Small Angle Scattering
Three SANS machines contribute to the pride of the group and are both workhorses and flagships of the ILL instrument suite. They are used for the determination of nano to microscopic structures on the lengthscale from 1nm to >1micron.
D11 (since 1972 – renewed in 2006-2009) serves a variety of scientific fields from soft matter, to biology, to condensed matter physics The instrument, which has always been intensely used for soft matter and biological research, is constantly being improved for the field of soft condensed matter and offers a wide variety of possible sample environments. The low Q option of the 80m instrument is unique (large detector – long detector & collimation distances – long wavelengths). By using the longest sample-detector distance of 39m D11 can access low q at short wavelength, avoiding problems of multiple scattering when using long wavelengths. The Q-range covered by D11 so far is spanning over the classical SANS Q-range plus the V-SANS q-range. It is currently being upgraded with a set of two high-resolution detectors that will make accessible the classical USANS q-range.
D22 (since 1994) is the highest flux SANS instrument in the world and still the reference for new developments. Its detector can handle high count rates and is perfectly suited for life sciences studies where the signal is often low. Its high flux is allowing the development of microfluidics and small sample volume measurements. The new options on D22 with white beam and increased wavelength spread (by tilting the selector) will give more flux that will benefit fast kinetic studies like stopped flow, time resolved rheology, TISANE, to cite some. Polarization option is planned, but still unclear whether IN15 will allow its use. The collimation of D22 has been upgraded in 2014-2015. D22 is unbeaten worldwide for the quality of its data. It is the most demanded of the three ILL SANS instruments.
D33 (since 2012) is a very tunable instrument combining most of the possible options for SANS: conventional SANS mode with monochromatic beam by using a velocity selector; TOF mode allowing an enhanced dynamic q-range and flexible wavelength resolution; TOF-GISANS (no need to vary the incident angle, favourable e.g. for aligned magnetic systems); polarized neutrons and 3He spin analysis; large sample area allowing the installation of bulky or very high field sample environments. SANS instruments at ISIS in TOF mode are competitive but will never reach the performance of D33 due to our ability to have flexible Dl/l. For the three SANS machines, the closest competitors, but with lower performances, in soft matter and biology are instruments at FRM-II and NIST. Despite the lower flux at NIST, great care in support laboratories and technical developments allows a high standard for the instrument suite.
Two complementary public reflectometers are world leading instruments for the study of thin films at interfaces (0.5-500 nm normal to the surface and 1-50 micron in-plane length-scales) with so far unbeaten performances and some unique features.
D17 (since 2000 as a devoted reflectometer) has a vertical sample geometry, can work both in TOF and monochromatic modes and has the option of polarisation analysis. It has the widest accessible q-range for a TOF machine (0.002-2Å-1) and is able to provide useful data in optimised conditions with measuring times down to 120 ms. The science performed covers three main areas: Soft Matter (55%), Biology (30%), Magnetism (12%) and applied materials science. A recently hired scientist is developing the instrument for polarised neutron reflectometry. The TOF-PNR option is finally ready. Time-resolved NR on D17 will become more frequent in future because only D17 covers two essential prerequisites: high flux and low background and broad wavelength range. D17 competitors include INTER and POLREF at ISIS, N-Rex at FRMII and SuperAdam, mainly for the PNR option.
FIGARO (since 2009), a TOF reflectometer with similar performances in terms of flux as D17 but with a horizontal sample geometry, specializes on scientific problems in soft matter, chemistry, physics and biology and free and confined liquid interfaces. Domains of interest include biophysics (DNA/lipid interactions), environment (global warming), health (pollution and nanotoxicology) and formulations (polymer/surfactant mixtures). Plenty of publicity has been generated recently to this effect. Sole existing competitor is INTER (ISIS) for the study of free liquid interfaces. Nevertheless, FIGARO was used as the benchmark instrument during the STAP meetings for reflectometry at the ESS as it is considered to be world leading due to its power, versatility, unique features and healthy publication record for such a young instrument. FIGARO is powerful and unique: (1) flexibility to tune flux vs resolution, (2) high flux on a reactor source optimized for kinetic measurements and (3) a reflection down time-of-flight option. This last feature is showing very powerful in the recent developments for liquid/liquid interfaces and surface rheology.
SuperADAM, a monochromatic reflectometer with vertical sample geometry and polarization option, is a CRG instrument devoted primarily to Swedish use. It has been recently fully rebuilt and moved to the H52 guide. In addition to the facility itself the Super ADAM project hosts a number of educational efforts, training and outreaching activities that are aimed to promote the existing and encourage new methods of neutron research within the Swedish research community. Since July 1st 2013 it is fully operated by Uppsala University and the CRG contract is signed until mid 2016. Super ADAM has a large variety of incident beam optics including two monochromators, large experimental area and modular design which allows flexibility currently unrivaled by other instruments of this type. Through its high resolution and polarization it excels in reflectivity measurements on magnetic thin films and multilayers. However a low resolution and high flux option for soft matter studies is foreseen and is under development (to be tested in 2015).
The Laue diffractometer LADI-III (since 1995 as LADI and 2007 as LADI-III) is used for single crystal neutron studies of biological macromolecules such as proteins or nucleic acids at high resolution (2.5 – 1.5 Å) providing unique information complementary to x-ray crystallography. By locating the position of protons or deuterons in a macromolecule and its bound solvent, knowledge of the protonation state of key amino-acid residues ligands or inhibitors, of the orientation of water molecules, of the hydration structure, it contributes to the understanding of a macromolecule’s specific function and behaviour. Due to the low flux of even the most intense neutron sources neutron macromolecular crystallography has historically been an intensity limited technique, requiring very large crystal volumes and long acquisition times. LADI-III has gone through a number of upgrades in recent years that puts it now in a world leadership position, despite the appearing of similar instruments to high flux facilities like FRM-II, SNS and J-Parc. LADI-III remains the world-leader in the field mainly due to the high flux available from the ILL reactor. The smallest crystals, largest systems and quickest data collections have all been done using LADI-III.
D16 (since 1976) is a versatile small momentum transfer diffractometer (q range 0.01-2.5 Å-1) with high Dq resolution (Dl/l=0.01) for the study of a wide range of partially ordered structures in biology, soft condensed matter and material science. D16 has been upgraded in 1999, moved once in 2007 and again in its final position on H52 in 2013-2014, where it enjoys now a dedicated design matching its geometry and intensity needs. It benefits from a high efficiency high resolution large area detector, MILAND, once more unique in its kind. The instrument is particularly well suited for high resolution studies of diffracting material with repeat spacings of the order of few tens of nanometer. Main applications involve biomembranes systems, molecular liquids, mesoporous materials and clays, magnetic materials. It is also possible to perform low resolution cristallography experiments on crystals of very large unit cells (viruses, lipoproteins, ...). Preliminary tests done at the end of last cycle showed a gain of a factor x10 in flux in the new position. The instrument characteristics are unique worldwide, the only similar instrument being AND/R at NIST, very successfully used for the diffraction of biomembranes but accessing a lower q range (and obviously lower flux).