D9 - Hot neutron four-circle diffractometer

It is used for precise and accurate measurements of Bragg intensities up to very high momentum transfer. The resolution allows routine recording of extended data sets for the detailed study of atomic disorder and atomic thermal motions.
The short wavelength allows the study of compounds containing absorbing elements like Gd or Sm.

Applications

General themes:

Structural phase transitions ;
Atomic anharmonicity ;
Structural disorder ;
Hydrogen bonding ;
Packing of organic molecules ;
Magnetic structures, especially Gd ;
Electron density studies ;
Twinning and superlattice problems ;
Ordering in alloys

Fundamentals of diffraction:

Extinction effects ;
Test of dynamical theory ;
Thermal diffuse scattering ;
Resonance scattering

Special use:

atomic resolution neutron holography

Instrument layout

Because of the short neutron wavelength very small atomic displacements can be identified, accurate to typically 0.001 Å.
D9 is equiped with a two-dimensional multidetector for a more accurate and secure data collection.

View of the hot neutron four-circle diffractometer D9

Here the instrument is shown with no sample mounted and no sample environment. In practice D9 is often used with the cold head of a cryocooler passing through the φ-ring of the eulerian cradle.

The Eulerian Cradle of D9

The Eulerian Cradle is the central part of a 4-circle diffractometer such as D9. Two circles, denoted φ and χ, are used to adjust the crystal orientation relative to the diffractometer axes. A third circle, ω, sets the orientation of the crystal lattice planes to the diffraction position. Finally the fourth circle 2θ, rotates the detector to the diffracted beam. The closed Eulerian Cradle of D9 is stout enough to accommodate sample environment devices such as a cryocooler, a closed shell furnace, etc.

Furnace on D9

The instrument is shown here equipped with a furnace mounted on the φ circle of the eulerian cradle.