NOTIZIARIO Neutroni e Luce di Sincrotrone - Issue 10 n.1, 2005

NOTIZIARIO

Neutroni e Luce di Sincrotrone

Vol. 10 n. 1 2005

Rivista del Consiglio Nazionale delle Ricerche

Rivista del Consiglio Nazionale delle Ricerche

NOTIZIARIO Neutroni e Luce di Sincrotrone

ISSN 1592-7822

www.cnr.it/neutronielucedisincrotrone

EDITORIAL C. Andreani

SCIENTIFIC REVIEWS Investigating large scale structures by combining small angle and ultra small angle neutron scattering F. Lo Celso, I. Ruffo, A. Riso and V. Benfante

Star-Like polymer solutions studies by light and neutron scattering G. Di Marco, N. Micali, R. Ponterio, V. Villari and A. Hainemann

Inelastic ultraviolet scattering beamline at Elettra C. Masciovecchio, A. Gessini, S. Di Fonzo and S.C. Santucci

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NOTIZIARIO Neutroni e Luce di Sincrotrone

Rivista del Consiglio Nazionale delle Ricerche Cover photo: Conformation of the pPEGMA graftpolymer, that, in a selective solvent, mimes a star-polymer. Differently from star polymers, however, its interaction potential is described by an adhesive hard-sphere model.

SUMMARY EDITORIAL

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..................................................................................................................................................

C. Andreani

SCIENTIFIC REVIEWS Investigating large scale structures by combining small angle and ultra small angle neutron scattering ....................................................................................................... 3 F. Lo Celso, I. Ruffo, A. Riso and V. Benfante

Star-Like polymer solutions studies by light and neutron scattering ........................................................................... 8 Il

è pubblicato a NOTIZIARIO Neutroni e Luce di Sincrotrone

G. Di Marco, N. Micali, R. Ponterio, V. Villari, A. Hainemann

cura del C.N.R. in collaborazione con la Facoltà di Scienze M.F.N. e il Dipartimento di Fisica dell’Università degli Studi Roma “Tor Vergata”.

Neutroni e Luce didi Sincrotrone

Inelastic ultraviolet scattering beamline at Elettra

Vol. 10 n. 1 Gennaio 2005 Autorizzazione del Tribunale di Roma n. 124/96 del 22-03-96

BRISP - A New Thermal Neutron Brillouin Scattering Spectrometer at the Institut Laue-Langevin ............................................................................................................. 20

DIRETTORE RESPONSABILE:

D. Aisa, E. Babucci, F. Barocchi, A. Cunsolo, F. D’Anca, A. De Francesco, F. Formisano, T. Gahl, E. Guarini, S. Jahn, A. Laloni, H. Mutka, W.-C. Pilgrim, A. Orecchini, C. Petrillo, F. Sacchetti, J.-B. Suck, G. Venturi

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C. Andreani COMITATO DI DIREZIONE:

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Finito di stampare nel mese di Gennaio 2005 PER NUMERI ARRETRATI E INFORMAZIONI EDITORIALI:

Desy Catena Università degli Studi di Roma “Tor Vergata”, Presidenza Facoltà di Scienze M.F.N. via della Ricerca Scientifica, 1 00133 Roma Tel: +39 6 72594100 Fax: +39 6 2023507 E-mail: desy.catena@uniroma2.it

Vol. 10 n. 1 January 2005

EDITORIAL

evelopments occurred at synchrotron ra-

D

conference, the annual event where the FEL commu-

diation and neutron facilities during 2004

nity gathers to discuss progress and new ideas in the

have been impressive. The construction of

field. The 2004 edition was hosted by the Sincrotrone

Diamond, the new synchrotron, is pro-

Trieste and took place in the “Stazione Marittima” at

gressing as scheduled, in South Oxfordshire on the

the waterfront in the centre of Trieste. The prize was

Chilton/ Harwell science campus. The ‘super micro-

awarded to Vladimir Litvinenko from BNL and Hi-

scope’ is housed in a striking doughnut-shaped

royuki Hama from Tohoku University in Japan, for

building over half a kilometre in circumference, cov-

their fundamental and pioneering contributions in the

ering the size of 5 football pitches, with first users ex-

development of Storage Ring Free Electron Lasers.

pected at the new X ray source in early in 2007. This will occur shortly before first neutrons on the Second

The scientific reports of this issue summarize recent

Target Station, which is also making great progress.

investigations of rocks and marbles, by the combina-

With a choice of first day instruments suite at the cut-

tion use of SANS and USANS techniques, and of

ting edge of technology, and that can adapt to meet

polymer solutions by light and neutron scattering,

the changing needs of our research communities.

and recent highlights from the IUVS and BRISP

Both initiatives are destined to transform the RAL site

beamlines installed at ELETTRA and ILL, respective-

in a major centre for condensed matter science, open-

ly. All these studies confirm the increasing dynamism

ing up new opportunities in bio-molecular science,

of the neutron and synchrotron radiation community.

nanoscale science, advanced materials and soft condensed matter.

Carla Andreani

The other two important projects in progress are JPARC and SNS. They are quite impressive too. The JAERI-KEK, the Joint Facility for High Intensity Proton Accelerators in Japan, is the new and exciting accelerator project aiming to produce MW-class high power proton beams at both 3 GeV and 50 GeV. Construction of J-PARC started in 2001 and the anticipat-

FOR INFORMATION ON: Advertising for Europe and US, rates and inserts please see:

www.cnr.it/neutronielucedisincrotrone

ed first beam is planned for in the summer of 2007.

The SNS source construction continues at Oak Ridge, Tennessee and the Central Laboratory and Office (CLO) Building is now completed, complete occupancy of the SNS staff officially occurred in fall 2004.

A last year event is the award of the FEL prize 2004 announced during the the Free-Electron Laser (FEL)

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Vol. 10 n. 1 January 2005

Conference Announcements please contact:

Ms. Desy Catena Tel. +39 6 72594100 Fax +39 6 2023507 e-mail: desy.catena@uniroma2.it

SCIENTIFIC REVIEWS Paper received June 2004

INVESTIGATING LARGE SCALE STRUCTURES

BY COMBINING SMALL ANGLE AND ULTRA SMALL ANGLE NEUTRON SCATTERING Fabrizio Lo Celsoa*, Irene Ruffob , Angelo Riso and Valerio Benfante a a Dipartimento di Chimica Fisica “F. Accascina” Università degli Studi di Palermo viale delle Scienze, 90128 Palermo (Italy)

b

Abstract Small Angle Neutron Scattering (SANS) and Ultra Small Angle Neutron Scattering (USANS) are used to investigate a variety of systems from rocks and marbles to biological samples and block copolimer solutions. The importance of combining the two techniques as well as the different models to fit the combined experimental data are here highlighted.

conditions. By combining SANS and USANS experiments scattering data covering five orders of magnitude in momentum transfer can be carried out. This is particularly important to gain information about fractal aggregation and in general, to distinguish between surface and mass fractals.

Istituto Superiore “U. Mursia”, Carini (Italy) *corresponding author email: locelso@libero.it fax: (+39) 091 590015, phone: (+39) 091 6459841

Introduction Investigation of large scale structures requires experiments involving small values of the momentum transfer q (q = 4πsinθ/λ, with 2θ the scattering angle and λ the wavelength of the scattered neutrons). Conventionally the small q neutron scattering technique is divided into two regions: the Small Angle Neutron Scattering (SANS) region corresponding to Q > 0.001 Å-1, and the Ultra Small Angle Neutron Scattering (USANS) region corresponding to Q< 0.001 Å-1. By combining the two techniques, today is possible to investigate structures with dimensions varying from nanometers all the way to several ten microns. Many natural and industrial materials are characterized by structures in the same range of dimensions. So combined SANS-USANS experiments are bound to become more and more common. Only recently, following the AWT [1,2] tail reduction method, USANS has developed into a powerful standard method for the investigation of large scale structures. Today USANS instruments reach a peak to noise ratio better than 105 coupled with a Q range from 10-5 to 10-2 Å-1, allowing full overlap with many SANS instruments. In addition measuring time of less than 30’ allows slow kinetics to be followed with time resolved USANS experiments. In this article we shall present a few cases ranging from natural materials (rocks, biogenic platforms, bones) to man made materials (block copolymers). We shall present some isothermal and also variable temperature Time Resolved Ultra Small Angle Neutron Scattering (TR-USANS) data which give the possibility to test the unimer-aggregate transition of an aqueous solution of a tri-block copolymer in a wide range of thermodynamic

Experimental USANS and SANS measurements were performed at the KWSIII and KWSII instrument of the neutron scattering facility FRJ-2 of the Forschungszentrum Jülich (Germany) [3], which covers the range 1.6x10-5<q<1.4x10-3Å-1 (λ =12.7Å) for the USANS and 10-3<q<0.2 Å-1 (λ =7Å) for the SANS. Experimental data were collected also at the HFIR USANS facility of the Oak Ridge National Laboratory (USA) which is a Bonse-Hart double-crystal diffractometer equipped with triple-bounce Si(111) channel-cut crystals, which have been modified by cutting an additional groove for a cadmium adsorber [1] and by very deep surface etching . Data obtained in three sections characterized by different theta-steps and accumulation times, have been desmeared, normalized by the primary incident neutron beam fluctuations, intensity variations due to monochromator positioning, sample thickness and sample transmission and then spliced to the high angle portion by means of standard techniques. USANS experiments were also performed at the neutron optical bench instrument S18 installed at the 58 MW high flux reactor at the Institut Laue-Langevin (Grenoble, France) [4]. In the double crystal spectrometer configuration, triple bounce channel cut perfect Silicon crystals are used as monochromator and analyzer, covering the -5 -2 -1 range 2x10 < q <5x10 Å . SANS measurements on the LOQ spectrometer of the Rutherford Appleton Laboratory (Chilton, UK) were performed with a fixed sample-todetector distance of 4.3 m and variable wavelength (2.210.0 Å, determined by time-of-flight), providing an effective q-range 0.01-0.22 Å-1 in a single measurement. The intensity of neutrons was recorded on a position-sensitive 64 x 64 pixel 2-D detector.

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Results Figure 1 shows USANS experimental data for a sample of rock called norite (coming from South Africa), which is granular crystalline rock consisting essentially of a triclinic feldspar (as labradorite) and hypersthene . Best fit to the experimental data were obtained by using the expression for a mass fractal as highlighted in eq. 1 [5]

with β = Dm – 1.

sample of limestone. Marbles can be considered as the result of the isochemical metamorphic evolution, in different conditions, of a parent rock (protolith): normally a sedimentary carbonate with a highly variable calciticdolomitic composition, or a previous marble. This involves the destruction of the originating minerals (mostly calcite-dolomite) and their recycling through a further crystallization process. Figure 2 shows the scattering cross section (open circles), obtained by means of USANS experiment, of such protolith, a sample of limestone. Lines are best fit of the data to a hierarchical struc-

Figure 1. USANS data for a sample of norite (South Africa). Solid lines represents best fit to the eq. 1.

Figure 3. USANS and SANS data for a sample of white italian marble (Carrara). Solid lines represents best fit to the eq. 2.

I(q) = q–1Γ(β)Lβcut [1+(qLcut)2]–β/2 sin[β arctan(qLcut)]

(1)

ture model which takes into account the existence of a network of fractal aggregates of size R formed by monodispersed solid primary particles of radius r [6].

The scattering intensity as a function of the scattering variable q reads: I(q) µ P(q, r, Ds) S(q, r, D, R)

where

Figure 2. USANS data for a sample of grey limestone. Solid lines represents best fit to the eq. 2.

In this case the experimental data, considering the fractal behaviour, span more than two decades in momentum transfer and more than four decades in intensity (referring to the single power law) with fractal dimension Dm=2.1 and upper cut-off length Lcut = 62000 Å.

A different behavior is observed when different kind of “rocks” are taken into account. In particular we will consider a marble sample and its strictly related parent, a

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⎛ 2 2 2⎞ P(q, r, Ds) = ⎜⎜1 + q r ⎟⎟ 3 ⎝ ⎠

and S( q, r , D, R) = 1 +

DΓ( D − 1) ⎛ 1 ⎞ ⎜⎜1 + ⎟ 2 ⎟ qr D ⎝ qR ⎠

1− D 2

(2) Ds − 6 2

sin[(D − 1)arctan(qR ) ]

P(q, r, Ds) being the form factor referring to the single primary particle and S(q, r, D, R) the structure factor that reflects the degree of order of primary particles along the aggregates.

Ds is related to the dimensionality of the interfacial region of the primary particles, and its value must be between 2 and 3 (Ds = 2 is for smooth particles following the Porod law I µ q-4).

D is the power law exponent of the fractal aggregates.

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Figure 3 shows the combined USANS-SANS experimental data for a white italian marble (Carrara); best fit were obtained according to eq. 2, applying the same model used for the limestone. Accordingly to the marble formation process, previously highlighted, the parameter values obtained from the fit procedure show the dimension of the primary particles increases going from the protolith (limestone, r = 800 Å, Ds = 2.9) to a marble of medium metamorphic degree (Carrara, r = 4600 Å, Ds = 2).

The thin section photograph (thickness of about 20 µm) observed in transmitted polarized light is reported in figure 4; it shows the macroscopic structure of the Car-

croscopy (SEM) have shown that vermetid shells are mainly constituted by calcium carbonate in the form of aragonite. SEM pictures clearly show both the structural units of the vermetid shells and, at progressive magnification, aragonite crystals (figure 5b,c and d). Experimental data concerning both solid sample and powders have shown a power law dependence, typical of fractal behaviour. Samples are probably constituted by fractal aggregates at different length scales or, in other words, a network of fractal clusters formed by solid primary particles with a rough surface. Experiments have been also performed doing contrast matching of the solid matrix

Figure 4. Thin section photograph showing the macrostructural characteristics (i.e. fabric) of the Carrara marble sample (polarized light, crossed Nicols). Actual size is 3.5 x 2.6 mm.

Figure 5. a) Macroscopic detail of a section of the vermetid gastropod Dendropoma petraeum shell. b), c) and d) SEM pictures of the latter sample at different magnification.

rara sample which is characterized by a homogeneously granoblastic fabric (i.e. homeoblastic) with very regular crystal boundaries, giving an overall polygonal to mosaic configuration (average grain size 0.35 mm). This is due to metamorphic equilibrium reached over very long time at the metamorphic temperature (300-400° C) [7].

USANS-SANS combined measurements were carried out to reveal fractal patterns in biogenic platforms, in particular the case of reefs built by Dendropoma petraeum.

A typical feature of many tropical and temperate rocky shores is the development of biogenic platforms at tide level resulting from a massive overgrowth of the cylindrical shells of vermetid gastropods. In the Mediterranean area, the vermetid gastropod Dendropoma petraeum is the dominant reef building species along the lower midlittoral fringe. Preliminary observations on macroscopic samples suggested that vermetid growth follows a fractal pattern (figure 5a). SANS and USANS measurements have been performed on a series of samples coming from different locations along the shoreline near Palermo (Sicily, Italy). Preliminary investigation by means of X rays diffraction and scanning electron mi-

(calcium carbonate) with a mixture of D2O and H2O in order to obtain structural information on the interfacial structure of wet sample. If a pore network is totally filled by the solvent and the contrast matching condition is reached, then the scattering from this system would be negligible but when the solvent partially fills a pore network then scattering from the part of the network filled by the liquid is negligible and only the scattering from the porosity that is effectively closed to the liquid will be measured. One contrast matching condition has been measured and a network of fractal clusters has been observed. In figure 6 it is reported the combined USANSSANS pattern in the best contrast match condition (D2O/H2O 70% w/w). Best fit were obtained by considering the system characterized by two length scales Lmax and Lmin. Above Lmax (about 1600 Å) the system is characterized by a surface fractal structure and experimental data have been fitted using eq. 3 [8,9] with a outer cut-off length of 5000 Å and Ds = 2.7. At shorther length the system shows a power law I µ q-α) with α < 3 characteristic of a pore (or mass) fractal and therefore eq. 4 can be used.

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I(q) = q–1Γ(β)Lβcut [1+(qLcut)2]–β/2 sin[(Ds-1) arctan(qLcut)] (3) where β = 5 – Ds .

I(q) = Ip [1+(qLmin/2)–Dp]e–q2L2min/20

(4)

The latter equation can be used for a network as a consequence of the aggregation of spherical pores of diameter Lmin and fractal dimension Dp (in this case Lmin = 88 Å and Dp = 2.48). The structure factor is represented by the term in brackets while the form factor is represented by the Guinier approximation for the scattering from a sphere of diameter Lmin.

structure with fractal dimension Dm = 2.65 and outer cutoff limit of 20000 Å, while at shorter distances a surface fractal structure can be seen (Lcut = 47.5 Å and Ds = 2.65) Finally, we present time and temperature resolved USANS experiments on a 25.3% w/v (indicated as B25) of the tri-block 25R5 reverse pluronic TM in D 2O. In the coblock each ethylene oxide (EO) segment are linked to two propylene oxide (PO) moieties. The polymer 25R5 corresponds to (PO)18-(EO)48-(PO)18 formulation. Previous time-of-flight (TOF) SANS experiments performed on this solution indicated a dramatic change of the forward scattering, upon heating the solution between room temperature and 60 °C. In particular, between 20

Figure 6. USANS and SANS data for a sample of dinosaur bone tissue.

Solid lines represents best fit to the eqs. 1 and 3.

Figure 8. Time resolved scattering patterns of the tri-block PPO-PEOPPO solution B25. The patterns were recorded within time frames of 20 minutes. Only selected patterns are shown in this graph. It can be seen clearly, that forward scattering increases with time.

Figure 7. USANS and SANS data for a sample of vermetid gastropod Dendropoma petraeum shell. Solid lines represents best fit to the eqs. 3 and 4.

Figure 9. Temperature dependant scattering patterns of the tri-block PPO-PEO-PPO solution B25. Forward scattering (I0) increases up to 32°C. From 33°C to 45°C I0 decreases dramatically to jump at 50°C into a DABlike scattering behaviour with p=6.

Figure 7 reports another example of neutron scattering from a biological sample: a dinosaur bone tissue. The combined USANS-SANS experimental data were fitted using a linear combination of equation 1 and 3. At length scales above 1300 Å the system exhibit a mass fractal

°C and 50 °C the system showed a gradual change in the degree of order. Figure 8 shows some selected time resolved scattering patterns of the tri-block recorded at 20 °C, immediately after preparing the solution. The acquisition time of each frame was 20 min. The increase of

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the scattering intensity with time indicates that the systems gets increasingly ordered with time and that clusters in the micrometer range are eventually formed. After approximately 3 hrs the structural changes of the system decline. At this point, a series of isothermal scattering experiments have been performed. Scattering frames of 20 min were recorded for a series of temperatures in the range 31-50 °C (figure 9). Since beginning the scattering patterns show an increase of forward scattering as a consequence of the formation of clusters.

From 33°C to 45 °C, the forward scattering decreases more than one order of magnitude, indicating increased disassembling of the clusters. In this temperature range

Conclusions Application of the combined USANS SANS techniques on a variety of systems has been here presented. Modeling of the experimental data, by means of the different scattering equations, have permitted to derive structural parameters and better understanding of the various systems up to length scales that, in some cases, overlap with the traditional microscopy techniques.

Acknowledgements We wish to thank the many colleagues and friends who helped us with the experiments reported here, particularly G.D. Wignall and J. S. Lin (ORNL, Oak Ridge, USA), R. K. Heenan (RAL, Chilton, UK), M. Baron (ILL, France), E. Uccello, S. Rotolo, I. Donato, S. Riggio and T. Dieli (University of Palermo). Financial support from CNR, European Community (for the program “Jülich Neutrons for Europe” under the 6th EU Framework Programme) and INFM is gratefully acknowledged.

References

Figure 10. Temperature dependant USANS and SANS combined patterns of the tri-block PPO-PEO-PPO solution B25

the scattering cross section can be described by a power law with the exponent α = 3.3. The last measurement was taken at the temperature of 50°C, where a sudden jump of the scattering intensity could be recorded and the solution became turbid. The scattering behaviour can be described by the two phase Debye–Anderson– Brumberger model (DAB) [10], with the exponent p = 6 as expressed in eq. 5.

I( q) = 8π a 3 φ 1φ 2 (∆ρ ) 2

1 1 + q 2a 2

p

1. M. M.Agamalian, G. D. Wignall, and R. Triolo, J. Appl. Cryst., 30, 345349, (1997).

2. M.M. Agamalian, A.R. Drews, J.G. Barker, C.J. Glinka, Physica B, Vol. 241-243, 189-191, (1998).

3. www.fz-juelich.de/iff/wns_kws3, www.fz-juelich.de/iff/wns_kws2 4. M. Hainbuchner, M. Villa, G. Kroupa, G. Bruckner, M. Baron, H. Amenitsch, E. Seidl, and H. Rauch, J. Appl. Crystallogr., 33, 851-854, (2000).

5. D.W. Schaefer and K.D. Keefer, Phys. Rev. Lett., 53, 1383-1386 (1984).

6. A. Emmerling, R. Petricevic, P. Wang, H. Scheller, A.Beck and J. Fricke, J. Non-Cryst. Sol., 185, 240-248 (1994).

7. C. Gorgoni, L. Lazzarini, P. Pallante and B. Turi, An updated and detailed reference database for the main Mediterranean marbles used in antiquity, Interdisciplinary studies on ancient stone, J. J. Herrmann, N. Herz and R. Newman eds, 115–131, Archetype, London (2002).

8. D.F.R Mildner. and P.L. Hall, J. Phys. D, 19, 1535-1545 (1986).

(5)

where a is the correlation length, ∆ρ is the scattering length density difference (contrast) and φ1 and φ2 represent the volume fractions of the two phases. The time resolved USANS series were taken in time frames of 30 min covering the q-range from 2x10-5 to 2x10-3 Å-1.

A clearer picture of the change in structure just described can be seen in figure 10 where we have reported USANS and SANS data at three temperatures, representative of different structure regimes.

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Paper received June 2004

STAR-LIKE POLYMER SOLUTIONS STUDIED

BY LIGHT AND NEUTRON SCATTERING G. Di Marcoa, N. Micali a, R. Ponterio a, V. Villari a, A. Heinemann b a) CNR - Istituto per i Processi Chimico-Fisici del CNR Sez. Messina, Via La Farina 237, I-98123, Messina, Italy

b) Hahn-Meitner-Institut, BENSC, Glienicker Strasse 100, D-14 109, Berlin, Germany

Introduction Linear, branched and hyper-branched polymers have different and unique mechanical, rheological and solution properties that depend on the chain structure and on both the type and degree of branching.[1,2] Such a wide tuning of the macroscopic behaviour starting from modifying branching junctures had attracted a great deal of interest not only for the application in the industrial and biomedical fields,[3-5] but also for an academic point of view.[6-8] The main goal in the study of polymers consists in finding a direct correlation between macromolecular chain structure and its macroscopic properties and in describing the system by using an ef-

structural properties of the polymer of poly(ethylene glycol) ethyl ether methacrylate (so-called pPEGMA [10]) in solution by Neutron Scattering, which shows, together with results previously obtained by some of us

by Light Scattering[11], that in particular solvents, the single polymer entity can take a star-like conformation, in which the methacrylate backbone is confined in the inner part (where solvent does not penetrate) by the PEO side chains.

Structure of pPEGMA pPEGMA is a graft polymer composed by oligomeric PEO units grafted to inert methacrylate chains (Fig.1).

Fig. 1. Monomer structure.

fective interaction between chains. Once this goal is reached the structure and thermodynamics of polymer solutions, as phase transitions, can be predicted.

A special class of branched polymers is constituted by the star-polymers whose physical properties, depending on the number of arms grafted to the central core, can change from those of polymers to those of colloid-like systems.

A great deal of interest, moreover, has been devoted to the formation of various structures constituted by polymer chains containing both hydrophobic and hydrophilic segments. Graft copolymers with side chains which are chemically different from the backbone take a great relevance, because their properties can be modulated by the combination of selective interactions with solvents. This occurrence implies a high engineering potential. [9] The results presented here report on a study of the

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â&#x20AC;˘

PEGMA, was already successfully used as polymeric matrix for the fabrication of electrochromic devices; [12-14] it joins the properties of both components: the PEO units assist the ionic diffusion when coupled with the salts and the inert metacrylate chains is useful in minimizing the crystallinity of the overall system. It represents one of the most reliable candidates in many applications, but, notwithstanding the large technological use, some structural mechanisms are not fully understood at the moment. The characterization of this polymer in solution would allow for a better understanding of its inner structure in the amorphous state and, then, for improving its efficiency. pPEGMA solutions have been prepared at different concentration in deuterated ethanol in a concentration range from 10-3 to 0.082 g/cm3 at a constant temperature value of 25°C.

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Summary of Light Scattering results The most general formula indicating the absolute scattered intensity from a system, under the assumption of a solution of monodisperse and centrosymmetric particles and under the hypothesis of independence of intermolecular and intramolecular averages, is: I(Q) ∝ P(Q)S(Q)

(1)

P(Q) and S(Q) being the normalized form factor and the structure factor respectively.

In a Light Scattering experiment equation (1) indicates the absolute excess scattered intensity from an isotropic system constituted by monodisperse particles, when illuminated with a monochromatic linearly polarized light:[15] I(Q)=HMWcP(Q)S(Q)

(2)

where c is the concentration in g/cm3, MW the molecular weight and H the optical constant equal to [16]: 2 2 4π n 4 λ 0N A

⎛ dn ⎞ ⎜ ⎟ ⎝ dc ⎠

vestigated concentration range the scattered intensity did not depend on Q, indicating that particles are too small to be “seen” by Light Scattering; therefore, it was be set P(Q)=1. For the interpretation of the absolute scattered intensity in the whole range of concentration (see Fig.2) a model for the concentration dependence of S(Q) is required. The Elastic Light Scattering experiment involves low Q values so that we used exact solutions for models implying S(0).

After having used the simple hard sphere solution of the Ornestein Zernike equation[17] for S(0) ([S(0)]–1 = 1+8φ, φ being the volume fraction) and checked the effect of a repulsive potential to be added to the hard sphere model, through a positive quadratic term in φ to the osmotic pressure,[18,19] without finding a fit result good enough, we took into account intermolecular attractive interactions together with the excluded volume interactions adopting the Baxter’s adhesive hard sphere model[20-22]. It describes the potential U(r) for a sphere of radius R as:

2 U( r) k BT

.

In the latter n is the refractive index of the solvent, λ0 the wavelength of light in vacuum and NA the Avogadro’s number.

As reported in reference [11], for the static and dynamic properties of pPEGMA/ethanol solutions we used a home made computer controlled goniometric apparatus with a duplicate Nd:YAG (532nm) laser linearly polarized orthogonally to the scattering plane. In the whole in-

Fig. 2. Absolute scattered intensity as a function of concentration. Black points refer to Static Light Scattering data (left Y-axis) and yellow points refer to Small Angle Neutron Scattering (right Y-axis). Both data sets are taken at low Q. Continuous line is the fit of the Static Light Scattering (SLS) data according to the Baxter’s potential.

⎧∞ ⎪ = ⎨− Ω ⎪0 ⎩

for 0 < r < R' for R' < r < R

(3)

for r > R

where R-R’ is the thickness of the adhesive layer, Ω the adhesive potential and kBT the thermal energy.

The analytical solution of the Ornstein-Zernike equation was found by Baxter in the Percus-Yevik approximation,[23] in the limit (called “sticking sphere” model) that the thickness approaches to zero but the stickiness parameter 1/τ=12exp [(R-R’)/R], remained finite. It is:

Fig. 3. Diffusion coefficient as a function of concentration. The vertical dashed lines indicate the crossover region.

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[S (0 )]

−1

= 1 + (8 −

2

)φ +

τ

18τ + 192τ

3

6τ

− 90τ 3

2

−1 2 φ

(4)

Fig.2 shows the fit according to the Baxter’s model from which, considering also equation (2), 1/τ=0.7±0.2, MW=45000 ± 2000 and c/φ=0.18 ± 0.01 g/cm3. The corresponding sphere radius was R≈5nm. The value of the overlap concentration, which defines the crossover to the semidilute regime, was obtained by the diffusion coefficient behaviour (dashed region in Fig. 3).

In the low concentration region the behaviour of D is described by the relation:[24-26] D=D0(1+kDc), being D0 the diffusion coefficient at infinite dilution and kD the dynamic virial coefficient. From D0, through the EinsteinStokes relation [24]

RH =

k BT 6πηD

(η being the solvent viscosity), the hydrodynamic radius of the polymer is obtained: it is RH=8.5 ± 0.5 nm. Increasing concentration above the dilute regime a crossover is

understood by looking at Fig.4, in which the representation of the more plausible pPEGMA conformation is reported. It looks to have a more compact solvent impenetrable zone in the inner part, where the methacrylate backbone is confined by the grafted swollen (short) PEO chains, so miming a sort of star-polymer.

Viewing pPEGMA as a star-like polymer, from the measured molecular weight the average number of PEO arms was estimated to be close to 135. Therefore, attractive intermolecular interactions can be attributed both to the depletion of the solvent because of the interpenetration of the arms and to the interaction between PEO arms. In fact, ethanol is a worse solvent than water for PEO, and polymer-polymer interaction can become competitive with the polymer-solvent interaction contribution.

Neutron Scattering experiment Once the system was characterized by Light Scattering and a conformation hypothesized, Small Angle Neutron Scattering (SANS) measurements are extremely useful in giving information on polymer size and in indicating if conformation is maintained also in the semidilute region beyond the overlap concentration.

The neutron scattering experiment was carried out us-

ing the SANS instrument V4 at the BENSC Facility of

Fig. 4. pPEGMA conformation for a number of arms equal to 48 performed using the ChemOffice energy minimization (MM2).

observed indicating the beginning of the semidilute region in which the linear behaviour is not fulfilled and data obey a power law with an exponent equal to 0.7, in agreement with that predicted by de Gennes[27,28].This crossover concentration represents the value at which spheres of radius RH come into contact.

The physical origin of the attractive interaction can be

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Fig.5 Scattering cross section at different concentration values: c=0.00095 g/cm3, c=0.002 g/cm3, c=0.0039 g/cm3; c=0.0059 g/ cm3, c=0.008 g/cm3, c=0.016 g/cm3, c=0.032 g/cm3, c=0.082 g/ cm3.

the Hahn-Meitner-Institute in Berlin. The two dimensional scattering contours were corrected for detector efficiency, instrumental background and transmission and converted (the program BerSANS was used) to scattering cross sections per unit volume using water for calibration. The resolution of the instrument in this configuration, λ/λ=0.1, was also taken into account in the data analysis.

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In a Small Angle Neutron Scattering experiment equation (1) becomes: I(Q)=N[Σibi -ρ0υpol]2P(Q)S(Q)

(5)

where N is the polymer number density, bi the atom scattering lengths, ρ0 the scattering density of the solvent and υpol the volume occupied by the polymer.

SANS spectra of pPEGMA/deuterated Ethanol are shown in Fig.5. Because at high Q values the coherent SANS cross section is superimposed to the incoherent background due to the hydrogen atoms of the polymer chains, the flat background at higher Q for different concentration has been subtracted before starting with the data analysis.

As it can be seen, the Structure Factor contribution becomes more and more evident increasing concentration above c=2.2x10-3 g/cm3. In fact, from an inspection of Fig.2, the intensity at low Q from SANS displays the same behaviour obtained by Light Scattering,[11] indicating that interactions are present at relatively low concentration values.

At the lowest concentration the interference effects can be considered negligible, so that the cross section of this

where ξ is the correlation length of the density distribution. It results ξ =5 nm.

Using the Kratky plot (Fig.7) is useful in describing the overall shape of the polymer chain molecule: in essence, the Kratky plot shows a clear peak for a compact conformation, but has a plateau shape and then increases monotonically for a flexible chainlike molecule. The peak present at all concentration values indicates that chains take a globular conformation and maintain it, at least up to c=0.082 g/cm3. From the peak position the radius of gyration can be determined by the Benoit form factor for star-polymers: [29]

P (Q ) =

2 4 fv

⎧ ⎨ ⎩

v=

2⎫

[v 2 ] − [1 − exp(−v 2 )] + f 2− 1 [1 − exp(−v 2 )] ⎬⎭ (7) f

QR g

3f −2 where and f is the functionality, that, in our case, is equal to the polymerization degree of the chain, namely 135, as evaluated by Light Scattering.[11] Although this method is strictly valid only for the θ state the obtained value of the radius of gyration is compatible with the correlation length.

Fig. 6. Inverse scattering cross section normalized by concentration for the most dilute solution. The continuous line is the fit according to relation (6).

Fig. 7. Kratky plot at c=0.008, as an example.

sample represents the “effective” form factor of the polymer. Up to Q=1 nm-1 the plot of the inverse normalized coherent cross section as a function of Q2 is linear (Fig.6), indicating that chains are not fully contrasted, but rather their distribution density decreases as described by the Ornstein-Zernike law:[17]

Conclusions Neutron Scattering measurements give clear information for completing the characterization of the polymer pPEGMA. In particular: - Chains take a globular shape with a more compact core constituted by the solvent phobic methacrylate part and a less compact shell around constituted by the more soluble PEO arms. The pattern related to the diffraction from the particle, in fact, indicates a non-homogeneous object whose correlation length is equal to 5 nm.

I (Q ) =

I (0 ) 2 2 1+ Q ξ

(6)

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- This star-like conformation could be responsible for the attractive part in the interparticle potential because the interpenetration of PEO arms can deplete the solvent or because of the fact that the quality of the solvent makes polymer-polymer and polymer-solvent interaction competitive.

- SANS data indicated that, at least up to 0.082 g/cm3, chains maintain their globular conformation without giving rise to any gel-network structures.

Further investigation are in progress in order to understand how the interaction with different solvents can affect the conformation of the chains or favour aggregation processes.

References 1. G.S. Grest, L.J. Fetters, J.S. Huang, and D. Richter, Adv. Chem. Phys.

XCIV, 67 (1996).

2. J. Roovers, L. Zhou, P.M. Toporowski, M. van der Zwan, H. Iatrou, and N. Hadjichristidis, Macromolecules 26, 4324 (1993).

3. H. Xie, and P. Zhou, Adv. Chem. Ser. 211, 139 (1986).

4. F.L. Baines, S. Dionisio, N.C. Billingham, and S.P. Armes, Macromolecules 29, 3096 (1996).

5. B. Wesslen, M. Kober, C. Freij-Larsson, A. Ljungh, and M. Paulsson, Biomaterials 15, 278 (1994).

6. M. Watzlawek, C.N. Likos, and H. Lowen, Phys.Rev. Lett. 82, 5289 (1999).

7. C.N. Likos, H. Lowen, M. Watzlawek, B. Abbas, O. Jucknischke, J. Allgaier, and D. Richter, Phys. Rev. Lett 80, 4450 (1998).

8. C. von Ferber, A. Jusufi, M. Watzlawek, C.N. Likos, and H. Lowen, Phys. Rev. E 62, 6949 (2000).

9. H.A.J. Battaerd, G.W. Treager, Graft Copolymers (Wiley-Interscience, 1967).

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â&#x20AC;˘

10. G. Di Marco, M. Lanza, A. Pennini, and F. Simone, Solid State Ionics 127, 23 (2000).

11. N. Micali, V. Villari, Phys. Rev. E, 67, p. 41401 (2003).

12. A. Pennisi, F. Simone, G. Barletta, G. Di Marco, M. Lanza, Electrochim. Acta, 44, 3237 (1999).

13. G. Di Marco, M. Lanza , A. Pennisi, F. Simone, Solid State Ionics 127, 23 (2000).

14. F.M. Gray, Polymer Electrolytes (Royal Soc. Chem., Cambridge, 1997).

15. N. Micali, F. Mallamace, in Light Scattering. Plrinciples and Developments, ed. W. Brown, p.381 (1996).

16. dn/dc=0.25 cm3/g and it is constant in the whole investigated concentration range.

17. L.S. Ornstein, and F. Zernike, Proc. Acad. Sci. Amsterdam 17, 793 (1914).

18. A.M. Cazabat, In Physics of Amphiphiles: Micelles, Vesicles and Microemulsions, International school of physics Enrico Fermi, Course XC, edited by V. Degiorgio and M. Corti (North-Holland 1985), p.723.

19. A.A. Calje, W.G.M. Agterof, and A. Vrij, in \emph{Micellization, Solubilization and Microemulsion}, vol. 2 (New York 1977).

20. R.J. Baxter, J. Chem. Phys. 49, 2770 (1968).

21. L. Lobry, N. Micali, F. Mallamace, C. Liao, and S.H. Chen, Phys. Rev. E 60, 7076 (1999).

22. Y.C. Liu, S.H. Chen, and J.S. Huang, Phys. Rev. E 54, 1698 (1996).

23. J.K. Percus, and G.J. Yevik, Phys. Rev. 110, 1 (1958).

24. Berne, B.J.; Pecora, R. Dynamic Light Scattering with Application to Chemistry, Biology and Physics, J. Wiley and Sons:New York, 1976.

25. Cummins, H.Z. Photon Correlation and Light Beating Spectroscopy; H.Z. Cummins and E.R. Pike, Eds.; Plenum Press: New York, 1974.

26. Schaefer, D.W.; Han, C.C. Dynamic Light Scattering, ed. R. Pecora Plenum: New York, 1985.

27. P.G. de Gennes, Scaling Concepts in Polymer Physics (Cornell Univ.

Press, Ithaca, New York, 1979) 28. M. Rubinstein , R.H. Colby, and A.V. Dobrynin, Phys. Rev. Lett. 73, 2776 (1994).

29. L. Willner, O. Jucknischke, D. Richter, J. Roovers, L.-L. Lin, and N. Hadjichristidis, Macromolecules, 27, 3821 (1994).

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Paper received November 2004

INELASTIC ULTRAVIOLET SCATTERING BEAMLINE AT ELETTRA C. Masciovecchio1, S. Di Fonzo1, A. Gessini1, G. Ruocco2, S.C. Santucci3 and F. Sette4 1 Sincrotrone Trieste, S.S. 14 km 163,5 in AREA Science Park 34012 Basovizza, Trieste, ITALY 2 Dipartimento di Fisica and CRS-INFM SOFT, Università di

Roma “La Sapienza”, P.le A. Moro 2, 00185 Roma, ITALY 3 Università di Perugia, Dipartimento di Fisica, Via Pascoli 1, 06100 Perugia, ITALY 4 European Synchrotron Radiation Facility, 6, Rue Jules Horowitz, BP 220, 38043 Grenoble, France

Abstract The recent construction of an Inelastic UltraViolet Scattering (IUVS) beamline at the ELETTRA Synchrotron Light Laboratory opens new possibilities for studying the density fluctuation spectrum, S(Q,E), of disordered systems in the mesoscopic momentum (Q) and energy (E) transfer region not accessible by other spectroscopic techniques. We will present first IUVS results obtained on two prototype samples such as liquid water and vitreous silica. In water we were able to measure the temperature dependence of the structural relaxation time showing that the divergence in the transport properties does not need an underlying critical behaviour but can be explained in the framework of the Mode Coupling Theory. In vitreous silica IUVS experiments gave clear experimental evidence of the presence of a step in the sound attenuation coefficient at wavelengths between 6 and 60 nm thus locating a characteristic length where sound waves interfere with glass inhomogenities.

tons at the visible light wavelengths. Optical spectrometers and interferometers can, however, reach a very high energy resolving power (namely E/∆E ~ 106-108). Recently, a UV laser source has been used to push the light scattering technique up to ~ 0.07 nm-1 (HIRESUV facility - see Fig. 1).

Introduction The physics of systems without translational invariance, such as liquids, dense fluids and glasses, has been fascinating scientists for many years. The understanding of liquid-to-glass transition mechanism, thermal anomalies at low temperatures, divergence of transport properties and relaxation phenomena, is a challenge that deserves strong experimental and theoretical efforts [1]. A large amount of information about the physical properties of these systems can be deduced by the experimental determination of the density-density correlation function, F(Q,t), or, equivalently, of its Fourier Transform, the dynamic structure factor S(Q,E), in the largest momentum (Q) and energy (E) transfer region. S(Q,E) is directly measurable by experiments of inelastic scattering of radiation and neutrons [2,3].

However, a single technique cannot completely cover, by itself, the entire range between interatomic distances and the continuum scale. Visible Light (1.5 - 2.5 eV) Scattering is a useful technique for studying a large class of materials, however it has the limitation that only very low momentum transfers, not higher than ~ 0.03 nm-1, can be studied due to the small momentum carried by the pho-

Fig.1. Kinematic regions accessible from the existent instruments (DMDP2000, FP, IN5, ID16, ID28, HIRESUV). The two lines represent typical range of speed of sound measured in glass-forming systems and fluids.

On the other hand the inelastic scattering of thermal neutrons gives the possibility of studying the dynamic structure factor S(Q,E) for momentum transfers much larger than those of light scattering. In fact, with the available techniques and instrumentation, it is possible to investigate the region of momentum transfer between ~ 3 nm-1 and ~ 2500 nm-1. However, due to the kinematic of the neutron-acoustic phonon scattering process, the accessible exchanged energy region is limited. Actually, only disordered systems with sound velocity smaller than 1.5 Km/s can be investigated with the existing instruments.

High-resolving power inelastic x-ray scattering (IXS) spectrometers have been constructed recently, and are

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now available for users at the ESRF in Grenoble (ID16 and ID28). These facilities have an energy resolution of ~1.5 meV and a range of momentum transfer between 0.8 nm-1 and 25 nm-1. In this case there are basically no kinematic limitations on the exchanged energy, and IXS has been extensively used to study the collective dynamics of disordered systems [1]. The limitation at low Q, in this case, lies in the limited energy resolution.

Fig.1 shows, in a log-log plot, the regions in the (Q,E) space where the various instruments are now available, the lines of two typical velocities of sound are also displayed. From the figure one can notice that in the range of exchanged momenta between 0.07 and 0.8 nm-1 there is a kinematic region where collective dynamics cannot be excited. However, this momentum transfer range is of fundamental importance to gain insight into the structure and dynamics of disordered systems.

As a matter of fact, in contrast to the crystalline case, in disordered systems the understanding of the atomic dynamics is complicated not only by the difficulties associated with the absence of translational invariance, but al-

particles around their quasi-equilibrium position. This is of the order of the inverse of the Debye frequency, whose value is comparable to that of a corresponding crystal with similar density and sound velocity. Moreover one has to consider that the topological disorder introduces a second length scale ξ beside the interparticle distance a.

The rich phenomenology observed in the dynamics of disordered systems is, therefore, often the consequence of the interplay between these different structural (a and ξ) and dynamic (τ, tD) scales.

The collective dynamics in the absence of translational invariance can be easily treated theoretically in two limiting cases, namely excitations with characteristic space and time scales which are either very long or very short compared to the disorder scale ξ, and to the relaxation time τ. The former corresponds to the hydrodynamic limit, where the system is seen as a continuum, whereas the latter corresponds to the single-particle kinetic limit, where the particle behaviour is described as a free motion between successive collisions. In contrast, an exhaustive theoretical understanding is still not available

Fig. 2. An overview of the vacuum chamber containing the 8 m focal length monochromator and analyser units.

so by the presence of other degrees of freedom, such as diffusion and relaxation in fluids, and hopping and tunnelling processes in glasses. The presence of these processes in disordered systems naturally introduces different time-scales, τ, which are usually strongly dependent on the specific thermodynamic state. These timescales affect the collective dynamical properties differently, depending on its value with respect to the time scale tD, characterising the vibrational dynamics of the

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in the intermediate region, defined by a length-scale comparable to the correlation length of the topological disorder and by a time scale comparable to tD. The possibility to investigate collective excitations in the mesoscopic region could help in shedding light on several relevant questions on the dynamics of disordered materials. Among them, we mention the following ones: i) Is the elastic continuum theory appropriate at mesoscopic length scale where the disorder of amorphous

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systems becomes relevant? ii) What is the origin of sound attenuation in glasses? iii) With respect the Debye behaviour of the corresponding crystal, what is the origin of the excess in the specific heat and the excess in the vibrational density of states found in glasses? iv) How does the structural relaxation affect the collective dynamics in glass-forming systems?

There are other points even more specific to this Q-region that could be reminded. These are: i) The critical scattering with highest intensities in the quasi-elastic region near Q=0, ii) the study of the transition from pure hydrodynamic to either generalised or kinetic behaviour in fluids, iii) the dynamics of all macro-molecular systems which have the maximum of their structure factor in the low-Q region, like clusters, colloids, emulsions and biological systems.

The recent construction of an Inelastic Ultra-Violet Spectrometer (IUVS) at the ELETTRA synchrotron laboratory [4] contributes to reduce the existing gap in momentum transfer to less than the 0.3 - 0.8 nm-1 range. Moreover, we would like to mention another very interesting application of this instrument, which at present has got very little attention simply because of the lack of tunability of the incident photon energy in both laser and x-ray based instruments. This is the possibility to tune the incident photon energy to be resonant with an electronic excitation of the system. In this case the scattering cross section is expected to increase substantially, and, in same case by various orders of magnitude. Moreover, in the hypothesis of a resonance broader than the typical collective excitations energy, which is a fraction of meV in the considered cases, the resonant scattering will allow to study specific phenomena where the scattering signal is usually very low. Among them and of particular importance is the scattering from surface waves, which gives information on the shear moduli and therefore on the transverse dynamics of the system, a quantity that can be accessed experimentally only by indirect ways.

The resonant Brillouin scattering would also open new possibilities not yet exploited in the usual light scattering experiments, as, for example, in the determination of the dynamics structure factors of specific species (in the presence of different atomic and/or molecular species the larger signal comes from the resonant one). Also, the comparison of measurements made on- and off-resonance would give the possibility to determine a whole set of partial dynamics structure factors. Finally, taking advantage of the different tensorial properties of the resonant and non-resonant cross sections, the resonant scattering technique could also be used to separate in the scattered intensity the rotational contributions from those arising from collision induced effects.

In the next section we will describe into details the IUVS instrument design. The following two sections are re-

porting on our recent investigations on water and vitreous silica, performed by IUVS at Q values around 0.1 nm-1, a region of great interest, where peculiar dynamical behaviours are expected, as inferred by results obtained through the complementary Brillouin Light Scattering (BLS) and Inelastic X-ray Scattering (IXS) techniques [5 -8].

The instrument In order to perform IUVS spectroscopy three main requirements for the incident radiation had to be fulfilled: i) photon energy in the 5 - 11 eV range (λ ~ 240 – 110 nm), ii) incident photon flux on the sample larger than 1011 photons/s, iii) resolving power of the order of 105 to 106, necessary to resolve the typical phonon-like excitations in the energy range of interest.

Because of the high flux needed, the radiation source for the IUVS beamline at ELETTRA has to provide at least 1015 photons/s/0.1%bw. This calls for an undulator of the maximum length compatible with available length in the straight sections of the storage ring (4.5 m). This requirement naturally implies a very high-emitted power and power density, which can be harmful to the optical elements of the beamline. For such a reason an exotic insertion device, the Figure-8 undulator [9], has been constructed as an alternative to the standard vertical field device. The main advantage of this solution is a much reduced on-axis power density, which is obtained with no penalty on the useful photon flux. Using a 32 mm period figure-8 undulator with maximum deflection parameters Kx = 3.4 and Ky = 9.4, at the exit of a 600 ? 600 mrad2 pinhole the total power of the synchrotron radiation is reduced to about 20 W while the first harmonic delivers 2 ·1015 photons/s/0.1%BW. The beam coming from the source has to be cleaned from the high order undulator harmonics and, for this reason, three reflections have been used allowing also the transfer of the radiation into the monochromator stage. More specifically the beam impinges on a gold coated GLIDCOP mirror internally water-cooled, which deviates the photons in the vertical plane with an angle of 6o. A second externally water-cooled silicon mirror is used to bring back the beam parallel to the floor.

The beam is then focused by a spherical silicon mirror onto the entrance slits of the monochromator with a demagnification 20 : 1 and with an incident angle of 85o.

Being the source size roughly 1 x 1 mm2, a spot of 50 x 200 µm2 (vertically the astigmatism makes the focus a larger) is obtained on the entrance of the monochromator. The Czerny-Turner Normal Incidence Monochromator (NIM) optical design has been chosen for the monochromator [10]. This design has the most desirable features when working below 11 eV, namely, resolution, high light-gathering power, simple scanning mechanism,

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and the advantages of fixed exit and entrance slits with no deviation in the direction of the exit beam. In this design light from the entrance slit is rendered parallel by a spherical concave mirror and reflected onto an echelle plane grating. A second spherical mirror that collects the diffracted beam and focuses it on the exit slit. The relative energy resolution, assuming that the intrinsic contribution coming from the grating is negligible, is given by the formula: (∆E/E) = δcotθ/2F, where δ is the slit opening, F is the focal length of the spherical mirror and θ is the blaze angle. Using δ = 50 µm, F = 8 m and θ = 70°, we get a relative resolution of 1.1·10-6. We decided to built 8 m focal length monochromator to match the best compromise between needed resolving power and mechanical feasibility. The grating used has 52 lines/mm and works at a blaze angle of 69o (∆E/E = 1.2·10-6).

At the exit of the monochromator the beam is impinging on a spherical mirror, which focuses the radiation on the sample on a spot size of about 30 x 100 µm2. A second spherical mirror is used to collect the radiation scattered from the sample and send it to the entrance slit of the analyser unit that has the same design as the NIM monochromator. The inelastic scattering spectra are collected by a low noise Peltier-cooled CCD camera placed at the

Fig. 3. Selection of inelastic UV scattering spectra of liquid and supercooled water (dots), taken at 6.7 eV incident photon energy and 0.09 nm-1 momentum transfer, at the indicated temperatures. The fit lines are superimposed. The red line is the experimental resolution.

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focal plane of the analyser, which allows to register the inelastic spectrum in one single shot, thus avoiding timeconsuming monochromator scans of the diffraction angle. The quantum efficiency of the detector is larger than 10% for incident energies in the 5 - 15 eV. The momentum transfer can be varied by changing the scattering angle φ and depends on the refraction index of the sample n via the formula: Q = (4πn/λ) sin(φ/2) being λ the incident photons wavelength.

The instrumental energy resolution has been measured by collecting the isotropic scattered intensity from a high roughness copper surface tilted with respect to the beam of about 40o. The measured instrumental relative energy resolution is ∆E/E = 2·10-6 indicating that the obtained performance is very close to the theoretical expectation 1.7·10-6 given by the convolution of the energy resolution of the analyser and the one of the monochromator. Fig. 2 is a picture of the vacuum chamber containing the monochromator and analyser optics.

Water Water has always occupied a unique role in the physics of liquids. Nevertheless, the scenario of properties like the negative melting volume, the density maximum in

Fig. 4. Structural relaxation time of water as a function of temperature.

Here we compare our IUVS results (solid blue circles) with IXS measurement (open squares [5]). The IXS results were interpreted as an Arrhenius behavior (dotted line). IUVS matches is the best sensitivity condition to supercooled water timescale below T ~ 280, where IXS becomes evidently less reliable. A power-law divergence of τ(T) towards 220 K has been obtained, in good agreement with Mode Coupling Theory predictions (MCT) (solid line). In the inset we show the temperature independence of the structural stretching parameter (solid diamonds) as foreseen by MCT.

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tural relaxation process. We analyzed the spectra with the viscoelastic model for the S(Q,E) [5], in the MCT framework. Details about the analysis are reported elsewhere [16]; here, we want to stress two main points: MCT foresees a stretched exponential behavior for the density autocorrelation function F(Q,t): F(Q,t) ∝ exp - (t/τ)β

(1)

where τ is the characteristic time of a structural relaxation process and β is the stretching parameter, predicted to be less than unity. Moreover, according to MCT, τ follows a power law divergence as a function of temperature [15]: Fig. 5. Inelastic ultraviolet scattering spectra of vitreous silica at the indicated temperatures. The full lines are the best fit to the data as discussed in the text. The dashed red line represents the instrumental function.

the normal liquid range -which makes this substance so fundamental in life and earth- as well as the apparent divergence of the transport properties in the supercooled temperature region, is still far from being well settled [11]. Different models have been proposed to explain the anomalous behaviour of water: 1) the existence of two liquid phases where a second critical point is supposed to be situated in the “no man’s land” temperature region [12,13]; 2) a singularity-free scenario model according to which the thermodynamic anomalies are ascribed to the presence of structural heterogeneities [14], and 3) the Mode Coupling Theory (MCT) which describes water features without resorting to an underlying thermodynamic singularity [15]. In this context, the need for experimental evidences, which can discriminate among these interpretative models, is evident. Although measurements of the S(Q,E) were performed by IXS [5] and BLS [6], a conclusive point was not reached, basically due to the fact that the best sensitivity condition (ωPτ ~ 1, where ωP is the frequency of the sound waves probed in the experiment and τ is the relaxation time) was never matched in the supercooled regime. As we will show in the following, IUVS frequency window matches the condition ωPτ ~ 1, allowing a precise determination of the relaxation parameters.

We performed IUVS measurements of dynamic structure factor of high purity H2O between 260 and 340 K, at 6.7 eV incident photon energy, and 0.09 nm-1 exchanged momentum. Further details about experimental setup can be found in [16].

In Fig. 3 we show a selection of IUVS spectra of liquid and supercooled water. The clear broadening of the Brillouin peaks – which is not resolution limited, as emphasized by superimposing the resolution function on the spectrum at 302.5 K – is the manifestation of the struc-

τ(T) ∝ (T–TMCT)–γ

(2)

MCT calculations and Molecular Dynamics simulations [17] have estimated the divergence temperature TMCT of water to be in the 220–230 K interval and γ =2.3 ± 0.2.

By fitting the model function reported in [16] to the IUVS spectra, we determined the temperature dependence

Fig.6. UPPER PANEL: Line-width parameter Γ (~ sound attenuation) in glassy SiO2 as a function of temperature, at Q=0.08 nm-1 (blue circles) and at Q = 0.035 nm-1 (green squares and diamonds). LOWER PANEL: Γ as a function of the exchanged momentum Q, for vitreous silica at the indicated temperatures. UIVS results are reported as blue dots. The dotted lines represent the two distinct Q2 behaviors, which are the best fit to Γ(Q) at high and low Q.

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of both the structural relaxation time and the stretching parameter of liquid and supercooled water. The obtained values are displayed in Fig. 4. Concerning the relaxation time, the comparison to IXS results of Ref. [5] shows the good agreement between the two techniques above room temperature. One can appreciate that, below 280 K, IXS values of τ become less reliable, while IUVS data show a clear deviation from the previous Arrhenius fit (dotted line) of high-temperature IXS data.

The MCT power-law expressed in Eq. (2) is able to reproduce the whole dataset of IXS and IUVS τ -values.

The power law diverges at TMCT = 220±10 K, and has an exponent γ = 2.3±0.2, in good agreement with previous determinations [17]. Moreover, the stretching parameter is temperature independent and close to 0.6, consistently with the value of γ as predicted by the MCT [15].

Our results strongly support the idea that, at ambient pressure, the divergence of the relaxation time in water has a dynamic origin, thus releasing the need of an underlying thermodynamic singularity for its explanation.

Vitreous Silica The interest towards the attenuation of sound waves in glasses is motivated by the still unsettled problem of the determination of its microscopic origin [18]. The acoustic absorption of SiO2 is quite constant with temperature above ≈100 K [19] and shows a quadratic dependence on Q both in BLS investigation range [8-10], that is up to Q ≈ 0.04 nm-1, and in IXS range [20] 1 - 10 nm-1.

The recent model of J.Fabian and P.B.Allen [18], explains both the T independence of attenuation and the Q2 behavior, suggesting that anharmonicity, i.e. the coupling of acoustic modes and thermal vibrations, can induce sound attenuation at ultrasonic and hypersonic frequencies. This model is supposed not to extend up to IXS frequencies, being limited below ≈100 GHz. The Q2 behavior in the THz region, obtained also in harmonic simulations of the glass, has been attributed to the topological disorder [20, 21].

A crossover regime in the attenuation mechanism can be thus inferred in the mesoscopic Q-range between 0.04 and 1 nm-1, which just corresponds to the IUVS investigation domain [7].

We availed ourselves of IUVS the machine to gain information about sound attenuation in glassy SiO2, in the unexplored region of transferred momentum between 0.078 and 0.105 nm-1 [22].

We measured the dynamic structure factor S(Q,E) of SiO2 between 25 and 300 K both using the undulator radiation and the 244 nm incident radiation generated by the UV-laser source.

In Fig. 5 we show a selection of IUVS spectra. The full lines are fits to the data; we used a model function made by the convolution of the experimental resolution func-

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tion with a Damped Harmonic Oscillator (DHO) model for the inelastic peaks [23].

This model for the S(Q,E) gives an appropriate estimate of the linewidth Γ of the Brillouin line both in the liquid and in the glassy state of matter [24]. Γ is simply related to the acoustic attenuation coefficient α through the relation Γ = 2α/hc.

In the upper panel of Fig.6 we report, as a function of temperature, the Γ/Q2 values obtained by the analysis of IUVS data of Fig.3. The values of Γ/Q2 taken from literature are also shown. Fig.6 demonstrates that, above ≈ 130 K, where a broad maximum can be inferred, IUVS and BLS data rescale into a single master-plot when Γ is normalized to Q 2. Moreover Γ(T) as measured by IUVS shows slight temperature dependence below 200 K. These results are in striking agreement with the model of Fabian and Allen for the acoustic attenuation in amorphous systems, based on the coupling of acoustic phonons with thermal vibrations (see Ref. [18], Fig. 2).

The smearing out of the peak at ≈ 130 K can be ascribed to the different Q-dependence of its intensity with respect to the high temperature plateau [19].

In the lower panel of Fig.6 we report the Q dependence of Γ. We found that the same quadratic dependence describes both BLS and IUVS data up to 0.105 nm-1, while such Q2 behavior, found at low Q’s, does not extrapolate up to IXS points that exhibit a higher attenuation and are evidently shifted up. In fact, the contribution to the attenuation from nonlinear effects should reach a plateau above some 0.1 nm-1[18] while the attenuation in the high Q regime should be dominated by topological disorder [25].

This comparison is the evidence that a change of attenuation mechanism occurs between Q=0.105 nm-1 and 1 nm-1. Further measurements are currently under development as a function of Q, in the mesoscopic region spanned by IUVS, in order to characterize this intriguing change in regime.

Conclusions In conclusion, we have shown the ability of inelastic UV scattering to study the collective dynamics of disordered systems in a kinematic region not accessible before.

In the case of water we determined the temperature dependence of the structural relaxation parameters in the temperature region where the transport properties start to diverge (i. e. in the undercooled region). The temperature behaviour of the structural relaxation time and stretching is in agreement with the mode coupling theory predictions, showing that, at ambient pressure, the divergence in the transport properties has a dynamic origin.

We have also shown some capabilities of IUVS technique in studying the sound attenuation mechanism in

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amorphous solids. In particular, the results obtained in SiO 2 support the anharmonicity model proposed by Fabian and Allen [18]. Also in this case, it is evident the unique role of Inelastic Ultra Violet Scattering in accessing the mesoscopic region, where a change of regime is expected in SiO2 attenuation coefficient, which cannot be revealed by means of other techniques.

Acknowledgements We wish to acknonwledge M. Altarelli for his vision and enthusiastic collaboration in the realization of yhe beamline project.

References 1. J. Jackle, Reports on Progress in Physics 49, 171, (1986). For recent reviews, see, for instance, Proceedings to the 3rd Workshop on Nonequilibrium Phenomena in Supercooled Fluids, Glasses and Amorphous Materials, Pisa, Italy, 2002 [Journal of Physics of Condensed Matter; 15, (2003); Proceedings to the 4th International Discussion Meeting in Relaxations in Complex Systems, Hersonissos, Crete, 2001 [Journal of Non-Crystalline Solid 307–310, 1–1080 (2002)]; Proceedings to the 8th International Workshop on Disordered Systems, Andalo, Italy, 2001, [Philosophical Magazine 82, No. 3 (2002)].

2. J.P. Boon and Sidney Yip, Molecular Hydrodynamics (McGraw-Hill, New York, 1980).

3. B. J. Berne and R. Pecora, Dynamic Light Scattering with applications to chemistry, biology and physics (Wiley, New York , 1976).

4. C. Masciovecchio, D. Cocco, A. Gessini, Proceedings of 8th International Conference of Synchrotron Radiation Instrumentation, San Francisco, California, 25-29 Aug 2003 (Warwick, American Institute of Physics, 2004), p. 1190.

5. G. Monaco, A Cunsolo, G. Ruocco, F. Sette, Physical Review E 60, 5505, (1999).

6. A. Cunsolo, M. Nardone, Journal of Chemical Physics 105, 3911,(1998).

7. G. Ruocco, F. Sette, R. Di Leonardo, D. Fioretto, M. Krisch, M. Lorentzen, C. Masciovecchio, G. Monaco, F. Pignon, T. Scopigno, Physical Review Letters 83, 5583, (1999).

8. R. Vacher, J. Pelous, Physical Review B 14, 823, (1976).

9. T. Tanaka, H. Kitamura; Nucl. Instr. and Meth. in Phys. Res.; A 364, 368, (1995).

10. M. Czerny and A.F. Turner, Z. Physik; 61, 792 (1930).

11. O. Mishima, E. Stanley, Nature 396, 329, (1998).

12. P.H. Poole, F. Sciortino, U. Essmann, and H.E. Stanley, Nature 360, 324, (1992).

13. O. Mishima , H.E. Stanley, Nature 392, 164, (1998).

14. P.H. Poole, F. Sciortino, T. Grande, H.E. Stanley, C.A. Angell, Physical Review Letters 73, 1632 (1994); T.M. Truskett, P.G. Debenedetti, S. Sastry, S. Torquato, Journal of Chemical Physics 111, 2647, (1999).

15. W. Goetze, L. Sjogren, Reports on Progress in Physics 55, 241, (1992).

16. C. Masciovecchio, S.C. Santucci, A. Gessini, S. Di Fonzo, G. Ruocco, and F. Sette, Physical Review Letters 92, 255507, (2004) 17. P. Gallo, F. Sciortino, P. Tagliatesta, S.H. Chen, Phisical Review Letters 76, 2733, (1996). P. F. Sciortino, P. Gallo, P. Tartaglia, S. H. Chen, Physical Review E 54, 6331, (1996). F.W. Starr, M.-C. Bellissent- Funel, H.E. Stanley, Physical Review Letters 82, 3629, (1999). F.W. Starr, F. Sciortino, H.E. Stanley, Physical Review E 60, 6757, (1999) .

18. J. Fabian, P.B. Allen, Physical Review Letters 82, 1478,(1999).

19. S. Hunklinger and M. v. Schickfus, Amorphous Solids, Low Temperature Properties (W.A. Phillips Springer-Verlag, Berlin, 1981) pp.81-105 20. F. Sette, M. Krisch, C. Masciovecchio, G. Ruocco, G. Monaco, Science 280, 1550, (1998).

21. T.S. Grigera, V. Martin-Mayor, G. Parisi, P. Verrocchio, Physical Review Letters 87, 085502, (2001).

22. C. Masciovecchio, A. Gessini, S. Di Fonzo, L. Comez, S.C. Santucci and D. Fioretto, Physical Review Letters 92, 247401 (2004).

23. B. Fak, B. Dorner, Institute Laue Langevin (Grenoble, France), Technical Report No. 92FA008S, (1992).

24. D. Fioretto, L. Comez, G. Socino, L. Verdini, S. Corezzi, P.A. Rolla, Physical Review E 59, 1899 (1999).

25. The role of structural disorder to the attenuation in the 1 and 10 nm-1 region has been recently confirmed by a comparison of IXS spectra obtained from the glass, the poly-crystal and the plastic-crystal phases of ethanol. See A. Matic, C. Masciovecchio, D. Engberg, G. Monaco, L Börjesson, S.C. Santucci and R. Verbeni, Physical Review Letters 93, 145502 (2004).

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Paper received March 2004

BRISP – A New Thermal Neutron Brillouin Scattering Spectrometer at the Institut Laue-Langevin c

D. Aisaa, E. Babuccia, F. Barocchib, A. Cunsoloc, F. D’Ancac, A. De Francescoc, F. Formisanoc, T. Gahld, E. Guarinib, S. Jahnd, A. Lalonic, H. Mutkae, W.-C. Pilgrimf, A. Orecchinic, C. Petrilloa,*, F. Sacchettia, J.-B. Suckd, G. Venturib a INFM and Dipartimento di Fisica, Università di Perugia, via A. Pascoli, I-06100 Perugia, Italy b INFM and Dipartimento di Fisica, Università di Firenze , via G. Sansone 1, I-50019 Sesto Fiorentino, Italy

INFM Operative Group in Grenoble, 6 rue J. Horowitz, F-38042 Grenoble Cedex 9, France d Institute of Physics, Materials Research and Liquids, TU Chemnitz, 09107 Chemnitz, Germany e Institut Laue Langevin, 6 rue J. Horowitz, BP 156, F-38042 Grenoble Cedex 9, France f Institute of Physical Chemistry, Philipps-University of Marburg, Germany

Abstract BRISP is an Italian-German project for the design, construction and operation of an innovative thermal neutron BRIllouin SPectrometer installed at the High Flux Reactor of the Institut Laue-Langevin (ILL, Grenoble). The project has been financed by INFM (Italy) and BMBF (Germany). The spectrometer exploits the time-of-flight concept to perform neutron inelastic scattering experiments over a wide energy range at low momentum transfer. Access to this region enables addressing a number of longstanding scientific questions where experiments have not been feasible until now due to the kinematic restrictions of existing neutron spectrometers. The new possibilities offered by BRISP span from the detailed investigation of magnetic dynamics in condensed matter to fluid dynamics in systems which are close to their liquid-vapour critical point.

Installation of all the instrument components has been completed and in last August the first extraction and imaging of the monochromatic beam have been accomplished. BRISP will start its commissioning phase at the beginning of the next Reactor cycle and it will be available to users by the end of 2005.

ty (> 2000 m s-1), which requires also large enough incoming neutron energies. Regarding magnetic systems, the (Q, E) range accessible to spectroscopic techniques is even more restricted and inelastic neutron scattering is practically the only reliable technique for dynamic studies of disordered samples with a small magnetic scattering cross-section. However, the mentioned gap affects also the investigation of magnetic systems because of the

Scientific and technical background Inelastic scattering of thermal neutrons at low momentum transfer represents an ideal tool to measure densitydensity and spin-spin correlation functions, due to the linear coupling of the probe to the system. The measurement of the cross section related dynamic structure factor S(Q, E) in the region of low wavevector transfer Q is specially valuable for the investigation of the dynamic behaviour of disordered and magnetic systems [1-4]. In the study of disordered systems, there still exists a wavevector transfer region of difficult experimental access which is enclosed between that characteristic of Brillouin Light Scattering (Q ~ 0.01 nm-1) and the one typically probed by conventional Inelastic Neutron and Xray Scattering (Q > 3-5 nm-1, usually). Such a gap limits, for example, the investigation of collective excitations in systems characterized by a relatively high sound veloci-

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Fig. 1 – Region of exchanged wavevector and energy (Q, E) presently accessible to X-ray, neutron and light with the existing instruments. The gap uncovered by these techniques is apparent.

magnetic scattering intensity increase on approaching the Q = 0 limit. The (Q, E) region covered by the different available techniques is shown in Fig. 1.

The scientific case and the motivations for accessing this dynamic region with a clean probe as that represented by inelastic neutron scattering have been widely debated and are well assessed. Because of the countless applications, we mention only a few scientific examples which would greatly benefit from the technical accomplish-

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ment of a dedicated instrument and refer the reader to the published literature on the subject [5-9].

The study of critical dynamics, with the open question of the conjectured breakdown of the universality of transport properties, is, for instance, one of the outstanding research topics which can be profitably addressed. Indeed, the scattering from critical fluctuations is maximized in the long-wavelength limit, where correlation length and compressibility diverge [10]. Also, the study of collective excitations in liquids and compressed gases, with an efficient disentanglement of the purely inelastic from the quasi-elastic components of the spectrum, represents an essential contribution to the development of meaningful and reliable theoretical models of the liquid state [5-7,11]. In particular, the investigation of the dynamic behavior of liquid metals at the atomic scale is of considerable interest because of those peculiar features in the excitation spectra that can no longer be interpreted by extending the description of the liquid from classical hydrodynamics [8]. Understanding the microscopic mechanisms responsible for the propagation and the decay of the correlated ionic motions is still a challenge in liquid metals, where the dynamic features cannot be disentangled by the interacting electron gas effects. Further, in the study of compressed gases there is a considerable interest to follow the crossover from hydrodynamic (Q l << 1, l the mean free path) to kinetic (Q l >> 1) regime by simply spanning the required Q l range, without changing conditions as important as the thermodynamic state of the system. In the end, the neutron sensitivity to hydrogen/deuterium could be quite profitably exploited to characterize the dynamic properties of novel composite materials, biopolymers and proton conductive membranes for fuel cells.

Experimentally, most of the mentioned research topics can be tackled only by neutron Brillouin scattering (NBS) or small-angle X-ray inelastic scattering. Indeed, the ordinary Brillouin scattering of light is affected by important restrictions due to the very small wavevector of the incident radiation. A well-known shortcoming of this approach is the reduced possibility of reaching high Q l values, except for extremely dilute gases. Such limitation practically prevents one from exploring deviations from the hydrodynamic regime, unless undesirable changes of the sample thermodynamic conditions are accepted.

NBS has the advantage over the X-ray counterpart that the incident energy, and with it the energy resolution, can be more easily adapted to the physical problem under investigation. In addition, the different shape of the instrumental resolution function for the two techniques, namely a long-tailed Lorentzian for X-rays and a nearly Gaussian function for neutrons, along with the atomic and mass number independence of the neutron scattering length, which does not limit the study to low Z sam-

ples, make NBS preferable in many cases. As a final note, we remind that the non-destructive nature of the neutron scattering technique is a clear benefit when studying biological systems.

In spite of this, NBS experiments still represent a challenge in the field of neutron spectroscopy, mainly because of either kinematic or beam-time restrictions imposed by the available instrumentation. So far, NBS measurements have been performed on both cold-neutron time-of-flight (ToF) instruments equipped with a smallangle detection option (like, in the past, the IN5 spectrometer at the ILL) and three-axis spectrometers (TAS) using thermal neutrons. High-flux ToF instruments available nowadays no longer allow for dedicated smallangle spectroscopy and, further, the access is often confined to a rather restricted dynamical range because of the typically low energy of the incoming neutrons. On the contrary, three-axis spectroscopy at thermal energies, despite the capability to span a far wider kinematic region, is often a less efficient technique in the study of isotropic samples, especially when several changes of the sample thermodynamic conditions and collection of extended energy spectra at many different Q values are simultaneously required. In this respect, beam-time limitations with TAS are prohibitive, whereas the ToF technique becomes essential thanks to the intrinsic characteristic of measuring the scattering law at many Q and E values simultaneously, without moving any part of the instrument.

The technical limitations which prevent carrying out neutron Brillouin scattering with the existing instruments can be overcome by the construction of a dedicated NBS ToF spectrometer capable of combining efficient and flexible small-angle access for low-Q spectroscopy at thermal neutron energies, with good energy resolution and high counting rate [12,13]. Fulfilling the whole of these requirements is quite a difficult task which demands a careful optimization of resolution and intensity at the sample.

To enable spectroscopic investigations over the 0.1-3 nm space range and 0.25-5 THz frequency region at the top performances allowed by the neutron technique, while simoultaneously bridging the gap in the kinematic (Q, E) range, a new and unique Brillouin spectrometer has been designed, built and installed at the High Flux Reactor of the ILL [14,15]. The project is framed into a CRG (Collaborating Research Group) agreement between ILL, providing the neutron beam, and the partners, responsible for the construction and operation on site of the instrument with their own personnel. In the year 2000 the two partners, the Istituto Nazionale per la Fisica della Materia for Italy and the Technical University of Chemnitz for Germany, signed the agreement with the ILL for the completion and operation of the neutron BRIllouin

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SPectrometer BRISP. The specific CRG B contract foresees that 70% of the available beam time is reserved for experiments involving the Italian and German scientific community, i.e. concerning research topics leading to significant advancements in the various fields of interest of the partners’ countries. This 70% fraction of beamtime is further shared between the Italian and German community with a 75-25% ratio, respectively. The remaining 30% of beam-time is managed according to the standard ILL procedures for public access to instruments, with experimental proposals undergoing the usual peer-review procedure by the ILL international panels.

Considering that in the initial phase of the project the ILL was bound only by the condition of providing the neutron beam, and that BRISP was assigned to the 35°inclined thermal beam tube IH3, exiting at 5 m height in the ILL reactor hall, the complex preparation of the instrument site started immediately in 2000. Further preparation works proceeded during 2001, including the design and construction of the 4 m-high seism-proof steel platform that allocates the spectrometer. With the platform installation coming to an end in mid 2002, and the definition and development of the main shielding and spectrometer components, BRISP started an intense construction and assembling phase, along with the parallel support of a simulation activity for component optimisation [16,17]. During 2004 imperative objectives of the BRISP project have been achieved, reaching goals in the instrument development as important as the extraction of the monochromatic beam and its first imaging on the detector [18,19]. Since the signature of the agreement, the development of the BRISP spectrometer has indeed overcome the related technical challenges, while progressively becoming a well-established accomplishment of a CRG activity at the ILL. As a result, a difficult pro-

ject at the earlier stages of instrument design, is presently a real instrument in the final assembling/commissioning phase. The new perspectives opened by this innovatory thermal Brillouin spectrometer are manifold: from the access to the microscopic ion dynamics of liquids and glasses with relatively high sound velocities (up to 3500 m/s), to spin dynamics studies, and bio-physics or material science applications. The energy and momentum transfer ranges available to BRISP with optimised resolution have a key-role for significant advances in several research fields, as enabled by the flexible design of the instrument. BRISP will be operational for users by the end of 2005, with 154 days per year reserved for the highlight proposals of the Italian and German scientific communities, and more than two months of ILL-managed public beam-time, out of total 220 days per year available with the ILL reactor working at the full rate of four cycles per year.

Instrument description and operation principle BRISP is a direct geometry ToF instrument, that is operated at fixed incident energy E0, which is optimized for small-angle neutron spectroscopy in the thermal region.

The working principle is based on a hybrid spectrometer configuration, where incoming neutrons are monochromatized via Bragg reflection at a multi-crystal focusing monochromator, which is coupled to a rapidly rotating Fermi chopper enabling a high-resolution ToF analysis of the scattered neutrons. The two-dimensional position sensitive detector (PSD), presently covering a detection area of 1.4 m2, is maintained under vacuum and can be translated along the incident beam direction between 1.5 and 6 m from the sample position. Depending on the sample-to-detector distance, the lower and upper angular limits of 0.6° and 20°, respectively, can be reached.

Fig. 2 - Schematic of the BRISP spectrometer showing the various components of the instrument from the source to the detector. After reflection of the 35°-inclined beam at the monochromator, neutrons travel parallel to the ground at 6 m height

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Some of the spectrometer components which have been especially designed for BRISP, like the new-concept second collimator [20], together with the very large area detector [15,21] considerably contribute to an outstanding performance of the instrument. A high signal-to-background ratio is possible only thanks to the under-vacuum (10-1 mbar) operation of the entire beam-line and to the careful and optimized shielding of all the sections of the instrument which, being installed inside the reactor hall, suffers from the relatively high level of environmental neutron and γ-ray radiation. An efficient separation of the different under-vacuum sections of the instrument is accomplished by gate valves. The sample chamber is kept under the cryogenic vacuum (up to 10-6 mbar) provided by a turbo-molecular pump.

The schematic of the spectrometer is shown in Fig. 2 and the characteristics of the main components are summarized in Table I. The overall spatial extension of the spectrometer, which is mounted on a platform at 4 m above the ground, is about 19 m.

A graphite insert in the IH3 in-pile beam tube determines the circular cross-section of the beam (6 cm diameter). At the exit of the IH3 beam tube an integrated neutron intensity of 5 x 1011 n/s is available with an energy distribution peaked at thermal energies and a rather long tail of more energetic neutrons extending up to 250 meV, approximately. An efficient shielding against fast neutrons in the primary beam, and gamma radiation produced inside the various materials surrounding the beam itself, was defined by an extended simulation work (MCNP code) [22], shaped and mounted. Indeed, the radiological dose rates at the spectrometer control cabin, that has to be accessible by users during instrument operation, must not exceed 2.5 mSv/h, a quite severe constraint. The executive design of both the plat-

form and the primary shielding was performed in compliance with the latest seismic regulation and safety procedures for nuclear installations. The BRISP primary shielding is composed of two different units, detached by a 60 mm safety gap, in order to ensure a mechanical decoupling between the instrument, sitting on the platform, and the reactor, in case of earthquakes. The first part surrounds the IH3 exit on the reactor wall, while the second, containing the Soller collimator and the monochromator, is placed on the front part of the instrument platform. A view of the platform, with the main components mounted on it, is shown in Fig. 3 while Fig. 4 shows a detailed drawing of the primary shielding.

A 0.4° collimation of the white beam in the scattering plane is achieved by a standard Soller collimator. The 35° inclination of the beam tube with respect to the horizontal plane fixes the monochromator Bragg angle θB at a value of 17.5°. Different incident energies can be chosen by using different monochromator crystals or different order of reflections. Two of the three planned monochromators already exist, that is Cu(111) and PG (see Table I).

A third monochromator, Cu(220), is foreseen to further extend the dynamical range. The twenty crystals composing a single monochromator are mounted on a mechanical support allowing for the separate orientation of each of the crystals. Overall curvatures of the monochromator surface can thus be adjusted to reach the focusing condition (in and normal to the reflection plane), normally at the detector position. A picture of the monochromator is given in Fig. 5 while Fig 6 shows the rocking curves resulting from the alignment of the PG monochromator.

A disk chopper, equipped with eight rectangular windows and rotating at a maximum frequency of 5000 rpm, produces broad neutron pulses. This device ensures a re-

Fig. 3 – Picture of the anti-seismic platform taken with some of the spectrometer components mounted on it. The primary shielding, the background chopper casemate, and the detector vacuum tank are clearly visible. The detector and its electronic box, not yet installed inside the vacuum chamber, is also visible on the platform.

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Soller collimator

α1 = 0.4° Length 700 mm, slit spacing 5 mm 16 Gd2O3 coated kapton sheets, thickness 75 mm

Monochromator

Single-face: 20 crystals in a 4x5 matrix, crystal size 40x20 mm2 Average mosaic spread h = 0.5° (expt. 0.4° to 0.6°) Two available monochromators for the selection of 3 incident energies: PG(002): E0 = 20.1 meV (λ0 = 2.02 Å, v0 = 1961 m/s) Cu(111): E0 = 51.9 meV (λ0 = 1.26 Å, v0 = 3151 m/s) PG(004): E0 = 80.3 meV (λ0 = 1.01 Å, v0 = 3919 m/s) A third monochromator is foreseen for 2005: Cu(220): E0 = 138.3 meV (λ0 = 0.77 Å, v0 = 5144 m/s)

Background chopper

Disk chopper (480 mm diam.) with 8 rectangular windows Rotation axis parallel to the beam Windows width: 60 mm Material: steel with Gd2O3 coating Maximum rotation frequency: 5000 rpm

Honeycomb multi-beam converging collimators [20]

α2 = 0.4° Honeycomb (hexagonal) converging tubes arrangement Length 2000 mm, tube wall thickness 0.3 mm Material: Al with Gd2O3 coating Convergence at 3 possible distances from the sample: a) 2 m - single tube surface 205 mm2 (entrance) and 136 mm2 (exit) b) 4 m - single tube surface 205 mm2 (entrance) and 153 mm2 (exit) c) 6 m - single tube surface 205 mm2 (entrance) and 164 mm2 (exit) Magnetically suspended 70 (w) x 30 (h) mm2 central opening Rotation axis: horizontal, perpendicular to the beam Material: steel with Cd coating Maximum rotation frequency: 15000 rpm Internal Soller collimator: αFC = 1.1°, length 13 mm 120 absorbing sheets, slit spacing 0.25 mm

Fermi chopper

Sample chamber

Diameter 500 mm, Height 550 mm Aluminum windows, thickness 1 mm Material: Al Vacuum level 10-6 mbar (with dedicated turbo-molecular pump) Ancillary equipment: Maxi Orange Cryostat (1.5-300 K, sample access 100 mm), furnace (300 - 2000 K, sample access 40 mm)

Detector

Type: two-dimensional array of single Reuter-Stockes position sensitive tubes 96 3He filled (15 bar) tubes, diameter 12.7 mm, length 1118 mm 1229 (w) x 1118 (h) mm2 detection area (1.4 m2), 13x11 mm2 spatial resolution In 2005: upgrade to 128 tubes of 1118 mm length + 32 tubes of 610 mm length, all of 12.7 mm diameter, for a total detection area of 2.1 m2.

Mounted with a mechanical support on a long translation stage Sample-to-detector distance Dsd: 1.5 to 6 m Detector vacuum tank: cylindrical vessel, diameter 2500 mm, length 8000 mm Material: AISI-304 stainless steel

Table I – Characteristics of the BRISP components.

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Fig. 4 – Drawing of the primary shielding showing its complex shape and the different materials necessary for an efficient shielding of both neutrons and gamma radiation.

duction of the background of the continuous beam and, by a proper phasing with the Fermi chopper, minimizes contamination by other-order reflections of the monochromator. The second collimator, 2 m long, is based on the focusing multibeam concept and is equipped with the recently proposed honeycomb design, specially developed for BRISP [20]. This two-dimensional converging device splits the monochromatic beam into several collimated (0.4° divergence) partial beams of decreasing hexagonal cross-section and converging at the detector position. This innovatory solution has the important advantage of combining a high transmission of the neutron beam with simultaneous convergence and collimation in both the vertical and horizontal scattering plane, as required for an efficient use of a two-dimensional detector with good angular resolution in both directions. A photo of the exit side of the honeycomb collimator is presented in Fig. 7. In order to adapt the beam convergence to different positions of the detector, three honeycomb collimators are available, optimized for a sample-to-detector distance D s-d = 2, 4, and 6 m, respectively. These are mounted on a rotating support which, in a revolver-like

fashion, allows for an easy positioning in the beam of the chosen collimator. A fourth – relaxed – collimation option, consisting only of two Cd diaphragms, is also available for a possible higher intensity request, though at the expense of energy and Q resolution. An optimal matching of the chosen two-dimensional converging collimator with the monochromator focusing configuration can be achieved by varying the curvature of the monochromator. After splitting and collimation of the monochromatic beam, a fast rotating Fermi chopper is used to produce the short neutron pulses needed to improve the ToF resolution and to provide the time-reference for the ToF analysis. This chopper, provided by the ILL and presently adapted to the BRISP configuration by a 1.1° internal Soller collimator, will be operated at a maximum angular velocity of 15000 rpm. The high-vacuum sample chamber of 50 cm diameter is separated by 1 mm aluminum windows from the rest of the vacuum line.

An Orange cryostat (1.5-300 K) and a furnace (300-2000 K) are available for temperature-controlled measurements. Finally, a large-area two-dimensional detector, composed of an array of presently 96 3He PSD tubes, is

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mounted on a translation stage inside a long vacuum chamber (2.5 m diameter, 8 m length), for collection of the scattered neutrons at any desired position between 1.5 and 6 m from the sample. The spatial resolution achievable with the PSD tube assembly amounts to 1.3 cm horizontally (due to tube distance) and 1.1 cm vertically. Fig. 8 shows a schematic of the detector assembly while the vacuum chamber inside which the detector can move is pictured in Fig. 9.

As for all direct geometry ToF spectrometers, each time channel of the detector at a given scattering angle θ can

pends on the sample-to-detector distance and the scattering angle through L1 = Dsd / cosθ. Since E0 is fixed, each value of the scattered energy E1 corresponds to a defined energy transfer E = E0 – E1. The ToF analysis of the neutrons collected at a given scattering angle thus provides an entire spectrum Iθ (E) at once. If the section of the detector plane with the Debye-Scherrer cone of opening angle 2θ is completely on the detector surface, as is the case for θ < θmax, the maximum possible intensity is then collected for this scattering angle. Since several scattering angles can be simultaneously measured, this technique allows for a very efficient collection of the whole energy spectra with varying θ . The measured spectra are proportional to the double differential cross section d2σ (θ, E) ⁄ dΩ dE of the sample, which embodies the dynamic properties of the system through the dynamic structure factor S(Q, E) [4].

The energy transfer range corresponding to a given exchanged wavevector Q is determined by the usual kinematic relation resulting from the combination of energy and momentum conservation:

Fig. 5 – Picture of the multi-crystal PG monochromator of BRISP mounted on its support for insertion inside the shielding. The 4x5 crystal matrix composing the monochromator surface is clearly visible in the insert.

be associated with a value of the final neutron energy E1.

This is achieved through the knowledge of the flight paths before (L 0, fixed) and after the sample (L 1, adjustable), the incident energy E0, and the total time of flight tF, according to the well known relations: 2

tF =

L0 L1 L1 ⎞ 1 1 ⎛ ⎟ = m + ⇒ E1 = m ⎜ v0 v1 2 ⎜⎝ t F − L0 v0 ⎟⎠ 2

⎛ ⎞ L1 ⎜ ⎟ ⎜ t − L m (2E )⎟ 0 0 ⎠ ⎝ F

2

(1)

where v0 and v1 are the neutron velocities before and after the scattering event, m is the neutron mass, and L1 de-

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Fig 6 - Experimental rocking curves of the aligned PG(002) monochromator. The curves were obtained by illuminating three different portions, each of dimension 70 mm x 86 mm, of the whole monochromator surface (208 mm x 86 mm). A quite regular and uniform alignment of the 20 crystals over the whole monochromator can be deduced, with an overall mosaic spread ηexpt. = 0.5°.

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E = E0 − E1 = ⇒

Q = k0

h2 (k2 − k12 ) , hQ = h (k 0 − k1 ) 2m 0

⎛ E ⎞ ⎟ − 2 cosθ 1+ ⎜⎜ 1− E0 ⎟⎠ ⎝

1−

E E0

(2)

where k0 and k1 are, respectively, the incident and final neutron wavevectors. Experimentally, the accessible Q-E region with neutrons of fixed initial energy E0 is that comprised between the two curves derived from Eq. 2 at the minimum and maximum available scattering angles. As inelastically scattered neutrons can either gain

Fig. 7 – Exit side of one of the honeycomb collimators.

energy from the sample (v1 > v0) or release energy to the sample (v1 < v0), one has to distinguish neutron energy gain from neutron energy loss spectra, which are separated from each other by the peak of the elastically scattered neutrons at E = 0 (v1 = v0). Concerning the neutron energy gain spectra, there is ideally no upper limit in neutron velocity. If working with a constant time bin ∆t, as it usually happens, the spectra get more and more compressed with increasing energy transfer, as – due to the non-linear relation between time and energy – the time bins correspond to larger and larger energy bins when progressing towards the start of the time frame (initiated by a pick-up signal from the Fermi chopper).

As neutrons cannot lose more energy than they have when arriving at the sample, in the neutron energy loss spectra there is an upper limit to the transferable energy (E ≤ E0). This also implies that the neutrons can emerge from the scattering event having lost nearly all their initial energy in the interaction with the sample. These very slow neutrons, which are spread over many time channels, will arrive at the detector later than the fastest neutrons from the next chopper pulse, and thus frame overlap is unavoidable. To reduce this effect, which es-

pecially produces a sloping background in the neutron energy gain spectra, one either electronically introduces a pause time at the end of the time frame before starting the next one, thus dropping the neutrons with v1 ≈ ∞, or one suppresses the next pulse by a corresponding phasing of the background and the Fermi chopper. In this way most of the very slow neutrons will fall between subsequent chopper pulses and disturb less the neutron energy gain spectra.

A simple, although non-optimized, way of estimating the effective energy transfer range consists in assuming the elastic time-channel tel to lie at half of the maximum available time-frame ∆tp. In this case, the maximum energy loss Emax (corresponding to the minimum neutron final energy) is determined by the flight-time tel + ∆tp / 2. The absolute value of the maximum energy gain, which corresponds to tel-∆tp/2, is far larger than Emax and the resulting E range is not centered at E = 0. Due to the non-linear dependence of energy on time, it is generally more convenient to exploit a non-symmetric time-registration interval around tel, with most of the available time-frame devoted to the acquisition of the ToF spectra at tF > tel. With such a choice the measurements can be adjusted to correspond directly to the, as large as possible, symmetric energy transfer range. This can be achieved through the combination of the condition tFmax - tFmin ≤ ∆tp with the requirement of a symmetric interval in energy transfer (E1max + E1min = 2 E0). The resulting fourth-degree equation for the highest (or lowest) admitted time-of-flight value can be solved graphically, for given flight-path, incident energy, and frame width.

From this solution, the corresponding E range can be calculated, as well as the (asymmetric) positioning of the elastic time-channel in the explored time-range.

In the case of BRISP, ∆tp amounts to 2 ms when the Fermi chopper rotates at 15000 rpm. This value and the

Fig. 8 – Schematic of the detector assembly. The detector plate, supporting the 3He tubes, and the nearly cylindrical electronic box mounted on the trolley are drawn.

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aforementioned criteria for the evaluation of the maximum symmetric energy transfer range, beyond which unacceptable frame-overlap effects occur, have been used to derive the values listed in Table II, for the various incident energies. The total time-of-flight of elastically (E1 = E0) scattered neutrons tel is also reported, at different sample-to-detector distances. Though details on the other quantities involved in the energy transfer evaluation (e.g. tFmax, tFmin, E1max, E1min) are not reported for sake of simplicity, it is worth mentioning that the elastic time-channel typically lies at the very beginning of the time-window, with usually more than 70-80% of the

acceptably accurate intensity measurements on the BRISP detector, the maximum scattering angles turn out to be 20°, 10°, and 7° at Dsd = 2, 4, 6 m, respectively.

Such angular limits will be extended by the addition of further detector tubes in 2005. The maximum beam-stop size, namely 136 mm diameter, was estimated by the McStas simulations of the spectrometer. Such a value corresponds to minimum scattering angles of about 2°, 1°, and 0.6°, when Dsd is varied as above. However, these lower angular bounds can be further reduced by adopting a radius-adjustable beam-stop, which is presently under construction. From the angular ranges, an imme-

E0(meV) ±E(meV), tel(ms)

±E (meV), tel(ms)

±E (meV), tel(ms)

for Dsd=2 m

for Dsd=4 m

for Dsd=6 m

20.1

±17.3 , 1.57

±13.5 , 2.59

±10.7 , 3.61

51.9

±48.4 , 0.98

±42.1 , 1.61

±36.1 , 2.25

80.3

±76.5 , 0.79

±69.2 , 1.30

±61.3 , 1.81

138.3

±134.2 , 0.60

± 125.5 , 0.99

±115.3 , 1.38

Table II - Maximum energy transfer symmetric ranges accessible with the incident energies available on BRISP, at three reference sample-to-detector distances (Dsd=2, 4, 6 m). The total time of flight of elastically scattered neutrons between Fermi chopper and detector, tel, is also reported.

Fig. 9 – The BRISP detector vacuum chamber. Four inspection viewports are available, one of these is mounted on a larger side flange for rapid maintenance access. The central flange on the front of the chamber (closed in this photograph) allows for the scattered beam access at the detector and will be coupled to the instrument vacuum beamline through a pneumatic gate-valve.

frame devoted to time-of-flight values larger than tel.

In small-angle instruments, the angular range is typically determined by the sample-to-detector distance, the size of the detector, and the size of the beam-stop, which protects the detector from damage by the direct beam. At a given detector distance, the beam-stop size determines the lowest scattering angle, while the detector maximum size (diagonal) fixes the highest scattering angle. For the typical “powder”-like samples to be studied on BRISP, the intensity collected by the two-dimensional detector at each given scattering angle θ will be recorded over the ring resulting from the intersection of the detector surface and the Debye-Scherrer cones of semi-aperture q ∆ θ⁄ 2 and θ + ∆ θ⁄ 2, respectively, in a dartboard-like fashion. Partial rings at the corners of a rectangular-area detector give access, though with less and less intensity as the corner is approached, to the higher scattering angles. By keeping ~1.5 m as a reasonable diagonal size for

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diate estimate of the wavevector transfers Q that can be probed with BRISP can be obtained. For example, assuming a global 1.3 cm space resolution of the detector and the worst conditions (i.e. Dsd = 2 m, and the smallest nominal angles for a flat detector) for the evaluation of the corresponding angular step (∆θ ~ 0.35°), the lowest Q value results to be between 1.1 and 1.3 nm-1 at 20.1 meV incident energy. The reported variation depends on the suitable energy extension of the data at the chosen value for the Q-interpolation. Indeed, the determination of the dynamic structure factor S(Q, E) from the constant-θ measurements of the ToF spectra requires a constant-Q interpolation between data collected at different angles, which unavoidably implies that the minimum effective Q is higher than the lowest instrumentally accessible wavevector transfer Qel min. Referring to the above example, at the same 20.1 meV incident energy, the difference in the minimum Q values reduces for longer distances of the detector (6 m), where ∆θ ~ 0.12° at most and the effective minimum Q cannot exceed the corresponding value of the minimum elastic exchanged wavevector Qel min, that is 0.3 nm-1, by more than 3%.

The dynamic regions covered by BRISP are shown in Fig. 10, for all the possible incoming energies. The full lines correspond to the results of Eq. 2, at the minimum and maximum scattering angle, respectively. The dashed lines, which represent the linear dispersion E = h cs Q, are also shown in each panel for two example propaga-

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Fig. 10 – Kinematic regions accessed by the BRISP spectrometer at the different incoming energies that are (from 20 to 80 meV) or will be available in a near future (138.3 meV). In each frame, the constant-θ curves are derived from Eq. 2, using the minimum (lower full curve) and maximum (upper full curve) scattering angle probed with BRISP. The dispersion lines (broken curves), corresponding to E=h cs Q, are reported in each frame for two example propagation velocities cs specified in each plot.

tion velocities cs. As the incident energy is increased from 20 to 138 meV, excitations propagating with higher and higher velocity become accessible. The monochromators presently available on BRISP enable dynamic investigations of systems characterized by a sound velocity up to 2500 m/s. Such a value will be increased to almost 3300 m/s by means of the new Cu(220) monochromator. Finally, the low-Q dynamic ranges probed at the different incident energies of BRISP can be compared in Fig. 11. All curves were calculated from Eq. 2, at 1° scattering angle. Estimates of the energy resolution lead to ∆E/E0 values ranging from 3% (at the lowest incident energy and highest sample-detector distance) to 6% (in the opposite case) [15], as also confirmed by the MCNP and McStas simulations of BRISP [16,17]. Concerning Q resolution, the uncertainties in incident and final neutron wavevectors and scattering angle give rise, taking also sample- and detector-element size into account, to ∆Q values below 0.2 (0.5) nm-1 at the lowest (highest) incident energy [15].

Neutron test measurements Progressing of the neutron components installation has been continuously accompanied by the implementation of radiological tests, aimed at measuring the neutron and gamma doses to assess the efficacy of the shielding.

With the primary shielding (~25 tons weight) installed, the first neutron tests were about the effective alignment of the neutron beam and the measurement of the flux before the monochromator position. This was accomplished by measuring the activation of several gold

disks, 1 cm diameter each, after a five-minutes irradiation in the BRISP neutron beam. A set of 25 disks, with a center-to-center spacing of 2.5 cm horizontally and 3.5 cm vertically, was mounted as a 5 x 5 matrix on an aluminum square support of 15 cm side, in order to map the flux at several points over an area of about 165 cm2.

The support was placed perpendicular to the beam, roughly at the position corresponding to the exit of the Soller collimator. The results, displayed in Fig. 12, show a fairly good centering of the beam (nominal center at x=7, y=-5 cm, experimental center at x=6.4, y=-5.7 cm) with a maximum measured flux equal to 4.6·109 n s–1

Fig. 11 – Low-Q dynamical region covered by BRISP at the different incident energies selected by the PG and Cu(111) monochromators. All curves were calculated from Eq. 2, at 1° scattering angle.

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cm–2. The average rate over the beam area is thus of the order of 1011 n/s. Such intensity is expected to reduce by approximately a factor 106 at the sample position, due to the transmission of the various optical components, as estimated by McStas simulations with the PG(002) monochromator and the intermediate honeycomb collimator [17]. Further, due to the focusing monochromator and converging collimator, the beam size at the sample covers an area of about 10 cm2, thus yielding an expected flux at the sample of the order of 104 n s-1 cm-2.

The most important tests have been carried out in JulyAugust this year, namely the first and successful extraction of the monochromatic beam and the first operation of the BRISP detector bank on the monochromatic beam.

The flat pyrolitic graphite monochromator, which had been separately characterized and aligned exploiting one of neutron test facility of the ILL, was installed on BRISP. Optimal extraction of the monochromatic beam required just a fine adjustment of the monochromator orientation and a minor alignment of the Soller collimator. The total flux was measured using a calibrated 3He monitor. An experimental value of about 2x108 n/s was obtained over a surface of about 15 cm2. The measured peak flux density was 1.5x10 7 n/cm2/s, a value quite close to the expectation. The image of the monochromatic beam, as collected by coupling a CCD camera to a 6Li doped ZnS scintillator, is shown in Fig. 13. During the same test cycle, the BRISP detector was lifted to the final test position on the upper part of the platform and positioned in the direct monochromatic beam, at about 3m from the monochromator.

First neutron pulses, due to background neutrons on the BRISP site, were recorded on the 64 analogue outputs of the detector bank and a first picture was obtained after connecting the detector to the data acquisition electronics.

On opening the beam shutters, the BRISP detector took its first images of the BRISP monochromatic beam with a 10 s acquisition time. The image is shown in Fig. 14.

Fig. 12 – Experimental flux distribution at the position of the Soller collimator exit, measured on the BRISP beam prior to the collimator installation. The beam center effective positioning can be compared to the nominal center, expected at x = 7, y = -5 cm.

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Based on the above flux values, one can give an estimate of typical count rates at the BRISP detector achievable with the first instrument setup, that is 20.1 meV incident energy. For instance, a hollow Vanadium cylinder, 1.5 cm diameter, 0.2 cm thickness, 4 cm height, is expected to give 2 x 10-2 n s-1, at the elastic time-channel, over the sol-

Fig. 13 – Image of the monochromatic beam of BRISP obtained using a CCD camera coupled to a 6Li doped ZnS scintillator.

id angle element subtended by the detection ring corresponding to 2° scattering angle. It is worth noting that the scattering power of such a sample, of the order of 10%, is about the lowest limit used for typical samples, as the multiple scattering intensity in typical NBS experiments is near to a constant background. About ten timechannels must be grouped for a rough comparison with three-axis spectrometers, which typically are set to measure energy spectra with a larger energy step, e.g. 0.2 meV. The BRISP count rate over ten time-channels corresponds to an acceptable 2.5% statistical accuracy (roughly 1450 counts at the peak of the vanadium ToF spectra) in two hours of data-acquisition time. Besides the absolute flux values, the power of the ToF technique is clear when one considers that complete ToF spectra at more than 20 different scattering angles (and consequently Q values) can be measured on BRISP at once.

Typically, on high-flux three-axis spectrometers operated for NBS spectroscopy, a similar accuracy (given the same sample) can be reached in three minutes, though for a single (Q,w) point. Thus complete spectra (e.g. 20 points in E) at 20 different Q values would require twenty hours. In twenty hours of data-acquisition time, BRISP is able to measure the same spectra with better than one percent accuracy.

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Concluding remarks During the forthcoming commissioning phase of the instrument, further developments will include the installation of the third monochromator unit (Cu(220)), in order

us to design, construct, install, and simulate the spectrometer. In particular, we wish to express our gratitude to the ILL personnel for the valuable assistance, support and advice we have always received.

Fig. 14 – First image of the monochromatic beam collected on the 3He BRISP detector.

to provide BRISP with an increased kinematic range extending to higher energy transfers. Although at the expense of intensity, time-resolution can also be improved by installing a different Soller collimator (length 30 mm, slit spacing 0.3 mm, aFC=0.6°) at the Fermi chopper, in order to reduce the pulse width to 6 ms. The use of Gd2O3coated silicon blades, in place of the present Gd2O3-coated aluminum ones, would also reduce background and spurious small-angle scattering. Another improvement, suggested by the McStas simulation results, can be achieved by substituting the existing rotor of the Fermi chopper with a new one having a higher central window (60 mm in place of 30 mm). Such a choice was shown to increase the simulated intensity by 40%, without appreciable changes in resolution and beam size. The extension of the present detector bank to a total of 160 tubes is already foreseen in 2005, while the possibility of collecting also the high-Q scattering can be a further interesting upgrade of the instrument, envisaged as a possible development. For this reason the sample chamber is already equipped with an appropriate window, glancing at a future wide-angle detector bank to be installed beside the chamber itself. Finally, a twin background chopper is foreseen in order to allow for standard maintenance of the existing one, without any risk of affecting the instrument operation cycles.

Acknowledgments We are pleased to acknowledge all the people that are or were involved in the BRISP project at some stage helping

References 1. Proceedings of the 2nd European Conference on Neutron Scattering, Physica B 276-278 (2000).

2. Proceedings of the ICNS 2001 - International Conference on Neutron Scattering, Appl. Phys. A S74 (2002).

3. Proceedings of the 3rd European Conference on Neutron Scattering, Physica B350 (2004).

4. D. L. Price and K. Sköld in Methods of Experimental Physics, vols. 23 AC, (Academic Press, London, 1987).

5. J.-B. Suck, Int. J. Mod. Phys. B 7 (1993) 3003.

6. P. Verkerk, J. Phys.: Condens. Matter 13 (2001) 7775.

7. Proceedings of the Vth EPS Liquid Matter Conference, J. Phys.: Condens. Matter 15, N. 1 (2003).

8. Proceedings of the Eleventh International Conference on Liquid and Amorphous Metals, Journal of Non-Crystalline Solids 312-314 (2002).

9. Proceedings of the International Workshop on Disordered Systems, Philos. Mag. B 82 (2002).

10. J. P. Hansen, I. R. McDonald, Theory of Simple Liquids, (Academic Press, London, 1986).

11. U. Balucani, M. Zoppi, Dynamics of the Liquid State (Clarendon Press, Oxford, 1994).

12. H. Mutka, J. Mol. Structure 293 (1993) 321.

13. S. Jahn and J.-B. Suck, Nucl. Instr. Meth. A 438 (1999) 452.

14. F. Formisano et al., Physica B 350 (2004) e795.

15. D. Aisa et al., Nucl. Instr. Meth. A, in press.

16. S. Jahn and J.-B. Suck, Appl. Phys. A 74 (2002) S1465.

17. G. Venturi et al., J. Neutron Research 11 (2003) 165.

18. The BRISP team, “Small-angle spectroscopy at thermal energies: the BRISP project at ILL”, to be published in the ILL Annual Report 2004.

19. See the BRISP web page at http://infmweb.fi.infn.it/BRISP 20. C. Petrillo et al., Nucl. Instr. Meth. A 489 (2002) 304.

21. P. van Esch et al., Nucl. Instr. Meth. A 526/3 (2004) 493.

22. S. Mahling-Ennaoui and S. Jahn, Proceedings of the ILL Millenium Symposium & European User Meeting, Grenoble 6-7 April 2001, 281.

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FRM II in Garching widely spread range of applications of the neutron source. The applications cover a large variety of high technology fields from basic research, applied science, medical treatments to industrial production. The FRM II has started the scientific program with the first call for proposals in October 2004. Access for European users is granted through the EU framework program 6 (FP6) within the neutron muon consortium NMI3.

Abstract The new neutron source FRM II in Garching has become operational in 2004. A large number of instruments will serve scientists from Germany and European countries to perform experiments with neutrons. In addition a positron source of high intensity is available for material science and nuclear physics. Irradiation facilities for isotope production, activation analysis and transmutation doping complete the

The Technische Universität München operates the new German neutron source FRM II in Garching near Munich. The highly optimized reactor produces an unperturbed flux of thermal neutron of 8 x 1014 neutrons/cm2s at a thermal power of 20 MW. Special care has been taken to optimize the 10 horizontal and 2 inclined beam tubes positioned tangential to the single fuel element.

The heavy water moderator serves

Figure 1 Instruments located in the experimental and neutron guide hall of the FRM II.

Type

Name

Instrument

Diffraction

Heidi Resi Spodi Stress-Spec Refsans Mira

single crystal diffractometer, hot source single crystal diffractometer, thermal source powder diffractometer, thermal source material science diffractometer reflectometer for bio-physics reflectometer, long wave length neutrons

Spectroscopy

Reseda TofTof NRSE-TAS Puma Panda

resonance-spin-echo spectr., cold source time-of-flight spectrometer, cold source three-axis spectr. Spin-Echo, thermal source three-axis spectrometer, thermal source three-axis spectrometer, cold source

Positrons

Nepomuc Nepomuc-PAES Nepomuc-CDB

positron beam (“open beam port”) positron auger spectrometer positron defect spectrometer

Radiography Tomography

Antares Nectar

radiography, tomography, cold source radiography, tomography, fission source

Particle physics

Mephisto

cold neutron beam, special experiments

Table I: List of instruments for the first call for proposals

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as thermal neutron source. In addition a liquid deuterium cold source (25 K) and a graphite hot source (2300 K) provide neutrons with shifted wave lengths. A converter facility produced fast neutrons (fission spectrum) for cancer irradiation and radiography. Further radiography and tomography can be performed by means of a dedicated cold neutron beam.

Instruments for neutron scattering are located in the experimental and neutron guide hall (see fig. 1). They have been designed and constructed by scientific groups from all over Germany. These groups originate from universities, neutron centers and Max-Planck institutes. After fin-

Âľ & N & SR NEWS

ishing the commissioning phase these groups will operate the instruments and support experiments from guest scientists. External users can apply twice a year for beam time through the Internet portal at http://user.frm2.tum.de where they can get additional informations concerning the user program. A list of the available instruments for the first call for proposals is given in table I.

Additional instruments are in the commissioning phase.

In addition to the scientific program the FRM II serves for industrial (commercial) applications. A silicon doping facility and 17 irradiation channels are focused on semiconductor industry, isotope production and neutron activation analysis. A special building has been constructed with laboratories to be rent by in-

dustrial companies to allow handling of the radioactive isotopes on site. Dedicated instruments for stress and strain analysis, texture analysis as well as radiography are ready to perform industrial investigations with neutron beams.

Juergen Neuhaus FRM II Garching

The Swedish Neutron Scattering Laboratory, NFL Studsvik Two research reactors are operated at Studsvik about 100 km south of Stockholm on the Baltic Coast. The reactors are operated commercially by a subsidiary of Studsvik AB for a range of activities. The academic use, for basic research and neutron scattering experimentation is the role of Neutron Research Laboratory that forms part of Uppsala University. The company uses the reactors for irradiations, isotope production and as a recent development for boron neutron capture therapy to treat some carcinomas.

The Swedish regulatory authority (SKI) renewed the licences for operation of both the R2 and R2-0 reactors for a period of 10 years from 1st July 2004. Studsvik can therefore plan for an extended period of use and some development of facilities. NFL has a distinct characteristic as a university laboratory although it also provides facilities to users from other institutions. These users come from Swedish universities, industry and a range of foreign laboratories. The R2 reactor operates at 50 MW thermal power and has a flux in the thermal moderator of about 2 ? 1014 neutrons cm2 s1.

A recent review of the activities at NFL has led to a focus on experimental activities that are relevant to

the interests of Swedish research community. Neutron scattering is a tool for many disciplines and the largest user groups comes from the areas of chemistry and materials science. For example, in solid state chemistry neutron diffraction is routine for structure determination of modern magnetic materials, solid electrolytes and energy storage systems. The ability to study under service conditions of high or low temperatures, under pressure or while undergoing reactions is particularly important. The trend towards nanoscience has resulted in fewer studies of large single crystals. Many modern materials are chosen because intrinsically they do not form large domains or crystals.

The installation of a second powder diffractometer, R2D2, shown in Figure 1 has been driven by growth in this area.

A second major area of growth at NFL is to support interests in soft matter and interface science. A reflectometer is being installed with components now ready in the shielding tank and progress already made on detector arm, slits etc.

There is a large community interested in this activity and we expect that this will further enhance the growth in users at Studsvik. Details of all the

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instruments at NFL can be found on the WWW site [2]. A range of science is pursued with various instruments.

Studies of nanoncrystalline and amorphous materials are very strong particularly using the multidetector

Figure 1. The newly installed R2D2 diffractometer with a compact design and large detector solid-angle. This is described in a paper by A. Wannberg et al. [1]

diffractometer for liquids and amorphous materials, SLAD. Combination of the complex sample environments such as in-situ hydrogenation

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Figure 2. A group of students from Chalmers Technical University, Gothenburg learning about a diffractometer in the R2 reactor hall in February 2004.

and work in the chemistry laboratory is also very common. An advantage of the NFL is very flexible and rapid scheduling. Measurements on samples that are unstable can be made very quickly.

The NFL staff are employed primarily by Uppsala University although some hold joint appointments with other institutions. Very close links with research and teaching in a range of university departments are an important and, rather unusual, feature of activities at NFL. Students in various science and engineering programmes at most of the major Swedish universities have the opportunity to visit Studsvik. Neutron scattering is taught as part of many courses such as magnetism, structural chemistry, crystallography and colloid science. Neutron techniques are also the subject of a few specialist courses. These teaching activities are certainly not just for Uppsala

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University: we have many undergraduate students visiting for practical sessions of varying duration who get ‘hands-on’ experience of neutron experiments and data analysis as well as lectures either at Studsvik or in their home university. This work helps greatly to reinforce awareness of the ease of use and access to neutrons in the scientific community.

The activity at the laboratory covers science from nuclear physics through to biology and engineering.

This short account can not describe all areas and readers can find more information on the WWW where the NFL annual reports are also provided. The work at the laboratory receives support from Swedish funding agencies such as the Research Council (VR) and various research foundations. There is a small contribution from the EU-NMI3 access programme (Contract N° RII3-CT2003-505925) that allows selected ex-

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periments of excellent quality from other countries in the European research area to be performed with financial support. Other experiments can be performed as collaborations with NFL or other Swedish scientists. This exchange of visitors is valuable and apart from Europe we have had visits in the last year from Russia, Ukraine, Pakistan and China.

Newly supported programmes for exchanges with China and Bangladesh have been announced

by VR/SIDA. References 1. A. Wannberg, M. Gronrös, A. Mellergård, LE. Karlsson, R.G. Delaplane, B. Lebech, Zeitschrift für Kristallographie – in press.

2. NFL web site: http://www.studsvik.uu.se/

Adrian R. Rennie NFL Studsvik

µ & N & SR NEWS

ESRF & ILL Contribution ESRF Section Latest applications for beam time at the ESRF A total of 900 new applications for beam time arrived at the User Office for the recent deadline, all of them submitted electronically. This compares with 752 submitted at the same period last year, and represents a record number of submissions for the 1st September deadline.

The distribution of proposals across major scientific areas this review round is shown in the figure. The nine Review Committees assessed the applications on the basis of scientific merit, and recommended projects for beam time on the 30 ESRF and 10 CRG beamlines open to users during the first half of 2005.

15th ESRF Users Meeting 8-9 February 2005 The annual ESRF Users Meeting will be held on the afternoon of Tuesday February 8 and the morning of Wednesday February 9,and will feature.

- a plenary session mainly devoted to an update of the technical and

strategic long-term options for the facility; - parallel scientific sessions, with invited talks, status reports from the beamlines, and open discussions on future improvements; - a Poster Session; - the prestigious ESRF Young Scientist Award ceremony and talk; - the 2005 Users’ Meeting keynote speech; - a “hard talk” plenary session where issues on the present status and the future of the ESRF will be debated; - a special celebration of 10 years of User Operation.

Satellite workshops: Synchrotron Radiation in Art and Archaeology Synchrotron radiation techniques provide powerful new ways to investigate records of our physical and cultural past. The purpose of this workshop is to discuss and explore the current and potential applications of synchrotron science to problems in archaeology and art conservation. It will bring together key members of the synchrotron com-

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munity and experts in the disciplines of Archaeology, Archaeologica Science, Art Conservation and Materials Science. This interdisciplinary workshop aims to report the latest research accomplishments, highlight ongoing projects and catalyse new interactions between fields.

New Science with New Detectors It is becoming increasingly clear that the next major advance in synchrotron science will come via dramatically improved or revolutionary detector concepts. This workshop will look at the future science at synchrotron radiation facilities and discuss the requirements for the detection systems needed.

Future events June 2005 - Workshop on “NonCrystallographic Phase Retrieval” June 2005 - High Pressure and Synchrotron Radiation July 2005 - International Workshop on Radiation Imaging Detectors IWORID-7 For more information, have a look at www.esrf.fr

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µ & N & SR NEWS

ILL Section News from the Scientific Council Overall, the subcommittees allocated 2436 days on all instruments (there were 100 days available for allocation this round). This represents 439 accepted proposals out of 598 submitted. Of the 40 Italian proposals submitted, 31 received beam time with a total of 115 days, corresponding to 4.7% of the total beam time available. The next Scientific Council with its subcommittee meetings will be from 30 to 31 March 2005.

ILL Call for Proposals The deadline for proposal submission is Tuesday, 15 February 2005, midnight (European time).

Proposal submission is only possible electronically. Electronic Proposal Submission (EPS) is possible via our Visitors’ Club (http:// www.ill.fr, Users & Science, Visitors’ Club, or directly at http:// vitraill.ill.fr/cv/), once you have logged in with your personal username and password.

The detailed guide-lines for the submission of a proposal at the ILL can be found on the ILL web site: www.ill.fr, Users & Science, User Information, Proposal Submission, Standard Submission.

The web system will be operational

from 1 January 2005, and it will be closed on 15 February, at midnight (European time). You will get full support in case of computing hitches. If you have any difficulties at all, please contact our web-support (club@ill.fr).

Instruments available The following instruments will be available for the forthcoming round: • powder diffractometers: D1A, D1B*, D2B, D20 • liquids diffractometer: D4 • polarised neutron diffractometers: D3, D23* • single-crystal diffractometers: D9, D10, D15*, VIVALDI • large scale structure diffractometers: D19, DB21, LADI • small-angle scattering: D11, D22 • reflectometers: ADAM*, D17 • small momentum-transfer diffractometer: D16 • diffuse-scattering spectrometer: D7 • three-axis spectrometers: IN1, IN3, IN8, IN12*, IN14, IN20, IN22* • time-of-flight spectrometers: IN4, IN5, IN6 • backscattering and spin-echo spectrometers: IN10, IN11, IN13*, IN15, IN16 • nuclear-physics instruments: PN1, PN3 • fundamental-physics instruments: PF1B, PF2

* Instruments marked with an asterisk are CRG instruments, where a smaller amount of beam time is available than on ILL-funded instruments, but we encourage such applications.

You will find details of the instruments on the web, http://www.ill.fr /index_sc.html.

Scheduling period Those proposals accepted at the next round, will be scheduled during the LAST CYCLE in 2005 (50 days). You are probably already aware of the fact that - due to reinforcement work of the reactor structure - the ILL has reduced the number of reactor cycles from 4.5 down to 3 cycles per year until 2006.

Reactor Cycles for 2005: Cycle n° 140 From 15/02/2005 To 06/04/2005 Cycle n° 141 From 15/04/2005 To 04/06/2005 Cycle n° 142 From 15/06/2005 To 04/08/2005 Start-ups and shut downs are planned at 8:30 am Workshops The following workshops are planned by the ILL in 2005: Neutron Spin-Echo, September 2005 Small Angle Inelastic Neutron Scattering IUPAB/EBSA Biophysics Congress, satellite meeting in Montpellier, August 2005; 3rd International Workshop on Nuclear Fission Product Spectroscopy, May 2005.

Giovanna Cicognani (ILL Scientific Coordinator) Roselyn Mason (ESRF Users’ Office)

Common Group photo of ILL Scientific Council and the ESRF Science Advisory Committee.

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MEETING REPORTS

SISN Annual Conference 8 - 9 June 2004 - Monte Conero (Italy) The Annual Conference of the Italian Neutron Scattering Society (Società Italiana di Spettroscopia Neutronica, SISN) took place this year on June 8th and 9th in the Hotel Monte Conero, a well-known resort on top of Monte Conero, a wonderful natural park, just south of Ancona and facing the Italian Adriatic coast.

More than sixty scientists gathered to discuss recent Italian activities in the field of neutron diffraction and scattering. The topics covered in the talks ranged from hard solid-state to soft condensed matter research. Invited talks were given by Valeria Arrighi (Heriot-Watt University, Edinburgh, Scotland), Livia Bove (OGG-INFM, Grenoble, France), Giovanna Cicognani (ILL, Grenoble, France), Fabrizio Fiori (University of Ancona, Italy).

This year a short (three-day) intensive school (Giornate Didattiche) was organised jointly with the Annual Conference. This initiative was mostly devoted to graduate and PhD students and to young researchers interested not only in understanding advantages and potentialities of the technique on a general basis, but also in finding practical applica-

tions in their own research fields.

The topic of this first edition of the “Giornate Didattiche” was: “Dynamics of Complex Molecular Systems”.

The teachers were Ubaldo Bafile (IFAC-CNR, Firenze), Antonio Deriu (University of Parma), Salvatore Magazù (University of Messina), Simone Melchionna (University of Roma ‘La Sapienza’), Ranieri Rolandi (University of Genova), Francesco Sacchetti (University of Perugia), Marco Zoppi (IFAC-CNR, Firenze).

The potentiality of Italian instruments at the ILL and at ISIS for studying the dynamics of complex molecular systems was also described in detail: - Ferdinando Formisano (OGGINFM, Grenoble) illustrated the state of art of the Brillouin spectrometer BRISP, presently under commissioning a the ILL; - Francesca Natali (OGG-INFM, Grenoble) presented a comprehensive overview of the application to biological and biophysical studies of the thermal backscattering spectrometer IN13 at the ILL; - Daniele Colognesi (IFAC-CNR, Firenze) reviewed recent investiga-

tions performed with TOSCA, a crystal analyser spectrometer at ISIS devoted to vibrational spectroscopy studies; - Roberto Senesi (University of roma ‘Tor Vergata’) illustrated the applications of deep inelastic scattering using the VESUVIO spectrometer at ISIS. In the afternoon, tutorial sessions were organised by Alessandro Paciaroni (University of Perugia) in order to provide direct contact with data reduction and analysis procedures.

Twenty-eight students from different Italian Universities (Ancona, Firenze, Genova, Parma, Palermo, Parma, Perugia and Trento) attended the intensive course enjoying also the natural surroundings of the site. The participants judged the initiative very positively; it will then be replicated in the years to come.

Antonio Deriu Università di Parma

Engineering Applications Workshop at ILL-ESRF 13-14 September 2004 - Grenoble (France) A workshop on Engineering Applications of Neutrons and Synchrotron Radiation took place on 13-14 September at ILL-ESRF in Grenoble, France. The workshop brought together around 100 leading scientists and engineers who discussed the application of neutron and synchrotron X-ray central facilities for materials science problems. The event was or-

ganised by the FaME38 materials engineering facility at ILL-ESRF. The programme included formal presentations, informal workgroup sessions and an opportunity to meet staff at the ILL-ESRF materials science beamlines. The formal presentations were structured into three sessions entitled Progress, Complementarity and Applications chaired by

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Giovanni Bruno (ILL), Thomas Buslaps (ESRF) and Darren Hughes (FaME38). The presentations showcased the state-of-the-art neutron and synchrotron X-ray facilities now available for engineering analysis and highlighted the materials science challenges facing industry today.

The keynote presentation in the Progress session was given by Peter

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Webster of FaME38. He highlighted the enormous potential of synchrotron X-rays and neutrons for the investigation of stresses in engineering components and showed how the recent creation of the FaME38 laboratory helps to optimise experimental efficiency. Mike Prime (LANL, USA) presented a technique that he has developed for measuring residual stress in the keynote talk for the Complementarity session. The ‘Contour Method’ measures deformation in an electro-machined surface and uses FE analysis to calculate the original residual stress field. It is particularly useful when used in association with neutron or synchro-

tron X-ray measurements to reveal the full stress field in components. In the session on Applications, Richard Burguete (Airbus, UK) gave an entertaining keynote presentation highlighting the materials science issues currently facing the European aerospace industry. He showed that failure analysis may be achieved using rigorous mechanical testing and non-destructive methods such as neutrons and synchrotron X-rays.

The range of topics of the full programme was diverse, reflecting current ‘hot’ research topics; residual stress analysis in aircraft wings; near-surface stresses arising from machining; imaging of bonded joints

in car components; biomedical applications. A number of new collaborations between on-site researchers and academic/industrial engineering groups were established during the workshop and many more are expected to develop after the event.

The workshop committee would like to thank everyone who helped with the event and making it an exciting forum. The Workshop Proceedings, which include abstracts of the oral presentations and posters, the programme and a list of participants, are available on the FaME38 website (www.ill.fr/fame38).

Darren Hughes FaME38

IEEE NSS/MIC satellite workshop on synchrotron radiation detectors Acknowledging the impact of synchrotron radiation research this year’s edition of the IEEE NSS /MIC held October16-22, 2004 in Rome aimed for extending the program in this field. In this occasion a one-day satellite workshop on synchrotron radiation detectors was organized which attracted 160 participants.

During the past 20 years synchrotron light sources and the associated optical components developed at a fast pace providing a remarkable increase of intensity and brightness. Ever since then research with synchrotron radiation has emerged to be one of the most powerful tools in almost every field of science and technology.

However, these sources can maintain their high level of competitiveness only if a new generation of x-ray and electron detectors is developed as well. Right now we are facing a situation in which it is mostly the detection device that limits the final data quality. Thus the workshop addressed to a serious problem faced by all synchrotron radiation sources: the lack of appropriate detectors.

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In contrast to other areas such as high energy physics where the detectors are tailored for one specific purpose / experiment only, in synchrotron radiation experiments one has to deal with a wide range of experiments. Therefore it is difficult to specify detectors which can be utilized in recent and future synchrotron radiation experiments. However a closer analyzes of detectors used in other fields such as neutron science, astrophysics, high-energy physics or medical imaging shows that state of the art detectors and electronics concepts already exist which could be - with some modifications- well suited for synchrotron radiation applications. On the other hand some recent synchrotron radiation detector concepts could be also very useful in other fields such as neutron science. Utilizing this knowledge pool on a mutual basis could ensure further exploitation of modern sources. Therefore this workshop aimed to bring together scientist from these fields and helped to foster interdisciplinary

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communication channels between the synchrotron radiation users and detector developers from the fields mentioned above.

An overall of 28 oral presentations and 15 posters gave a rather complete overview of the detector development situation in synchrotron radiation covering solid state (pixel) devices, gaseous detectors and spectroscopic systems.

The US perspective in the field were represented by S. Gruner, Cornell University, presenting recent results in analog x-ray pixel array detectors, followed by P.Siddons, Brookhaven National Lab. describing multi element silicon detectors for x-ray spectroscopy and S. Friedrich from Lawrence Livermore National Lab. showing how superconducting tunnel junctions can be used as high resolution x-ray detectors.

G.E. Derbyshire, CCLRC Rutherford Appleton Lab, C.Hall and B.R. Dobson from CLRC Daresbury Lab. gave complete overview about the outstanding detector development in the UK. It seems that at present Eu-

MEETING REPORTS

rope and especially the UK is the center of this activity. C. Norris from Diamond Light source presented plans how these developments can be incorporated in a state of the art synchrotron light source. M. Kocsis, A. Bravin, J.-C. Labiche and C. Ponchut showed developments at the European Synchrotron Radiation Facility ranging from gaseous detectors over CCDs to Ge – strip detectors and Si pixel devices.

C. Venanzi, University of Trieste, INFN Trieste and A. Castoldi, Politecnico di Milano, presenting multi channel silicon counting devices for x-ray imaging with synchrotron radiation demonstrated that Italy in this field is fairly advanced and playing internationally a leading role. In the frame of the recent construction of the Australian Synchrotron Light source the Australian perspective were represented by T.F. Beverigde, Monash University and A.B. Rozenfeld, University of Wollongong. Industrial detector research and development were represented by C.Kenney, Molecular Biological Consortium, USA, S.G. An-

gello, Area Detector System Cooperation, USA and J. Hendrix, marreseach, Germany. The latter demonstrated an outstanding advanced large area amorphous selenium based imager for real-time crystallography.

M.Suzuki, Spring 8, Japan showed the use of multi channel YAP imagers in high energy x-ray applications and recent results of the first large area Si pixel detector for macromolecular crystallography were presented by C.Broenniman, Paul Scherrer Institute. Both detectors represent a bridge to neutron science since they were already used in both fields. G. Gorini, University di Milano Bicocca, Italy and B. Gebauer, Hahn Meitner Institute, Germany, demonstrated how similar are the concepts in neutron detection and x-ray detection. Developments of photon counting devices based on MCPs in combination with CMOS pixel chips for ground based astronomy are well suited for UV synchrotron radiation applications as shown by B.Mikulec, University of Geneva, Switzerland.

About 20 researcher of the former Soviet Union were supported by the INTAS grant no 0369 661 to participate the workshop which gave L.Shekhtman, Budker Institute for Nuclear Physics, Russia the possibility to report on his detector for dynamic studies of explosion and detonation waves with synchrotron radiation. As in all areas of research also detector development relies on young researchers. Therefore the organizers are grateful to the IA-SFS (Integrating Activity on Synchrotron and Free Electron Laser Science of the European sixth framework program) for the support of young researchers to participate this workshop. The workshop finished with a presentation of M.Bertolo, Sincrotrone Trieste, Italy about the funding opportunities with in the European Sixth frame work program and beyond which gave rise to stimulating discussions how to join forces for future detector developments for synchrotron radiation and neutron science.

Ralf Hendrik Menk Sincrotrone Trieste

School of Neutron Scattering Francesco Paolo Ricci 21st September - 2nd October 2004 - Palau

Students and teachers in Palau

The goal of the various editions of the “School of Neutron Scattering Francesco Paolo Ricci” has been advanced training for young European researchers at post-graduate and postdoctoral level, typically between 25 and 30 years old. Its primary ob-

jective is to present the current methodology of static and dynamic neutron scattering techniques to scientists using scattering methods at large scale facilities. Based on the positive experience with the six previous editions (1994, 1996, 1998, 2000, 2002), this year’s event was again organized at the Hotel “Capo d’Orso” located not far from Palau, a recreation centre in the Sardinia coast near La Maddalena. The School run from September 21st through October 2nd 2004. The school was attended by 28 students, while lectures were delivered by a total of 23 teachers. It provided a forum for learning and ex-

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Nobel Laureate Prof. R.A. Marcus with some attendees.

changing experience in using complementary experimental techniques.

The School was organised by the Associazione “F. P. Ricci” (web site http://www.

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fis.uniroma3.it/sns_fpr/), with the financial support of the the Italian National Research Council, CNR, NMI3 - Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy, the INFM (Udr Tor Vergata) and of four Italian Universities (Milano-Bicocca, Palermo, Roma Tor Vergata, and Roma Tre). Directors of the School were dr. F. Aliotta (CNR, Messina) and prof. R. Triolo (Università di Palermo). Central theme of the School was the application of Small Angle and Ultra Small Angle Scattering techniques. Leading scientists from Europe and from the United States drawn from Universities and National and International Laboratories have delivered a total of 55 lectures and 2 after dinner Nobel lectures, given by Prof. R. A. Marcus, 1992 Nobel Laureate. Prof. Marcus, a Chemist with great human characteristics coupled to an outstanding scientific curriculum, has captured the attention of the School attendees by strongly motivating them. One morning has been dedicated to the synergy between Experimental and Computational physics, and the complementarities of neutrons and X-rays has been highlighted. Finally a strong program of at least 20 hours of practical sessions has completed the training of the young attendees.

The program of the school has focused on the following areas: •The fundamentals of the interaction of neutrons and X-rays with matter •Neutron production and experimental instrumentation •Theory and application of various neutron experimental techniques •Correction and Analysis of experimental data collected at International Facilities Subjects for lectures included: Interactions of X-rays and Neutrons with Matter. Neutron Generation and Detection. Neutron Instrumentation. Inelastic Scattering. Magnetic Scattering. Small Angle Scattering. Ultra Small Angle Scattering. Amorphous

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Scattering. In summary, basic information on data interpretation, on the complementarity of the different types of radiation, as well as information on recent applications and developments were presented. The school was successful in providing a broader understanding of scattering methods and their application for resolving structural and dynamic problems. In this respect, the analysis of the answers of a questionnaire handed out to the participants for quality assessment, revealed a positive impact on future research activities of the attendees. In addition, on the afternoon on Friday September 24 th two interesting events took place: Dr. Colin Carlile, Dr. P. Radaelli and dr. M. Agamalian, on behalf of Dr. I. Anderson, gave highlights on the Millennium Program (ILL), on the ISIS II target, and on SNS Project, respectively. These presentations meant to upgrade information on the instrumentation which will be available in the near future.

A Mini Symposium on the application of atomic and nuclear techniques for Conservation, Restoration and Preservation of Cultural Heritage, took place. Local and Regional Authorities, together with experts and High Level Officials of Academic and Research Organizations participated.

Archaeology and archaeometry are two emergent fields in materials science with an increasing demand of access to neutron and SR-based techniques. The purpose of the symposium was to discuss and explore the current and potential applications of synchrotron science to problems in archaeology and art conservation, bringing together key members of the neutron and synchrotron community and experts in the disciplines of Archaeology, Archaeological Science, Art Conservation and Materials Science. Speakers reported their latest research accomplishments, highlight ongoing projects, and catalyse new interactions between these fields. The was to help identify problems in Eu-

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ropean Archaeology that can benefit from the application of atomic and nuclear techniques. A series of 15 minutes presentations covering a wide spectrum of techniques used in the field of Conservation, Restoration and Preservation of Cultural Heritage solicited the interest of the audience for almost four hours. Organizers of the Symposium were C. Andreani and G. Cinque of the University of Rome Tor Vergata, G. Gorini and M. Martini of University of Milano-Bicocca, A. Granelli of the University of Rome “La Sapienza” & LUISS, and V. Coda Nunziante of CNR, Rome. Professor R. Viale, President of “Fondazione Rosselli” and Chairman of the Symposium, closed the Symposium by highlighting the fundamental role that Italy could have in the field of Conservation, Restoration and Preservation of Cultural Heritage, thanks to its unique collection of works of art. His final remark “Italy has a wealth of cultural heritage unique in the world. Technological innovation in the area of Conservation, Restoration and Preservation of Cultural Heritage has a great strategic interest and deserves attention from the leading political forces” underlined the great appreciation for the topics discussed. In addition, dr.

Colin Carlile, Editor of the Journal of Neutron Research, in appreciation for the quality of the presentations, has suggested to collect all the presentations in a special issue of JNR. Professor Rudolph A. Marcus in his after dinner Nobel Conference on September 30th has summarized some of his latest work, connected with some of the topics discussed in the School. Most important, has given useful suggestions to the attendees and has personally signed and presented the Certificate of Attendance.

At the end, attendees have been given a form and have been asked to fill it with their grading of the teaching and support activities.

R. Triolo

MEETING REPORTS

Italian use of ISIS The Consiglio Nazionale delle Ricerche (CNR) supports research activities of the Italian Community in the field on Neutron and Muon Scattering. This is a long established and highly successful collaboration the Italian community benefit for thanks to the international agreement between the CNR and CCLRC. It involved the scientif-

and Molecular Assembly. In the last twenty years the British and Italian teams have also jointly collaborated in R&D projects on neutron as well as muon instrumentations, designed and constructed several innovative neutron and muon instruments and are presently involved in new projects on the target station ISIS II.

ic exploitation and development of this world leading pulsed neutron source ISIS, based at Rutherford Appleton Laboratory (UK). The Italian Partnership Agreement with ISIS was originally signed in 1985, and has continued uninterrupted since then. It has been highly successful for both partners, favouring a remarkable growth of the Italian scientific community in this field. The Italian neutron community is nowadays composed by about 500 researchers, biologists, biotechnologists, chemists, engineer â&#x20AC;&#x2122;s , geologists, physicists from CNR, other Research Institutions and Universities, all together constituting about 25% of non British users of the ISIS facility. In the last four years this community has used, on average, about 6.8 % per year (see Figure 1) of the ISIS beam team. The averaged ISIS beam time allocated to Italian teams has been labelled according to the new CNR thematic areas: 83 % in Material Science (see Figure 2), 6.6 % in Earth Sciences, Environmental Science and Cultural Heritage, 8.6 % in Energy and Transport 2 % in Manufacturing, Food Science

More recently, Italian scientists have taken a strong lead to progress the development of new detectors and detector concepts for the benefit of a wider European community. The second target station will provide additional and unique, world-leading experimental facilities for the scientific community, offering an unrivalled potential for structural and dynamical studies of condensed matter using cold neutrons. The research program will be strongly interdisciplinary, with particular emphasis on soft condensed matter, biological sciences and advanced materials.

The CCLRC-CNR collaboration provides a continuous vital training ground and backup for the Italian community of users and to multidisciplinary areas of research. Recent

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examples of research initiatives that have benefited from this collaboration include investigation on ISIS of candidate hydrogen storage technologies, and Italian archaeological specimens - helping scientists understand how, and from what they were constructed. In some cases the instruments are part of a network which supports a large campaign of measurements and might involve co-operation across several similar or complementary facilities, and across international boundaries. For the younger researchers and PhD students this represents an excellent opportunity for multi-national research co-operation where to develop a culture of cross-border co-operation.

Recently an additional opportunity for Italian scientists working in both neutron, muon. and Synchrotron Radiation (SR) has come along to make them operate in close collaboration for R&D research in area such as novel instrumentation and detections for photon and neutron scattering and SR. In May 2004 the FAMELab Memorandum of Understanding has been signed. This involves some of the leading European institutions operating in these areas of research, including CCLRC (ISIS and Diamond)UK, ELETTRA I, CNR (INFM)-I, LENS-I, INSTM-I, British-Italian Universities, the Delft University of Technology-NL and the SNS (USA).

These institutions will collaborate for R&D in instrumentation development, a critical issue to ensure efficient utilisation for the sources and to allow continued development of more sophisticated and powerful experimental techniques.

Maria Antonietta Ricci Chairman of the CNR Neutron Scattering Committee

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CALENDAR

Nov 27 - Dec 2, 2005

SYDNEY, AUSTRALIA

International Conference on Neutron Scattering (ICNS 2005) Contact: Brendan Kennedy E-mail: B.Kennedy@chem.usyd.edu.au URL: http://www.sct.gu.edu.au/icns2005/

Apr 25 - 29, 2005

SANTA FE, USA

ICANS-XVII Conference on the International Collaboration on Advanced Neutron Sources Santa Fe, USA

May 8 - 12, 2005 Feb 9 - 11, 2005 Joint ESRF-CNRS Workshop SR2A 2005 - “Synchrotron Radiation in Art and Archaelogy”.

TENNESSEE, USA

51st International Instrumentation Symposium. Knoxville, Tennessee, USA.

May 16 - 20, 2005 Feb 9 - 11, 2005

GRENOBLE, FRANCE

TENNESSEE, USA

PAC 05. Knoxville, Tennessee, USA.

Conference on EPSRC-ILL Millennium Projects.

May 28, 2005 Feb 13 - 17, 2005

SAN FRANCISCO, USA

I Symposium on “Neutron Diffraction Characterization on Mechanical Behavior” TMS Annual Meeting

Feb 14 - 25, 2005

Annual Meeting of the American Crystallographic Association - ACA 2005 one day software workshop on Structure Solution and Refinement of difficult structures using powder diffraction Lake Buena Vista, Florida, USA

JULICH, GERMANY

36th IFF Spring School: Magnetism goes Nano: Electron Correlations, Spin Transport, Molecular Magnetism

Feb 20 - March 25, 2005

FLORIDA, USA

May 26 - 28, 2005

GRENOBLE, FRANCE

Spring 2005 Conference on EPSRC-ILL Millennium Projects Institut Laue-Langevin, Grenoble, France

GRENOBLE, FRANCE

European Resarch Course for users of large experimental systems (Deadline for application: 18 October 2004).

June 20 - July 2, 2005

GRENOBLE, FRANCE

Content Meeting (CONtinuous source Time-of-flight, Evolution, Novelties and Targets for future).

Apr 2, 2005

GRENOBLE, FRANCE

Workshop on Reflectometry, Off-specular Scattering and GISANS Institut Laue Langevin, Grenoble, France http://neutron.neutron-eu.net/n_news/n_calendar_of_ events/n-events-2005/694

Apr 18 - 23, 2005

Aug 6 - 13, 2005

International Conference on Muon Spin Rotation, Relaxation and Resonance Oxford, UK

BUDAPEST, HUNGARY

Central European Training School on Neutron Scattering Budapest, Hungary http://neutron.neutron-eu.net/n_news/n_calendar_of_ events/n-events-2005/693

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OXFORD, UK

Vol. 10 n. 1 January 2005

CALL FOR PROPOSAL

Call for proposals for

Call for proposals for

Neutron Sources

Synchrotron Radiation Sources

BENSC

ALS

Deadlines for proposal submission are: 15 march 2005 and 15 september 2005

Deadlines for proposal submission are: 15 march 2005 and 1 june 2005

ILL

BESSY

Deadline for proposal submission is: 15 february 2005

Deadlines for proposal submission are: 15 february 2005 and 4 august 2005

ISIS

DARESBURY

Deadlines for proposal submission are: 16 april 2005 and 16 october 2005

Deadlines for proposal submission are: 30 april 2005 and 31 october 2005

LLB-ORPHEE-SACLAY

ELETTRA

Deadline for proposal submission is: 1 october 2005

Deadlines for proposal submission are: 28 february 2005 and 31 august 2005

SINQ

ESRF

Deadlines for proposal submission are: 15 may 2005 and 15 november 2005

Deadlines for proposal submission are: 1 march 2005 and 1 september 2005

FZ Juelich Deadline for proposal submission is: 1 february 2005.

GILDA Deadlines for proposal submission are: 1 may 2005 and 1 november 2005

HASYLAB Deadlines for proposal submission are: 1 march, 1 september and 1 december 2005

LURE Deadline for proposal submission is: 30 october 2005

MAX-LAB Deadline for proposal submission is: february 2005

NSLS Deadlines for proposal submission are: 31 january, 31 may and 30 september 2005

Vol. 10 n. 1 January 2005

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FACILITIES

LUCE DI SINCROTRONE SYNCHROTRON SOURCES WWW SERVERS IN THE WORLD (http://www.esrf.fr/navigate/synchrotrons.html) ALS Advanced Light Source Berkeley Lab, 1 Cyclotron Rd, MS6R2100, Berkeley, CA 94720 tel: +1 510.486.7745 fax: +1 510.486.4773 http://www-als.lbl.gov/ Tipo: D Status: O

ANKA Forschungszentrum Karlsruhe Institut für Synchrotronstrahlung Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen, Germany tel: +49 (0)7247 / 82-6071 fax: +49-(0)7247 / 82-6172 http://hikwww1.fzk.de/iss/

APS Advanced Photon Source Bldg 360, Argonne Nat. Lab. 9700 S. Cass Avenue, Argonne, Il 60439, USA tel:+1 708 252 5089 fax: +1 708 252 3222 http://epics.aps.anl.gov/welcome.html Tipo: D Status: C

ASTRID ISA, Univ. of Aarhus, Ny Munkegade, DK-8000 Aarhus, Denmark tel: +45 61 28899 fax: +45 61 20740 http://www.aau.dk/uk/nat/isa Tipo: PD Status: O

BESSY Berliner Elektronen-speicherring Gessell.für Synchrotron-strahlung mbH BESSY GmbH, Albert-Einstein-Str.15, 12489 Berlin, Germany, tel +49 (0)30 6392-2999 fax +49 (0)30 6392-2990 http://www.bessy.de Tipo: D Status: O

BSRL Beijing Synchrotron Radiation Lab. Inst. of High Energy Physics, 19 Yucuan Rd.PO Box 918, Beijing 100039, PR China tel: +86 1 8213344 fax: +86 1 8213374 http://solar.rtd.utk.edu/~china/ins/IHEP/bsrf/bsrf.html Tipo: PD Status: O

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CAMD Center Advanced Microstructures & Devices Louisiana State University, Center for Advanced Microstructures & Devices, 6980 Jefferson Hwy., Baton Rouge, LA 70806 tel: (225) 578-8887 fax. (225) 578-6954 Fax http://www.camd.lsu.edu/ Tipo: D Status: O

CHESS Cornell High Energy Synchr. Radiation Source Wilson Lab., Cornell University Ithaca, NY 14853, USA tel: +1 607 255 7163 fax: +1 607 255 9001 http://www.tn.cornell.edu/ Tipo: PD Status: O

CLS Canadian Light Source, University of Saskatchewan, 101 Perimeter Road, Saskatoon, SK., Canada. S7N 0X4 http://www.cls.usask.ca/ Tipo:D status:C

DAFNE INFN Laboratori Nazionali di Frascati, P.O. Box 13, I-00044 Frascati (Rome), Italy tel: +39 6 9403 1 fax: +39 6 9403304 http://www.lnf.infn.it/ Tipo:P Status: C

DELTA Universität Dortmund,Emil Figge Str 74b, 44221 Dortmund, Germany tel: +49 231 7555383 fax: +49 231 7555398 http://prian.physik.uni-dortmund.de/ Tipo: P Status: C

DIAMOND Diamond Light Source Ltd, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX http://www.diamond.ac.uk/ Tipo:D status:C

Vol. 10 n. 1 January 2005

FACILITIES

ELETTRA Sincrotrone Trieste S.C.p.A., Strada Statale 14 - Km 163,5 in AREA Science Park, 34012 Basovizza, Trieste, Italy tel: +39 40 37581 fax: +39 40 226338 http://www.elettra.trieste.it Tipo: D Status: O

Kurchatov Kurchatov Inst. of Atomic Energy, SR Center, Kurchatov Square, Moscow 123182, Russia tel: +7 95 1964546 Tipo: D Status: O/C

ELSA Electron Stretcher and Accelerator Nußalle 12, D-5300 Bonn-1, Germany tel:+49 288 732796 fax: +49 288 737869 http://elsar1.physik.uni-bonn.de/elsahome.html Tipo: PD Status: O

LNLS Laboratorio Nacional Luz Sincrotron CP 6192, 13081 Campinas, SP Brazil tel.: (+55) 0xx19 3287.4520 fax: (+55) 0xx19 3287.4632 http://www.lnls.br/ Tipo: D Status: C

ESRF European Synchrotron Radiation Lab. BP 220, F-38043 Grenoble, France tel: +33 476 882000 fax: +33 476 882020 http://www.esrf.fr/ Tipo: D Status: O

LURE Bât 209-D, 91405 Orsay ,France tel: +33 1 64468014; fax: +33 1 64464148 http://www.lure.u-psud.fr Tipo: D Status: O

EUTERPE Cyclotron Lab.,Eindhoven Univ. of Technol, P.O.Box 513, 5600 MB Eindhoven, The Netherlands tel: +31 40 474048 fax: +31 40 438060 Tipo: PD Status: C

MAX-Lab Box 118, University of Lund, S-22100 Lund, Sweden tel: +46 46 109697 fax: +46 46 104710 http://www.maxlab.lu.se/ Tipo: D Status: O

HASYLAB Notkestrasse 85, D-2000, Hamburg 52, Germany tel: +49 40 89982304 fax: +49 40 89982787 http://www-hasylab.desy.de/ Tipo: D Status: O

NSLS National Synchrotron Light Source Bldg. 725, Brookhaven Nat. Lab., Upton, NY 11973, USA tel: +1 516 282 2297 fax: +1 516 282 4745 http://www.nsls.bnl.gov/ Tipo: D Status: O

INDUS Center for Advanced Technology, Rajendra Nagar, Indore 452012, India tel: +91 731 64626 http://www.ee.ualberta.ca/~naik/accind1.html Tipo: D Status: C

NSRL National Synchrotron Radiation Lab. USTC, Hefei, Anhui 230029, PR China tel +86-551-5132231,3602034 fax +86-551-5141078 http://www.nsrl.ustc.edu.cn/en/enhome.html Tipo: D Status: O

KEK Photon Factory Nat. Lab. for High Energy Physics, 1-1, Oho, Tsukuba-shi Ibaraki-ken, 305 Japan tel: +81 298 641171 fax: +81 298 642801 http://www.kek.jp/ Tipo: D Status: O

Pohang Pohang Inst. for Science & Technol., P.O. Box 125 Pohang, Korea 790600 tel: +82 562 792696 fax: +82 562 794499 http://pal.postech.ac.kr/english.html Tipo: D Status: C

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FACILITIES

Siberian SR Center Lavrentyev Ave 11, 630090 Novosibirsk, Russia tel: +7 383 2 356031 fax: +7 383 2 352163 http://ssrc.inp.nsk.su/english/load.pl?right=general.ht ml Tipo: D Status: O

SLS Swiss Light Source Contact address: Paul Scherrer Institut, User Office, CH5232 Villigen PSI, Switzerland Tel: +41 56 310 4666 Fax: +41 56 310 3294 E-mail slsuo@psi.ch http://sls.web.psi.ch Tipo: D Status: O SPring-8 2-28-8 Hon-komagome, Bunkyo-ku ,Tokyo 113, Japan tel: +81 03 9411140 fax: +81 03 9413169 http://www.spring8.or.jp/top.html Tipo: D Status: C

SOLEIL Centre Universitaire - B.P. 34 - 91898 Orsay Cedex http://www.soleil.u-psud.fr/ Tipo: D Status:C SOR-RING Inst. Solid State Physics S.R. Lab, Univ. of Tokyo, 3-2-1 Midori-cho Tanashi-shi, Tokyo 188, Japan tel: +81 424614131 ext 346 fax: +81 424615401 Tipo: D Status: O

SRC Synchrotron Rad. Center Univ.of Wisconsin at Madison, 3731 Schneider DriveStoughton, WI 53589-3097 USA tel: +1 608 8737722 fax: +1 608 8737192 http://www.src.wisc.edu Tipo: D Status: O

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SRRC SR Research Center 1, R&D Road VI, Hsinchu Science, Industrial Parc, Hsinchu 30077 Taiwan, Republic of China tel: +886 35 780281 fax: +886 35 781881 http://www.srrc.gov.tw/ Tipo: D Status: O SSRL Stanford SR Laboratory 2575 Sand Hill Road, Menlo Park, California, 94025, USA tel: +1 650-926-4000 fax: +1 650-926-3600 http://www-ssrl.slac.stanford.edu/welcome.html Tipo: D Status: O

SRS Daresbury SR Source SERC, Daresbury Lab, Warrington WA4 4AD, U.K. tel: +44 925 603000 fax: +44 925 603174 E-mail: srs-ulo@dl.ac.uk http://www.dl.ac.uk/home.html Tipo: D Status: O

SURF III B119, NIST, Gaithersburg, MD 20859, USA tel: +1 301 9753726 fax: +1 301 8697628 http://physics.nist.gov/MajResFac/surf/surf.html Tipo: D Status: O

TERAS ElectroTechnical Lab. 1-1-4 Umezono, Tsukuba Ibaraki 305, Japan tel: 81 298 54 5541 fax: 81 298 55 6608 Tipo: D Status: O

UVSOR Inst. for Molecular ScienceMyodaiji, Okazaki 444, Japan tel: +81 564 526101 fax: +81 564 547079 Tipo: D Status: O

D = macchina dedicata

D = dedicated machine

PD = parzialmente dedicata

PD = partially dedicated

P = in parassitaggio

P = parassitic

O = macchina funzionante

O = operating machine

C = macchina in costruzione

C = machine under construction

Vol. 10 n. 1 January 2005

FACILITIES

NEUTRONI NEUTRON SCATTERING WWW SERVERS IN THE WORLD (http://www.isis.rl.ac.uk) Atominstitut Vienna (A) Facility: TRIGA MARK II Type: Reactor. Thermal power 250 kW. Flux: 1.0 x 1013 n/cm2/s (Thermal); 1.7 x 1013 n/cm2/s (Fast) Address for information: 1020 Wien, Stadionallee 2 - Prof. H. Rauch Tel: +43 1 58801 14111; Fax: +43 1 58801 14199 E-mail: boeck@ati.ac.at; http://www.ati.ac.at Wap: wap.ati.ac.at NRU Chalk River Laboratories The peak thermal flux 3x1014 cm-2 sec-1 Neutron Program for Materials Research National Research Council Canada Building 459, Station 18 Chalk River Laboratories Chalk River, Ontario - Canada K0J 1J0 Phone: 1 - (888) 243-2634 (toll free) Phone: 1 - (613) 584-8811 ext. 3973 Fax: 1- (613) 584-4040 http://neutron.nrc-cnrc.gc.ca/home.html Budapest Neutron Centre BRR (H) Type: Reactor. Flux: 2.0 x 1014 n/cm2/s Address for application forms: Dr. Borbely Sándor, KFKI Building 10, 1525 Budapest - Pf 49, Hungary E-mail: Borbely@power.szfki.kfki.hu http://www.iki.kfki.hu/nuclear FRJ-2 Research Reactor in Jülich (D) Type: Dido reactor. Flux: 2 x 1014 n/cm2/s Prof. D. Richter, Forschungszentrums Jülich GmbH, Institut für Festkörperforschung, Postfach 19 13, 52425 Jülich, Germany Tel: +49 2461161 2499; Fax: +49 2461161 2610 E-mail: neutron@fz-juelich.de http://www.neutronscattering.de FRG-1 Geesthacht (D) Type: Swimming Pool Cold Neutron Source.

Flux: 8.7 x 1013 n/cm2/s Address for application forms and informations: Reinhard Kampmann, Institute for Materials Science, Div. Wfn-Neutronscattering, GKSS, Research Centre, 21502 Geesthacht, Germany Tel: +49 (0)4152 87 1316/2503; Fax: +49 (0)4152 87 1338 E-mail: reinhard.kampmann@gkss.de http://www.gkss.de

HMI Berlin BER-II (D) Facility: BER II, BENSC Type: Swimming Pool Reactor. Flux: 2 x 1014 n/cm2/s Address for application forms: Dr. Rainer Michaelsen, BENSC, Scientific Secretary, Hahn-Meitner-Insitut, Glienicker Str 100, 14109 Berlin, Germany Tel: +49 30 8062 2304/3043; Fax: +49 30 8062 2523/2181 E-mail: michaelsen@hmi.de; http://www.hmi.de/bensc IBR2 Fast Pulsed Reactor Dubna (RU) Type: Pulsed Reactor.

Flux: 3 x 1016 (thermal n in core) Address for application forms: Dr. Vadim Sikolenko, Frank Laboratory of Neutron Physics Joint Institute for Nuclear Research 141980 Dubna, Moscow Region, Russia.

Tel: +7 09621 65096; Fax: +7 09621 65882 E-mail: sikolen@nf.jinr.dubna.su http://nfdfn.jinr.ru/flnph/ibr2.html ILL Grenoble (F) Type: 58MW High Flux Reactor.

Flux: 1.5 x 1015 n/cm2/s Scientific Coordinator Dr. G. Cicognani, ILL, BP 156, 38042 Grenoble Cedex 9, France Tel: +33 4 7620 7179; Fax: +33 4 76483906 E-mail: cico@ill.fr and sco@ill.fr; http://www.ill.fr IPNS Intense Pulsed Neutron at Argonne (USA) for proposal submission by e-mail send to cpeters@anl.gov or mail/fax to: IPNS Scientific Secretary, Building 360 Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439-4814, USA Phone: 630/252-7820; Fax: 630/252-7722 http://www.pns.anl.gov/ IRI Interfaculty Reactor Institute in Delft (NL) Type: 2MW light water swimming pool.

Flux: 1.5 x 1013 n/cm2/s Address for application forms: Dr. A.A. van Well, Interfacultair Reactor Institut, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands Tel: +31 15 2784738; Fax: +31 15 2786422 E-mail: vanWell@iri.tudelft.nl; http://www.iri.tudelft.nl

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FACILITIES

ISIS Didcot (UK) Type: Pulsed Spallation Source.

Flux: 2.5 x 1016 n fast/s Address for application forms: ISIS Users Liaison Office, Building R3, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX Tel: +44 (0) 1235 445592; Fax: +44 (0) 1235 445103 E-mail: uls@isis.rl.ac.uk; http://www.isis.rl.ac.uk

NIST Research Reactor, Washington, USA National Institute of Standards and Technology-Gaithersburg, Maryland 20899 USA Center Office: J. Michael Rowe, 6210, Director NIST Center for Neutron Research E-mail: mike.rowe@nist.gov http://www.ncnr.nist.gov/

JAERI (J) Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-11, Japan.

Jun-ichi Suzuki (JAERI); Yuji Ito (ISSP, Univ. of Tokyo); Fax: +81 292 82 59227; Telex: JAERIJ24596 http://www.ndc.tokai.jaeri.go.jp/

NRI Rez (CZ) Type: 10 MW research reactor.

Address for informations: Zdenek Kriz, Scientif Secretary Nuclear Research Institute Rez plc, 250 68 Rez - Czech Republic Tel: +420 2 20941177 / 66173428; Fax: +420 2 20941155 E-mail: krz@ujv.cz / brv@nri.cz; http://www.nri.cz

JEEP-II Kjeller (N) Type: D2O moderated 3.5% enriched UO2 fuel.

Flux: 2 x 1013 n/cm2/s Address for application forms: Institutt for Energiteknikk K.H. Bendiksen, Managing Director Box 40, 2007 Kjeller, Norway Tel: +47 63 806000, 806275; Fax: +47 63 816356 E-mail: kjell.bendiksen@ife.no; http://www.ife.no

PSI-SINQ Villigen (CH) Type: Steady spallation source.

Flux: 2.0 x 1014 n/cm2/s Contact address: Paul Scherrer Institut User Office, CH-5232 Villigen PSI - Switzerland Tel: +41 56 310 4666; Fax: +41 56 310 3294 E-mail: sinq@psi.ch; http://sinq.web.psi.ch

LLB Orphée Saclay (F) Type: Reactor. Flux: 3.0 x 1014 n/cm2/s Laboratoire Léon Brillouin (CEA-CNRS) Submissio by email at the following address : experience@llb.saclay.cea.fr http://www-llb.cea.fr/index_e.html

TU Munich FRM, FRM-2 (D) Type: Compact 20 MW reactor.

Flux: 8 x 1014 n/cm2/s Address for information: Prof. Winfried Petry, FRM-II Lichtenbergstrasse 1 - 85747 Garching Tel: 089 289 14701; Fax: 089 289 14666 E-mail: wpetry@frm2.tum.de http://www.frm2.tu-muenchen.de

NFL Studsvik (S) Type: 50 MW reactor. Flux: > 1014 n/cm2/s Address for application forms: Dr. A. Rennie, NFL Studsvik S-611 82 Nyköping, Sweden Tel: +46 155 221000; Fax: +46 155 263070/263001 E-mail: user.admin@studsvik.uu.se http://www.studsvik.uu.se

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SPALLATION NEUTRON SOURCE, ORNL (USA) http://www.sns.gov/

Vol. 10 n. 1 January 2005

NOTIZIARIO

Neutroni e Luce di Sincrotrone

Vol. 10 n. 1 2005

Rivista del Consiglio Nazionale delle Ricerche

Rivista del Consiglio Nazionale delle Ricerche

NOTIZIARIO Neutroni e Luce di Sincrotrone

ISSN 1592-7822

www.cnr.it/neutronielucedisincrotrone

EDITORIAL C. Andreani

SCIENTIFIC REVIEWS Investigating large scale structures by combining small angle and ultra small angle neutron scattering F. Lo Celso, I. Ruffo, A. Riso and V. Benfante

Star-Like polymer solutions studies by light and neutron scattering G. Di Marco, N. Micali, R. Ponterio, V. Villari and A. Hainemann

Inelastic ultraviolet scattering beamline at Elettra C. Masciovecchio, A. Gessini, S. Di Fonzo and S.C. Santucci

Âľ &N&SR NEWS MEETING AND REPORTS CALENDAR CALL FOR PROPOSAL FACILITIES

ISSN 1592-7822

Vol. 10 n. 1

January 2005 - Aut. Trib. Roma n. 124/96 del 22-03-96 - Sped. Abb. Post. 70% Filiale di Roma - C.N.R. p.le A. Moro 7, 00185 Roma