nnls_vol14-n2_09

L. Malavasi, G. Chiodelli, G. Flor, C. Tealdi

Electronic Structure of Complex Materials revealed by Resonant X-Ray Bragg Diffraction V. Scagnoli, S.W. Lovesey

Research Infrastructures First Users at the ISIS Second Target Station M. Bull

EUPhoS: a New Bright Light Source G. De Ninno, M. Coreno et al.

Muon & Neutron & Synchrotron Radiation News ESS Bilbao Initiative Workshop Multi-MW Spallation Neutron Sources C. Oyon

School and Meeting Reports ICNS 2009 held in Knoxville

Consiglio Nazionale delle Ricerche School – Meeting

Solid State Ionic Materials Investigation by Neutron Scattering

M & N & SR News

M. Ferrario

Infrastructures

Green Light from the SPARC FEL project

Scientific Reviews

Scientific Reviews

www.cnr.it/neutronielucedisincrotrone

ISSN 1592-7822 - Vol. 14 n. 2 September 2009 - 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

Consiglio Nazionale delle Ricerche

School and Meeting Reports

M & N & SR News

Research Infrastructures

Scientific Reviews

www.cnr.it/neutronielucedisincrotrone

SUMMARY

published by CNR (Publishing and Promotion of Scientific Information) in collaboration with the Physics Department of the University of Rome Tor Vergata

Consiglio Nazionale delle Ricerche

Editorial News Italian and British Scientists celebrate strong partnership in Neutron Scattering…………… 2

Vol. 14 n. 2 Settembre 2009 Aut. Trib. Roma n. 124/96 del 22-03-96

M. Bull

Scientific Reviews Green Light from the SPARC FEL project…………… 4 M. Ferrario

Solid State Ionic Materials Investigation by Neutron Scattering…………… 6 L. Malavasi, G. Chiodelli, G. Flor, C. Tealdi

Electronic Structure of Complex Materials revealed by Resonant X-Ray Bragg Diffraction…………… 12 V. Scagnoli, S.W. Lovesey

EDITOR

C. Andreani

Research Infrastructures First Users at the ISIS Second Target Station…………… 21 M. Bull

EUPhoS: a New Bright Light Source…………… 23 G. De Ninno, M. Coreno et al.

EXECUTIVE EDITOR

M. Apice EDITORIAL OFFICE

L. Avaldi, T. Guidi, S. Imberti, L. Palumbo, G. Paolucci, R. Triolo, M. Zoppi EDITORIAL SERVICE AND ADVERTISING FOR EUROPE AND USA

P. Casella, A. Minella

Muon & Neutron & Synchrotron Radiation News ESS Bilbao Initiative Workshop Multi-MW Spallation Neutron Sources…………… 33 C. Oyon

School and Meeting Reports ICNS 2009 held in Knoxville…………… 35

CORRESPONDENTS AND FACILITIES

M. Bertolo (I3-IA-SFS) A. Claver (NMI3) A.E. Ekkebus (SNS) ON LINE VERSION

V. Buttaro CONTRIBUTORS TO THIS ISSUE

M. Bull, A. Claver, S. Cordon, H. Schober

Call for Proposals…………… 38 Calendar…………… 40

REQUEST OF PREVIOUS ISSUES AND EDITORIAL INFORMATION

P. Casella, A. Minella E-mail: nnls@roma2.infn.it GRAPHIC AND PRINTING

Facilities…………… 42

omgrafica srl Via Fabrizio Luscino 73 00174 Roma

Finito di stampare nel mese di Settembre 2009

Cover photo.

The Nimrod instrument at ISIS.

Editorial News

Italian and British Scientists celebrate strong partnership in Neutron Scattering M. Bull Head of Communications ISIS, Didcot, UK

Dr. André Taylor, ISIS Director, and Professor Luciano Maiani, CNR President, at the ISIS Second Target Station.

Strong relations between the Italian and UK neutron scattering and science communities have been further strengthened with a visit by Professor Luciano Maiani, president of the Italian Consiglio Nazionale delle Ricerche (CNR), to the ISIS Pulsed Neutron and Muon Source. The visit in March was one of his first engagements after taking office as the new President of the CNR. ISIS at the Rutherford Appleton Laboratory near Oxford and is owned and operated by the UK’s Science and Technology Facilities Council. A £145 million pound new research centre, the ISIS Second Target Station, has recently been completed allowing scientists to expand their work into the key research areas of soft matter, advanced materials and bio-science.

At a ceremony to inaugurate the newest instrument at the new target station, Nimrod, and to celebrate the excellent and long-standing working partnership between Italy, the UK and ISIS in neutron scattering, Professor Maiani said: «I’m very proud to inaugurate Nimrod. It represents the long and precious collaboration between the CNR and STFC. This instrument represents another important step in the study of matter with neutron scattering, which will offer important information to the Italian scientists whose work uses ISIS and confirms Italian excellence in this field of research».

In response, Dr Andrew Taylor, ISIS Director, said that Professor Maiani’s visit recognised the importance of neutron scattering and the strength of Italian scientists in this field of research. «We are delighted to show the achievements of Italian science at ISIS during this visit and celebrate the continuation of this long-standing partnership for the years to come» he said.

Professor Maiani also noted that neutrons are an essential tool, for the investigation of matter at the microscopic scale. «There is the possibility for many applications: from electronics to the design and manufacture of new materials, all kinds of biomedical devices, the environment and the protection of cultural property» he said.

A LONG AND PRODUCTIVE SCIENTIFIC COLLABORATION

Professor Maiani unveiled a plaque to inaugurate the Nimrod instrument and celebrate ongoing collaboration between Italy and the UK.

Italian scientists have had long-lasting connections with ISIS. Scientific collaboration between Italy and the UK on neutron scattering started in the early 1980s, before ISIS was operational, with work on the Harwell Electron Linac, the first pulsed neutron source at the Harwell site. A new neutron source at the Harwell Campus was approved in 1977. Based around a proton synchrotron accelerator, ISIS produced its first neutrons in late 1984 and it was officially inaugurated in October 1985. That same year, an agreement to cooperate on neutron scattering science for the exploitation and development of ISIS was signed between the Italian CNR and the Rutherford Appleton Laboratory. It has been renewed several times over the years in 1990, 1993, 1996, 2001 and now most recently in 2008 stretching forward to 2014. After nearly 25 years of neutron scattering research, Italy is now one of the major partners in ISIS.

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The partnership has produced a wide-range of collaborative science programmes, frequent exchange and discussion of new ideas and has trained many young scientists in the skills needed to get the best results out of neutron scattering experiments. As a result, Italy has become much more than just a contributing partner to operations at ISIS. Around 100 scientists from around Italy are regular users of ISIS for their research. They represent the institutions of the CNR and universities including Roma Tor Vergata, Roma Tre, Roma La Sapienza, Milano-Bicocca, Milano, Ancona, Brescia, Cagliari, Firenze, Genova, Messina, Modena, Napoli, Palermo, Parma and Perugia. Scientific interests are very broad and include liquids and disordered materials, bio-science, cultural heritage, engineering, magnetism and advanced materials.

The Italian neutron science community also has a long-standing enthusiasm for the development of advanced neutron instruments at ISIS. These include the Prisma and Tosca spectrometers, and development of high energy neutron spectroscopy and detectors through the eVerdi project for the Vesuvio instrument. Italy has also contributed to the Sandals instrument for disordered materials. More recently, the Ines instrument has been constructed for cultural heritage studies, the development of new techniques such as neutron tomography and for training Italian scientists in neutron scattering methods.

Italy was also one of the partners in a European consortium which established the first muon beam line on ISIS for the investigation of the properties of matter by muon spectroscopy measurements. Italy has also co-ordinated, on behalf of a European consortium, a European Union Framework Programme 6 project to provide for novel instrumentation for the ISIS Second Target Station Project.

Dr. Marco Zoppi, CNR - Istituto Sistemi Complessi, explains how neutron scattering gives important results across a wide range of research.

NIMROD AND FUTURE PROJECTS

Most recently, the CNR is a major partner in the construction of the Nimrod instrument. Nimrod is one of the seven phase one instruments that have been built at the ISIS second target station. It allows liquids and glassy materials to be examined in minute detail and will contribute to the understanding of many current and emerging fields of technology.

The manufacture and supply of the vacuum tank for the instrument, worth more than 0.5M â‚Ź, is an impressive piece of engineering, some 8m x 4m x 4m in size.

It is critical to the performance of the instrument and was built by SIMIC SpA, Camerana. The high specification engineering required for the vacuum tank has allowed Italian industry to contribute to a world-leading scientific endeavour and has enabled new capability in engineering to be demonstrated.

Italian collaborations with ISIS teams also include instrument simulation, development of ceramic shielding materials, neutron radiography techniques, and the design of a sample changer. The sample changer was manufactured by RMP s.r.l., Rome.

For the second phase of instruments at the ISIS second target station, Italy is a major partner in two instruments. Chipir will be used for testing of electronics with high energy neutrons. Imat is an instrument for neutron imaging of engineering materials and cultural heritage objects. It is expected that close collaborations with Italian industry and academia in the development and exploitation of both of these instruments will continue for many years ahead.

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The Nimrod instrument at ISIS. The instrument vacuum tank manufactured by SIMIC S.p.A, Camerana lies along the centre of the instrument and is surrounded by neutron detectors.

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Green Light from the SPARC FEL project M. Ferrario INFN-LNF

After the successful results obtained at FLASH (DESY-Hamburg) and for the first time in Italy another Free Electron Laser (FEL) has been “switched on� in Europe. This goal has been achieved at the INFN Laboratories in Frascati by a group of scientist belonging to INFN, ENEA and CNR, funded by the Italian Minister of Research (MIUR) and partially by the EUROFEL Project within the 6th Framework Programme of UE. The name of the FEL project is SPARC (Sorgente Pulsata Autoamplificata di Radiazione Coerente) and it is the prototype of a larger user facility named SPARX [see these journal, Vol 14, n. 1 2009] that will enable the production of hard X-rays photon beams.

It will be the micro-scope, or more precisely the nano-scope, of the new millenium and it will certainly bring new perspectives to the Italian research community with a wide range of applications including nano-technology and bio-medical applications.

Figure 1. Layout of the SPARC FEL project. A 1 nC, 10 ps long electron beam is generated inside a 15 cm long RF accelerating structure (Gun) by a copper photocathode illuminated by a UV laser pulse. The beam is captured, accelerated up to 5 MeV and injected in three accelerating RF structures (Linac) that drive the beam up to 150 MeV. The beam in then matched to the six undulator modules, 2 m long each, where the radiation process takes place.

An external low power laser pulse can be injected in the undulator together with the electron beam (Seeding) in order to be amplified by the interaction with the electrons. Alternatively the electron beam can be driven in the parallel beam line where a THz radiation source has been recently installed.

The SPARC group has been able to observe a radiation of 500 nm (green light) by injecting a 150 MeV electron beam into a 15 m long undulator.

More technically a FEL is a device able to generate intense and short wavelength radiation pulses as the one required to investigated single

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molecule, protein and virus structures and to observe ultra-fast bio-chemical processes with unprecedent spatial and time resolution.

The FEL consists in a long undulator, a chain of small magnets with alternate polarity, that drives a high current electron beam, injected by a linear accelerator, into sinusoidal trajectories.

Inside the undulator the electron beam radiates coherent synchrotron radiation at a resonant wavelength that depends directly on magnetic field strength and it is inversely proportional on the square of the electron beam energy.

For these dependence it is possible to change the emitted radiation wavelength by simply varying the electron beam energy or the magnetic field strength, allowing in this way to tune the “color� of the emitted radiation to best fit the requirements of the application.

Figure 2. Photo of the SPARC photoinjector showing the 3 accelerating structures with 2 long solenoids.

Figure 3. Photo of the SPARC FEL taken from the undulator end.

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Solid State Ionic Materials Investigation by Neutron Scattering L. Malavasi, G. Flor and C. Tealdi

ABSTRACT

Department of Physical Chemistry “M. Rolla” and INSTM, Università di Pavia, Italy CNR - IENI Sezione di Pavia, Università di Pavia, Italy

In this paper we will give an overview of some recent results obtained by means of neutron scattering techniques on solid state ionic materials. In particular, we will discuss the application of pair distribution function (PDF) analysis of neutron total scattering data on a recently discovered fast oxide ion conductor, La2Mo2O9, thus highlighting the importance of studying the short-range structural features of conducting solids. In addition, we will present the results of a detailed investigation about the structure-properties correlation carried out on the most promising proton conductor, i.e. Y-doped BaCeO3, with emphasis on the importance of collecting neutron diffraction data under experimental condition which will then allow to get reliable correlations between structure and functional properties.

G. Chiodelli CNR - IENI Sezione di Pavia, Università di Pavia, Italy

The field of solid state ionics (SSI) deals with ionically conducting materials in the solid state and numerous devices based on such materials. Solid state ionic materials cover a wide spectrum, ranging from inorganic crystalline and polycrystalline solids, ceramics, glasses, polymers, composites and nano-scale materials.

One of the most exciting and investigated class of SSI materials is the one of oxide ion and proton conducting electrolytes. The interest on these phases is related to their application in solid oxide fuel cells (SOFCs) where the mobile species can be oxide ions or protons. One of the most know electrolyte for SOFCs is yttra-stabilized zirconia (Y2O3 doped ZrO2 - YSZ) which is already used in real devices working at high temperature (>800°C). The research in this field is extremely active and aimed at discovering new electrolytes with advanced properties and in particular with high ionic conductivities at lower temperatures. This is the case, in particular, of proton conducting materials, such as acceptor-doped BaCeO3, where the highest values of proton conductivity is usually achieved around 500°C. However, the research in the field of proton electrolytes is more recent with respect to oxide ion materials and new compositions are reported frequently in the current literature.

Since few years we have started a systematic investigation of several – well established or recently discovered – solid state ionic materials by neutron scattering techniques. The use of neutrons has significant advantages in the study of these oxides. For example, the sensitivity of neutron diffraction (ND) to both the light atom positions and site occupancies have made the technique invaluable in the structural characterization of such compounds. In fact many oxide ion and proton conducting materials give origin to extensive oxygen non-stoichiometry as a function of temperature which is at the basis of their working mechanism. Our approach to the use of ND in SSI materials is also aimed at investigating their structural properties under “working conditions” (for example, for proton conducting oxides we usually collect data under “dry” and “wet” gas environments where water incorporation promotes the proton conductivity) and in the same experimental conditions used to collect the most Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

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important functional properties measurements such as electrical conductivity and thermal analysis. This allowed us to give reliable correlations between the structural evolution of a material and, for example, the conductivity trend as a function of temperature. In addition to ND, we used, for the first time on SSI materials, neutron total scattering measurements and pair distribution function (PDF) analysis for the investigation of the local order of oxide ion and proton conducting oxides.

PDF is a well know technique in the field of disordered materials while its application to crystalline compounds is more recent and become possible thanks to the evolution of neutron and synchrotron dedicated facilities. This technique is based on the acquisition of a powder diffraction pattern where all the coherent scattering coming from the sample is taking into account, that is both the Bragg and diffuse scattering. A fundamental requisite in order to get high resolution of the PDF in the real space is to extend the Q-range of the data collection to – ideally – infinite. However, since the resolution is then limited by the thermal vibration of the atoms, a reasonable Q-range is usually around 30-35 Å-1. A detailed description of this technique in the case of crystalline solids can be found in [1].

In the following we will give few examples of some results we obtained through the application of neutron scattering techniques on two different kinds of SSI materials: 1) a recently discovered oxide ion conductor, La2Mo2O9 (named LAMOX), and 2) the most known proton conductor, i.e. Y-doped BaCeO3.

The search for new fast oxide ion conductors led to the discovery in 2000 of the LAMOX compound [2] by the Lacorre’s group. This compound exhibits a first order phase transition from the non-conductive monoclinic phase (α) to the highly-conductive cubic phase (β) at around 580°C with the latter phase having ionic conductivity of approximately 6x10-2 Scm-1 at 800°C. The structure of the low temperature phase was solved by I.R. Evans et al in 2005 [3] resulting in one of the most complex oxide structures reported up to now with 312 crystallographically independent atoms. Based on the atoms arrangement in the α-form the Authors proposed that the structure of the β-phase corresponds to a time average version of the room-temperature monoclinic structure [3]. The structure of the cubic form was proposed in 2000 by Lacorre [2] and then revised in 2001 [4]. This was determined by means of neutron diffraction and led the Authors to propose a model where two of the three available oxygen sites (O2 and O3) are partially occupied and characterized by huge atomic displacement parameters (up to Beq~20 Å2 for the O3 site).

The presence of a strong modulation in the neutron diffraction patterns (due to diffuse scattering) of the conducting β-phase of LAMOX led to the conclusion that a strong static disorder of oxygen atoms occurs in this phase which was considered to be the source of the high oxygen mobility. This case is a typical one where the use of a probe of the average structure can not reveal all the details of this complex compound leading to a loss of structural details which may be of great importance in understanding the underlying conduction mechanism. Our approach in this case was to apply the PDF technique from neutron total scattering data in order to get further insight into the structural features of the two polymorphs of LAMOX (the α- and β-phases), test the 9

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available models for the two phases, and try to better understand the correlation between the monoclinic and cubic polymorphs.

We remark that the use of total scattering measurements allows to get both the average (through analysis of the ND patterns) and the local (through the PDF analysis) structure.

Experiments on LAMOX where carried out at the time-of-flight LANSCE neutron facility in Los Alamos (USA – NM) on the NPDF instrument collecting data on the α-phase (at 500°C) and β-phase (at 600°C). Figure 1 shows a selected region of the LAMOX neutron patterns at 500°C (lower part) and 600°C (upper part) as a function of Q [5].

The 500°C pattern is fully compatible with the monoclinic reference structure while the 600°C pattern is in total agreement with the cubic reference structure. However, as can be seen in the diffraction pattern of the sample at 600°C there is a peculiar undulation of the diffuse background which is peaked at around 3 Å-1 (highlighted by a curve). The common analysis of ND patterns

Figure 1. Neutron diffraction patterns of La2Mo2O9 at 500°C (lower part) and 600°C (upper part).

The inset shows a small part of the pattern on an expanded scale for both temepratures for comparison.

Reprinted with permission from L. Malavasi et al., J. Am. Chem. Soc., 2007, 129 (21), pp. 6903-6907.

Copyright 2007 American Chemical Society.

Figure 2.

Panel A: comparison between the experimental PDFs of LAMOX at 500°C (blue line) and 600°C (red line) and their difference (black line).

Panel B: comparison between the calculated PDFs of LAMOX from the monoclinic (blue line) and cubic (red line) models. Details about the calculated PDFs are in the text.

Reprinted with permission from L. Malavasi et al., J. Am. Chem. Soc., 2007, 129 (21), pp. 6903-6907.

Copyright 2007 American Chemical Society.

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by Rietveld methods neglect this contribution by simply fitting it as a background and subtracting it from the ND patterns. As mentioned above, the use of total scattering method and PDF analysis allow to take into account the contribution of this diffuse scattering as well which is related to local deviations of the long-range order.

Figure 2 (Panel A) shows the experimental PDFs at 500°C and 600°C extracted from the diffraction patterns reported in Figure 1 in the r-range extending to 20 Å together with the difference curve calculated by subtracting the PDF of the 500oC data from the PDF of the 600oC data.

The comparison of the data sets clearly reveals that the PDFs of the monoclinic and cubic samples are substantially identical over the range investigated. This result implies that the local structure of the two polymorphs of LAMOX is the same, as opposed to the average structures, which are markedly different as shown above. For comparison, panel B reports the calculated PDFs for the cubic and monoclinic structures thus showing how the PDF should look if the local structure would really change from the monoclinic to the cubic phases.

This comparison helps in developing an intuitive feeling about how large the 10

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changes in the PDF would be at this phase transition if the two phases were fully ordered.

The observation that the PDFs of cubic and monoclinic LAMOX are substantially identical is a clear indication that the static disorder of the monoclinic structure, which is represented by the 216 oxygen atoms possessing different and unique atomic positions, is in a sense replaced in the cubic phase by a distribution of the oxygen ions which is locally the same as in the monoclinic phase but no longer long-range ordered.

The loss of long-range order would allow the structure to become dynamic, consistent with increased ionic conductivity though our current diffraction data do not separate the static and dynamic components explicitly. Also the refinement of the experimental data (not shown) was possible, for the data at 600°C, i.e. in the cubic LAMOX, only by using as starting model the monoclinic structure. Any attempt to refine the high-temperature data led to low agreement factors and, in addition, to unrealistic oxygen atoms

Figure 3. Neutron Diffraction (ND) patterns of BCY at the temperatures investigated. Inset: details of ND patterns around the region where main peaks are located. Temperatures are the same as in the main Figure.

Reprinted with permission from L. Malavasi et al., Chem. Mater., 2008, 20, pp. 2343-2351. Copyright 2007 American Chemical Society.

occupancies and again huge atomic displacement parameters. The main result presented so far, i.e. the equivalence of the local structure in the monoclinic and cubic phase, is of great importance since it demonstrates that what is usually considered as a “disordered oxygen distribution” has actually a well defined local structure which is the same as in the monoclinic phase but dynamic. As it has been suggested by Evans and co-workers, the structure of the oxide ion conducting phase corresponds to a time-averaged version of the monoclinic phase5. However, by using an advanced characterization techniques we took a step further in elucidating the correlation between the α and β-phase of LAMOX by directly showing this relationship through the PDF analysis. This understanding allowed us to consider different possible oxygen ion conduction paths in the conducting β-phase of LAMOX by considering, as a starting point, the monoclinic structure. For a more detailed description of this topic the reader is referred to [5].

This work on the LAMOX materials was the first application of the atomic-pair distribution function analysis to the study of an oxygen fast-oxide ion conductor of actual interest in the SOFC community. Our results have shown that a clear 11

Figure 4. TGA trace of BaCe0.80Y0.20O2.9 sample under air (solid line) and oxygen content as a function of temperature as determined from the refinement of the oxygen occupancy. Reprinted with permission from L. Malavasi et al., Chem. Mater., 2008, 20, pp.

2343-2351. Copyright 2007 American Chemical Society.

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and reliable description of the local atom arrangement in the LAMOX structure can only be achieved through the application of a local probe such as the PDF. This allowed us to directly determine that the transition from the monoclinic to the cubic phase of LAMOX is a transition from a static to a dynamic distribution of the oxygen defects while preserving the monoclinic local structure.

As mentioned above, the other very active field in SSI materials is related to the investigation of proton conducting oxides for SOFCs working in the intermediate temperature range (500-700°C). At the moment, the most promising material still remains the acceptor doped barium cerate, BaCeO3.

Our attention on this material turned on the study of the correlation between its structural evolution as a function of temperature and its functional properties in the same temperature range. We remark that most of the neutron diffraction measurements at high-temperature are currently carried out under high vacuum for technical reasons such as the oxidation of vanadium container routinely employed in ND measurements. In collaboration with D1A instrument scientist at ILL (Dr. Clemens Ritter) we have optimized an “open-furnace” configuration for high-T ND collection allowing also the selection of appropriate gas flux during the measurement runs.

On the optimally doped BaCe0.80Y0.20O2.9 proton conductor we carried out an extensive investigation of structural and functional properties as a function of temperature under controlled and analogous experimental conditions for all the characterizations [6]. Figure 3 displays the neutron diffraction (ND) patterns acquired on the BaCe0.80Y0.20O2.9 sample at the different temperatures investigated (30-800°C). The inset highlights a region showing clear changes.

As already previously stated, neutron diffraction is a more sensitive probe with respect to X-ray diffraction for the study of cerates due to both the possibility to get valuable information related to superlattice intensity and for the lack of form-factor fall with Q [7].

By means of Rietveld refinement of the ND data we could define the evolution of the crystal structure of BaCe0.80Y0.20O2.9 as a function of temperature. This can be summarized as follows: a. from RT to 400 it is monoclinic with space group I2/m; b. at 500°C the materials adopts the orthorhombic Imma structure; _ c. at 600 and 700°C it is rhombohedral (R _ 3 c) and d. finally at 800°C it becomes cubic (Pm 3 m).

The refinement of the oxygen occupancies can give important information not only on the oxygen stoichiometry as a function of temperature but also on the location of the oxygen vacancies which are the site of water incorporation according to: (1) Figure 4 shows the variation of weight determined from thermogravimetry, collected under the same experimental conditions employed for the acquisition of the neutron diffraction patterns, and the oxygen content of BaCe0.80Y0.20O2.9 calculated from the oxygen occupancies. First of all we note that the refined occupancy at RT is around 2.90(4), in good agreement with the nominal oxygen content of the sample. This oxygen content remains practically Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

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constant until about 600°C and then starts to decrease. The oxygen content derived from oxygen occupancy at 800°C is 2.79(4). The comparison with the TGA trace reveals a good agreement between the weight variation and the oxygen content change with temperature. The weight change in the thermogravimetric measure is ascribable to the change in the oxygen content only. This can be concluded by the reversible behaviour of the weight variation with T (not shown). The oxygen content at 800°C determined from the TGA curve is 2.82, which is in fairly good agreement with the oxygen content determined from the Rietveld refinement.

Figure 5 displays the Arrhenius plot of the electrical conductivity data of the BaCe0.80Y0.20O2.9 sample collected under the same conditions as the neutron diffraction experiments. The conductivity increases as the temperature increases with an evident slope change around 500°C. The activation energies before and after the slope change are about 0.85 eV and 0.35 eV, respectively.

Under the measurement conditions the only mobile defects are oxygen vacancies. Their concentration remains practically constant until 700°C as determined in this work by means of TGA and Rietveld refinement of oxygen occupancies (see Figure 4). The increase of conductivity by raising temperature is due to an increase of defects mobility until the highest temperatures, where the reduction in the oxygen content contributes to the increase in the oxygen vacancies concentration. The observed change in the activation energy _ falls in the region of a phase transition of BaCe0.80Y0.20O2.9 (Imma➝R 3 c) thus suggesting a possible origin for this slope change.

To conclude, in this review article we have given a couple of examples of the use of neutron scattering in the field of SSI. We believe that these examples clearly demonstrate the usefulness related to the investigation or re-investigation of electrolyte and/or cathode materials by means of advanced characterization probes using neutrons.

The application of PDF which will become more and more a “user-friendly” technique in the future may reveal fascinating and still unsolved question related to this class of materials such as the nature of non-conducting to conducting phase transitions and the ion diffusion pathways. In addition, the work on cerates showed the importance of collecting structural data in experimental conditions analogous to those employed for conductivity measurements which allows a reliable structure-property correlation. Our efforts in this direction are towards the optimization of experimental set-ups in order to carry out in “operando” structural measurements which will open a very promising field of investigation for SSI materials.

Figure 5. Arrhenius plot of electrical conductivity in air for BaCe0.80Y0.20O2.9. Reprinted with permission from L. Malavasi et al., Chem. Mater., 2008, 20, pp. 2343-2351. Copyright 2007 American Chemical Society.

REFERENCES 1. Egami, T. and Billinge, S.J.L. (2003) Underneath the Bragg peaks: structural analysis of complex materials, Pergamon Press, Elsevier, Oxford, England 2. Lacorre, P., Goutenoire, F., Bohnke, O., Retoux, R., Laligant, Y., Nature 404, 856-858 (2000) 3. Evans, I.R., Howard, J.A.K., Evans, J.S.O. Chem. Mater. 17, 4074-4077 (2005)

4. Goutenoire, F. et al. Mater. Chem. 11, 119-124 (2001) 5. L. Malavasi, H. Kim, Simon J.L. Billinge, Th. Proffen, C. Tealdi, G. Flor, J. Am. Chem. Soc. 129, 6903-6907 (2007) 6. L. Malavasi, C. Ritter, G. Chiodelli, Chem.

Mater. 20, 2343-2351 (2008) 7. Knight, K.S. Solid State Ionics 145, 275 (2001)

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Electronic Structure of Complex Materials revealed by Resonant X-Ray Bragg Diffraction V. Scagnoli European Synchrotron Radiation Facility, F - 38043 Grenoble Cedex 9, France

S.W. Lovesey ISIS Facility and Diamond Light Source Ltd., Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, UK

ABSTRACT

Some recent resonant x-ray Bragg diffraction experiments on complex materials are surveyed, with attention to motifs of multipoles supported by valence electrons. This powerful and versatile x-ray method is ideal to study the charge, magnetic and orbital degrees-offreedom of electrons. In a quest to disentangle the electron degrees-of-freedom unfamiliar atomic multipoles can be encountered, e.g., atomic chirality and magnetic charge, especially when dealing with complex materials, like multiferroics, where electronic charge and magnetic ordering can coexist. The direct observation of such multipoles is of immense importance for microscopic models describing the magnetic and electronic charge properties as they might represent the order parameter. Such sensitivity allows, e.g, the direct observation of the enantiomorphic screw-axis in chiral crystals, such as tellurium, low quartz and Berlinite.

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Since first measurements of magnetic diffraction with x-rays [De Bergevin & Brunel 1980], tremendous advances in x-ray diffraction applications to study charge, magnetic and orbital degrees of freedom have been achieved. In particular, the advent of third generation synchrotron x-ray source has unveiled a new range of applications for Bragg diffraction. To this extend the high brilliance, energy tunability and high polarization level of synchrotron radiation have proven fundamental to reach these goals.

In particular, the possibility to perform diffraction experiments at the absorption edges of interest presents many benefits. The contribution of the resonant atom is enhanced, making visible very small contributions, currently at the level of one part in 108, which would otherwise go undetected.

Moreover, polarization analysis yields even more valuable information because scattering channels with rotated polarization, forbidden in Thomson scattering, can be different from zero.

In this respect, the simple description of the motif of magnetic moments in a crystal by a cartoon in which vectors, representing dipole moments, are placed at sites occupied by magnetic ions has proven limited. For many magnetic materials such a cartoon conveys but a small fraction of essential information about magnetism that can depend on all components of angular anisotropy in unfilled electron states. In general, therefore, a family of multipole moments is required for a comprehensive representation of electron degrees of freedom.

Multipoles (named by the Greek word for the number 2K) have a rank K, with K=0 (scalar or monopole), K=1 (dipole), K=2 (quadrupole), K=3 (octupole), etc., and they are usually defined to have definite signs for the discrete symmetries of time reversal and parity (behaviour under inversion of space coordinates, x, y, x → -x, -y, -z). A cartoon of the electron density that can be associated with some multipole is given in Fig. 1.

Resonant x-ray diffraction probes multipoles in a crystal with directness of purpose not available with any other experimental method in the science of materials. Seminal observations of this diffraction came from Templeton and Templeton [Templeton & Templeton 1982] and Finkelstein et al. [Finkelstein et al. 1992], with timely theoretical analyses by Dmitrienko [Dmitrienko 1983] and Carra and Thole [Carra & Thole 1994]. In 2005, Dmitrienko et al.

[Dmitrienko et al. 2005] surveyed experiments on non-magnetic materials utilizing resonant diffraction. At about the same time, Lovesey et al. [Lovesey et al. 2005] and Collins et al. [Collins et al. 2007] shaped theoretical concepts in resonant x-ray diffraction and absorption by both non-magnetic and magnetic materials. Coexistence of spontaneous order in the charge and the magnetic degrees-of-freedom of electrons is a multiferroic modification of properties of intense current interest in materials science [Cheong & Mostovoy 2007, Kimura et al. 2003, Eerenstein et al. 2006, Smirnov et al. 2009, Fiebig 2005]. There are counterintuitive atomic properties whose existence summons 14

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in to play unfamiliar electron variables. These are entities significant to an atomic theory of electron properties and, also, directly observable in x-ray diffraction [Lovesey et al. 2005, Collins et al. 2007].

If the magnetic ion site symmetry is a centre of inversion symmetry only parityeven multipoles are allowed. Parity-even multipoles, which we label 冓TK冔 (Angular brackets denote the expectation value of the enclosed quantum mechanical operator), possess a one-to-one correspondence between rank and sign with respect to time reversal, namely, time-odd (time-even) multipoles have odd (even) rank. Also, parity-even multipoles with even K originate from true-tensors, and multipoles with odd K originate from pseudo-tensors. In particular, the parity-even multipole with K=1 is a time-odd pseudo-vector (axial vector) proportional to the magnetic moment associated with the ion.

When the centre of inversion symmetry is absent, parity-odd multipoles can be different from zero and such multipoles with even K are pseudo-tensors and those with odd K are true-tensors. Parity-odd, time-even multipoles are called polar, and here denoted by 冓UK冔 (ungerade). Polar multipoles with rank 0 and 1 have an immediate physical significance, for chirality = 冓U0冔 and displacement = 冓U1冔. Parity-odd, time-odd multipoles, denoted by 冓GK冔 (gerade), are called magneto-electric by analogy with a necessary condition for the magneto-electric effect that the inversion is accompanied by time reversal. The magneto-electric monopole, 冓G0冔, is analogous to magnetic charge while the dipole, 冓G1冔, is usually called an anapole, or toroidal moment. Let us note that, magnetic charge in a symmetric version of Maxwell’s equations is odd for each discrete symmetry C (charge), P (parity), and T (time) [Goldhaber 1977, Milton 2006].

The multipolar contribution to the measured Bragg intensity is determined by the nature of the resonant event. In keeping with standard practice in absorption spectroscopy, absorption via the electron dipole (quadrupole) and magnetic dipole are labelled E1 (E2) and M1 (electric and magnetic dipole operators are represented by polar (R) and axial (μ) vectors, respectively).

However, scattering is a two-stage process and E1-E1 is the strongest process, unless forbidden by selection rules. Many factors contribute to selection rules.

Since E1 has a definite parity the E1-E1 event is parity-even and it can only reveal electron properties with the same condition. The same reasoning applies to the quadrupole event E2 for E2-E2 scattering processes. Electric dipole E1 and magnetic dipole M1 (electric quadrupole E2) moments have opposite parities. Thus the E1-M1 (E1-E2) event is parity-odd and capable of revealing atomic polar and magneto-electric multipoles.

The size of the family of multipoles visible in diffraction depends on the actual resonant events, of course. The triangle rule for addition of angular momentum applied to two dipoles (K=1) shows E1-E1 and E1-M1 resonant events allow K=0,1,2. Thus engaging an E1-M1 process in diffraction by a magnetic crystal accesses both chirality and magnetic charge. Similarly, E1-E2 allows K=1,2,3 and E2-E2 allows K=0,…,4.

Being parity-odd the E1 photo-electric event connects atomic states with opposite parity. Direct observation of multipoles possessed by d-like valence electrons, by resonant Bragg diffraction, therefore demands absorption to occur at an intermediate state that is p-like, which is called an L-state, or L-edge. E1 15

Figure 1. Electron density associated with different multipoles.

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absorption at an intermediate state which is s-like, and called the K-edge, gives access to p-like valence states at the absorption site that contain second-hand information of minimal value on d-like multipoles. However, some information can be obtained at the K-edge by accessing the quadrupole resonance through the p-d hybridization, which makes quadrupole events often observable.

RESONANT SCATTERING AMPLITUDE AND UNIT-CELL STRUCTURE FACTOR

The atomic picture of resonance consists in the excitation, by an incoming photon, of a core electron to empty intermediate states. The electron returns then to the same core-hole emitting a photon of the same energy as the incoming one.

The scattering amplitude is generally calculated from quantum-electrodynamics [Lovesey et al. 2005, Collins S P et al. 2007, Lovesey S W & Collins S P 1996].

It is developed in terms of the small quantity E/mc2 where E is the primary photon energy and mc2 = 0.511 MeV. At the second level of smallness in this quantity the amplitude contains resonant processes that may dominate all other contributions to the amplitude should E match an atomic resonance with an energy D. Assuming also that virtual intermediate states are spherically symmetric, to a good approximation, the scattering amplitude in the region of a resonance is of the form, f ⬇ Fμ’ν /(E - Δ + iΓ/2) = Gμ’ν ,

Figure 2. Shown is the Cartesian coordinate system (x, y, z) adopted for Bragg diffraction and the relation to states of polarization, labelled s and p, in the primary (unprimed) and secondary (primed) beams of photons.

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(1)

where Γ is the total width of the resonance. In (1), Fμ’ν is a unit-cell structure factor for Bragg diffraction in the scattering channel with primary (secondary) polarization ν (μ’). We use the standard convention of labelling these polarization states (Fig. 2), in which σ-polarization is normal to the plane of scattering and π-polarization is parallel to the plane. Corrections to (1) required by angular anisotropy in intermediate states are discussed in several places [Lovesey 1997, 18. Lovesey et al. 1998, Lovesey et al. 2003, Mulders et al. 2006, Lovesey et al. 2008].

The unit-cell structure factor, Fμ’ν, contains 冓 Jˆ μ’ (-q’) Jˆ ν(q)冔 where Jˆ ν(q) is the current operator for electrons and a primary (secondary) photon wave-vector q (q’). The expectation value of the product of current operators is performed with the equilibrium, electron ground-state wave-function. Evaluated with q = q’ = 0 structure factors describe diffraction with enhancement by E1 events.

The first correction to the current of electrons, in an expansion in terms of the wave-vector, introduces additional resonant contributions E1-M1, E1-E2, E2E2, etc. Since the current operator is derived within QED it contains the electron spin operator. In consequence, M1 is proportional to the magnetic moment of the resonant ion μ = L + 2S, where L and S are electron operators for orbital and spin angular momenta, respectively.

The presence of S in the M1 operator allows enhancement at a K-edge which would otherwise be forbidden on account of zero orbital angular momentum.

To engage the M1 event in diffraction, or dichroism, valence and intermediate states have common angular momentum, because matrix elements of L and S are diagonal with respect to orbital angular momentum. Thus absorption at a K-edge can engage M1 when s-like valence states are available. In addition, intermediate and valence states must not be orthogonal. Parity-odd events, e.g.

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E1-M1 and E1-E2, are allowed when valence states at the site of the resonant ion are an admixture of orbitals with different parities, which can occur when the site is not a centre of inversion symmetry. This requirement on the resonant site does not mean that the crystal structure must be non-centrosymmetric.

We can now introduce the generic expression for a unit-cell structure factor: Fμ’ν = ΣK JKμ’ν . DK . ΨK,

(2)

where the spherical tensor JKμ’ν describes the condition of the primary and secondary photons. There is a different JKμ’ν for each resonant event. The quantity DK in (2) is a rotation matrix employed to orientate the crystal in right-handed Cartesian coordinates (x, y, z) that describe the scattering geometry (Fig. 2). As before, we choose s-polarization parallel to the z-axis, and the Bragg wave-vector (q - q’) anti-parallel to the x-axis. The rotation matrix is a function of the azimuthal angle, ψ, that measures rotation of the crystal about the Bragg wave-vector. Variation of intensity with changes in ψ provides information on anisotropy in valence shell, since for a spatially isotropic distribution no dependence on ψ is expected. The anisotropy reflects directly the presence of high order multipoles.

Lastly in (2), ΨK is a structure factor of the form, ΨK = Σn 冓TK冔n exp {i dn.(q - q’)},

(3)

where the sum runs over all resonant ions in a unit-cell of the crystal. The Bragg condition for diffraction is met when the wave-vector (q - q’) coincides with a reciprocal lattice vector. Equation (3) is written in terms of parity-even multipoles, 冓TK冔, but it can be used also for parity-odd multipoles.

K where the projection Q can take In general, angular components of ΨK, ΨQ (2K+1) integer values that satisfy -KⱕQⱕK, do not map directly on to angular components of the electron structure. The presence of multi-axis, non-collinear order in the crystal is one case where it is unsafe to assume correspondence K between angular components ΨK and electron structure. Expressions for Jμ’ν appropriate for E1-E1, E1-E2, E2-E2 and E1-M1 events have been given in previous publications [Scagnoli & Lovesey 2009; Lovesey & Scagnoli 2009] We are now ready to present some recent results that illustrate the sensitivity of resonant x-ray Bragg diffraction. Energy spectra (collected by continuously adjusting the sample and detector positions while sweeping the incident photon energy to fulfil the Bragg law condition) and azimuthal-angle scans as well as polarization analysis play a pivotal role to determine the nature of the resonance event(s) source of the observed intensities.

Figure 3. Views of atomic structure in R quartz (right) and L quartz (left) along the a axis and the b axis, respectively. The a and b axes lie in the plane normal to page surface. Blue and red spheres represent Si and O atoms, respectively. Lines show the unit cell with hexagonal axes. Reproduced from reference [Tanaka et al. 2008].

QUARTZ: RIGHT OR LEFT HANDED?

Enantiomers, or stereoisomers, have crystal structures that are mirror images of each other and are thus handed, like our right and left hands. Physical properties of enantiomers are identical except for optical activity, which rotates linearly polarized light by equal amounts but in opposite directions. While conventional x-ray Bragg diffraction can determine crystal structures, it does not distinguish right- and left-handed crystals. However, resonant x-ray diffraction, 17

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using circularly polarized x-rays, can reveal the handedness of crystals through a coupling of x-ray helicity with the enantiomorphic screw-axis.

Sensitivity of resonant x-ray Bragg diffraction to the handedness of crystals is readily inferred by examination of the scattered intensity. We describe x-ray polarization by purely real Stokes parameters P2 and P3 [Lovesey et al. 2005, Collins et al. 2007] and with full polarization (P2)2 + (P3)2 = 1. The parameter P2 is the mean helicity in the beam, and P3 is the linear polarization with P3 = +1 (-1) corresponding to complete linear σ-polarization normal (PI-polarization parallel) to the plane of scattering (Fig. 2).

With this notation, the total diffracted intensity from a primary beam endowed only with circular polarization (P3 = 0) is, Io = P2 Im.{(Gσ’π)*(Gσ’σ) + (Gπ’π)*(Gπ’σ)} + 1⁄2 {|Gσ’π|2 + |Gσ’σ|2+ |Gπ’π|2 + |Gπ’σ|2},

(4)

where an amplitude Gμ’ν is defined in (1), and * denotes complex conjugation.

For Thomson scattering the coefficient of P2 is identically zero, because there

Figure 4. Azimuthal-angle dependence of the reflection (0,0,1) of R and L quartz. Filled (open) circles represent the integrated intensity of R quartz measured with LCP (RCP) primary beam, and filled (open) triangles represent the integrated intensity of L quartz measured with RCP (LCP) primary beam.

Each continuous line is a fit to data. Insets show 2q-scan profiles of the reflection (0,0,1) observed with y = 0. After Tanaka et al. [Tanaka et al. 2008].

are no contributions to diffraction in channels with rotated polarization, σ’-π & π’-σ. However, the coefficient can be different from zero for resonant diffraction since all four channels of scattering may be different from zero. Such is the case when the crystal contains an enantiomorphic screw-axis. Thanks to the specificity of resonant Bragg diffraction, Tanaka et al. were able to reveal the handedness of quartz enantiomers [Tanaka et al. 2008]. in low-quartz Silicon ions use sites with multiplicity 3 and Wyckoff letter a in P 31 2 1 (#152, right-handed, R in the following) and P 32 2 1 (#154, lefthanded, L in the following). It is possible to show [Lovesey et al. 2008] for the reflection (0,0,l) that structure factors ΨK, defined as in (3), of the enantiomorphic space-group pair obey the identity, K (#154) = (- 1)K ΨK (#152), ΨQ -Q

that in turn leads to structure factors which satisfy, Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

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(5)

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Fμ’ν(#152, y) = ± {Fμ’ν(#154, ψ)}*,

(6)

with the plus (minus) for a parity-even (odd) event and ψ the azimuthal angle.

If we look back at (4) for the total intensity Io , it follows from (6) that the coefficient of P2 is of opposite sign for the enantiomers (the reader is advised to consult reference [Lovesey et al. 2008] for a more complete discussion of the Fμ’ν properties). In other words, in diffraction enhanced by a single resonant event, circular polarization (x-ray helicity) and crystal chirality are directly coupled. Fig. 4 shows integrated intensity at the reflection (0,0,1) as a function of azimuthal angle, ψ, from R and L forms of quartz. A sinusoidal modulation exhibiting the three-fold periodicity proper to an enantiomorphic screw-axis, 31 or 32, is observed. Integrated intensity for R quartz for incident left circular polarization (LCP) and that of L quartz for right circular polarization (RCP) are comparable, and there is a pronounced intensity modulation on sweeping the azimuthal angle.

By inverting the primary circular polarization, respectively for the two crystals, the integrated intensities are still comparable with each other, while the intensity modulation has almost disappeared. Tanaka et al. attributed [Tanaka et al. 2008] this asymmetry to an admixture of E1-E1 and E1-E2 events. If only one event

Figure 5. Magnetic ordering on the Mn substructure in phase (i) T = 35K and phase (ii) T = 15K of terbium manganate as suggested by neutron scattering [Kenzelmann et al. 2005]. In phase (ii) a spiral phase violates parity (inversion symmetry) allowing an electric polarization, represented by a (red) arrow along c.

contributed to diffraction, intensities for LCP and RCP for a given form of quartz would exhibit a perfect antiphase relation delete with the same intensity variation as a function of the azimuthal angle. Similar arguments would apply if we consider L and R quartz with the same primary circular polarization.

TbMnO3: INTRICATE COUPLING BETWEEN CHARGE AND MAGNETIC DEGREES-OF-FREEDOM

TbMnO3 has recently attracted much attention because of its multiferroic properties [Fiebig 2005]. In an interval of temperature 28 K < T< 41 K, which we call phase (i), magnetization exists on the Mn substructure which is collinear, polarized along b, and incommensurate with a wave-vector q ~ 0.28 b* (Fig. 5 (i)), while Tb ions are not magnetically ordered. Long-range magnetic order is accompanied by a modulation of the Mn substructure with sinusoidal displacements along c. Within the temperature range 7 K < T< 28 K, called phase (ii), a multiferroic state sets in. A spatially varying electric dipole moment, associated with Mn displacements, undergoes a first-order transition to a ferroelectric phase that contributes spontaneous polarization along c (Fig. 5 (ii)).

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Simultaneously, magnetization on the Mn substructure becomes non-collinear with a component along c. Terbium magnetic moments in phase (ii) display noncollinear order, with transverse polarization along a and wave-vector q.

Observation of a magnetically controlled ferroelectric polarization in terbium manganate demonstrates a giant magnetoelectric effect [Kimura et al. 2003].

Below 7 K, labelled phase (iii), Tb moments adopt the same configuration as in phase (ii) but the wave-vector is distinctly different, namely, q’ ~ 0.42 b*. We focus now on recent resonant x-ray Bragg diffraction studies [Voigt et al. 2007, Mannix et al. 2007].

In an effort to understand modifications to terbium manganate occurring in the different phases, many azimuthal-angle scans as well as energy dependence at the Mn K and Tb L3 edges were collected. Let us recall major findings. In phase (i) Mannix et al. [Mannix et al. 2007] found A-type (0,4 ± q, 1) and F-type (0,4 ± q, 0) reflections at the Mn K and Tb L3 edges, and only A-type reflections

Figure 6. Data collected in the p’-s channel at a C-type reflection (0,3 + q,0) in phase (ii) are reproduced from Fig. 20 in Mannix et al. [Mannix et al. 2007]. Data were gathered with a primary energy corresponding to the E1-E1 event around 7.520 keV in the vicinity of the Tb L3 edge. The origin of the azimuthal angle, y, is denoted by a vertical line, displaced by 90∞ from the origin used by Mannix et al.[ Mannix et al. 2007].

Figure 7. Observed energy profile (crosses) of the (0, 0, 1/2) compared to fits of the theory including absorption correction with wave-function taken from [Tanaka et al. 2004].

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with a primary photon energy far from absorption edges. Presence of diffracted intensity at the Tb L3 edges is attributed to Tb 5d-state polarization induced by ordering of Mn magnetic moments.

The development of a non-collinear Mn substructure in phase (ii) removes inversion symmetry. An E1-E2 scattering channel is then allowed in resonant xray Bragg diffraction. Indeed, pronounced differences in energy spectra collected at the Mn K and Tb L3 edges are clearly visible (Figs. 10, 13 and 14 in reference [Mannix et al. 2007]). A new set of satellite reflections (0, 3 ± q, 0), associated with non-collinear ordering (C-type), was observed at the Tb L3 edge but not at the Mn K edge. These experimental observations were successfully analysed by using a method that does not rely on knowledge of the space-group symmetry of the low temperature phases of TbMnO3, which is not precisely known [Scagnoli & Lovesey 2009]. Fig. 6 shows a calculated azimuthal-angle dependence of the C-type reflection (0, 3 + q, 0) in the rotated channel of polarization in the vicinity of the Tb L3 edge. Solid curve is a fit to intensity proportional to the expression (t - cos ψ + d cos 2ψ + u sin ψ + w sin 2ψ)2 [Scagnoli & Lovesey 2009] which provides the physical origin in terms of atomic multipoles of the various parameters. Good agreement between calculated and observed intensities is evident. We do not discuss here the physical meaning of these 20

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parameters that can be found elsewhere [Scagnoli & Lovesey 2009]. The important result is that the low-temperature satellite reflections originate from dipole-dipole (E1-E1) and dipole-quadrupole (E1-E2) events, while the quadrupole-quadrupole (E2-E2) event can be excluded. Presence of the E1-E2 event in diffraction suggests an intricate coupling between charge and magnetic degrees of freedom in terbium manganate. The direct observation of atomic like magneto-electric multipoles is of immense importance for microscopic models describing the magnetic and electronic properties of magnetically driven multiferroics as they represent the electronic order parameter.

DyB2C2: CORE-HOLE SPLITTING AND HIGHER ORDER MULTIPOLES

DyB2C2 has attracted much attention lately as its high antiferroquadrupolar (AFQ) ordering temperature TQ = 24.7 K allows one to study this phenomenon conveniently. At room temperature, DyB2C2 crystallizes in the tetragonal P 4/m b m structure and undergoes a structural transition with small alternating shifts of pairs of B and C atoms along c at TQ [Adachi et al. 2002] which reduces the symmetry to P 42/m n m [Tanaka et al. 1999]. Below TN = 15.3 K, antiferromagnetic order (AFM) is observed with complex moment orientations due to the underlying orbital interaction [Yamauchi et al. 2005].

Resonant X-ray diffraction at the Dy L3 edge has been used to elucidate Dy dipole and quadrupole motifs [Adachi et al. 2002, Tanaka et al. 1999, Yamaguchi et al. 2005]. A dipole transition (E1) occurs between Dy 2p and 5d shells and a quadrupole transition (E2) between Dy 2p and 4f shells. The first and dominant process probes the quadrupolar order of the 5d states and the latter transition probes the quadrupolar order of the 4f states. The quadrupolar origin of the reflection has been confirmed by azimuthal scans.

In order to explain the observed azimuthal behaviour at the (0, 0, l/2) charge forbidden reflection and their energy dependence a model which implied cancellation of quadrupole (rank 2) and hexadecapole (rank 4) contributions was put forward [Tanaka et al. 2004]. An alternative description of the same results is based on the interference between the E1 and E2 resonances [Matsumura et al. 2005]. No contribution of the hexadecapole moment appears in this model that has the appeal to use the simple mechanism of interference rather than invoke complex ordering of four rank multipoles. However, the mixing parameter of E1 and E2 processes is fixed at unity in the analysis but this is not a priori justified. To verify the presence of such interference phase plates together with Stokes analysis could be employed, as recently done for K2CrO4 [Mazzoli et al. 2007; FernĂĄndez-RodrĂ­guez et al. 2008].

In this respect the RXS in the soft x-ray regime has the benefit to access directly the Dy 4f states via the E1 transition. No E2 event contributions are therefore present. These advantages encouraged Mulders and al. [Mulders et al. 2006] to perform a resonant diffraction experiment in the soft x-ray regime with all the complications proper to an ultra-high-vacuum experiment.

Results turn out to be not as simple as expected. An E1-E1 resonant process alone cannot explain the complicate energy profile shown in Fig.7.

Mulders and al. propose that this particular shape of the energy dependence of the (0, 0, 1/2) reflection is caused by the splitting of the 3d core states. The splitting implies the presence of multiple interfering resonators and 21

Figure 8. Dy charge density and multipole motif in the AFQ phase of DyB2C2. The basal plane is indicated in grey. Note the 90? zig-zag alignment of the Dy orbitals along c and the canted zig-zag alignment along [110]. A spherical charge density has been subtracted to emphasize the asphericity.

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REFERENCES 1. Adachi H et al. 2002 Phys. Rev. Lett. 89 206401 2. Carra P & Thole B T 1994 Rev. Mod. Phys. 66 1509 3. Cheong S -W & Mostovoy M 2007 Nature Matter. 6 13 4. Collins S P et al. 2007 J. Phys.: Condens. Matter 19 213201 5. De Bergevin F & Brunel M 1980 Acta.

Crystallogr., Sect. A 37 314 6. Dmitrienko V 1983 Acta. Crystallogr., Sect.

A: Found. Crystallogr. 39 29 7. Dmitrienko V et al. 2005 Acta. Crystallogr., Sect.

A: Found. Crystallogr. 61 481 8. Eerenstein W et al. F 2006 Nature 442 759 9. Fernández-Rodríguez J et al. 2008 PRB 77 094441 10. Fiebig M 2005 J. Phys. D: Appl. Phys. 38 R123-R152 11. Finkelstein K D et al. 1992 Phys. Rev. Lett. 69 1612 12. Goldhaber A S 1977 Phys. Rev. D 16 1815 13. Kenzelmann M et al. 2005 Phys. Rev. Lett. 95 087206 14. Kimura T et al. 2003 Nature 426 55 15. Lovesey S W & Collins S P 1996 X-ray scattering and absorption by magnetic materials (Oxford: Clarendon Press) 16. Lovesey S W 1997 J. Phys.: Condens. Matter 9 7501 17. Lovesey S W et al. 1998 J. Phys.: Condens.

Matter 10 501 18. Lovesey S W et al. 2003 J. Phys.: Condens.

Matter 15 4511 19. Lovesey S W et al. 2005 Phys. Rep. 411 233 20. Lovesey S W et al. 2008 J. Phys.: Condens.

Matter 20 272201 21. Lovesey S W and Scagnoli V 2009 to appear in J. Phys.: Condens. Matter 22. Mannix D et al. 2007 Phys. Rev. B 76 184420 23. Matsumura T et al. 2005 Phys. Rev. B 71 012405 24. Mazzoli C et al. 2007 Phys. Rev. B 76 195118 25. Milton K A 2006 Rep. Prog. Phys. 69 1637 26. Mulders A M et al. 2006 J. Phys.: Condens.

Matter 18 11195 27. Scagnoli V & Lovesey S W 2009 Phys. Rev. B 79 035111 28. Smirnov A I et al. 2009 Phys. Rev. Lett. 102 037202 29. Tanaka Y et al. 1999 J. Phys.: Condens. Matter 11 L505 30. Tanaka Y et al. 2004 Phys. Rev. B 69 024417 31. Tanaka Y et al. 2008 Phys. Rev. Lett. 100 145502 32. Templeton D & Templeton L 1982 Acta.

Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 38 62 33. Voigt J et al. 2007 Phys. Rev. B 76 104431 34. Yamauchi H et al. 1999 J. Phys. Soc. Japan 68 2057

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consequently adds structure to the energy profile. In this model the intraatomic quadrupolar interaction partially lifts the core hole degeneracy. The energy splitting is determined by the strength of the intra-atomic interaction and the relative amplitudes are determined by the 4f wave-function. Expression (1) for the scattering amplitude must now be rewritten to take into account presence of several oscillators at the E1 resonance created by the splitting of the core state. The scattering amplitude will now explicitly depend on the total angular momentum J=3/2, 5/2 (respectively for the M4 and M5 edge) and the corresponding magnetic quantum number -JⱕMⱕJ of the core hole. Therefore, three (two) resonant oscillators should be considered at the M5 (M4). The consequences of this analysis are that higher rank multipoles can now enter the expression of the scattering amplitude. The dependence on the higher 4f multipoles arises from the splitting of the core hole states, which results in the M dependence of the amplitudes of the different harmonic oscillators. Tensors with rank up to 6 (hexacontratetrapole) are invoked to describe the observed energy dependence. The resulting charge density and multipole motifs for the Dy ions is depicted in Fig. 8.

This model merely demonstrates that including the intra-atomic interaction is a viable approach and accounts for the multiple spectral features and their broad distribution in energy. We note that the empty states of the 4f shell selected by the resonant diffraction process, and their corresponding relative transition intensities, are not necessarily the same as for the absorption process.

Resonant diffraction is sensitive to the difference between electronic states while absorption spectroscopy is sensitive to its average.

CONCLUSION

To conclude, resonant x-ray Bragg diffraction proves to be a versatile technique that can be applied to different materials, ranging from antiferromagnetic to multiferroic systems. Taking advantage of element and site specificity, polarization analysis and azimuthal-angle scans, resonant x-ray Bragg diffraction proves itself an ideal tool to investigate subtle and enigmatic ordering of charge and magnetic phenomena. We have seen how, using circularly polarized x-rays, it can reveal the handedness of crystals through a coupling of x-ray helicity with the enantiomorphic screw-axis. Another strength of resonant x-ray diffraction is the ability to unveil small changes in electric and magnetic degrees-of-freedom that cannot be easily detected with other ordinary techniques, such as x-ray high-resolution powder diffraction. An example is TbMnO3 whose orthorhombic P b n m structure proves incompatible with the multiferroic effects observed on the Mn site. In this space group, sites occupied

by Mn ions possess an inversion symmetry that does not allow admixture of orbitals of different parity, a key ingredient to multiferroicity. With resonant xray diffraction such symmetry breaking effects are easily detectable. Finally, we have shown its sensitivity to the different electric transition channels. In this respect, the experimental results might be difficult to interpreter as exemplified by the case of DyB2C2. However, these results, amongst them the picture cartoon of the electron density in term of multipoles (with the caveat explained in the introduction), can provide fundamental information to develop microscopic theories that could describe the rich behaviour of such systems.

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Research Infrastructures

First Users at the ISIS Second Target Station After five years of construction, the ISIS Second Target Station opened its doors for the first scheduled experiment at the end of May. Professor Jeff Penfold, the Chief Scientist for the ISIS Second Target Station led a team from Oxford University and ISIS carrying out the experiment on the Inter reflectometer. The team expect the results to lead to significant advances in understanding of the surface chemistry of systems that range from lung surfactants to fabric conditioners.

“We explored for the first time how the layered structures formed by surfactants at a liquid surface dis-assemble in real time,” said Professor Penfold. “When I first started using neutron scattering for these kind of chemistry studies in the early 1990s, experiments such as these would have been unimaginable. The new optimized instruments on the second target station now allow us to see in a minute what used to take a day. It’s a real boost for studies in soft matter and will allow us to take a major step forward in our understanding.”

“This first experiment on one of our seven new instruments is a very important milestone in the project and a significant day for the global science community,” said Dr Andrew Taylor, ISIS Director.

“The Second Target Station builds on the success and expertise we have developed over the past 20 years in the UK at ISIS and allows us to move further into the areas of soft matter, advanced materials and bioscience. We will be carrying out fundamental research that will shape the technological advances of tomorrow.”

Neutron beams at ISIS can be used like “super x-rays” to study materials at the atomic level. Neutron scattering experiments allow the location of atoms and

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M. Bull Head of Communications ISIS, Didcot, UK

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the forces between them to be measured. ISIS has been doing this since 1984 and has established itself as a world leader in the physical and life sciences serving an international community of over 2,000 scientists.

Professor Keith Mason, Chief Executive of the UK Science and Technology Facilities Council that owns and operates ISIS said that the he start of research on the ISIS Second Target Station was a major day for UK science and demonstrated the wisdom of long-term government investment in research.

“The ISIS team can be justifiably proud of their achievement in delivering this major new research facility on time and on budget,” he said. “The ISIS Second Target Station will play a major role in delivering on STFC’s vision to maximise the benefits of our research for the UK and global communities’’.

The first experiment at the ISIS Second Target Station is the start of a £400k major new research programme funded by the EPSRC (Engineering and Physical Sciences Research Council) awarded to Professor Jeffrey Penfold (ISIS, STFC) and Professor Bob Thomas (University of Oxford). The research will use

neutron scattering techniques to reveal how multilayer structures at surfaces and interfaces can self-assemble. These structures are found in a wide range of applications in biology and technology including aspects of soft lubrication (hair and fabric conditioners) and bio-lubrication.

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EUPhoS: A New Bright Light Source ABSTRACT

Using the Elettra storage-ring free-electron laser, we have implemented a light source generating sub-picosecond (ps) coherent optical pulses in the VUV spectral range. The setup relies on the frequency up-conversion of a high-power external signal (provided by a Ti:Sapphire laser) and makes use of a relativistic electron bunch as resonating medium. The produced VUV pulses have peak power in MW range, variable polarization, high shot-toshot stability and control of the timing parameters at the ps level. In this paper, we present the experimental layout, as well as the characterization of the temporal and spectral features of the emitted light. The radiation can be exploited for new experiments in the fields of dynamical phenomena, non-linear physics, magnetism and biology.

INTRODUCTION

Over the last few years, a strong demand has emerged for a source of radiation in the vacuum ultraviolet (VUV) spectral range with high brilliance, close-tofull coherence, variable polarization, bandwidth approaching the transform limit, and stable temporal structure in the femtosecond time scale. Much progress in this direction has been achieved through high-harmonic generation using fs lasers [1]. But nowadays, the possibility to realize a source with all the above mentioned characteristics relies principally on single-pass free electron lasers (FELs). A direct impact from FELs is expected on a large number of disciplines [2], including (bio-) materials sciences, nanosciences, plasma physics, and chemistry, where the use of ultrashort VUVand/or x-ray femtosecond pulses can tackle complex transient phenomena with femtosecond time resolution.

In a FEL, the light is generated when a relativistic electron beam passes through the static and periodic magnetic field produced by an undulator. FELs can be operated in several different schemes. The most promising ones are based on the self-amplification of the electron-beam spontaneous emission (SASE), and on the generation of coherent harmonics from an input signal provided, e.g., by a conventional laser (seeding). A SASE source can produce very high brilliance [3], but the pulse temporal structure results from the envelope of a series of micropulses with random intensity and duration. In contrast, seeded FELs can deliver coherent optical pulses with tailored temporal and spectral profiles [4,5]. In the standard seeded scheme, generation of coherent harmonics (CHG) is obtained by coupling the input signal with the electron bunches extracted from a linear accelerator (linac). Proof of principle experiments in this configuration were first performed at Brookhaven laboratory (Upton, USA) [4,5], where coherent emission at the third harmonic (260 nm) of a Ti:sapphire laser was produced. Based on these promising results, several projects are currently under development worldwide (see, e.g., [6]), with the aim of supplying users with new bright and coherent light sources in the VUV and soft x-ray spectral regions.

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G. De Ninno Physics Department, Nova Gorica University, 5000 Nova Gorica, Slovenia G. De Ninno, E. Allaria, G. Cautero, F. Curbis, M.B. Danailov, A. Demidovich, B. Diviacco, E. Karantzoulis, L. Romanzin, P. Sigalotti, C. Spezzani, S. Tileva and M. Trovo Sincrotrone Trieste, S.S. 14 km 163.5, 34149 Trieste, Italy M. Coreno CNR-IMIP, Area della Ricerca di Roma, Montelibretti, c/o Gas Phase beamline, Lab. Elettra, 34149 Trieste, Italy F. Curbis Physics Dep.t, Trieste University, 34100 Trieste, Italy and HASYLAB-DESY, Hamburg, Germany

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As an alternative to single-pass linac-based devices, electrons can be provided by a storage ring (SR), as shown in Fig. 1. Electron bunches circulating into a SR are generally characterized by lower peak currents and higher relative energy spreads compared to bunches delivered by modern linacs. As a consequence, linac-based FELs can be expected to produce optical pulses whose energy is 3-4 orders of magnitude larger than that of pulses produced by SR CHG. However, using electrons recirculated in a SR presents some important advantages. Indeed, in a SR, the electron-beam properties, notably the mean energy and the peak current, are ‘‘thermalized’’ by a long-lasting periodic dynamics. This in principle results in a very good reproducibility of the seeding process and, as a consequence, in an excellent shot-to-shot stability of the optical pulse produced at the end of the device. On the contrary,

Figure 1. Schematic layout of the CHG setup implemented on the Elettra SR. The SR is filled with a relativistic electron bunch, which interacts in the modulator with an external (Ti:sapphire) laser of wavelength λ. In the magnetic chicane, electrons are subdivided in micro-bunches separated by λ. Finally, in the radiator, they emit coherently at λ/n, n being an integer number. The radio-frequency cavity is used to provide electrons with the energy they lose during one turn of the ring.

successive electron bunches delivered by a linac are generally characterized by significant fluctuations of the mean electron-beam energy and current.

According to theoretical calculations [7], this may result in a conspicuous shotto-shot instability of the emitted harmonic power. Moreover, SR CHG allows the production of harmonic pulses at relatively high repetition rates (order of 1 kHz, or even higher), to the benefit of average harmonic power. Only FELs based on superconducting linacs can perform the same, while normalconducting devices are limited to repetition rates of the order of 100 Hz. Finally, the coherent harmonic light generated by a SR is naturally synchronized to the synchrotron radiation emitted by undulators and bending magnets, and this makes easier the design and the realization of pump-probe experiments. Proof of principle of SR CHG was first performed at LURE (Orsay, France) [8] using a Nd:YAG laser (fundamental wavelength at 1.06 μm) to generate (third) harmonic coherent radiation at 355 nm.

Recently, coherent emission at 260 nm, the third harmonic of a Ti:sapphire laser, was observed at UVSOR (Okazaki, Japan) [9].

The source layout is shown in Fig. 1. The region of seed electron interaction is composed of two APPLE identical independent undulators (10-cm period, 2-m long), separated by a magnetic chicane. Apple-II undulators allow us to freely determine the polarization of the emitted light. The seed laser is a Ti:sapphire, having a fundamental wavelength of 794 nm, a maximum repetition rate of 1 kHz and a maximum energy per pulse of 2.5 mJ. A nonlinear optical crystal was used to generate second harmonic pulses with energy of up to 800 μJ and duration of 120 fs FWHM, so that CHG was seeded at 397 nm. The process leading to CHG can be described as follows [12]. The laser is focused into the first undulator (called the modulator, and tuned at the seed wavelength), and synchronized with the incoming electron bunch. The laser-electron interaction

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in the modulator leads to a modulation of the electron energy. When the beam crosses the magnetic chicane, the energy modulation is converted into a spatial microbunching of electrons at the period of the seed wavelength. As this microbunching is nonsinusoidal, when analyzed in the frequency domain it contains significant harmonics of the fundamental. Finally, these microbunched electrons radiate coherently in the second undulator (called the radiator), which is tuned at a harmonic of the first. The extracted power is proportional to the square of number of seeded electrons.

In this paper we report about the realization of a new light source based on SR CHG. Taking advantage of the FEL undulator system installed on the Elettra SR [10], we have generated ultrashort (close to 100 fs FWHM) coherent UV pulses at 132 nm (sixth harmonic of a Ti:sapphire laser), with fully adjustable polarization, relatively high repetition rate (1 kHz) and bandwidth close to the transform limit. The pulse train is very stable and the peak power is orders of magnitude above that of standard synchrotron radiation. The radiation was used for a test experiment in which a topographic image of a patterned SiO2 sample was recorded using a SPELEEM microscope [11, 12]. In the following, we describe the experimental setup and provide a complete characterization of the source.

EXPERIMENTAL SETUP

The experimental setup for CHG at Elettra is based on the SR- FEL equipment [13-15]. The general layout is shown in Fig. 2. Although on a reduced scale, the scheme is equivalent to the layout designed for seeded single-pass FELs [5, 6]. However, in this case the electron beam is re-circulated in the SR.

In the following, we describe the experimental setup, which is composed of three main blocks: the optical klystron (OK) (i.e., the suite of modulator, dispersive section and radiator), the seed laser and the front- end station used both for the detection/diagnostics of the CHG pulses, and to focus the harmonic light into an experiment end- station. We will also report on some important issues concerning the temporal (longitudinal) and transverse alignments of the laser and electron beams.

Figure 2. a) FEL optical klystron b) Front-end station c) Laser hutch and back-end station d) mirror chamber. The continuous line corresponds to the electron beam trajectory, the dashed line is the optical path of the seed laser and the dotted line indicates the path of the CHG output.

THE ELETTRA OPTICAL KLYSTRON

The two APPLE-II type permanent magnet undulators, together with an 27

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electromagnetic chicane, constitute modulator (ID1), radiator (ID2) and dispersive section of the OK (see Fig. 2a). Wavelength and polarization of the undulators are independently tunable. The emitted wavelength, λ, is determined by the following resonance condition [20]: (1) Here K represents the strength of the undulator and is proportional to the onaxis peak field and to the magnetic period λw; θ is the emission angle measured with respect to the undulator’s axis and γ is the normalized electron beam energy. The previous resonance condition allows one to select the suitable resonant wavelengths for the two undulators, i.e., the seed wavelength for ID1 and the wavelength of the harmonic one wants to generate for ID2.

To maximize the coupling between the electromagnetic field and the electron bunch inside the modulator, the seed polarization must be the same as the polarization at which ID1 is set. The results presented here were obtained for linear horizontal polarization. ID2 can be set either for linear or circular polarization. This determines the polarization of the coherent emission. The dispersive section strength is varied to optimize the micro-bunching of the electron beam. More details about the Elettra’s OK are provided in [16].

In our case the radiator is not long enough to reach saturation in the CHG process. Nevertheless, as it will be shown in the following, the obtained experimental results make this setup an attractive radiation source.

THE ELETTRA STORAGE RING

Elettra is a third generation synchrotron light source. It was designed to work at electron beam energies in the range 1.5-2 GeV. Nowadays, to satisfy the users community requests, Elettra is operating at 2.0 or 2.4 GeV. This allows to shift the photon emission spectrum from bending magnets and insertion devices to higher energies. Since the modulator must be tuned to the wavelength of the seed laser, λ ≥ 260 nm, the limitation on the minimum undulator gap restrict the values for suitable beam energy for CHG to the range 0.75-1.5 GeV. This represents the main limitation to the compatibility of CHG experiments with standard users operation, and makes necessary to allocate accelerator studies dedicated shifts for this activity.

When a seeded CHG experiment is performed, one has to take into account the potential beam instabilities that can limit or prevent the light amplification. As the output power of the CHG process depends quadratically on the number of electrons interacting with the seed multiplied by the bunching factor – the latter being proportional to the laser power – any fluctuation of the overlap between the electron beam and the laser will result in significant deterioration of the output power stability. Electron-beam instabilities are particularly harmful when Elettra operates at the FEL energy range because of the increased radiation damping times that can not dump the perturbations coming from the wake fields, interaction of the electron bunch with the vacuum chamber [17].

Wake fields increase the electron-beam energy spread with increasing current [13]. In fact, the energy spread smears out the micro bunching process, hampering or precluding the FEL.. A typical example of this effect is shown in Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

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Fig. 3. The double sweep streak camera detects the light emitted from a bending magnet as a function of time, with a resolution of about 3 ps. The short time acquisition (0 to 300 ps range) is displayed on the horizontal axis and is repeated synchronously with the radio frequency (RF) (i.e. with the electron bunch orbit). Consecutive short time acquisitions are displayed along the vertical axis (the range is 0 to 42 ms). Figures 3a and 3b have been obtained with a beam current of about 10 mA, at a beam energy of 0.9 GeV and 1.5 GeV, respectively. In the first case a modulation with period of about 10 ms (i.e. 100 Hz) is clearly visible that is not present at higher energy. The measurement was obtained in few bunch mode (4 bunches) to exclude the contribution from coupled bunch instabilities.

During CHG operation, Elettra is operated in single bunch (SB) mode. The data presented in this manuscript have been obtained at electron beam energy of 0.9 or 1.1 GeV that allows to stably store up to 6 mA. The typical electron bunch length for those beam energy and current value is 30 ps FWHM.

Figure 3. Double sweep streak camera acquisitions at Elettra SRPM. Beam current ~ 10 mA in 4 bunches, beam energy 0.91 GeV (a) and 1.5 GeV (b).

THE SEED LASER

The laser system consists of a Kerr-lens, mode locked Ti:Sapphire oscillator and a regenerative amplifier. The oscillator (based on a modified KMLabs kit [18], is a passively mode locked Ti:Saphire laser, in which the cavity length has been adjusted to give a repetition rate which is a multiple of the revolution frequency of the bunch for synchronization purpose. While the oscillator can generate pulses as short as 20 fs, for this experiment it has been set to about 12 nm FWHM in the 780-800 nm range to match the bandwidth required by the regenerative amplifier (Legend HE, Coherent Inc, [19]). The latter provides pulses of 2.5 mJ energy and 100 fs duration.

By second and third harmonic generation in BBO crystals, the wavelength ranges of 390-400 nm and 260-267 nm can also be covered with pulse energies of about 0.8 mJ and 0.3 mJ, respectively. Thus the peak power is high enough for seeding the electron bunch also in the blue and UV [20]. As constrained by the resonance condition and the limit imposed by the minimum gap value of the modulator, as the seeding wavelength is shortened one can increase the electron beam energy, yielding a more stable and longer lifetime electron beam. The laser system is located in the FEL back-end station, in a temperature-controlled hutch, so as to minimize thermal drifts of the optical alignment (see Fig. 2c).

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To optimize the energy transfer from the laser to the electron bunch, thus yielding the best micro-bunching with the lowest seed power, the laser pulses must be precisely aligned with respect to the electron bunch both in space and time. This alignment required the development of special diagnostics [16].

ALIGNMENT AND TIMING

In a linac-based scheme, to evaluate the relative position of electron beam and laser, one can intercept both beams with a fluorescent screen positioned in the interaction area, and then move one with respect to the other. In our case, transverse alignment is complicated by the fact that the electron beam is recirculated in the storage ring and would be dumped by the insertion of a screen in the interaction area. Therefore measuring the relative position of the two beams requires an indirect method that makes use of a mirror with a central hole mounted in the chamber located after the front-end exit (see Fig. 2d). The position and angle of the mirror can be adjusted by means of in-vacuum stepper motors and piezoelectric actuators with a resolution of 0.5 Îźm for the three spatial coordinates and of 10 nrad for pitch and yaw angles. The alignment procedure is detailed in [16].

To ensure the stability of the transverse alignment, we checked the pointing stability of the laser beam. The results are compatible with the geometry of the experiment. Indeed, the laser waist is placed at the centre of the modulator, which is located 17 m upstream the last mirror used to direct the seed laser. We measured a spatial fluctuation in the interaction region lower than 0.03 X 0.09 mm2. Since the dimension of the laser beam at this distance is nearly 1 mm2, we can conclude that the laser pointing stability is not an issue for the transverse alignment. Besides transverse alignment, the laser must be synchronized to the storage ring RF (= 499.654 MHz) and suitably delayed, so that the seed can temporally overlap the electron beam inside the modulator. The cavity length of the oscillator has been chosen to determine a mode locking frequency as close as possible to RF/6 ~83.3 MHz. The discrepancy from this value is small enough to be compensated by means of a piezoelectric actuator on which is mounted one of the mirrors of the laser cavity. This action is continuously accomplished by means of a phase locked loop (PLL) logic implemented in the synchronization unit Time-Bandwidth CLX-1100. If the oscillator is locked to RF/6, the relative phase between the oscillator itself and the SB orbit is constant after every revolution inside the SR. Indeed, the Elettra harmonic number (i.e., the number of RF cycles in an orbit period) is 432, which is divisible by 6.

The train of pulses coming from the oscillator enters the regenerative amplifier.

The output of the latter (i.e. the seed pulse) is naturally synchronized with the oscillator, but its maximum repetition rate is 1 kHz while the SB revolution occurs at 1.16 MHz. To maintain a constant delay between the seed and the SB orbit every time that the seed pulse is produced, we trigger the Pockelsâ&#x20AC;&#x2122; cells of the amplifier with a period that is an entire multiple of the orbit period. Further details about timing can be found in [16].

DIAGNOSTICS

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vacuum area from the atmosphere. Here, the light is detected and characterized by means of a 750 mm, Czerny-Turner spectrometer. This instrument mounts two gratings both blazed for UV for medium (600 l/mm) and high dispersion (3600 l/mm). After dispersion, the light can be focused either onto a liquid nitrogen cooled CCD detector or, by means of a deflecting mirror, on the exit slits after which is mounted a photomultiplier tube (PMT). The CCD can record in a single acquisition an entire spectrum, whose width and resolution depends on the grating in use. The CCD suitable for very weak intensity but the minimum integration time is about 50 ms. For this reason, to extract only the contribution of the harmonic emission, we need to acquire and subtract the spontaneous emission background.

The PMT is a single-channel detector but has a good efficiency and a fast response (rise-time ~500 ps). It is used for single-shot measurements in a given bandwidth that depends on the grating dispersion and on the width of the exit slits. The light can be also transported outside the hutch to be focused into an Figure 4. Intensity of the UV pulses vs acquisition time. The signal was acquired using a photomultiplier (PMT) placed downstream a monochromator. Note that the PMT does not allow to resolve the sub-ps temporal scale on which the coherent pulse evolves.

This, in turn, does not permit direct detection and therefore appreciation of the effective amplitude difference between the seeded and the spontaneous signals, their true ratio being a factor about 104 (see text). In (a) the radiator is tuned for circular polarization; in (b) the radiator is tuned for linear polarization.

experimental end-station. We can insert in the optical path different sets of interferential mirrors that allow separating and recombining harmonics and seed. This configuration permits optically delaying one signal with respect to the other to perform pump and probe experiments. The optical path, from the MgF2 window to the end-station and through the spectrometer can be purged with N2 flow to reduce the atmosphereâ&#x20AC;&#x2122;s absorption in the deep UV range.

The SR-FEL beamline shares the OK with the Nano Specroscopy beamline [21] on the Elettra SR exit 1.2. The transport of the harmonic pulses produced on the FEL branch of this beambline, is simply accomplished by means of a switching mirror chamber. The Nano Spectroscopy beamline is equipped with a SPELEEM microscope and it has been used to perform a proof-of-principle experiment that demonstrates the usability of the CHG source [12].

THE SOURCE PERFORMANCE

Figure 4 shows the intensity of the monochromatized radiation at 132 nm (i.e., the third harmonic of the seed) vs the acquisition time. The radiator is tuned either for circular [Fig. 4(a)] or for linear [Fig. 4(b)] polarizations. The enhanced peaks correspond to the coherent signal generated by the seeded electron bunch, while the small side peaks represent the spontaneous (i.e., 31

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unseeded) incoherent radiation. When the radiator field is set for circular polarization, the field-electron coupling is strengthened and, as a consequence, the optical gain is enhanced. This explains why the signal in circular polarization is about a factor 2 stronger than that generated when the radiator is in planar polarization. The electron bunch revolution frequency is about 1.16

Figure 5. Quadratic dependence of the coherent harmonic detected using a PMT vs (normalized) bunch current. Dots represent experimental data; the curve is a fit obtained using a quadratic function.

Figure 6. (a) Spectrum of the coherent emission at 132 nm (linear polarization). The integration time is 1 ms; the spectrum is obtained after subtraction of the background due to spontaneous emission. (b) Spectrum of spontaneous and coherent emission for the case in which the radiator is tuned at 203 nm, i.e., slightly mismatched with respect to the second harmonic of the seed laser (198.5 nm).

MHz, corresponding to an interbunch period of 864 ns. This means that the bunch is seeded (i.e., generates coherent emission) only once every about 1160 turns. Hence, the repetition rate of the spontaneous (incoherent) emission generated by the beam at every pass through the undulators is much higher than that of coherent emission. Spontaneous emission produces background noise, which may be disturbing when the light is used for experiments. As we shall see, the problem can be solved by using a gated detector.

As shown in Fig. 4, the seeded signal in circular polarization is a factor about 25 above spontaneous emission, which becomes a factor about 104 if one takes into account the difference between spontaneous and coherent pulse durations, i.e., about 30 ps and 100 fs (FWHM), respectively. We assume here that the duration of the harmonic coherent pulse, Î&#x201D;t, is slightly shorter than the seed pulse duration. Such an assumption is supported by numerical simulations Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

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performed using the numerical code GENESIS [22].

For the reported experiment, the Elettra SR was operated in single-bunch mode, the electron energy was set at 1.1 GeV and the current per bunch was about 0.6 mA (corresponding to a peak current of 14 A). In these conditions, the number of measured photons per coherent pulse was of the order of 109.

The quadratic dependence of the harmonic signal on beam current, which is the signature of coherence, is shown in Fig. 5. Data were obtained from a scan of the relative position of the seed pulse within the electron bunch. The CHG signal is then plotted versus the effective electron-beam current at the location of the seed pulse. The current is normalized to the bunch peak current. The spectrum of the coherent signal at 132 nm (radiator for linear polarization) is shown in Fig. 6(a), after subtraction of the radiator spontaneous emission. A direct measurement of the spectral width gives a bandwidth, Δλ, of about 0.33 nm FWHM. Assuming Gaussian temporal and spectral profiles, at the transform limit one would get Δt=0.44 λ2/c Δλ ~ 77 fs FWHM, which is close to the value predicted by GENESIS. Data shown in Fig. 6(b) demonstrate the good spectral stability of the source.

In this case, the radiator is tuned at λ0 = 203 nm, i.e., is slightly mismatched with respect to λ2 = 198.5 nm, which is the second harmonic of the seed laser.

As already explained, at the undulator entrance, the electron beam is ‘‘prepared’’ to emit coherently at one of the harmonics of the seed. Coherent

Figure 7. Acquisition of the coherent signal during 200 ms (i.e., 200 turns pulses).

emission at λ2 still occurs provided the relative mismatch (λ0 – λ2)/λ0 does not exceed the FEL gain width ~1/N, N being the number of radiator periods. The effect of the mismatch on the radiator emission is shown in Fig. 6(b), where the measured spectrum is reported. As it can be seen, while the part of the spectrum generated by spontaneous emission is centered around the ‘‘detuned’’ wavelength (i.e., 203 nm), the position of the coherent signal is ‘‘locked’’ to the second harmonic of the seed laser. For the considered case, (λ0 – λ2)/λ0, which is well within the FEL gain width 1/N = 5%. A fundamental feature of a light source to be exploited for user experiments is the shot-to-shot stability of the emitted power.

The reproducibility of our source is shown in Fig. 7, where the acquisition of 200 consecutive pulses is reported as a function of time. A very good stability is found, with fluctuations of the order of few percent. As already mentioned, this 33

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is mainly due to the very good electron-beam stability, which is a common characteristic of all modern storage rings. An important role is also played by the low seed-electron timing jitter, which is about 2 ps in our case. Such a value is small enough to guarantee that, during consecutive shots, the laser ‘‘seeds’’ beam portions containing very similar numbers of electrons. Concerning longer term reproducibility, for relatively low current values (< 1 mA), i.e., for a relatively long beam lifetime, we observed a very stable behavior over several hours.

CONCLUSIONS

In conclusion, we implemented a presently unique light source, which is able to produce ultrashort coherent photon pulses in the VUV spectral region. Our results show that seeded coherent harmonic generation on electron storage rings can significantly extend the capabilities of presently available light sources. In particular, the most evident advantages of coherent harmonic generation with respect to standard synchrotron radiation rely on the time structure and the coherence of the generated optical pulses. It is worth stressing that there is a quite wide margin for improving the currently achieved performance. Indeed, seeding with the third harmonic of the Ti:sapphire (i.e., 265 nm) will provide the possibility of extending the source wavelength range well below 100 nm (e.g., tuning the radiator at the third harmonic of the seed, 88.3 nm). Moreover, the maximum repetition rate at which the harmonic signal can be produced (1 kHz) is presently limited only by the seed laser repetition rate. Given the rapid progress in the development of high repetition rate Ti:sapphire amplifiers, we anticipate a significant increase of the average harmonic power in the next few years. Potential applications of the source we have developed range from atomic and molecular physics to the study of electronic excitations on surfaces, interfaces, and nanostructures.

ACKNOWLEDGMENT

We thank the Elettra accelerator team.

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Methods Phys. Res., Sect. A 500, 1 (2003); N. Gedik et al., Science 316, 425 (2007); A. Cavalieri, Nature (London) 448, 651 (2007).

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4. A. Doyuran et al., Phys. Rev. Lett. 86, 5902 (2001).

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18. www.kmlabs.com 19. www.coherent.com 20. F. Curbis, et al., in Proceedings of FEL Conference 2006.

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Muon & Neutron & Synchrotron Radiation News

ESS Bilbao Initiative Workshop Multi-MW Spallation Neutron Sources CURRENT CHALLENGES AND FUTURE PROSPECTS

C. Oyon

ESS Bilbao has designed a comprehensive, international and collaborative R&D programme which is already addressing some of the critical design challenges of the ESS and providing a collaborative platform for research efforts across Europe.

Within this R&D programme, ESS Bilbao organised the ESS Bilbao Initiative Workshop held in Bilbao in March when more than 160 worldwide experts gathered to discuss the status, plans, issues and challenges facing the development of high-power, long-pulse spallation sources and synergies with other on-going related projects.

The workshop succeeded in its goal of bringing together people working on programmes of relevance to high power spallation neutron sources from major centres of excellence worldwide, such as SNS, ISIS, INFN, CERN, CEA Saclay, J-Parc, FZ JĂźlich, CSNS, IN2P3, FNAL, LANL, PSI, SCK-CEN, ILL, ANL, JLAB and IPN Orsay among others and identifying the challenges that next generation of machines will encounter and how these might be addressed by a series of truly collaborative, international research efforts.

The conclusions of the workshop have been published in a document www.workshop2009.essbilbao.com/cas/wshopdoc/conclusions.pdf that highlights the current challenges, addresses future prospects and defines a number of collaborative development programmes.

The workshop also attempted to put together the user´s point of view of such a neutron facility as ESS and the requirements of accelerator and target experts in order to obtain a preliminary set of parameters that fulfils the needs of the three groups. As a result of this interaction and taking the basic ESS parameters defined in the ESFRI roadmap (5MW, 1 GeV, 150 MA, 16.7 Hz) and a number of on-going research activities set up by ESS Bilbao as starting point, a tentative set of parameters for the ESS lineal accelerator has been established with the aim of simplifying the linac design and increasing reliability. In essence, the current has been decreased (75 mA) and the final energy has been increased (2.2 GeV), keeping the linac elements essentially the same. The decrease in the current allows for an increase of the cavity gradient which results in an increase in the linac energy while keeping the linac length unchanged. The originally proposed repetition rate has been increased to 20 Hz, which is acceptable to the user community and avoids problems in operating the linac. The pulse length may also be reduced to 1.5 since this value is preferred by neutron scientists and also facilitates a number of RF equipment design activities.

With this set of parameters in mind, the accelerator component group has discussed the present status, issues and challenges and future R&D developments needs for cavities and cryomodules, with special reference to power couplers, transition from warm to cold sections with the application of spokes cavities, higher order modes, cryomodules and cryogenics. They have

ESS Bilbao, Spain

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Muon & Neutron & Synchrotron Radiation News

also established a number of recommendations for the area of high power RF arquitecture The beam dynamics and diagnostics group addressed the problems of modelling codes, radiation issues and longitudinal and transverse measuring techniques. Their recommendations come in three main subareas, beam diagnostics, where the experts clearly recommend more diagnostic equipment than envisaged, linac FE, where they have specified an approach to obtaining a high reliability FE system capable of meeting the specified parameters, considering each major component of the FE separately: ion source, LEBT and RFQ, and beam dynamics, where the clear conclusion is that a detailed study of the beam-line form the linac to the target must be carried out The target group has identified eleven R&D and conceptual design activities needed to support development of the ESS target: two of them for the mercury target (cavitation damage of mercury vessel target, avoidance of boiling mercury), four activities for the rotating target (maintenance concept and overall configuration for a rotating solid target, irradiated tungsten database development, instrumentation for rotating solid targets, rotating target seals, bearings and drives, tungsten cladding) and four aspects of general appliance, structural performance, beam profile diagnostics, elimination of high energy shutters and moderator development.

Neutron Applications in Earth, Energy and Environmental Sciences Series: Neutron Scattering Applications and Techniques Liyuan Liang, Romano Rinaldi and Helmut Schober (Eds.) 2009, XVIII, 638 p. 35 illus., Hardcover ISBN: 978-0-387-09415-1

Neutron Applications in Earth, Energy and Environmental Sciences offers a comprehensive overview of the wide ranging applications of neutron scattering techniques to elucidate the fundamental materials properties at the nano-, micro- and meso-scale, which underpin research in the related fields of Earth, Energy and Environmental Sciences.

Introductions to neutron scattering fundamentals and instrumentation are paired with a thorough review of the applications to a large variety of scientific and technological problems, written through the direct experience of leading scientists in each field. Tailored to a wide audience, this volume provides the novice with an inspiring introduction and stimulates the expert to consider these non-conventional problem solving techniques in his/her field of interest.

Earth and environmental scientists, engineers, researchers and graduate students involved with materials science will find Neutron Applications in Earth, Energy and Environmental Sciences a valuable ready-to-use reference.

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School and Meeting Reports

ICNS 2009 Held in Knoxville The International Conference on Neutron Scattering (ICNS) was held at the Knoxville Convention Center in downtown Knoxville, Tennessee, US, May 3-7, 2009. This setting was immediately adjacent to the Sunsphere, a symbol of the 1982 World’s Fair. The previous ICNS was held in Sydney, Australia in 2005; previous North American venues were Toronto, Canada in 1997 and Santa Fe, New Mexico, US in 1985. The Program Committee was chaired by Paul Butler with co-chairs Meigan Aronson and Lee Robertson. The Committee reviewed over 650 abstracts submitted for talks and integrated over 240 talks including plenary and invited talks into ten topical areas and 41 sessions. The talks will be published in Journal of Physics – Condensed Matter. Over 650 registrants attended the Conference from six continents and 29 countries. It was sponsored by the Neutron Scattering Society of America (NSSA), led by cochairs Simon Billinge and Gregory Smith, hosted by Oak Ridge National Laboratory (ORNL) and held using the meeting services of the Materials Research Society.

The ICNS formally began with an opening reception on Sunday evening attended by about 350. The opening was preceded by 17 satellite events including a meeting of international neutron facility directors. Discussions by the directors included expanding collaborative development programs, identifying helium-3 needs in neutron detectors, and developing more inclusive web and education initiatives. The first speakers of the Conference focused on the state of neutron scattering and outreach to the broader scientific communities and to the public. Bruce Gaulin, president of NSSA, noted that with the new facilities being constructed and newly operating: there has never been a better time to be a neutrons scatterer! Thom Mason, director of ORNL and chair of the Local Organizing Committee for the 1997 ICNS conference in Toronto, Canada, described the importance of materials science research in identifying energy solutions for the international economies. He urged the neutron science community to reach out and involve the broader scientific community in their studies as everyone’s help is needed to achieve our energy goals.

In his keynote address, John Root, director of the Canadian Neutron Beam Centre, emphasized making the value of neutron scattering common knowledge. He invited audience participation in responding to the question of how to make neutron scattering into “common knowledge.” Root asked the audience, “When was the last time you read an article in the popular press crediting neutron scattering as the investigative technique responsible for improving life or the economy?” He proposed that one-sentence answers are necessary to communicate to the public and the non-neutron scattering scientific community about questions such as why neutron scattering is important, what are its benefits, and what has it done for us lately? Root also recommended strengthening and expanding neutron science competencies outside of the facilities to broaden the base of the user community.

37

Clemson University students visit the Oak Ridge National Laboratory exhibit.

Highlights of ORNL Tour On Monday evening, more than 150 registrants participated in tours of neutron sources at Oak Ridge National Laboratory. More than half visited both the High Flux Isotope Reactor (HFIR) and Spallation Neutron Source (SNS), while the others visited only the SNS. Each of the participants was provided a sandwich and refreshments when they departed SNS for Knoxville.

The tour was well-timed as it enabled a greater understanding of ORNL’s scientific resources and appreciation of their capabilities in time to apply for the next call for proposals for beam time, whose closing date is August 31, 2009.

This call will include nine instruments and HFIR and ten at SNS as part of this call for proposals.

More information on ORNL’s neutron scattering program and instrument capabilities can be found at http://neutrons.ornl.gov.

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School and Meeting Reports

The plenary lectures were given by renowned scientists across a spectrum of research. On Monday, Tonya Kuhl (Univ. California, Davis, California, US) reported on neutron and x-ray reflectometry and grazing diffraction studies of single phospholipid membranes. Omar Yaghi (Univ. California, Los Angeles, California, US) discussed using reticular chemistry to form metal-organic frameworks. On Tuesday, Alberto Podjarny (IGBMC, CNRS, France) focused on new opportunities in protein neutron crystallography and Chun Loong (Sun YatSen Univ., Guangzhou, China) described current and efforts relating to neutron scattering facilities in China. In the Wednesday plenary lecture, David Mandrus (Oak Ridge) provided an overview of new iron-based superconductors, and on Thursday, Collin Broholm (Johns Hopkins Univ., Baltimore, Maryland, US) explored quantum magnetism through neutron scattering.

In the final plenary lecture Sunil Sinha (Univ. California, San Diego, US) summarized the accomplishments of neutron scattering over the past half

Alberto Podjarny discusses using neutrons in protein crystallography.

Dieter Richter present the Walter H채lg Prize lecture.

John Root gives the ICNS keynote address.

century and identified challenges for the future. Beginning with the tremendous accomplishments, he then identified the techniques that might be considered as the competitors yet are complementary: synchrotron x-rays, direct imaging, and scanning probes. Neutron scattering is at a disadvantage because it does not generate appealing images. He concluded by also expressing the conviction expressed previously by John Root in the opening keynote talk that it is necessary to sell neutron scattering to the public.

A special event was the awarding of the Walter H채lg Prize to Dieter Richter of Research Center, J체lich, Germany. This prize is awarded every two years by the European Neutron Scattering Association, to a European scientist for an outstanding program of research in neutron scattering with a long term impact on scientific and/or technical neutron scattering applications. This award recognizes his work towards understanding the dynamics of polymers and biological macromolecules using high-resolution neutron scattering techniques.

A meeting of this magnitude and scope is not possible without financial support from generous sponsors and we would like to thank the neutron scattering centers of Oak Ridge National Laboratory, Los Alamos National Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

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School and Meeting Reports

Laboratory, National Institute of Standards and Technology, National Research Council Canada, ESS Bilbao, ESS Hungary, ESS Scandinavia, HelmholtzZentrum Berlin, Australian Nuclear Science and Technology Organization, Forschungszentrum Jülich GmbH, Forschungsneutronenquelle Heinz MaierLeibnitz, Institute Laue-Langevin, Rutherford Appleton Laboratory, Indiana University Low Energy Neutron Source, Laboratorie Leon Brillouin, and the US Department of Energy and the NMI3 Project for their generous financial support. We are also grateful for support from our industrial sponsors, GE Energy and Kurt J. Lesker Company.

The next international meeting in the ICNS series will be in Europe in 2013 at a location to be determined. The Materials Research Society has summarized the ICNS in issues of Meeting Scene.

They are archived at: www.mrs.org/s_mrs/sec.asp?CID=19397&DID=242208 (Side bar)

Sunil Sinha gives the final plenary talk.

Young scientists participate in the Walk-Around Banquet, a popular feature of the ICNS.

ICNS BY THE NUMBERS

1 Walter Hälg Prize awarded (to Dieter Richter) 2 Poster sessions with over 300 posters 10 Plenary speakers 17 Satellite meetings or discussion sessions 28 Exhibitors 40 Member International Advisory Committee 41 Plenary and science sessions 74 Invited speakers 100 Student scholarships 150 Visitors to ORNL neutron facilities 225 Speakers across 10 subject areas 656 Submitted abstracts

Photo credit for all images: Gopal Rao, Materials Research Society

39

Oak Ridge Neutron Scattering Facilities RECENT EVENTS The National School on Neutron and X-ray Scattering will be held at Oak Ridge and Argonne National Laboratories during May 30 - June 13, 2009. The main purpose of this School is to educate graduate students on the utilization of major neutron and xray facilities. Lectures, presented by researchers from academia, industry, and national laboratories, will include basic tutorials on the principles of scattering theory and the characteristics of the sources, as well as seminars on the application of scattering methods to a variety of scientific subjects. This year, 60 graduate students from 41 U.S. colleges and universities will conduct 6 short experiments at Argonne’s Advanced Photon Source and Oak Ridge’s Spallation Neutron Source and High Flux Isotope Reactor facilities to provide handson experience for using neutron and synchrotron sources. The U.S Department of Energy pays for the expenses of students to attend this School.

As part of the ICNS, a Town Hall meeting was held to receive input on the Second Target Station for the Spallation Neutron Source at Oak Ridge National Laboratory.

More than 100 attendees participated. The U.S. Department of Energy has given its initial approval to begin plans for a Second Target Station for the Spallation Neutron Source. The reference concept is that the STS takes every third pulse from the accelerator to operate at 20Hz (50 msec intervals).

This long-pulse mode for the STS uses an unchopped (and uncompressed) 1 ms beam pulse. The STS model uses parahydrogen moderators, beryllium reflector, and a mercury target to produce 20 neutron beams. A rotating solid target is also a viable option and further research is being pursued.

Discussions pointed out that the 20 Hz frequency may not be optimal for some of the proposed instruments, and it was agreed that this warrants further study. Discussions also pointed out the need to allocate adequate project resources to be the development of detectors, data analysis, software, and sample environment equipment.

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Call for Proposal

[Deadlines for proposal submission]

Neutron Sources http://pathfinder.neutron-eu.net/idb/access

15th October 2009

BNC http://www.bnc.hu/modules.php?name=News&file=article&sid=39

1st September 2009

BENSC http://www.helmholtz-berlin.de/userservice/neutrons/user-info/call-for-proposals_en.html#c63361

At anytime during 2009

GeNF - Geesthacht Neutron Facility www.gkss.de/index_e_js.html

16th September 2009

ILL www.ill.eu/users/experimental-programme/

14th September 2009

JCNS FZ-Jülich www.jcns.info/jcns_proposals/

1st October 2009

LLB - Laboratoire Léon Brillouin http://pathfinder.neutron-eu.net/idb/access

15th September 2009

NPL - Neutron Physics Laboratory http://pathfinder.neutron-eu.net/idb/access

15th November 2009

SINQ – Swiss Spallation Neutron Source http://pathfinder.neutron-eu.net/idb/access

Synchrotron Radiation Sources www.lightsources.org/cms/?pid=1000336#byfacility

19th October 2009

AS - Australian Synchrotron www.synchrotron.org.au/content.asp?Document_ID=5305

1st September 2009

BESSY www.ihep.ac.cn/bsrf/english/userinfo/beamtime.htm

Proposals are evaluated twice a year

BSRF - Beijing Synchrotron radiation Facility www.ihep.ac.cn/bsrf/english/userinfo/beamtime.htm

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Call for Proposal

30th September 2009

CFN - Center for Functional Nanomaterials www.bnl.gov/cfn/user/proposal.asp

30th October 2009

CHESS - Cornell High Energy Synchrotron Source www.chess.cornell.edu/prposals/index.htm

16th September 2009

CLS â&#x20AC;&#x201C; Canadian Light Source www.chess.cornell.edu/prposals/index.htm

1st October 2009

DIAMOND - Diamond Light Source www.diamond.ac.uk/ForUsers/Welcome

31st August 2009

ELETTRA https://vuo.elettra.trieste.it/pls/vuo/guest.startup

1st December 2009

FELIX - Free Electron Laser for Infrared experiments www.rijnh.nl/research/guthz/felix_felice/

1st September and 1st October, 2009

HASYLAB - Hamburger Synchrotronstrahlungslabor at DESY http://hasylab.desy.de/user_info/write_a_proposal/2_deadlines/index_eng.html

30th September 2009

NSLS - National Synchrotron Light Source https://pass.nsls.bnl.gov/deadlines.asp

30th September 2009

NSRRC - National Synchrotron radiation Research Center www.nsrrc.org.tw/

6th November 2009

PF - Photon Factory www.nsrrc.org.tw/

15th September and 15th October, 2009

SLS - Swiss Light Source http://sls.web.psi.ch/view.php/users/experiments/proposals/opencalls/index.html

1st August 2009

SRC - Synchrotron Radiation Center www.lightsources.org/cms/?pid=1000336

1st July, 1st September and 1st December, 2009

SSRL - Stanford Synchrotron Radiation Laboratory www.ssrl.slac.stanford.edu/users/user_admin/deadlines.html

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Calendar August 1-7, 2009-05-05

Zuoz, Switzerland - Lyceum Alpinum 8th PSI Summer School on Condensed Matter Research http://school.web.psi.ch/html/index.shtml

August 2-5, 2009

Bonn, Germany - Gustav-Stresemann-Institut PNSXM 2009 - Polarized Neutrons and Synchrotron X-rays for Magnetism 2009 http://www.fz-juelich.de/iff/pnsxm2009

August 2 -7, 2009

Waterville, USA - Colby College X-RAY SCIENCE, Gordon Research Conference http://www.grc.org/programs.aspx?year=2009&program=xray

August 2-7, 2009

Santa Fe, New Mexico - Inn and Spa at Loretto SAGAMORE XVI - TopicsSpin densities and related phenomena: Neutron scattering studies of magnetic systems http://www.sagamorexvi.org/index.shtml

September 14-18, 2009

Karlsruhe, Germany ICXOM20 - 20th International Congress on X-ray Optics and Microanalysis http://icxom20.fzk.de/

September 20-23, 2009

Hamburg, Germany - DESY Auditorium GISAS neutron and x-ray based grazing incidence small-angle scatterin https://indico.desy.de/conferenceDisplay.py?confId=797

September 20-25, 2009

Berlin - Dresden, Germany - DBB FORUM SRF09 - 14th International Conference on RF Superconductivity http://www.helmholtz-berlin.de/events/srf2009/

September 21-25, 2009

Melbourne, Australia - University of Melbourne ISRP-11-11th International Symposium on Radiation Physics http://mcmconferences.com/isrp11/

September 23-25, 2009

Argonne, USA - Argonne National Laboratory On-line Brillouin Spectroscopy at GSECARS: Basic Principles and Application for High Pressure Research http://cars9.uchicago.edu/gsecars/dac_brillouin_workshop/brillouin_workshop.htm

September 27-28, 2009

Feldafing, Germany Off-Spec 2009: Theory and Data Analysis for Grazing Incidence and Off-Specular Scattering http://www.jcns.info/Workshop_OffSpec/

September 27-October 2, 2009

Melbourne, Australia - Melbourne Convention and Exhibition Centre SRI2009 - The 10th International Conference on Synchrotron Radiation Instrumentation http://www.sri09.org/

September 28-October 1, 2009

Bad Honnef (Germany) Ultrafast x-ray methods for studying transient electronic structure and nuclear dynamics http://www.udkm.physik.uni-potsdam.de/WEH.htm

October 5-7, 2009

Argonne, ILL, USA 2009 CNM User Meeting http://nano.anl.gov/events/2009_cnm_user_meeting.html

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Calendar

October 5-7, 2009

Grenoble, France - ILL - Institut Laue-Langevin SKIN2009: Studying Kinetics with neutrons (SANS and Reflectometry) http://www.ill.eu/html/news-events/workshops-events/skin2009/

October 5-8, 2009

Tutzin, Germany Trends and Perspectives in Neutron Scattering on Soft Matter http://www.jcns.info/Workshop_Softmatter/

October 5-7, 2009

Grenoble, France - ILL - Institut Laue-Langevin SKIN2009: Studying Kinetics with neutrons (SANS and Reflectometry) http://www.ill.eu/html/news-events/workshops-events/skin2009/

October 12-13, 2009

Villigen, Switzerland - PSI JUM@P ‘09 First Joint Users’ Meeting of the PSI facilities (SLS, SINQ, SmuS) http://neutron.neutron-eu.net/n_news/n_calendar_of_events/n-events-2009

October 15-17, 2009

California, USA 2009 ALS Annual Users’ Meeting http://www.lightsources.org/cms/?pid=1000068

October 18-21, 2009

Menlo Park, California 2009 SSRL/LCLS Annual Users’ Meeting http://www-conf.slac.stanford.edu/ssrl-lcls/2008/2009.asp

October 23-24, 2009

Madison, USA SRC 2009 Users’ Meeting http://www.lightsources.org/cms/?pid=1000068

November 10-12, 2009-05-05

Mito, Japan - Hotel Lake View Mito The 5th International Conference on Mechanical Stress Evaluation

by Neutrons and Synchrotron Radiation http://nsrc.jaea.go.jp/mecasens-5/

November 2-4, 2009

Lund, Sweden MAX-lab 22nd Annual User Meeting http://www.maxlab.lu.se/usermeeting/index.html

November 12-13, 2009

Berlin-Adlershof, Germany First Joint BER II and BESSY II User Meeting http://www.lightsources.org/cms/?pid=1000068

November 19-21, 2009

Amman, Jordan 8th SESAME Users’ Meeting http://www.sesame.org.jo/users/sesameusers.aspx

November 30-December 4, 2009

Boston, USA 2009 MRS Fall Meeting http://www.mrs.org/s_mrs/sec.asp?CID=9546&DID=198609

December 2-7, 2009

Alexandria, Egypt - Institute of Nuclear Materials Management International conference on Advanced Methods of Laser Applications in Nuclear science and Neutron Scattering http://www.iaea.org/cgi-bin/maeps.page.pl/search.htm

December 14-16, 2009

Grignano, Trieste (Italy) Thermodynamic Unstable Proteins: Chance or Necessity? – Workshop http://www.elettra.trieste.it/events/2009/1214/

December 16-18, 2009

Trieste, Italy Probing Magnetic Dynamics With Ultrashort Coherent X-Ray Pulses http://www.elettra.trieste.it/events/

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Facilities

Neutron Scattering WWW SERVERS IN THE WORLD http://idb.neutron-eu.net/facilities.php

BNC - Budapest Research reactor

ILL Grenoble (F)

Type: Swimming pool reactor, 10MW Phone: +36 1 392 2222 Phoneefax: +36 1 395 9162 Email: tozser@sunserv.kfki.hu http://www.kfki.hu/brr/indexen.htm

Type: 58MW High Flux Reactor.

Phone: + 33 (0)4 76 20 71 11 Fax: + 33 (0)4 76 48 39 06 Phone: +33 4 7620 7179 Fax: +33 4 76483906 Email: cico@ill.fr and sco@ill.fr http://www.ill.eu

BENSC - Berlin Neutron Scattering Center IPNS - Intense Pulsed Neutron at Argonne

Glienicker Strasse 100, D-14109 Berlin, Germany Phone: +49-30 / 80 62 - 0 Fax: +49-30 / 80 62 - 21 81 Email: info@helmholtz-berlin.de http://www.helmholtz-berlin.de/

Phone: 630/252-7820 Fax: 630/252-7722

for proposal submission by e-mail send to cpeters@anl.gov or mail/fax to IPNS Scientific Secretary, Building 360 http://www.pns.anl.gov/

FLNP - Frank Laboratory of Neutron Physics ISIS Didcot

Phone: (7-49621) 65-657 Fax: (7-49621) 65-085 Email: belushk@nf.jinr.ru http://flnp.jinr.ru/25/

Type: Pulsed Spallation Source.

Phone: +44 (0) 1235 445592 Fax: +44 (0) 1235 445103 Email: uls@isis.rl.ac.uk http://www.isis.rl.ac.uk

FRG-1 Type: Swimming Pool Cold Neutron Source.

Phone: +49 (0)4152 87-0 Fax: +49 (0)41 52 87-1403 Email: reinhard.kampmann@gkss.de http://www.gkss.de/about_us/contact/research_reactor/index.htm

JCNS Juelich Centre for Neutron Science Forschungszentrum Juelich, D-52425 Juelich, Germany Email: neutron@fz-juelich.de http://www.jcns.info

FRM II Type: Compact 20 MW reactor.

Phone: +49 (0) 89 289 14965 Fax: +49 (0) 89 289 14995 Email: Winfried.Petry@frm2.tum.de http://www.frm2.tum.de/en/index.html

JRR-3M

HFIR

JEEP-II Reactor

ORNL, Oak Ridge, USA Phone: (865)574-5231 Fax: (865)576-7747 Email: ns_user@ornl.gov http://neutrons.ornl.gov

Type: D2O moderated 3.5% enriched UO2 fuel.

Phone: +47 63 806000, 806275 Fax: +47 63 816356 Email: kjell.bendiksen@ife.no http://www.ife.no/index_html-en?set_language=en&cl=en

Fax: +81 292 82 59227 Phoneex: JAERIJ24596 Email: www-admin@www.jaea.go.jp http://www.jaea.go.jp/jaeri/english/index.html

HIFAR Phoneephone numbers

ANSTO Switchboard: + 61 2 9717 3111 ANSTO Facsimile: + 61 2 9543 5097 Email: enquiries@ansto.gov.au http://www.ansto.gov.au

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Facilities

KENS

RID - Reactor Institute Delft (NL)

Institute of Materials Structure Science High Energy Accelerator research Organisation 1-1 Oho, Tsukuba-shi, Ibaraki-ken,?305-0801, JAPAN Email: kens-pac@nml.kek.jp http://neutron-www.kek.jp/index_e.html

Type: 2MW light water swimming pool.

Phone: +31 15 27 87774 Fax: +31 15 27 82655 Email: I.Hagman@tudelft.nl http://www.rid.tudelft.nl/live/pagina.jsp?id=b15d7df9-7928-441e-b45d6ecce78d6b0e&lang=en

KUR - Kyoto University Research Reactor Institute Kumatori-cho Sennan-gun, Osaka 590-0494,Japan Phone: +81-72-451-2300 Fax: +81-72-451-2600 http://www.rri.kyoto-u.ac.jp/en/

LANSCE Phoneephone: 505-665-1010 Fax: 505-667-8830 Email: tichavez@lanl.gov - lansce_users@lanl http://www.lansce.lanl.gov/

LLB Orphée Saclay (F)

SINQ Villigen (CH) Type: Steady spallation source Phone: +41 56 310 2111 Fax: +41 56 310 2199 Email: sinq@psi.ch http://sinq.web.psi.ch

SNS - Spallation Neutron Source Phone: 865.574.1301 Fax: (865) 241-5177 Email: ekkebusae@ornl.gov http://neutrons.ornl.gov

Type: Reactor. Flux: 3.0 x 1014 n/cm2/s Secrétariat Europe: Phone: 0169085417 Fax: 0169088261 Email: experience@llb.cea.fr http://www-llb.cea.fr

NCNR - NIST Center for Neutron Research Phone: (301) 975-6210 Fax: (301) 869-4770 Email: Robert.dimeo@nist.gov http://rrdjazz.nist.gov/

NPL - NRI Type: 10 MW research reactor.

Phone: +420 2 20941177 / 66173428 Fax: +420 2 20941155 Email: krz@ujv.cz and brv@nri.cz http://neutron.ujf.cas.cz/

NRU - Chalk River Laboratories Phone: 613-584-8293 Fax: 613-584-4040 http://neutron.nrc-cnrc.gc.ca/home_e.html

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Facilities

Synchrotron Radiation Sources WWW SERVERS IN THE WORLD www.lightsources.org/cms/?pid=1000098

ALBA - Synchrotron Light Facility

CAMD - Center Advanced Microstructures & Devices

Phone: +34 93 592 43 00 Fax: +34 93 592 43 01 http://www.cells.es/

Phone: +1 (225) 578-8887 Fax: +1 (225) 578-6954 Email: leeann@lsu.edu http://www.camd.lsu.edu/

ALS - Advanced Light Source Phone: +1 510.486.7745 Fax: +1 510.486.4773 Email: alsuser@lbl.gov http://www-als.lbl.gov/als/

CANDLE - Center for the Advancement of Natural Discoveries using Light Emission Phone/Fax: +374-1-629806 Email: baghiryan@asls.candle.am http://www.candle.am/index.html

ANKA Phone: +49 (0)7247 / 82-6071 Fax: +49-(0)7247 / 82-6172 Email: info@fzk.de http://ankaweb.fzk.de/

CESLAB - Central European Synchrotron Laboratory Phone: +420-541517500 Email: kozubek@ibp.cz http://www.synchrotron.cz/synchrotron/Central_Europeanl_Synchrotron

_Laboratory_EN.html

APS - Advanced Photon Source Phone: (630) 252-2000 Fax: +1 708 252 3222 Email: fenner@aps.anl.gov http://www.aps.anl.gov/

CFN - Center for Functional Nanomaterials Phone: +1 (631) 344-6266 Fax: +1 (631) 344-3093 Email: cfnuser@bnl.gov http://www.bnl.gov/cfn/

AS - Australian Synchrotron Phone: +61 3 9655 3315 Fax: +61 3 9655 8666 Email: contact.us@synchrotron.vic.gov.au http://www.synchrotron.vic.gov.au/content.asp?Document_ID=1

CHESS - Cornell High Energy Synchrotron Source

BESSY - Berliner Elektronenspeicherring Gessellschaft.für Synchrotronstrahlung

CLIO - Centre Laser Infrarouge d’Orsay

Phone: +49 (0)30 6392-2999 Fax: +49 (0)30 6392-2990 Email: info@bessy.de http://www.bessy.de/

Email: accueil-clio@lcp.u-psud.fr http://clio.lcp.u-psud.fr/clio_eng/clio_eng.htm

CLS - Canadian Light Source

BSRF - Beijing Synchrotron Radiation Facility Phone: +86-10-68235125 Fax: +86-10-68222013 Email: houbz@mail.ihep.ac.cn http://www.ihep.ac.cn/bsrf/english/main/main.htm

Notiziario Neutroni e Luce di Sincrotrone - Vol. 14 n. 2

Phone: 607 255-7163 Fax: 607 255-9001 http://www.chess.cornell.edu/

Phone: (306) 657-3500 Fax: (306) 657-3535 Email: clsuo@lightsource.ca http://www.lightsource.ca/

CNM - Center for Nanoscale Materials Phone: 630.252.6952 Fax: 630.252.5739 http://nano.anl.gov/facilities/index.html

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Facilities

CTST - UCSB Center for Terahertz Science and Technology University of California, Santa Barbara (UCSB), USA http://sbfel3.ucsb.edu/

DAFNE Light INFN-LNF Phone: +39 06 94031 Fax: +39 06 9403 2582 http://www.lnf.infn.it/

DELSY - Dubna ELectron SYnchrotron Phone: + 7 09621 65 059 Fax: + 7 09621 65 891 Email: post@jinr.ru http://www.jinr.ru/delsy/

DELTA - Dortmund Electron Test Accelerator FELICITA I (FEL) Fax: +49-(0)231-755-5383 http://www.delta.uni-dortmund.de/index.php?id=2&L=1

DFELL - Duke Free Electron Laser Laboratory Phone: 1 (919) 660-2666 Fax: +1 (919) 660-2671 Email: beamtime@fel.duke.edu http://www.fel.duke.edu/

Diamond Light Source Phone: +44 (0)1235 778000 Fax: +44 (0)1235 778499 Email: useroffice@diamond.ac.uk http://www.diamond.ac.uk/default.htm

ELETTRA - Synchrotron Light Laboratory Phone: +39 40 37581 Fax: +39 (040) 938-0902 http://www.elettra.trieste.it/

ELSA - Electron Stretcher Accelerator Phone: +49-228-735926 Fax: +49-228-733620 Email: roy@physik.uni-bonn.de http://www-elsa.physik.uni-bonn.de/elsa-facility_en.html

ESRF - European Synchrotron Radiation Lab. Phone: +33 (0)4 7688 2000 Fax: +33 (0)4 7688 2020 Email: useroff@esrf.fr http://www.esrf.eu/

FELBE - Free-Electron Lasers at the ELBE radiation source at the FZR/Dresden Phone: +49 351 260 - 0 Fax: +49 351 269 - 0461 Email: kontakt@fzd.de http://www.fzd.de/db/Cms?pNid=471

FELIX - Free Electron Laser for Infrared eXperiments Phone: +31-30-6096999 Fax: +31-30-6031204 Email: B.Redlich@rijnh.nl http://www.rijnh.nl/felix/

FOUNDRY - The Molecular Foundry 1 Cyclotron Road Berkeley, CA 94720, USA http://foundry.lbl.gov/index.html

HASYLAB - Hamburger Synchrotronstrahlungslabor DORIS III, PETRA II / III, FLASH Phone: +49 40 / 8998-2304 Fax: +49 40 / 8998-2020 Email: HASYLAB@DESY.de http://hasylab.desy.de/

HSRC - Hiroshima Synchrotron Radiation Center HiSOR Phone: +81 82 424 6293 Fax: +81 82 424 6294 http://www.hsrc.hiroshima-u.ac.jp/english/index-e.htm

iFEL Phone: +81-(0)72-897-6410 http://www.fel.eng.osaka-u.ac.jp/english/index_e.html http://www.eng.osaka-u.ac.jp/en/index.html

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Facilities

INDUS -1 / INDUS -2 Phone: +91-731-248-8003 Fax: 91-731-248-8000 Email: rvn@cat.ernet.in http://www.cat.ernet.in/technology/accel/indus/index.html http://www.cat.ernet.in/technology/accel/atdhome.html

KSRS - Kurchatov Synchrotron Radiation Source Siberia-1 / Siberia-2 Phone: 8-499-196-96-45 http://www.lightsources.org/cms/?pid=1000152 http://www.kiae.ru/ (in Russian)

LCLS - Linac Coherent Light Source IR FEL Research Center - FEL-SUT Phone: +81 4-7121-4290 Fax: +81 4-7121-4298 Email: felsut@rs.noda.sut.ac.jp http://www.rs.noda.sut.ac.jp/~felsut/english/index.htm

Phone: +1 (650) 926-3191 Fax: +1 (650) 926-3600 Email: knotts@ssrl.slac.stanford.edu http://www-ssrl.slac.stanford.edu/lcls/

LNLS - Laboratorio Nacional de Luz Sincrotron ISA Institute for Storage Ring Facilities - ASTRID-1 Phone: +45 8942 3778 Fax: +45 8612 0740 Email: fyssp@phys.au.dk http://www.isa.au.dk/

Phone: +55 (0) 19 3512-1010 Fax: +55 (0)19 3512-1004 Email: sau@lnls.br http://www.lnls.br/lnls/cgi/cgilua.exe/sys/start.htm?UserActiveTemplate=l

nls%5F2007%5Fenglish&tpl=home

ISI-800

MAX-Lab

Phone: +(380) 44 424-1005 Fax: +(380) 44 424-2561 Email: metall@imp.kiev.ua

Phone: +46-222 9872 Fax: +46-222 4710 http://www.maxlab.lu.se/

Jlab - Jefferson Lab FEL

Medical Synchrotron Radiation Facility

Phone: (757) 269-7767 Fax: (757) 269-7848 http://www.jlab.org/FEL

Phone: +81-(0)43-251-2111 http://www.nirs.go.jp/ENG/index.html

MLS - Metrology Light Source Kharkov Institute of Physics and Technology - Pulse Stretcher/Synchrotron Radiation Phone: +38 (057) 335-35-30 Fax: +38 (057) 335-16-88 http://www.kipt.kharkov.ua/.indexe.html

KSR - Nuclear Science Research Facility - Accelerator Laboratory Fax: +81-774-38-3289 http://wwwal.kuicr.kyoto-u.ac.jp/www/index-e.htmlx

Physikalisch-Technische Bundesanstalt Phone: +49 30 3481 7312 Fax: +49 30 3481 7550 Email: Gerhard.Ulm@ptb.de http://www.ptb.de/mls/

NSLS - National Synchrotron Light Source Phone: +1 (631) 344-7976 Fax: +1 (631) 344-7206 Email: nslsuser@bnl.gov http://www.nsls.bnl.gov/

NSRL - National Synchrotron Radiation Laboratory Phone: +86-551-3601989 Fax: +86-551-5141078 Email: zdh@ustc.edu.cn http://www.nsrl.ustc.edu.cn/en/

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Facilities

NSRRC - National Synchrotron Radiation Research Center

SESAME Synchrotron-light for Experimental Science and Applications in the Middle East

Phone: +886-3-578-0281 Fax: +886-3-578-9816 Email: user@nsrrc.org.tw http://www.nsrrc.org.tw/

E-mail: hhelal@mailer.eun.eg http://www.sesame.org.jo/index.aspx

NSSR - Nagoya University Small Synchrotron Radiation Facility Phone: +81-(0)43-251-2111 http://www.nagoya-u.ac.jp/en/

SLS - Swiss Light Source Phone: +41 56 310 4666 Fax: +41 56 310 3294 Email: slsuo@psi.ch http://sls.web.psi.ch/view.php/about/index.html

SOLEIL San-31 Hyoja-dong Pohang Kyungbuk 790-784, Korea Email: ilguya@postech.ac.kr http://pal.postech.ac.kr/eng/index.html

Phone: +33 1 6935 9652 Fax: +33 1 6935 9456 Email: frederique.fraissard@synchrotron-soleil.fr http://www.synchrotron-soleil.fr/portal/page/portal/Accueil

PF - Photon Factory

SPL - Siam Photon Laboratory

Phone: +81 (0)-29-879-6009 Fax: +81 (0)-29-864-4402 Email: users.office2@post.kek.jp http://pfwww.kek.jp/

Phone: +66-44-21-7040 Fax: +66-44-21-7047, +66-44-21-7040 ext 211 http://www.slri.or.th/new_eng/

PAL - Pohang Accelerator Laboratory

SPring-8 PSLS - Polish Synchrotron Light Source Phone: +48 (12) 663 58 20 Email: mail@synchrotron.pl http://www.if.uj.edu.pl/Synchro/

Phone: +81-(0) 791-58-0961 Fax: +81-(0) 791-58-0965 Email: sp8jasri@spring8.or.jp http://www.spring8.or.jp/en/

RitS Ritsumeikan University SR Center

SRC - Synchrotron Radiation Center

Phone: +81 (0)77 561-2806 Fax: +81 (0)77 561-2859 Email: d11-www-adm@se.ritsumei.ac.jp http://www.ritsumei.ac.jp/se/re/SLLS/newpage13.htm

Phone: +1 (608) 877-2000 Fax: +1 (608) 877-2001 http://www.src.wisc.edu/

SSLS - Singapore Synchrotron Light Source - Helios II SAGA-LS - Saga Light Source Phone: +81-942-83-5017 Fax: +81-942-83-5196 http://www.saga-ls.jp/?page=173

Phone: (65) 6874-6568 Fax: (65) 6773-6734 http://ssls.nus.edu.sg/index.html

SSRC - Siberian Synchrotron Research Centre VEPP3/VEPP4 Phone: +7(3832)39-44-98 Fax: +7(3832)34-21-63 Email: G.N.Kulipanov@inp.nsk.su http://ssrc.inp.nsk.su/english/load.pl?right=general.html

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Facilities

SSRF - Shanghai Synchrotron Radiation Facility http://ssrf.sinap.ac.cn/english/

SSRL - Stanford Synchrotron Radiation Laboratory Phone: +1 650-926-3191 Fax: +1 650-926-3600 Email: knotts@ssrl.slac.stanford.edu http://www-ssrl.slac.stanford.edu/users/user_admin/ura_staff_new.html

SuperSOR - SuperSOR Synchrotron Radiation Facility Phone: +81 (0471) 36-3405 Fax: +81(0471) 34-6041 Email: kakizaki@issp.u-tokyo.ac.jp http://www.issp.u-tokyo.ac.jp/labs/sor/project/MENU.html

TSRF - Tohoku Synchrotron Radiation Facility Laboratory of Nuclear Sciente Phone: +81 (022)-743-3400 Fax: +81 (022)-743-3401 Email: koho@LNS.tohoku.ac.jp http://www.lns.tohoku.ac.jp/index.php

UVSOR - Ultraviolet Synchrotron Orbital Radiation Facility Phone: +81-564-55-7418 (Receptionistâ&#x20AC;&#x2122;s office) Fax: +81-564-54-2254 Email: webmaster@ims.ac.jp http://www.uvsor.ims.ac.jp/defaultE.html

SURF - Synchrotron Ultraviolet Radiation Facility

VU FEL - W.M. Keck Vanderbilt Free-electron Laser Center

Phone: +1 (301) 975-4200 http://physics.nist.gov/MajResFac/SURF/SURF/index.html

Email: b.gabella@vanderbilt.edu http://www.vanderbilt.edu/fel/

TNK - F.V. Lukin Institute Phone: +7(095) 531-1306 / +7(095) 531-1603 Fax: +7(095) 531-4656 Email: admin@niifp.ru http://www.niifp.ru/index_e.html

INFORMATION on Conference Announcements and Advertising for Europe and US, rates and inserts can be found at: www.cnr.it/neutronielucedisincrotrone

P. Casella, A. Minella E-mail: nnls@roma2.infn.it

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