Instrument description

Reactor hall, inclined thermal beam IH4
 
Monochromator
Cu (331) or (442) or (113) in transmission at θ=45°
λ/2 contamination ~0.1% at λ=1.17 Å ; ~2% at λ=1.54 Å
wavelength resolution see figure
Sample
beam size 10 mm
flux at specimen
(measured by gold foil)
7.8 x 106 n cm-2 s-1 at λ = 1.176 Å
1.8 x 106 n cm-2 s-1 at λ = 0.855 Å
3.0 x 106 n cm-2 s-1 at λ = 1.54 Å
Angular ranges
Normal beam mode -5° < 2θ <135°
-181° < ω <181°
-9° < ν <32°
Bisecting geometry with  Eulerian Cradle
(some configurations are not possible)
-5° < 2θ <100°
-2.5° < ω <50°
120° < χ <270°
-181° < φ <181°
Detector
Bidimensional microstrip detector (80*80 mm2)
3He mono-detector (20 mm useful Ø)
Sample environment
Displex 2K ... 300K
Orange cryostat 1.8K ... 300K
Dilution refrigerator (20 mK)
Cryomagnet vertical field 6T and 8 T
ILL can supply upon request: standard dilution refrigerators; furnaces; pressure cells; and a superconducting magnet with vertical or horizontal fields; to be mounted in normal beam mode

The instrument D15 is a single-crystal diffractometer of the Harwell MK VI design. It is installed on an inclined beam tube (IH4). To compensate for the inclination of the incident beam, the scattering vector of the monochromator is tilted to bring the monochromatic beam into the horizontal plane. Three wavelengths can be set up (0.85Å, 1.17 Å, and 1.54Å) with corresponding flux at the sample of 1.8 106, 7.8 106, and 3.0 106 n/s/cm2 respectively.

The instrument can be operated in either four-circle or normal-beam mode. When a low background and higher efficiency are needed a mono-detector can be installed. Otherwise 80*80 mm2 bidimensional microstrip detector is available.

For the normal-beam geometry D15 has its own orange cryostat superconducting magnets 6T (gap of 25 mm diameter 45 mm) and 10T (gap and diameter 10 mm) are available. A low temperature insert (50 mK) can be used in the orange cryostat and the 6T magnet. Pressure cells (up to 3 GPa), uniaxial stress apparatus, and furnaces from ILL can also be installed

D15 is used for a wide range of physical problems including the determination of magnetic phase diagrams, of pressure-temperature phase diagrams or a combination of all these. It is also often used for determination of magnetic and nuclear structures in preparation for spin density studies with polarised neutrons.

Solving a crystallographic or magnetic structure requires to collect a large number of Bragg reflexions. Starting from the experimental data, special softwares allow determine the atomic positions as well as the magnetic moments.