the four-circle and two-axis modes.
The versatile diffractometer D10 can be used in four different configurations:
- standard four-circle;
- standard two-axis;
- four-circle with energy analysis;
- two-axis with energy analysis.
The automatic monochromator protection allows a continuous change of the incident wavelength. Vertically focussing monochromator and analyser crystals increase the efficiency of the instrument. The sample and analyser tables move independently on air cushions, and the change between diffraction and triple-axis configurations can be made within the control program.
Two detectors are available in the diffraction configuration, an 80x80 mm2 two-dimensional microstrip detector for three-dimensional resolution in reciprocal space, or a single 3He detector when the highest efficiency and lowest background are required. In the diffraction configuration the detector may be inclined up to 30° to the equatorial plane to increase the out-of-plane access. A second single 3He detector is mounted on the analyser table for the triple-axis configuration. Background acquisitions can be made with the diffraction detector at the same time as scans are made in triple-axis mode.
In the four-circle mode, the offset C-shaped Eulerian cradle can be equipped with a helium-flow cryostat (1.6 K to 450 K, or 0.1 K to 10 K in dilution mode), or a hot-air furnace (up to 1000 K), both with full four-circle accessibility. A double-mirror furnace (up to 1800 K in air, in argon, or in vacuum) can be used with access to at least a quadrant of reciprocal space. In the two-axis mode, all standard ILL cryostats, furnaces, pressure cells and cryomagnets can be mounted with computer control of the double-axis tilt stage to allow limited out-of-plane access. Computer control of the temperature is possible for all standard cryostats and furnaces, and of the magnetic field for all standard cryomagnets.
D10 is controlled by a PC running under Linux. The control program, which can be run via command lines or via an intuitive graphical user interface, is identical to those used on other four-circle and powder diffractometers at the ILL, with additional commands for operation in inelastic mode with syntax familiar to the users of the triple-axis spectrometers.
Data-analysis software includes routines for raw-data display (including LAMP), integration of Bragg reflections, fitting of multi-peaked profiles, and plotting of general sections in reciprocal space, as well as common crystallographic refinement packages for nuclear and magnetic structures (CCSL, shelx, upals, Fullprof), and the display package Cerius.