Notice of SWING

The continuous scattering in the neighborhood of the direct X-ray beam is related to the existence of heterogeneities in the matter, these heterogeneities having dimensions of several tens to several hundred times the X-ray wavelength. Indeed, the scattering at small angles of X-rays yields incomparable information on the size and morphology of the electronic heterogeneities, on their size distribution and on their mutual interactions. These measurements are performed on such a large number of particles that reliable mean values can be extracted from them.

The proposal aims at defining a high performance, "easy-to-use" beamline, which would fit with the specific needs of users willing to perform Small Angle X-ray Scattering (SAXS) experiments, no matter their scientific discipline. The development of Synchrotron Radiation (SR) centers has boosted these types of experiments, mainly through two of the SR characteristics. First, the flux is many orders of magnitude higher than that emitted by classical sources, which allows to study much weaker scatterers samples, or in-situ time dependent phase transitions. Secondly, the SR sources (specially undulators) have very small divergences in both horizontal and vertical directions. Since SAXS experiments give information in the reciprocal space, the larger the scattering particle, the smaller the scattering angle. Therefore, the scale of observable particles depends strongly on the quality of the beam (low divergence, high collimation). One last, but not least quality of SR for such experiments, is the energy tunability which allows to adapt the X-ray wavelength to the sample (for example, biological samples require to minimize the absorption because of X-ray damages, whereas metallurgical samples may need to avoid exciting any strong fluorescence). The tunability can also be used to perform labeling experiments: each type of atom contributing (or not contributing) to the scattering can be revealed through the variations of its atomic scattering factor which appear when tuning the X-ray wavelength near its absorption edge.

All these characteristics explain why the concerned fields of research are so numerous, from biology to soft condensed matter or material science, the studied samples being liquids, gels or solids in transmission, or even in reflection (the technique is called GISAXS, for grazing incidence SAXS, and is widely used to study nanomaterials).

The technical specificities required for an excellent SAXS beamline, in terms of optics and general settings, are basically the same whatever the scientific interest of the user. The slits will be designed and manufactured to minimize the background signal, so as to make full use of the high natural collimation of the beam emitted by the undulator. The beam quality of in-vacuum undulators on SOLEIL will be fully exploited to obtain altogether a small and virtually constant beam size whatever the detector position. In particular, the estimated vertical size of the beam (FWHM) should allow to reach Q_min = 2.5 10^-4 Å^-1 at 10 m. This resolution of 2.5 micrometers would allow most USAXS (ultra small angle SAXS) experiments to be carried out in the usual pinhole geometry, instead of having to perform Bonse and Hart measurements with an analyser.

Conversely, all the requirements which are specific to a scientific community or to a peculiar experiment should essentially concern the sample environment. This is an essential aspect of this proposal, namely to supply the user with a variety of possible "up-to-date" sample environments and to make the interchange of sample environments extremely flexible. A final important characteristic of the beamline is its easiness of use, especially for a non-specialist user. Strong commitment should thus be put to automate wherever possible the operation of the beamline.

Under such considerations, the proposed SAXS beamline will have a very high flexibility and easiness of use which, with a somewhat lower brilliance compared to the ESRF undulators, will largely overrun its bending magnet sources.

Molecular biophysics uses SAXS to study the organization of membranes and of biopolymers like DNA and proteins, the interactions between proteins and/or lipids contributing to rationalize their crystallization and to the solubilization of membrane proteins. Functional biological systems at a higher level of integration are also studied like muscle, molecular motors or cellular organelles like ribosome. Molecular biophysics also studies the conformation of biological macromolecules, their conformational modifications associated with catalytic or regulatory properties, the formation of complexes with partner molecules (small ligands, proteins, nucleic acids or lipids) often central to their activity, or even the association of a very large number of molecules leading to supramolecular assemblies like viruses, microtubules or other organelles. These studies are presently undergoing a spectacular expansion associated with the development of powerful data analysis software, with the improvement of the quality of data recorded with synchrotron radiation, particularly at third generation rings; and finally with the increasing availability of high resolution tridimensional structures (protein crystallography, NMR), which constitute a starting point for the analysis of protein conformations in solution, isolated or within a complex. Within the field of molecular biology in which structural genomics comes as a complement to genome sequencing, small-angle X-ray scattering is one component of post-genome structural studies. To compare the three-dimensional structure in the crystal and in solution, to validate the existence in solution of an oligomer or of a complex characterised in the crystal, to determine the mode of association of two partners whose complex cannot be crystallised, to characterise the frequently observed rigid body movement of protein domains following ligand binding, to study the (un)folding of a protein following a physico-chemical perturbation, to contribute to the optimisation of crystallisation conditions, these are but a few of the questions solution scattering can address. All those conformational transitions can be studied at equilibrium (titration) or far from equilibrium by provoking a fast perturbation of the system and following the relaxation towards the new equilibrium state. Finally, it has been shown that low resolution crystallography can provide very useful information on large particles like viruses, whose nucleic acid is only ordered at low resolution. The possibility of collecting such data should be planned at the design stage of the SAXS instrument.

In material sciences, studies are developing along two main directions: nanoprecipitates in the bulk and thin layers of nanomaterials. In the bulk, the morphology, organization and chemical composition of the nanoprecipitates are to be determined. The chemical composition can be obtained using the so-called "anomalous labelling", i.e. the variation of the atomic scattering factor as a function of photon energy close to the absorption edge of the investigated element. This labelling method can be applied to a variety of systems like metal alloys, colloids, ferrofluids or polyelectrolyte gels. This kind of study obviously requires a continuously tunable wavelength. On monocrystals, correlations will be determined between the size and shape of the precipitates (studied by small-angle scattering) and the displacement fields (obtained by measuring the Huang scattering around Bragg peaks).The knowledge of these distortions are crucial for a better understanding of the mechanisms of demixtion of real metal alloys which are very different from the isotropic and continuous models usually used.

The research on thin layers of nanomaterials is undergoing an explosive development. These play an increasingly important role in several technological domains like opto-electronics, non linear optics, catalysis, magnetic thin or multi layers, nano-electronics, carbon nanotubes, etc. In all cases, the nanoclusters are present in thin layers, supported or buried, and must be studied using grazing incidence techniques to obtain information on the size, shape and distribution of these clusters.

Modern solid-state chemistry is interested in the controlled synthesis of various micro and mesoporous materials, most notably in its structural and kinetic aspects. The study of heterogeneous catalysis, of great industrial importance, belongs to the same category. In supported catalysis, it is necessary to determine the "smooth or rough" surface state at the nanometer scale in order to understand the kinetics of reagent adsorption. For the inorganic polymerisation aiming at obtaining the most homogeneous mixed oxydes, the knowledge of microdomains and heterogeneities, directly accessible by SAXS with hard X-rays, is crucial. This is also true of the chemistry of low temperature sintering process, used to obtain controlled segregation in materials with special optical properties.

The physico-chemistry of amphiphilic molecules, in particular their solubilisation, their self-assembly, the identification, understanding of the resulting phases and their possible transitions, is one of the traditional fields of use of SAXS methods. The field of surfactants is moving towards mixed systems with components of various origins: polymeric (latex), mineral (clays) or biological (DNA, proteins or lipids). In particular, the study of lipids crystallisation in emulsion is developing. Surfactants are also used to obtain mesoporous templated structures, with well defined pore sizes and possible hexagonal or cubic symmetry of the porous framework. These structures are obtained through an assembly mechanism where organic species, ionic or non-ionic surfactants or copolymers (template), interact with inorganic precursors (silica,…) of the future inorganic framework.

The new thermotropic mesophases recently discovered often display an organisation on the scale of hundreds of nanometers. Furthermore, the field of lyotropic liquid crystals is being enriched with new colloidal objects: biological macromolecules, mineral particles.

SAXS is also widely used to study the organisation of a variety of colloids and the structure of gels constituted by 3-D networks of low mass compounds or polymers in a liquid. The formulation, blending, thermal and mechanical treatments of polymers represent a particularly important industrial stake.

Beyond the above catalogue, open scientific questions are common to several communities. These communities are usually separated in physics, chemistry, life sciences or science of the universe, not to mention the technological aspect of environmental studies. This dispersion makes exchanges between different communities more difficult, with the exception of some summer schools, some GDRs dedicated to interdisciplinary aspects and some periodic congresses. As an illustration, a few of these questions will be mentioned which are currently investigated in several French groups, and which will still be open when SOLEIL comes into operation:

• Large scale organisation and combination of thermodynamic and kinetic factors in chemical reactions yielding self-assembled structures; self-assembly is the central problem of the synthesis of mesoporous solids used as catalysts or filters.
• Combination of entropic and electrostatic terms of multicharged systems for which the interaction between charged objects of the same sign can become attractive: this is one of the keys to a better understanding of self-associating polyelectrolytes with complex topology, of ionomers and other membranes used in fuel cells as well as of numerous biological systems.
• Smoothness of specially designed long-lasting materials (cements, glasses, vitroceramics and catalysts) and nanoporosity, the first stage in corrosion, have characteristics driven by mechanisms of dissolution-recondensation. SAXS is perfectly suited for a direct in situ characterisation, since classical methods using gas adsorption or thermo-porosimetry are severely perturbing these fragile structures.
• The effects induced by a hydrodynamic shear gradient are diverse. Relations between structures and rheological properties are therefore complex. Similarly, dispersion processes generate poorly characterised stresses within materials. These two classes of problems can be addressed by non-equilibrium experiments. The applications to radiochemistry also belong to this category.
• The effect of a magnetic and/or electric field on colloidal suspensions can lead to their crystallisation, thereby generating rich phase diagrams and original rheological behaviours. The use of hydrostatic pressure can also be envisaged.
• The organisation of interfaces or of extended defects on the scale of hundreds of nanometers leads to the formation of mesophases like swollen lyotropic cubic phases or TGB phases (twist-grain boundary phases). These structures which reflect subtle equilibria between various interactions can a priori be investigated by SAXS.

The combination of SAXS with methods of statistical physics and with a knowledge of interactions between objects results in a very powerful method of investigation of all these homo and hetero associations.

Many industrial fields have a direct interest in a SAXS beam-line at SOLEIL: materials, e.g. formulation for longer lasting glasses, in bulk or in fibres, and concrete; metallurgy for the design of alloys; formulation of solid polymers; solubilisation in emulsions, micro-emulsions and clathrate-like solid microstructures studied in oil industry; cosmetic industry; pharmaceutical industry for drug vectorisation; vaccine diffusion, redispersion of solid tablets, solubilisation in physiological conditions without precipitation, monitoring of parenteral solutions; food industry: formulation for the distribution of food, from thickening agents to powder dispersion; mining industry: flotation of ores based on the selective adsorption of surfactants; biotechnology: e.g. the biomimetic synthesis of structured phosphates, carbonates and mimics of mother-of-pearl.

Enrico Dainese
Dipartamento di Strutture, Funzioni e Patologie Animali e Biotecnologie
Universita degli Studi di Teramo
P.zza A.Moro n. 5
64100 Teramo, Italia

Michel Desmadril
Directeur-adjoint de l'IBBMC
Institut de Biochimie et de Biophysique Moléculaire et Cellulaire
Faculté des Sciences d'Orsay
Bâtiment 430
91405 Orsay Cedex

Arnaud Ducruix
Laboratoire de Cristallographie et RMN Biologiques
UMR 8015 CNRS
Faculté de Pharmacie
4, Avenue de l'Observatoire
75270 Paris cedex 06

Francoise Livolant
Laboratoire de Physique des Solides
Universite Paris Sud
Bat 510
91405 Orsay Cedex

Jean-Luc Popot
C.N.R.S. UPR 9052
Institut de Biologie Physico-Chimique
13, rue Pierre-et-Marie-Curie

F-75005 PARIS
Véronique Receveur
AFMB-CNRS
31 Chemin Joseph Aiguier
13402 Marseille cedex 20

Felix Rey
CNRS UPR 9053
Laboratoire de Génétique des Virus
91198 Gif-Sur-Yvette Cedex

Jean-Pierre Samama
C.N.R.S.-I.P.B.S.
Groupe de cristallographie biologique
205 route de Narbonne
31077 TOULOUSE Cedex

Annette Tardieu
Equipe Interactions macromoléculaires
Laboratoire de Minéralogie Cristallographie de Paris (LMCP)
UMR 7590 CNRS - P6, P7.
75005 Paris

Marc AIRIAU
Responsable Laboratoire de Caractérisation des Milieux Dispersés
CRA/APC/CPH
Rhodia Recherches
52, rue de la Haie Coq, 93308 Aubervilliers.

Philippe Barois
Directeur de Recherche
Directeur du GDR 606
Sous-Directeur du CRPP
Avenue Albert Schweitzer,
F-33600 PESSAC

Annie Brûlet
LLB
C.E. Saclay
91191 Gif sur Yvette

Jean-Pierre Cotton
Laboratoire Léon Brillouin
CEA/Saclay
91191 GIF/Yvette

Olivier Diat
CEA Grenoble
DSM/DRFMC/SI3M/PCI(polymères conducteurs ioniques)
UMR SPAM 5819 (CEA-CNRS-Universite J. Fourier)
Bat. C5 P. 547
17 av. des Martyrs
38054 Grenoble Cedex 9

Patrick Davidson, Marianne Impéror
Laboratoire de Physique des solides
Bât 510
Université Paris-Sud, 91405 Orsay

Michel OLLIVON
UMR 8612 du CNRS
Equipe Physico-Chimie des Systèmes Polyphasés
Université Paris Sud
5, rue J-B. Clément, 92296
Châtenay-Malabry

Pascal Andreazza
Centre de Recherches sur la Matiere Divisée
CNRS - Université d'Orléans
Orléans

Alain Dauger
SPCTS - UMR CNRS n°6638
ENSCI - 47 Av. Albert Thomas
87065 Limoges

Evelyne Fargin, Thierry Cardinal
Groupe des Matériaux pour l'optique
Institut de Chimie de la Matière Condensée de Bordeaux
Domaine universitaire
33608 Pessac cedex

Thierry Gacoin
Groupe de Chimie du Solide
Laboratoire de Physique de la Matière Condensée
Ecole Polytechnique
91128 Palaiseau Cedex

Michael Gunnar Garnier
Universität Basel
Institut für Physik
Klingelbergstrasse 82
4056 Basel
Switzerland

André Naudon
Laboratoire de Métallurgie Physique
UMR 6630 du CNRS
UFR Sciences, bâtiment SP2MI ; Téléport 2,
Bd Pierre et Marie Curie, BP 30179
86962 Futuroscope-Chasseneuil Cedex

Bruno Palpant
Laboratoire d'Optique des Solides
Université Pierre et Marie Curie
Case 80
Tour 13, couloir 13/14, 4ème étage
4, place Jussieu
75252 Paris cedex 05

Frédéric Petroff
Unité Mixte de Physique CNRS/THALES (CNRS-UMR137)
Domaine de Corbeville
91404 Orsay

Jean-Claude Pivin
CSNSM-IN2P3
Bâtiment 108
Orsay Campus
91405 Orsay

Brigitte Prével
DPM CNRS-UMR-5586
Bat: L. Brillouin
Université Claude Bernard Lyon 1
43 Bd du 11 novembre 1918
69622 Villeurbanne cédex

Christian Ricolleau
Laboratoire de Minéralogie-Cristallographie de Paris (LMCP)
Université Paris 7 - Denis Diderot / CNRS UMR 7590
75005 Paris

Colette Servant
Laboratoire de Métallurgie Physique
Université Paris-Sud
91405 Orsay

Rosalia Serna
Instituto de Optica, CSIC, Serrano 121
28006 Madrid, Spain

• to study both options of sagittal focusing with a mirror or with the second crystal of the monochromator. Having a mirror as the last optical element before sample might not be the best choice for minimising background noise.
  
  
• to optimise the monochromator for an easy use of the wide bandpass multilayer system. This option could become a very frequent operation mode of the monochromator
  
  
• to consider from the beginning a possible implementation of a Fresnel zone plate to obtain a microbeam
  
  
• to open the potentiality of the beamline to magnetic studies by producing circularly polarised light with a quarter wave plate
  
  
• to pay attention to the development of experiments taking advantage of the coherence of the light. Recent photon correlation experiments in the small angle range have given unique information on the dynamics of colloids and polymers,
  
  
• the beamline scientists are advised to consider carefully how high energy GISAXS studies on liquids could be implemented on this set up.