Hot neutron four-circle diffractometer

Reactor hall, hot neutron beam H3

Monochromators
Cu (220)
Take-off angle 2θM	13 - 56 °
Wavelength λ	0.25 - 0.85 Å

Sample
Beam size	0.6 x 0.6 cm2
4-circle ranges	-20 <2θ <120° -34 <ω <48° 80 <χ< 200° -179 <Φ< 179°
Lifting-counter range	-12.5 <ν< 25°

Detector
Position sensitive with 32 x 32 pixels
Pixel size	2 x 2 mm² 0.25° x 0.25°
Sensitive area	64 x 64 mm²
Sample-detector distance	40 cm

Sample environment
Displex cryostat with J-T stage	2 K
Peltier cooler gas flow furnace	850 °C
Closed shell furnace	1000 °C
4-circle He-flow cryostat	2 K

Instrument Description

The diffractometer D9 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 wavelength of the neutrons is among the shortest available at any reactor in the world.

The monochromator is a Cu crystal in transmission geometry using the (220) planes.

The instrument is placed on a Tanzboden floor allowing a continuous choice of wave-lengths in the range from 0.35 to 0.85 Å. In order to suppress λ/2 contributions several resonance filters are available (0.48 Å, 0.55 Å, 0.70 Å and 0.84 Å).

In its standard ‘four-circle’ geometry the sample holder is an Eulerian cradle with offset χ-circle. A recent development also allows measurement in ‘normal beam’ (lifting-counter) geometry (i.e. measurement with cryomagnet, orange cryostat, etc.)

A small two-dimensional area detector is available for studies of satellites and twinning. It covers 32 x 32 pixels of (0.25°)2, and programs are available for intensity integration using this system.

Measurement of one Bragg-reflection normally takes a few minutes, and recording of a full set of data a few days. If the crystal is studied as a function of temperature, pressure or other, the total measurement time is about a week.