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INSTRUMENTS | (Updated 28 September 2006 by Gabriel Cuello) |
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In this page you will find a very short description of our instruments.
If you
are interested in more detailed information, you can follow
the link
for the corresponding
Yellow Book entry (mantained by the SCO) or
the link
for the official page of the instrument (mantained by each Instrument Scientist).
Powder diffractometers
| D1A high-resolution two-axis diffractometer |
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| D2B high-resolution two-axis diffractometer |
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| D1B two-axis diffractometer |
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| D20 high intensity two-axis diffractometer with variable resolution |
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| D4 liquids and amorphous diffractometer |
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| SALSA strain analyser for engineering applications |
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| D3 polarised hot neutron diffractometer |
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| D9 hot neutron 4-circle diffractometer |
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| D10 thermal neutron 4-circle & three-axis diffractometer |
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| D15 thermal neutron normal-beam diffractometer |
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| D19 4-circle diffractometer with 2D PSD for large unit cells |
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| D23 thermal neutron normal-beam diffractometer + polarised neutron option |
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| VIVALDI thermal beam Laue diffractometer |
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| ORIENT EXPRESS new thermal beam Laue diffractometer |
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These two-axis diffractometers are used to investigate the structure of powders, liquids and amorphous materials. Diffraction group machines use relatively short wavelength neutrons (0.3 to 2.0 Å) to resolve structures to atomic resolution, in contrast to diffractometers in the Large Scale Structures group that use long wavelength neutrons for lower resolution of larger structures. Usually a large composite monochromator, up to 300 mm high, is used to select a narrow band of wavelengths and focus it onto the sample.The monochromator may be made from several crystals of pyrolytic graphite, copper or germanium. Large multi-detectors and linear position-sensitive detectors (PSDs) cover a large solid angle for maximum efficiency.
The two high-resolution powder diffractometers D1A and D2B are used mainly for Rietveld refinement, with scans lasting from 30 minutes to several hours. They are complemented by two high-flux medium-resolution powder machines, D1B and D20, which are used mainly for temperature scans and other types of fast experiment, especially on small samples. D4, on the short wavelength hot source, is used for liquids and amorphous materials, together with D20.
High-resolution two-axis diffractometer D1A |
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| D1A is still unique in being able to provide high resolution at long wavelengths, with shorter wavelength contamination eliminated by the guide tube. D1A is particularly suited to magnetic structures and other large dspacing studies, such as zeolites. D1A-stress provides very high lateral resolution, and allows stress determination to within as little as 50 mm of a surface or interface. | |
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Very high-resolution two-axis diffractometer D2B |
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| D2B was designed to achieve the ultimate resolution, limited only by powder particle size (Δd/d ~ 5 x 10-4), but was built so that an alternative high flux option, with resolution comparable to that of D1A but much higher intensity, could be chosen at the touch of a button. D2B then has very high intensity at D1A resolution, or very high resolution at D1A intensity. Being on a beam tube in the reactor hall, it can use wavelengths as short as 1.05 Å, impossible on D1A. The D2B detector bank was recently replaced by a pseudo-2D detector with 6 times the solid angle, and data can now be collected on samples as small as 500 milligrams in a few hours, or normal samples of a few grams in a few minutes. | ||
Two-axis diffractometer D1BD1B has always been in very high demand for real time experiments, and for very small samples because of its high efficiency position sensitive detector (PSD). Although it is a CRG instrument, (run by a CNRS team and Spain), it is available 50% of the time for scheduled ILL experiments. Complete diffraction patterns covering 80° at moderate resolution can be collected in a few minutes. |
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High-intensity two-axis diffractometer D20 |
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| D20 has extremely high flux with a very large PSD and opens up new possibilities for real-time experiments on very small samples. The complete diffraction pattern at 1536 positions covering the whole scattering range can be obtained in as little as a few hundred milliseconds (or more typically a few seconds), and then repeated automatically as a function of temperature, pressure, magnetic field, etc. Higher monochromator take-off angles up to 120° provide good resolution over the complete diffraction pattern, which can be obtained in a few minutes, even with small samples. |
Liquids and amorphous diffractometer D4D4 on the hot source, is designed to use short wavelength neutrons to measure diffraction patterns over a large Q-range from non-crystalline materials (glasses, liquids, amorphous solids) with excellent accuracy and to characterise their local atomic order. D4 shares a beam with the three-axis spectrometer IN1 and is therefore only available for about 50 % of the time. However the complete scattering range is covered by a large array of microstrip detectors, making the machine very efficient and very stable for different measurements on small samples, with isotopic replacement used to enhance contrast of particular atomic species. |
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Strain analyser for large scale engineering applications SALSA |
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| SALSA is the new ILL strain imager dedicated to the determination of residual stresses in a broad range of applications in terms of components and materials. It is in fact designed for diffraction measurements in “real” engineering components and optimised for stress determination in metallic components. |
Single-crystal diffraction is a powerful method for the investigation of structural details in condensed matter. Hot neutrons are required to uncover the finest details in the nuclear positions and neutron spin polarisation is a handle to separate mixed components (nuclear polarisation, magnetic and electronic scattering).
A characteristic of the four-circle diffractometers is the use of Eulerian cradles for orienting the sample crystals, with the detector moving in a horizontal plane. Normal-beam diffractometers have a mechanism for tilting the counter out of the horizontal plane, thus enabling the installation of heavy equipment for special crystal environments (cryostats, magnets, etc.).
These diffractometers can be used to find:
Structural data of this kind are required for a large number of systems, ranging from organic molecules to high temperature superconductors. Often studies are made as a function of temperature, pressure and magnetic field which may lead to important modifications of the crystal structure.
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The spin polarised hot neutron beam facility D3 |
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D3 and D9 use neutrons from the hot source with wavelengths as short as 0.3 Å. It is therefore possible, using D3, to measure magnetic structure factors up to sin θ/λ = 2 Å-1. D3 is a diffractometer with a polarised incident neutron beam. In practice, the instrument is set at a Bragg peak of an already known crystalline structure. Then, by simply reversing the beam polarisation, D3 performs a highly sensitive measurement of the spin-dependent nuclear magnetic interference amplitude term which is present in the Bragg scattering of polarised neutrons from a small single crystal specimen magnetised in a field. With polarisation analysis and Cryopad, D3 carries out spherical neutron polarimetry experiments. In the case of magnetic structures, this leads to the direct determination of the magnetic interaction vector. Hence, D3 is a very powerful tool for solving complex AF structures that had proven to be intractable with other techniques. Moreover, when the magnetic and nuclear scattering occurs at the same position in reciprocal space, D3 allows a precise determination of the AF magnetisation distributions. D3 can also be used for many purposes other than diffraction experiments, e.g. the search for the T-odd asymmetry of light particle emission in 239Pu ternary fission. |
Hot neutron four-circle diffractometer D9 |
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For structural analysis beyond the determination of average atomic positions, high-resolution nuclear density maps are required. D9 is ideally suited for this purpose. Because of the short wavelength very small atomic displacements can be identified, accurate to typically 0.001 X. A two-dimensional multidetector is employed. Various models of anharmonicity are used, involving many parameters that can only be determined by including reflections at high momentum transfers. Structural data from D9 are also used:
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The three-axis diffractometer D10D10 is unique in being the only four-circle diffractometer with optional energy analysis as on three-axis spectrometers. It also possesses a unique four-circle cryostat for temperatures as low as 0.1 K, and offers high reciprocal space resolution and low intrinsic background, to medium real space resolution. It is intended primarily for conventional crystallography, detailed study of modulated structures, quasielastic scattering and diffuse scattering. |
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The two-axis diffractometer D15 |
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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 (0.85 Å, 1.17 Å, and 1.54 Å) with corresponding
flux at the sample of 1.5 106, 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 monodetector can be installed. Otherwise 80×80 mm2 bidimensional microstrip detector is available. |
The large structures diffractometer D19D19, with its 120° × 30° position sensitive detector, is the monochromatic thermal neutron single crystal/fibre diffractometer of choice for determination of crystal structures with unit cells in the range of 103 to 105 Å3. Examples of single crystal studies include organometallic complexes, proteins, helium single crystals, acetylene polymers, liquid crystals,Vitamin B12, cyclodextrin complexes. Fibre work includes studies of DNA, cellulose, filamentous viruses and many industrial fibres. |
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The two-axis diffractometer D23 |
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D23 is a double-monochromator two-axis diffractometer with a lifting detector mounted on an arc (normal beam geometry). It is installed on the thermal neutron guide H25 that is equipped with a supermirror-coating, and thus offers a high flux and a very good signal to noise ratio. D23 is designed to work with or without polarised neutrons, with wavelengths in the range 1 – 3 Å. It can support special sample environments (high field cryomagnets up to 15 Tesla, pressure cells, dilution fridges, etc.) and is well suited to the determination of magnetic structures, magnetic phase diagrams and magnetization distribution maps. |
The thermal beam Laue diffractometer VIVALDI |
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VIVALDI is Laue diffractometer using the same technique as LADI
(good-quality macromolecular diffraction
data rapidly obtained on a quasi-white cold-neutron
beam with a large-area cylindrical detector based on neutron image plates),
but on a thermal neutron beam and is very well suited to fast data collection
from the smaller unit cells of interest to physicists, chemists and materials
scientists.
VIVALDI covers fields of interest such as magnetism, charge (nuclear) density waves, highpressure studies and structural phase transitions. It allows rapid preliminary investigation of new materials, even when only small single crystals are available, and is particularly well suited to surveys of reciprocal space.The detector is also suitable for some types of diffuse scattering experiments on a monochromatic beam. | |
The new Laue diffractometer ORIENT EXPRESSORIENT EXPRESS allows Laue patterns to be taken at different positions of the detector with respect to the incident beam. Full back-reflection geometry (α = 180°) as in the case of the film detector can be achieved but in much shorter time. The diffractometer is composed of a two-dimensional detector mounted on a 2θ arm, a two-stage tilt goniometer mounted on an ω rotation, and a video system for the optical alignment of the crystal with respect to the incident neutron beam. The diffractometer is located at the end of the thermal neutron guide H24 at the guide hall ILL17. |
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