50 Years of Neutron Backscattering Spectroscopy

2 Sept 2016, 09:00 → 3 Sept 2016, 16:45 Europe/Berlin

Lecture Hall & Faculty Club (Institute of Advanced Study (IAS) - Technische Universität München (TUM))

Winfried Petry

50 Years of Neutron Backscattering Spectroscopy

50 years ago, in 1966 Heinz Maier-Leibnitz proposed the idea of neutron backscattering for achieving high energy resolution in neutron spectroscopy. The same year Bert Alefeld published his first experiments from a Silicon neutron backscattering setup at the ‘Atomic Egg’, the FRM reactor in Garching near Munich. These experiments did show for the first time that the energy resolution of neutron spectroscopy could be extended by two orders into the micro eV range.

This great improvement in energy resolution opened the door to previously unseen phenomena as well as the exploration of longer time scale molecular motions in a plethora of systems. Since first results, backscattering spectroscopy with neutrons has contributed to active fundamental research in the fields of life sciences, energy materials, complex systems. It has proved an essential tool to study dynamics in polymers and biological systems, near the glass transition of different types of glass formers, in confinement and near surfaces, of reorientational motions in crystals, of rotational tunnelling and of diffusion in metals and alloys or of spin excitations and nuclear hyperfine splitting.

We invite you to celebrate with us the 50th birthday of Neutron backscattering spectroscopy and all the people that have contributed to its history. The workshop will start with a historical view on the early times and places of neutron backscattering:  the FRM I, Garching,  the Dido reactor in Jülich, the Institute Laue-Langevin in Grenoble (France) and the ISIS Pulsed Neutron and Muon Source in Didcot (UK). We are very pleased to welcome the pioneers of neutron backscattering spectroscopy, Anton Heidemann and Manfred Birr, as honor guests.

Looking ahead the workshops aims to showcase the importance of the neutron backscattering technique for scientific progress and the impact of key instrumentation advances,  including innovative ideas for backscattering at  pulsed neutron sources.

The workshop will take place at the research campus of Garching near Munich on the 2nd and 3rd September 2016.
It is hosted by the Heinz Maier-Leibnitz Zentrum (MLZ) und jointly organized by ILL, ISIS and MLZ.

On Saturday afternoon, after lunch, a guided tour through FRM II is offered. If you're interested in, please do not hesitate to register. Please note, that the number of available places is limited.

The workshop is a satellite meeting of QENS 2016 to be held in Berlin on the 5th-8th September 2016 <http://www.helmholtz-berlin.de/events/qens-2016/index_de.html>. Munich offers excellent train and flight connections to Berlin and thus we hope to see many scientists who are interested in high energy resolution in Garching.

Best wishes,

Winfried Petry (FRM II/MLZ) - Thomas Brückel  (JCNS/MLZ)

Bernhard Frick (ILL) - Victoria Garcia-Sakai (ISIS)

 

                        

Friday 2 September

09:00 → 10:15 Registration and Coffee

10:15 → 10:45 Welcome by MLZ Rep + Research Landscape in Munich 50yrs ago

10:15 Welcome

Speaker: Winfried Petry (FRM II - TUM)

10:30 Backscattering spectroscopy: How it all began

Everything began with an idea of Heinz Maier-Leibnitz in 1966 : why not use perfect crystals as monochromators for neutrons with a Bragg angle of 90°? He claimed that the backscattered beam should be highly monochromatic. One of his students, Berthold Alefeld, showed experimentally that the idea was right. Then two thesis students developed the first ‘Rückstreuspektometer’ at the FRM in Garching. Quasielastic neutron scattering from glycerol and the hyperfine interactions in V2O3 could be studied with µeV resolution. At that time many neutron scatterers were quite skeptical about the usefulness of this kind of research but there were also some believers who pushed the field forward. The most important supporter was Tasso Springer. This workshop being held 50 years later in 2016 will show that a sentence attributed to Maier-Leibnitz is true: *The development of a new method, when ever its precision, sensitivity or resolution is much better than everything that existed in this field before, creates « new physics ».* The research done at the FRM under Maier-Leibnitz half a century ago was aimed at the development of new ideas. Quite a number of them opened new fields in research which later matured through the work carried out at the ILL and other neutron scattering centers around the world. I would like to dedicate this welcome to the late Berthold Alefeld. He was an outstanding experimentalist who produced an incredible number of new ideas in this field. One important example was his proposal of a phase space transformer. Berthold Alefeld is the real father of backscattering spectroscopy.

Speaker: Anton Heidemann (Grenoble)

10:45 → 11:25 Historical Talks on Neutron Backscattering

10:45 The pathway of neutron backscattering: from Garching to Grenoble

With the invention of neutron backscattering in Munich µeV-spectroscopy combined with Ångström-sensitivity became accessible, albeit in a tedious way due to the low count rate. However, the technique found its way to more powerful reactors with cold sources and large guides, and a suite of innovative instrument designs widely exploiting beam focussing and including an active phase space optimisation with a moving mosaic crystal did do way with this shortcoming. Over the years neutron backscattering has enjoyed innovative developments and today the count rate is enhanced by more than 4 orders of magnitude. This allows now to consider novel advancements aiming for an improved energy resolution and a widened energy transfer range.

Speaker: Prof. Andreas Magerl (University Erlangen-Nürnberg)

11:05 First ToF Backscattering at Spallation Sources

The neutron backscattering technique first entered into my consciousness when I was attending a conference on hydrogen in metals in 1972 in Jülich. One of the names in hydrogen in metals at the time was Georg Alefeld and his brother Bert Alefeld was also attending the conference. I asked him about his backscattering spectrometer and we headed off in his VW Beetle to the Dido Reactor on the Jülich site and I saw for the first time the large silicon analyser he had set up on his spectrometer where he had measured hyperfine splitting in vanadium oxide. At that time I was completing my PhD on a 5 MW reactor at Aldermaston where I had built a rotating crystal spectrometer. Its resolution was of the order of 100 microelectronvolts and itself represented an improvement in resolution over what was available on ToF machines. I was impressed to find that there was a machine with a resolution 100 times better. A few years later having worked on the rotating crystal spectrometer at Ispra as an EU post doc I returned to the UK where plans to build what was later renamed as the ISIS spallation source were being put together. Discussions on the instrument suite for ISIS had not yet started and I was posted to the ILL in Grenoble as the UK link person. It was there that I received a telex one day from George Stirling asking me to provide an outline design for a high resolution spectrometer to be built on ISIS. I discussed this request with Julia Higgins and Reinhard Scherm who were in those days in the ILL’s ToF group, and Reinhardt simply said why not put IN10 on the end of a long neutron guide. I had been thinking of a direct geometry time of flight machine but this idea was appealing and I began working on a design which ultimately resulted in the construction of the IRIS backscattering spectrometer at ISIS. At that time the political wisdom was that spallation sources were for thermal and epithermal neutrons whereas reactors were for cold neutrons. The intensity of cold neutrons on ISIS could not compete. But was I supposed to spend 10 years of my life building an instrument that would be a pale imitation of IN5 and IN10. Accordingly I did everything that I could to enhance the delivery of cold neutrons to my instrument. That meant asking for a bulky liquid hydrogen moderator coupled to the reflector and a large area neutron guide. It was, along with HRPD, the first neutron guide to be installed on a spallation source. It caused the ISIS target station engineers sleepless nights. They were worried about the fast neutrons streaming out of this hole in the target station. It proved not to be the case and the neutron beam at the IRIS sample position could be stopped with half a millimeter of cadmium. However in order to arrive at an instrument that was competitive with the Instruments that were available at ILL a large number of challenges presented themselves, the gamma sensitivity of the detector, the thermal diffuse scattering coming from the graphite analyser and a number of other things. On reflection if these problems had been identified in advance it might well have been that the instrument would never even have been started. Fortunately this was not the situation and I will tell that story from a personal viewpoint at this 50th anniversary meeting.

Speaker: Dr Colin Carlile (Uppsala University)

11:25 → 12:40 Innovations in Backscattering

11:25 Neutron backscattering at NIST

The NIST High Flux Backscattering Spectrometer (HFBS) was the first backscattering instrument constructed in the U.S. With over 250 publications to its credit, it has been one of the NCNR’s flagship instruments. In this presentation we will describe a brief history of HFBS from inception to the first user experiment. In addition, we will describe one of the instrument’s most innovative features – the first implementation of a phase space transform chopper, originally proposed by Schelten & Alefeld.

Speaker: Dr Robert M. Dimeo (Director, NIST Center for Neutron Research)

11:40 The Design and Construction of the Spallation Neutron Source near-backscattering spectrometer BaSiS

The first instrument officially adopted as part of the Oak Ridge National Laboratory Spallation Neutron Source (SNS) was the beam line 2, near-backscattering spectrometer that eventually was named BaSiS (Backscattering Silicon Spectrometer). BaSiS was the first silicon-based backscattering spectrometer to be installed at a short-pulse spallation neutron source. The original charge from the user community was to develop a spectrometer “with a Q-range of <0.1 inv. Å to ~4 inv. Å at an energy resolution of ~5 microeV.” Early in the conceptual design phase it was apparent that these requirements could be met or bettered with a near-backscattering spectrometer using Si(111) as the high-resolution and Si(311) as the high-Q analyzer respectively. The main distinguishing feature of BaSiS is its large dynamic range that was a consequence of using time-of-flight explicitly to determine the incident neutron wavelength. For a reasonable instrument length, BaSiS required a narrow cold-neutron emission time distribution from the moderator to match the energy resolution of the analyzer crystals. This requirement strongly influenced the characteristics of the SNS poisoned, decoupled cold para-hydrogen moderator that ultimately proved in high demand by many of the SNS suite of diffractometers. This talk will review the main elements of the BaSiS design, noting how they differed from more conventional high-resolution backscattering spectrometers and how they determined the final operating characteristics of the instrument.

Speaker: Dr Kenneth Herwig (Oak Ridge National Laboratory)

11:55 SPHERES: the SPectrometer for High Energy RESolution at FRM II

SPHERES is a third-generation backscattering spectrometer with phase-transform chopper, located at a cold-neutron guide of FRM II, and in routine operation since 2007. For technical details, see [1,2,3]. In this talk, for a unique assembly of experts, I will not so much celebrate what we have achieved, but rather discuss the subtle difficulties that limit the accuracy of this fine experimental method. I will also highlight recent progress in modelling beam deflection by thick mosaic crystals [4]. [1] Wuttke et al, SPHERES, Jülich's high-flux neutron backscattering spectrometer at FRM II. Rev. Sci. Instrum. 83, 075109 (2012). [2] Wuttke & Zamponi, Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES. Rev. Sci. Instrum. 84, 115108 (2013). [3] Khaneft et al, Upgrading the Neutron Backscattering Spectrometer SPHERES. II. Faster Phase-Transform Chopper with Wider Deflector Mosaic. In preparation. [4] Wuttke: Multiple Bragg reflection by a thick mosaic crystal. Acta Cryst. A 70, 429-440 (2014).

Speaker: Joachim Wuttke (JCNS at MLZ)

12:10 A performance boost for reactor backscattering - IN16B at ILL

The new flexible high flux sub-µeV backscattering spectrometer IN16B at ILL is in full user operation with its Si111 configuration, offering more than a factor of 10 higher flux, a better signal-to-noise ratio, a wider dynamic range and an improved energy resolution than its predecessor IN16. Furthermore a Si311 configuration is commissioned and a GaAs200 and a time-of-flight option (BATS) are planned for commissioning end 2016. In this talk we present the main instrumental features which characterise this largely improved spectrometer: quasi ballistic focusing guide, background chopper, PST, Doppler drive and increased analyser solid angle in the vacuum housing of the secondary spectrometer. We report on the performance of the above mentioned instrument configurations as measured on standard samples.

Speaker: Mr Bernhard Frick (Institut Laue-Langevin)

12:25 A time-of-flight type near backscattering spectrometer DNA in J-PARC

A time-of-flight (TOF) type near-backscattering spectrometer (n-BSS), DNA was built and started operation in 2012 at the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). DNA is a unique instrument among spallation pulsed neutron facilities over the world in terms of n-BSS equipped with a high-speed pulse-shaping disc-chopper. Neutron beam from the coupled moderator which provides most intense but broadest pulse among all three moderators in MLF is handled flexibly in pulse width by this chopper with keeping intensity and making symmetrical pulse in a TOF spectrum. Si crystal analyzers with back-coated by neutron absorber extremely reduces unfavorable background scattering of the instrument so as to reach signal-to-noise ratio of ~100,000. Those factors gave big advantage to enlarge application fields to dynamical behaviors of atoms and spins in bio-molecules, soft-materials and strongly-correlated electron system in nanosecond timescale or in micro-eV energy region.

Speaker: Dr Kaoru SHIBATA (Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency (JAEA))

12:40 → 14:00 Lunch

14:00 → 16:20 Major Science Fields tackled with Backscattering: I

14:00 Almost 50 years of rotational tunneling

4 years after observations of almost free rotation in solid methane II (Kapulla and W. Gläser, 1970) B. Alefeld and A. Kollmar performed the first backscattering experiment. Together with that on methane tunneling it set the start to many more neutron experiments dedicated to quantum rotations. Neutron spectra with well-defined lines, both benefitted from theoretical work and stimulated it; the principal centers were Erlangen (A. Hüller) and Kyoto (T. Yamamoto). A large diversity of systems can be found in the Tunneling Atlas (M. Prager, A. Heidemann). In parallel the basics of “coherent” and “incoherent” tunneling (P. Trommsdorff) remained in the focus. A review (W.P.,1981) summarizes the initial activities. Important generalizations comprise rotation-translation coupling (P. Schiebel,~1995), partial deuteration (K. Maki et al, 1981) and intermolecular coupling (M. Neumann et al., 2000). Scientists from other experimental techniques - nmr (S. Clough and A. Horsewill), optics (P. Trommsdorff) and specific heat (Jim Morrison) - also became experts in high resolution neutron scattering, particularly backscattering and time-of-flight experiments. Today tunneling experiments are rather infrequent guests at modern instruments. The field could greatly benefit from the extended dynamical ranges, higher intensity and also some-what improved resolution.

Speaker: Werner Press (IEAP University Kiel, Germany)

14:20 On the confinement of liquids in mesoporous hosts

Confinement presents an unprecedented opportunity to produce and study new materials properties on the nanometer scale. Over the past decades, fundamental questions arising from systems confined in nanochannels have been addressed by impregnation of molecular fluids within nano/mesoporous structures. For pore sizes smaller than few tens of nanometers, strong interfacial and finite size effects dominate the static and dynamical properties of the confined phase, revealing physicochemical properties that have usually no equivalent in the corresponding bulk system. Neutron methods possess unique space and time-scale resolutions to address the structure and the molecular dynamics of such systems. Based on illustrations extracted from pioneering works and from the more recent literature as well, we will present a review of the current advances in the field, as well as some openings for future studies.

Speaker: Dr Denis Morineau (CNRS - Institute of Physics of Rennes)

14:40 Polymer Dynamics: Highlights from Neutron Backscattering Spectroscopy

A polymer is a condensed matter system where the structural units are macromolecules –big molecules built up by repetition of a more or less simple chemical motif (monomer) mainly based on carbon and hydrogen atoms. Polymers display rich and complex dynamics, including different atomic and molecular processes, which spread over very different time and length scales. On the one hand, polymers are considered canonical glass-formers, thereby showing the typical dynamic processes of this broad class of systems (anomalous vibrations, local relaxations, secondary $\beta$-process and the so-called $\alpha$-relaxation). On the other hand, polymers also show unique large-scale dynamic processes that are related to their macromolecular nature. Neutron backscattering spectroscopy has contributed to unveil many important aspects of these dynamical processes. Some of them will be highlighted in this talk: (i) resolving the ‘mystery’ of methyl group tunneling in polymers and glasses; (ii) molecular interpretation of the $\gamma$-relaxation in engineering thermoplastics; (iii) correlation between non-Debye behavior and Q-behavior of the $\alpha$-relaxation in glass-forming polymers; (iv) deducing the ‘Rouse rate’ from low-Q incoherent scattering in polymers and nanocomposites. New applications in the field of complex materials based on polymers are also envisaged.

Speaker: Prof. Juan Colmenero (Centro de Fisica de Materiales CSIC-UPV/EHU)

15:00 Using Backscattering Spectrometers to Study Dynamics of Soft Matter and Complex Systems

Molecular motion in soft matter, including polymers, reaches a high degree of complexity, far beyond that observed in small molecules. Chain connectivity plays a major role and, as a result, dynamic processes extend over an exceedingly wide time and length scale. Therefore, a complete, accurate picture of molecular motion in these systems can only be achieved by combining experimental techniques which sample complementary frequency (or time) ranges. In this respect, quasi-elastic neutron scattering (QENS) has proven to be a unique tool, capable of providing simultaneous frequency and spatial information on molecular motions that are relevant for understanding mechanical and rheological properties of bulk polymers. In this talk, selected experimental data collected in the past twenty five years on a range of backscattering spectrometers such as IRIS (ISIS, UK), IN10 and IN16 (ILL, France) will be discussed. Starting from early measurements on sub-Tg relaxations in polymer-polymer mixtures, the aim is to demonstrate how a combination of backscattering spectrometers can be exploited to separate dynamic processes but also to understand the effect of topology on polymer motion and the interplay between components in complex systems such as polymer blends and nanocomposites.

Speaker: Dr Valeria Arrighi (Heriot-Watt University)

15:20 QENS for Material Science

Last minute change as replacement for Sandrine Lyonnard.

Speaker: Dr Didier Blanchard (Technical University of Denmark (DTU))

15:40 Intrinsic Proton Dynamics in Hydrous Silicate Melts as seen by QENS at elevated Temperature and Pressure

We present quasielastic neutron scattering results on hydrous silica, sodium aluminosilicate, and sodium trisilicate melts with 10mol% total water content, studied at high temperature under high pressure. Combining neutron timeof- flight spectrometry with neutron backscattering, intrinsic, microscopic proton dynamics is investigated on a timescale from 0.2 ps up to 1 ns between 850K and 1250K. All three hydrous silicate melts exhibit a relatively slow proton dynamics, although the melt viscosity is drastically reduced upon water dissolution. The self-diffusion coefficient of proton in the hydrous sodium trisilicate melt is on the order of 10−11 m2s−1, two orders of magnitude slower than the sodium dynamics in the corresponding dry melt. The proton dynamics in hydrous silica and albite is not faster than that time scale. We show that the transport mechanism involving not only -OH but also molecular water species. All protons are mobile during the transport of the water instead of diffusion of a specific water speciation. These characteristics of the proton structural relaxation in the melt can be attributed to a transport in a complex H-bonding environment involving water and the Si-O matrix.

Speaker: Prof. Andreas Meyer (Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, Köln)

16:00 → 16:20 Coffee at Posters

16:20 → 17:50 Science overview from Backscattering Workhorses

16:20 Science from IRIS and OSIRIS

IRIS and OSIRIS are the cold neutron spectroscopy work horses at the ISIS Facility. Both spectrometers are applying a near backscattering geometry and hence do not achieve the very high energy resolution of classical backscattering spectrometers. However, they offer a unique combination of high resolution and wide dynamic range, which opened avenues into new applications. These instruments currently support a productive scientific community using quasielastic and low-energy inelastic neutron scattering techniques. The range of science covers for example areas from low energy spectroscopy in correlated electron systems to studies on the dynamics in energy relevant materials and dynamics of biological macromolecules.

Speaker: Dr Franz Demmel (ISIS facility)

16:35 Science from IN13

The idea to use neutron diffusion in backscattering mode is motivated by the very high instrumental resolution in this special configuration. On the thermal neutron backscattering spectrometer IN13 at the Institut Laue Langevin (ILL), one of the oldest spectrometers operated by a French–Italian Collaborative Research Group (CRG), the energy variation is obtained by adjusting the d-spacing of a monochromator crystal by cooling or heating it. The energy resolution is of the order of 8 ueV. In addition, the relatively high energy of the incident neutrons (16 meV) allows to span a wide range of momentum transfer Q ≤ 4.9 Å-1. The spectrometer IN13 allows the investigation of a space-time window up to 30 Å and 0.1 ns, providing information on single particle motions observed by incoherent neutron scattering. The instrument is mainly devoted to life science, but scientific applications can also be found in areas of material science, solid state physics and chemistry.

Speaker: Prof. Judith Peters (Université Grenoble Alpes)

16:50 Science from the High Flux Backscattering Spectrometer

The high flux backscattering spectrometer (HFBS) at NIST has been operational since the late 1990s. Over the last decade and a half, a number of current scientific topics have seen significant advancement using the HFBS. In this talk I am going to focus mainly on three topics - I will start with polymer dynamics which will include segmental dynamics of homopolymers and influence on it by a variety of media e.g. other homopolymer and nanoparticle surfaces. In low molecular weight materials, water outweighs any other small molecule and has been a topic of choice for several decades and as a result, a considerable progress has been made on the water dynamics in various media e.g. under geometrical confinement and in the form of hydration water in biomolecules. I will also discuss briefly dynamics of various biomolecules e.g. RNA and specifically proteins. Lastly, I will touch upon hydrogen dynamics in metal complexes e.g. in borohydrides.

Speaker: Madhu Sudan Tyagi (NIST Center for Neutron Research and Department of Materials Science and Engineering)

17:05 From classical applications to new materials – science done at SPHERES

The neutron backscattering spectrometer SPHERES (SPectrometer for High Energy RESolution) at MLZ is in user operation since 2007. It enables investigations on a broad range of scientific topics. An overview will be given of science done at SPHERES- from the ‘classical’ applications of backscattering like hyperfine splitting to investigations on new materials like high temperature polymer electrolyte fuel cells.

Speaker: Dr Michaela Zamponi (JCNS at MLZ, Forschungszentrum Juelich GmbH)

17:20 Science from IN16B

The very substantially increased neutron flux of IN16B [1,2] compared to its predecessor IN16 permits to carry out new types of experiments that have not been possible before as well as to significantly increase the accuracy of the results in all experiments. This presentation shall provide a few selected examples of experiments performed recently on IN16B addressing various topics [3-7], including yet unpublished results. A particular emphasis will be on fundamental aspects of soft matter and biomolecular dynamics addressing for instance the diffusion of drug molecules in supramolecular gels, the influence of peptide molecules on membrane fluctuations in thin-film as well as vesicle membrane samples, and the diffusion of model proteins in solution. [1] B.Frick et al., Z.Phys.Chem. 224,33 (2010); [2] M.Hennig, B.Frick, T.Seydel, J.Appl.Cryst. 44,467 (2011); [3] A.Hill et al., J.Chem.Phys. 140, 044709 (2014); [4] M.Grimaldo et al., J.Phys.Chem.B 118, 7203 (2014); [5] P.Ondrejkovic et al., Phys.Rev.Lett. 113, 167601 (2014); [6] M.Appel et al., J.Chem.Phys. 142, 114503 (2015); [7] S.Mitra et al, J.Phys.Chem. B 120, 3777 (2016).

Speaker: Dr Tilo Seydel (Institut Max von Laue - Paul Langevin)

17:35 Science from BASIS

Besides the high count rate, the strongest advantage of BASIS is a combination of the high energy resolution and broad range of energy transfers. The former is sufficient for resolving the slower translational dynamics. The latter allows probing the faster localized dynamics. Simultaneous measurement of multiple components provides a powerful tool for studying the spatial characteristics of “soft” confinement, when the transient cage made by particle neighbors relaxes on the resolution scale of the experiment. While the science supported by BASIS is diverse, the unifying theme of many seemingly disparate projects is the power of QENS to elucidate the spatial characteristics of the microscopic diffusion and relaxation processes through the Q-dependence of scattering signal. The near-backscattering arrangement of the detectors at BASIS helps eliminate systematic bias in the energy resolution at low scattering angles, which is characteristic of exact backscattering geometry, thereby yielding unbiased Q-dependence of the data at low momentum transfers. The relatively high, for a backscattering spectrometer, Q-resolution of BASIS, is also instrumental for extracting the spatial information on the microscopic dynamics. The instrument upgrade includes a full set of Si(311) analyzer crystals, which much extends the accessible Q- and energy transfer range.

Speaker: Dr Eugene Mamontov (Oak Ridge National Laboratory)

17:50 → 19:15 Poster Session

17:50 An Instrument-Concept for Dynamics of Complex (Bio-) System from Elastic Scattering

We have devised an instrument to measure purely elastic-scattering over a wide range of energy-resolutions as efficiently as possible. Its clientele would be those who wish to study the dynamics of complex biological systems where the inelastic and quasi-elastic signals are too intractable. Nevertheless, the overall timescales of dynamical transitions can be obtained from inflection(s) in the plot of elastic-intensity against energy-resolution. This is the energy-analogue of the well-known temperature-scan (or fixed-window scan) in which the dynamics of the system is driven through the fixed elastic-resolution of an instrument by ramping the sample-temperature. We will discuss how a backscattering approach can be used, but in which the energy-width of the incident beam can be tailored to scan the resolution over a wide range. In addition to simplicity and improved efficiency, there is the potential to focus on small samples (~1mm3), which is a considerable advantage for biological materials usually available in limited quantities. This instrumental-concept can be used on continuous or pulsed neutron sources. Numerical simulations of the basic design have been successfully done by McStas, so that technical details and performance are presented in details.

Speaker: Dr Antonio Benedetto (Paul Scherrer Institut)

17:50 Dynamics of pharmacologically active compounds - felodipine and lacidipine: QENS and NMR study combined with molecular dynamics and density functional theory simulations

Molecular dynamics of felodipine and lacidipine (derivatives of 1,4-dihydropyridines, calcium channel blockers) were explored by solid-state nuclear magnetic resonance (NMR) and quasi-elastic (QENS) neutron scattering experiments. The experimental results were further combined with DFT and molecular dynamics (MD) simulations, providing a quantitative description of the intramolecular motions. Both NMR spin-lattice relaxation and QENS measurements - performed on spectrometers with different resolution (backscattering - IN16, time-of-flight - IN5 and IN6) revealed the existence of dynamically inequivalent methyl groups. The activation parameters for their reorientation were determined. The temperature dependence of the correlation times c established both from NMR and QENS experiments are in very good agreement. Our analysis, supported by the MD and DFT calculations, relates the different dynamics observed for each methyl group with the calculated potential barriers in the crystal structure [1]. 1. A. Pajzderska, K. Drużbicki, A. Kiwilsza, M. A. Gonzalez, J. Jenczyk, J. Mielcarek, J. Wąsicki On the Molecular Dynamics in Long-Acting Calcium Channel Blocker Lacidipine: Solid-State NMR, Neutron Scattering and Periodic DFT Study, 2016 RSC Advances, in press

Speaker: Dr Aleksandra Pajzderska (A.Mickiewicz University, Faculty of Physics, Poznan, Poland)

17:50 Influence of straight medium chain alcohols on the dynamics of phospholipid model membranes

An important part of biological plasma cell membranes is the lipid bilayer, functioning as a two-dimensional matrix, separating different cell spaces and serving as an anchorage for e.g. proteins. Incorporation of foreign amphiphilic molecules such as a series of 1-alcohols into the cell membrane changes membrane properties such as bilayer thickness, lipid packing and lateral pressure profile. We have used QENS in the 300 ps time range by time of flight spectroscopy at TOFTOF and in the 1ns time range by backscattering spectroscopy at SPHERES in order to investigate the effects of alcohols on the local dynamics of multilamellar (MLV) and unilamellar vesicles (ULV) in excess of water. In the 300ps time range the dynamics is slower for undoped multilamellar than for undoped unilamellar vesicles, i.e. interlamellar forces seem to play a role for the membrane lipid diffusion.The dynamics of multilamellar vesicles is getting faster when adding hexanol. In the 1 ns regime MLV show similar effects but not as conclusive as at a time scale of 300ps. The results of these experiments will be presented and discussed.

Speaker: Thomas Gutberlet (Forschungszentrum Jülich)

17:50 Intracellular Water – an Overlooked Target of Drug Activity? Cisplatin´s Impact in Breast Cancer Cells Probed by Neutron Techniques

The first neutron scattering study of intact human cells is reported, addressing the subject of solvent-slaving to a drug by directly probing intracellular water to ascertain structural and dynamical variations upon drug exposure. This study is based on the assumption that the behaviour of cytoplasmic water determines both the conformation and function of biomolecules. Inelastic and quasi-elastic neutron scattering spectroscopy experiments with isotope labelling were performed, for monitoring interfacial water response to the widely used anticancer drug cisplatin in human metastatic breast cancer cells. This is an innovative way of tackling a drug´s pharmacodynamics, searching for alternative targets in order to improve chemotherapeutic efficiency. Intracellular water was found to behave differently in drug-free and cisplatin-exposed cells: concentration-dependent structural changes coupled to a progressive mobility reduction were unveiled, concurrent with variations in the native organisation of water molecules within the intracellular medium as a consequence of drug action. These results constitute the first reported experimental proof of a drug´s impact on the cytomatrix by neutron techniques, and lead to a better understanding of the in vivo mode of action of antitumour agents, at a molecular level, allowing a rational design of improved drugs.

Speaker: Prof. MPM Marques (Unidade I&D “Química-Física Molecular”, Univ. Coimbra, Portugal)

17:50 Investigation of Molecular Dynamics: Exceed the Gaussian Approximation

We investigate the dynamics of bio-molecules with the help of incoherent neutron scattering. For elastic data sets the mean square displacement (MSD) as a function of temperature is extracted which may depend strongly on the instrument resolution, Q-range and analysis method employed. This makes it difficult to compare quantitatively data sets from different bio-molecules and experimental data with MD simulations. Our goal is to find out how quantitatively MD simulations can reproduce the trends of experimental data over a range of different systems and instruments and under many different conditions like temperature, pressure, hydration, pH/pD or crowding. In addition, it is important to figure out to what extent such trends may depend on sample preparation, data reduction and data analysis. Generally, from elastic data the MSD is extracted based on the Gaussian approximation with Q values normally not exceeding 2Å-1. Here, we present data on a larger momentum transfer range - up to Q=5Å-1 as measured on the neutron backscattering spectrometer IN13 at the Institute Laue Langevin (ILL) - and investigate the accuracy of different models which have been proposed lately. This could point to the extraction of more information from elastic data sets.

Speaker: Mr Dominik Zeller (Université Grenoble Alpes, Laboratoire Interdisciplinaire de Physique (LiPhy), 38044 Grenoble, France)

17:50 Molecular dynamics of conjugated polymers and its influence on organic solar cell performance

Conjugated polymers are the main components of a new generation of organic optoelectronic devices, of which organic solar cells are the most promising ones. A summary of quasielastic neutron scattering experiments carried out on P3HT, P3OT and the low band-gap PCPDTBT conjugated polymers during the past few years on different backscattering spectrometers, both on ILL (IN10, IN16 and IN16B) as well as on ISIS (IRIS, OSIRIS in time-of-flight mode) will be presented. Both quasielastic and elastic scattering experiments have been performed, and a discussion on fitting models and their ability to explain the molecular dynamics (and structure) of the polymers will be discussed. The new capabilities offered by IN16B, such as inelastic fixed window scans will also be presented. The polymers, acting as electron donors upon light excitation and mixed with electron acceptors such as fullerene derivatives, create a “bulk heterojunction” which is the core of fully operational organic solar cells. The performance of the cells is related to the polymer dynamics at different temperatures, and only the combination of neutron scattering and I-V electronic measurements will provide sufficient information to improve future mixtures and fabrication procedures for more efficient and stable solar cells.

Speaker: Dr Antonio Urbina (Technical University of Cartagena, UPCT)

17:50 Overview of the low temperature cation local dynamics in (CH3NH3)PbI3 perovskite

(CH3NH3)PbI3 hybrid perovskite has recently emerged again on the front of the scene because of its very good emissive properties which permit it to be used in new generation of high performance solar cells exhibiting efficiencies up to 22%. Electronic properties of this material are highly influenced by the local dynamics of cations. We will show how EFWS and IFWS scans recorded on IN16B can give unique and instructive overview of these dynamics in the 50-180 K temperature range. Moreover we will compare the results obtained on the fully hydrogenated compound and those obtained on the partially deuterated one (CD3NH3)PbI3. In particular these measurements confirm rotational local motions of both CH3 and NH3 rotors in the orthorhombic phase exhibiting one energy of activation of 42-46 meV and relaxation times in the 1000 to 30 ps range. Importantly enough, beyond the transition temperature of 160K, while rotor dynamics are no more within the spectrometer resolution, the measurements on IN16B suggest emergence of a new slower dynamics which can be consistently related to measurements performed ta higher temperatures on TOF IN5 spectrometer with a 100µeV energy resolution

Speaker: Dr DAVID DJURADO (CNRS - CEA Grenoble)

17:50 Perspectives for very high pressure experiments on backscattering instruments: IN16b

Neutron scattering measurements under pressures beyond ca. 2 GPa (20 kbar) allow sample volumes of not more that 100 mm^3. This limits severely their applications on high-resolution instruments, in particular backscattering spectrometers. Here we present some feasibility measurements on liquid glycerol under pressure to ca. 2 GPa, carried out at IN16b at the ILL, at ambient temperature. The pressure technique uses highly transparent ceramic anvils with ‘panoramic’ view on the sample and forces generated by a Paris-Edinburgh-type load frame. The data suggest that under certain conditions, and after some investment, high-pressure measurements in the multi-GPa range may become quite routine in the near future.

Speaker: Dr Stefan Klotz (IMPMC, Université P&M Curie)

17:50 Photoactivation Reduces Side-Chain Dynamics of a LOV Photoreceptor

We used neutron scattering experiments to probe the conformational dynamics of the light, oxygen, voltage (LOV) photoreceptor PpSB1-LOV from Pseudomonas putida in both the dark- and light-state. Global protein diffusion and internal macromolecular dynamics were measured using incoherent neutron time-of-flight and backscattering spectroscopy on the picosecond to nanosecond time scales. Mean square displacements of localized internal motions and effective force constants describing the resilience of the proteins were determined on the respective time scales. Photoactivation significantly modifies the flexibility and the resilience of PpSB1-LOV. On the fast picosecond time range small changes in the MSD and effective force constants are observed, which are enhanced on the slower nanosecond time scale. Photoactivation results in a slightly larger resilience of the photoreceptor on the fast picosecond time scale, whereas on the nanosecond range a significant less resilient structure of the light-state protein is observed. For a residue resolved interpretation of the experimental neutron scattering data we analyzed MD simulations of the PpSB1-LOV X-ray structure. Stadler et al. Photoactivation Reduces Side-Chain Dynamics of a LOV Photoreceptor. Biophysical Journal, 2016, 1064-1074

Speaker: Dr Andreas Stadler (FZ Jülich)

17:50 Protein diffusion in crowded solutions

New backscattering spectrometers give an unprecedented access to the hierarchical dynamics of proteins in solution [1-3]. The new tools can for instance be used to explore the biologically important impact of macromolecular crowding on the global and internal dynamics of proteins in an aqueous environment. Moreover, the effect of salt-induced charges on the protein diffusion becomes accessible [4]. The global translational center-of-mass motion on the nanosecond time scale and its dependence on the protein volume fraction can be interpreted in terms of the short-time diffusion of colloidal hard spheres [1]. Recent experiments additionally indicate a qualitative agreement of the internal protein motions, consisting of backbone and side-chain motions, with intuitive expectations in a wide temperature range from the native to the denatured state [1-2]. Recent systematic measurements as a function of the salt-induced charges show a universal scaling behavior of the protein diffusion depending on the salt concentration and crowding [4]. [1] M.Grimaldo et al., JPCB 118, 7203 (2014); [2] M.Grimaldo et al., PCCP 17, 4645 (2015); [3] M.Grimaldo et al., EPJ Web of Conf. 83, 02005 (2015); [4] M.Grimaldo et al., JPCL 6, 2577 (2015).

Speaker: Dr Tilo Seydel (Institut Max von Laue - Paul Langevin)

17:50 Pushing the resolution limit of neutron backscattering: A GaAs option for IN16B at ILL

Since its beginning, the developments in neutron backscattering instrumentation have been primarily focussed on increasing the intensity, while little progress has been made in enhancing the energy resolution. This is restricting investigations like on hyperfine splitting, rotational tunnelling or diffusive processes in solids, e.g. with relevance for battery materials. During an ongoing ’GaAs extension’ project, we are developing a prototype spectrometer with a crystal surface corresponding to 1/10 of a full scale instrument, aiming at an energy resolution δE < 50 neV FWHM and an energy transfer range ∆E = ±5 µeV. Measurements in a dispersion-free two-crystal setup on IN10 of commercial GaAs wafers yield convolved line widths of 17–28 neV FWHM, confirming the possibility to significantly improve the energy resolution. Yet, in order to retain this high resolution in a full scale instrument, all other limiting parameters need to be controlled to a similar level. This includes variations of the lattice parameter $∆a/a < 10^{-6}$, the angular misalignment ∆θ < 0.1°, and the temperature variation ∆T < 0.1 K. In addition, a temperature gradient of 3.3 K/m along the 3m high analysers is required to compensate the gravitational energy shift of 103 neV/m.

Speaker: Mr Kristijan Kuhlmann (Friedrich-Alexander University Erlangen-Nürnberg / Institut Laue-Langevin)

17:50 Quasi-Elastic Neutron Scattering Studies on Solid Electrolytes for solid-state Lithium Batteries

The development of better batteries is paramount for the spread of renewable electricity production and utilisation. Limited improvement are expected for lithium-ion battery, because of the use of organic liquid electrolytes. An alternative is to use solid electrolyte instead. The high temperature (> 383 K) phase of lithium-borohydride, is a fast Li+ conductor. The fast conduction is kept at room temperature by stabilizing the phase via solid solution with Li-halides or confinement of LiBH4 in nanoporous scaffolds. We have studied, in LiBH4:LiI, the Li+ diffusion using QENS and DFT. Lithium defects are easily formed at room temperature and low energy barriers were found between stable defect sites, favoring high defect mobility (Fig.1-a). QENS was also used to probe the dynamic of the BH4− anions in LiBH4 confined in nanoporous SiO2. Four quasi-elastic components were found in two different temperature domains. (Fig.1-b). The narrow components, at high temperature, are associated with reorienting BH4− in crystalline LiBH4, while the broader components at low temperature, with much more rapidly reorienting BH4−, can be associated with the LiBH4 located at the SiO2 surfaces, suggesting that the high conductivity occurs at the interface between LiBH4 and SiO2.

Speaker: Dr Didier Blanchard (DTU)

17:50 Saccharide-Based Systems for Food Science and Biomedical Applications

Over past years, using elastic and quasielastic neutron scattering, we studied saccharides and saccharide-lipid complexes of interest for biomedical and food science applications. In food science, we focused on glucose and two of its polymeric forms, amylose and amylopectin: the two main components of starch. In the temperature range 20K - 350K, they show a dynamic transition similar to that of hydrated proteins. The fact that we observe this feature also in a relatively small molecule like glucose supports the hypothesis that this transition is driven by the interaction of the macromolecule with the fluctuating H-bond network of the solvent. In pharmacology, nano- and microparticles made up from sugar-lipid complexes find applications as highly biocompatible drug carriers. A detailed understanding of particle–solvent interactions is of key importance in order to tailor their characteristics for delivering drugs with specific chemical properties. We investigated lecithin/chitosan nanoparticles prepared by autoassembling the components in an aqueous solution. The scattering can be described by a simple confined-diffusion model. In the lyophilized state only hydrogens in the polar heads are mobile within the experimental time-window. In hydrated samples, the diffusive dynamics involves also a significant part of the lipid tails.

Speaker: Prof. Maria Di Bari (Department. of Physics and Earth Sciences, University of Parma, Parco Area delle Scienze, 7/A, 43124 Parma, Italy)

17:50 Tunneling of the methyl protons of mesitylene trapped in a tris-(bromo-phenoxy)-triazine "

We have studied the transitions between the ‘rotational levels’ of methyl groups of molecules isolated in cages or channels. First was studied the 1.3.5-trimethylbenzene C9H12 (mesitylene: Mes) trapped in channels of 2.4.6-tris-(bromo-phenoxy-)-1.3.5-triazine C21H12Br3N3O3 (BrPOT). The isolated guest molecules have a symmetry three, their methyl groups are equivalent, they have a tunnelling gap of 0.01 meV in the crystal. From literature the BrPOT containing Mes molecules is trigonal. INS experiments were conducted on TOFTOF and on IN5. Measurements were programmed from 1.6 K unto 50 K, with neutrons of 8.5 and 3 Å. Three pairs of tunnelling lines were recorded at 0.40, 0.20 and 0.07 meV and others above 1.4 meV. A new determination of the structure of the compound was done at 100 K: it is monoclinic with beta=118.9°, the Mes molecules are aligned in channels and inclined at 28° of the axis b. The methyl groups are now low hindered and submitted to three different hindering potentials of six-fold symmetry corresponding to slightly different environments. Results on other guests with quasi free methyl rotors will be presented.

Speaker: Prof. Jean Meinnel (University of Rennes)

17:50 Understanding the mechanism of proton conductivity in Metal- Organic Frameworks by QENS

Polymer electrolyte membrane fuel cells (PEMFCs) represent an appealing option as alternative clean energy systems. Currently, commercially used proton conductors are based upon acidic polymers such as Nafion with conductivity of 10−2 S/cm in presence of water and at temperatures below 80 oC. Rational design of new electrolyte materials to tackle current technical limitations is critical to increase the efficacy of PEMFCs. Recently, metal-organic frameworks (MOFs) have been considered as alternative candidates for proton conducting applications as a result of their crystallinity (allowing insight into the proton-conduction mechanism), modular nature, tunable pores and thermal stability. A new phosphonate-based MOF, denoted MFM-500(Ni) was synthesised and displays proton conductivity of 4.5×10−4 S/cm at 98 % relative humidity and 25 °C.1 The intrinsic proton diffusion mechanism in MFM-500(Ni) was elucidated via a combination of X-ray diffraction and quasi-elastic neutron scattering (QENS) studies giving a remarkable contribution to knowledge in this area. It was demonstrated that proton conduction in MFM-500(Ni) is mediated by a “free diffusion inside a sphere” model, representing the first example of such a mechanism observed in a MOF.

Speaker: Dr Simona Pili (The University of Manchester)

17:50 Use of back scattering other than in a pi - spectrometer

Please access the abstract via the attached file.

Speaker: Dr Colin Carlile (Uppsala university, Sweden)

17:50 Water dynamics in glass ionomer cements

Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this analysis, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with backscattering data from IN10 at ILL we were able to relate the water structure in the liquids to the materials properties. The analysis shows that the distinct dynamics of the liquids used in preparation of the GIC influence and to a certain extend control hydrogen binding to the GIC structure.

Speaker: Ms Marcella Berg (University of Copenhagen)

19:15 → 20:00 Refresh

20:00 → 22:00 Dinner and BSS Cake

Saturday 3 September

09:15 → 09:55 Major Science Fields tackled with Backscattering: II

09:15 How neutrons perceive the formation of a glass, or, how to become a neutron scattering user thanks to backscattering!

Working on the glass transition phenomenon requires a thermodynamic and dynamical description of the materials, molecules, polymers or proteins. In text books, the phenomenon is described as a kinetic phase transition, arising between an out-of-equilibrium solid and a very viscous supercooled liquid as temperature decreases. Starting neutron scattering experiments by using backscattering technique allows non specialist users to catch immediately this description, and makes understandable the space dependence (Q) and the timescale of the process, both inputs essential for any theoretical approach. Here I would like to illustrate how backscattering experiments are essential to disentangle the roles of various control parameters on the glass formation, such temperature and pressure, molecular interactions or molecular weight dependence for polymers, or confinement dimension and surface interaction.

Speaker: Dr Christiane Alba-Simionesco (CNRS, Laboratoire Léon Brillouin)

09:35 The Protein Dynamical Transition from Back-Scattering Displacements

With the fast evolution of molecular dynamic simulations of proteins in the eighties, experimental methods covering structural fluctuations on a picosecond time scale came into focus. Time of flight methods and neutron backscattering provided numerous reality tests of virtual molecular biology. From the experimental side came the idea to expand the physiological range down to low temperatures, to discriminate molecular processes according to the exponential divergence of their correlation times. This approach required total control over the solvent, preventing it from crystallization. Fortunately the solvent could be reduced to a tiny deuterated hydration shell without depressing biological function severely. As a result, the scattering contribution of the protein hydration shell was low and the adsorbed water prevailed in a liquid state even at low temperatures. This concept opened a window to record protein fluctuations within a broad range of time scales (1). One important result was the behaviour of the protein mean square displacements with temperature: Two striking transitions in the T-dependence were observed with hydrated proteins at 180 and 240 K. The second transition requires fully hydrated proteins and was thus termed the PDT. It reflects water-coupled collective motions. Other transitions were assigned to side-chain rotation and fast hydrogen bond fluctuations (1-3). 1) W. Doster, S. Cusack and W. Petry, Nature 337,754 (1989) 2) W. Doster, H. Nakagawa and M.S. Appavou, J. Chem. Phys. 139, 45105 (2013) 3) W. Doster, Critical WebSite: WWW.bioneutron.de

Speaker: Dr Wolfgang Doster (Technische Universität München)

09:55 → 10:55 Recent science from Backscattering -- Contributed talks: I

09:55 My Experience with Neutron Backscattering Spectrometer

I, for the first time used a backscattering spectrometer is IRIS, at ISIS facility, UK, way back in 1990, to study quantum rotational tunnelling of NH4+ ions in mixed ammonium metal-alkali halides, during my stay at ISIS facility. It was found that at very low concentration (c) of the NH4+ ions behave like 'almost' free rotors. The spectra were described successfully by distribution of tunnelling lines at higher concentration. We are the first to observe quantum rotational tunnelling in a polymer system during my stay at UPV, Sansebastian, Spain. Other than IN16, at ILL, Grenoble, by virtue of its shape of the resolution function, it could not have been possible to observe this. PVAc being glassy in nature the rotational tunnelling was seen as 'quasielastic' like at 2.4 K. The data were described by considering the distribution of tunnelling lines as obtained from the distribution of energy barriers for classical hopping at high temperature. In recent times we have unravelled complex dynamical landscape in everyday use surfactant micelles using IRIS and TOF data. Elastic scan is one of the interesting technque to study dynamical transition. We have studied various systems using IRIS and IN16 (B) through elastic scan.

Speaker: Prof. Ramaprosad Mukhopadhyay (Bhabha Atomic Research Centre, Mumbai 400085, India)

10:10 The short life of MARS

MARS is an indirect TOF backscattering spectrometer at SINQ, PSI. MARS can be instrumentally best compared to the IRIS spectrometer at ISIS, but it was optimized for complementary research, i.e. high energy resolution and clean spectra in the inelastic region (magnetism). The secondary instrument consists of alternating 10 inelastic units and 12 diffraction detectors, arranged symmetrically at both side. Commissioning was in 2006, and first user experiment in 2007. Since 2012 the secondary instrument hosts the prototype of the CAMEA multiplexing analyzer back-end, which will be built both at PSI and at ESS. Presently the instrument is not in a regular user operation, but beam time can be requested via an informal proposal at any time. The SINQ upgrade project will be the end of the instrument; according to the present plan MARS will be shut down in 2018. This presentation is aimed to be a kind of memoir, going through the history both from instrumentational and from scientific point of view.

Speaker: Dr Fanni Juranyi (Paul Scherrer Institute)

10:25 High Pressure Cell for Simultaneous Neutron Scattering and Dielectric Spectroscopy

We present a novel experimental device to perform simultaneous incoherent quasi-inelastic neutron scattering with dielectric spectroscopy at high pressures. The cell has been designed to be utilized in a temperature range of 2-315 K and for a maximum pressure of 500 MPa. High tensile aluminium alloy was selected due to its low neutron absorption and incoherent scattering cross section. In this cell, we include a new component: two metal electrodes with a cylindrical geometry that form a capacitor in order to register the dielectric properties of the system. Main components of the high pressure cell are shown in the figure below. This setup is a unique tool for studying a variety of systems with dynamics on a large window of time scales, such as viscous liquids, polymers and proteins. By performing simultaneous dielectric and neutron spectroscopy we are able to monitor slow and fast dynamics under exactly the same environmental conditions (container, temperature and pressure). The setup has been successfully tested for the first time at the backscattering instrument IN16b collecting dielectric spectroscopy data in parallel with both fixed window scans and full quasielastic spectra.

Speaker: Dr Alejandro Sanz (Roskilde University)

Image Abstract_Alejandro_Sanz_img.jpg

10:40 Sorbate Dynamics in Zeolite Catalysts: Tandem QENS and Simulation Studies

See file attached

Speaker: Dr Alexander O'Malley (Cardiff University)

10:55 → 11:20 Coffee & Poster

11:20 → 12:05 Recent science from Backscattering -- Contributed talks: II

11:20 Understanding ion transport in fuel cells: towards in-operando experiments

High-temperature polymer electrolyte fuel cells (HT-PEFC) are promising electrochemical energy converters. Because of the high operation temperature of 160° - 180°C HT-PEFCs have a high CO tolerance [1]. The fundamental investigation of the proton conductivity will help to optimize performance and increase sufficiency of the fuel cells. For example, the understanding of the proton diffusion mechanism in the membrane electrode assembly (MEA) plays a key role in proton conductivity of fuel cells. The MEA is the central part of the HT-PEFC, which consists of two catalytic layers separated by a proton exchange membrane, typically polybenzimidazole-type (PBI) polymer films doped with phosphoric acid (PA). Neutron scattering offers a unique opportunity to study dynamical properties of hydrogen-containing materials. Backscattering spectroscopy gives insight into local proton transport of phosphoric acid in the PBI membrane [2] and in adjacent electrode layers [3] separately as well as in the complete MEA. [1] W. Lehnert et. al, in Innovations in Fuel Cell Technology (Eds. R. Steinberger-Wilckens, W. Lehnert), RSC Publishing, Cambridge 2010, pp 45) [2] O. Holderer et. al, Int. J. Hydrogen Energy 39 21657 – 21662 (2014) [3] M. Khaneft et. al, J. Fuel Cells 2016

Speaker: Dr Marina Khaneft (JCNS at MLZ)

11:35 QENS Studies of conjugated polymer MEH-PPV

MEH-PPV (poly[2-methoxy-5-(2_-ethylhexyloxy)-1,4-phenylenevinylene] is one of the most common conjugated polymers which continues to be of high interest in the area of polymer-based solar cells research, because of its good thermo-mechanical properties, stability, ease of processing, low-costs etc... We present recent quasi-elastic neutron scattering measurements of this electroluminescent active model system, which document the temperature evolution of the polymer dynamics. The data reveals a highly anharmonic side chain dynamics, which can be described by a stretched exponential function. The possible effects of this non-Debye dynamical behavior on the materials properties will be discussed.

Speaker: Dr Souleymane Diallo (Oak Ridge National Laboratory)

11:50 Dynamics of Partially Folded and Unfolded Proteins Investigated with Quasielastic Neutron Scattering

Protein folding is a fundamental process in molecular biology. Apomyoglobin (apo-Mb) – myoglobin without the heme group – is less stable then Mb and can be trapped in different folded, partially folded molten globules und unfolded states under equilibrium conditions depending on the chosen solvent conditions. I will present an investigation on the dynamics of the protein in its different folded states by quasielastic neutron backscattering (IN16, IRIS) and time-of-flight (IN5, IN6) spectroscopy [1,2]. The samples have been measured in the solution state to allow for solvent induced effects and to enable reversible thermodynamic properties. Global protein diffusion and internal macromolecular dynamics could be separated from the recorded spectra. Detailed insight into the properties of the internal dynamics of the different folded states of the protein was obtained. Our results point out the relevance of protein dynamics for stability and folding of Mb. 1. Stadler, Koza, Fitter; Determination of Conformational Entropy of Fully and Partially Folded Conformations of Holo- and Apomyoglobin; Journal of Physical Chemistry B, 119, 72-82 (2015) 2. Stadler, Demmel, Ollivier, Seydel; Picosecond to Nanosecond Dynamics Provide a Source of Conformational Entropy for Protein Folding; submitted

Speaker: Dr Andreas Stadler (FZ Jülich)

12:05 → 13:05 The Future Instrumentation has started

12:05 Design and first results from EMU at ANSTO

The Australian Neutron Scattering Centre at ANSTO has recently installed a cold-neutron backscattering spectrometer at the OPAL research reactor. The spectrometer, called EMU, is based on Si (111) crystal backscattering and extracts neutrons from a cold neutron guide via a double HOPG (002) crystal premonochromator setup. Backscattering is realized by implementing spherical focusing between the Si (111) crystal monochromator and analyser arrays, as first performed on the IN16 spectrometer. Incident neutron energies are modulated through fast oscillations of the monochromator using a “Doppler drive”, yielding a net energy transfer range of ± 31 μeV. The FWHM energy transfer resolution is 1.2 μeV at the elastic line. A unique feature of EMU is maintaining its high energy resolution from 1.95 to ~0.1 Å-1 momentum transfers that is, the backscattering condition is equally satisfied at all scattering angles, albeit at the cost of neutron incident flux at low scattering angles. Neutron events are resolved by two 3He linear-position sensitive detector arrays. Key results from the instrument commissioning are presented to compare performance against design objectives. Upgrades possibilities are also presented. EMU is available with standard sample environment from late 2016 to external users .

Speaker: Dr Nicolas R. de Souza (Australian Nuclear Sceince and Technology Organisation)

12:25 BATS and GaAs for IN16B at ILL

The neutron backscattering spectrometer IN16B at ILL was conceived with the flexibility to receive new concepts of instrument developments in the future. Two additional instrument configurations are being implemented at the moment, both aiming to increase the dynamic range of the spectrometer in different directions (see figure): The backscattering and time-of-flight spectrometer option **BATS** turns IN16B into a flexible, inverted ToF instrument by adding a high speed chopper system 34 m upstream of the sample position. This extends the energy transfer range by nearly one order of magnitude. In the case of Si111 analyzers a movable window of ±250 μeV with a tunable resolution of 2‑9 μeV FWHM will be provided. With the **GaAs** prototype option, the feasibility for a user-scale spectrometer with significantly improved energy resolution is explored, aiming at 50 neV resolution in a Q‑range of 0.2 to 2 Å$^{-1}$ with several μeV energy transfer range. This prototype bears many challenges in the instrument design, but it can certainly open new experimental opportunities and possibly new science. Commissioning of both these options is planned for the end of 2016.

Speaker: Dr Markus Appel (FAU Erlangen-Nürnberg)

12:45 Backscattering spectroscopy does miracles

I will present the conceptual design for the backscattering time-of-flight spectrometer MIRACLES approved for construction at the ESS and discuss on the avenues that it will open for neutron backscattering spectroscopy. MIRACLES’s remarkable flexibility - variable resolution, high flux and extended energy and momentum transfer range - is attributed to: 1. The long-pulse time structure and low repetition rate of the ESS source, 2. The chopper cascade that tailors the moderator pulse in the primary part of the spectrometer and 3. The bent Si(111) analyser crystals arranged in near-backscattering geometry in the secondary spectrometer. Analytical calculations and Monte-Carlo simulations show that MIRACLES will provide variable elastic energy resolution between 2 and 32 μeV, when using λ ≈ 6.267 Å, with an energy transfer range centred at the elastic line from –600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (Si(333)), δ(ℏω) can be relaxed to 300 μeV and ℏω from 10 meV in energy gain to –40 meV in energy loss. Measurements of low-energy excitations will be possible by shifting the dynamic wavelength range between 2 and 20 Å. [1] N. Tsapatsaris et al. EPJ Web of Conferences, **83** (2015) 03015. [2] N. Tsapatsaris et al. *submitted*.

Speaker: Prof. Heloisa Bordallo (Niels Bohr Institute, University of Copenhagen, Copenhagen, 2100, Denmark & ESS ERIC, 22100, Lund, Sweden)

13:05 → 13:20 Sketchnotes and Concluding Remarks

Speakers: Dr Robert M. Dimeo (Director, NIST Center for Neutron Research), Winfried Petry (FRM II - TUM)

13:20 → 14:20 Weißwurst und Bretzel

14:15 → 16:45 Guided tour through FRM II

This tour needs pre-registration! It takes at least 90 min.

14:20 → 15:50 Departure