ISIS

Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK

T: +44 (0)1235 445592 F: +44 (0)1235 445103 E: isisuo@stfc.ac.uk

www.stfc.ac.uk

Head office: Polaris House, North Star Avenue, Swindon SN2 1SZ, United Kingdom.

Establishments at: Rutherford Appleton Laboratory, Oxfordshire; Daresbury Laboratory, Cheshire;UK Astronomy Technology Centre, Edinburgh; Chilbolton Observatory, Hampshire; Isaac Newton Group,La Palma; Joint Astronomy Centre, Hawaii.

ISIS 2009The ISIS Neutron and Muon Source

Annual Report

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ISIS 2009The ISIS

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ISIS AR09 flat cover 4/12/09 11:51 Page 1

ISIS 2009The ISIS Neutron and Muon Source Annual Report

ISIS 2009 was produced for the ISIS Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK

ISIS Director, Dr Andrew Taylor01235 446681

ISIS User Office01235 445592

ISIS Facility Web pageshttp://www.isis.stfc.ac.uk

ISIS 2009 production team: Philip King, Bryan Jones, Alex Hannon, David Clements

Design and layout: Ampersand Design Ltd, Ardington (01235 861444)

Printed by: ESP Colour Limited and STFC Photographic and Reprographic Services

September 2009

© Science and Technology Facilities Council 2009

Enquiries about copyright, reproduction and requests for additional copies of this report should be addressed to:

STFC Library and Information Services,Rutherford Appleton Laboratory,Harwell Science and Innovation Campus,Didcot, Oxfordshire, OX11 0QX

email: library@stfc.ac.uk

Neither the Council nor the Laboratory accept any responsibility for loss or damage arising from the use of information contained in any of their reports or in any communication about their tests or investigations.

ISIS AR09 flat cover 4/12/09 11:51 Page 2

1

CON

TENTS

ISIS 2009

ContentsForeword ..................................................................................................... 3

Highlights of ISIS science ............................................... 6Materials for advanced electronics ............................................................................. 8

Competing interactions: studies of frustration ........................................................ 10

Structural investigations of technologically-relevant materials ............................. 12

Applications of complex molecules .......................................................................... 14

Superconductivity and magnetism ........................................................................... 16

A variety of technologies – man-made and natural! .............................................. 18

Developments and events ...................................... 22Second Target Station instruments shine! ................................................................ 24

New science from instrument and technique advances ......................................... 28

Accelerator and target developments ...................................................................... 32

A year around ISIS ...................................................................................................... 34

ISIS Publications 2008-2009 ............................. 40ISIS Publications 2008-2009 ..................................................................................... 42

ISIS Seminars 2008-2009 ........................................................................................... 52

ISIS in facts and figures .............................................................................................. 54

Beam statistics 2008-2009 ........................................................................................ 56

ISIS 2009ISIS provides world-class facilities for neutron and muon investigations ofmaterials across a diverse range of science disciplines. ISIS 2009 details thework of the facility over the past year, including accounts of science highlightsand descriptions of major instrument and accelerator developments, togetherwith progress on the Second Target Station Project and the facility’spublications for the year.

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ISIS 2009

ISIS is, and is destined the world’s

▼ HRH Prince Andrew theDuke of York visited ISIS inApril. Here he is beingintroduced to the facility byDirector Dr Andrew Taylor.09EC1664

Professor John Beddington, CMGFRS, Government Chief ScientificAdviser and Head of the GovernmentOffice for Science, visited the ISISSecond Target Station in Novemberwith STFC Chief Executive Prof KeithMason (left). 09EC4671

▼ David Willetts MP, Shadow Ministerfor Universities and Skills, visiting ISIS inFebruary with his son Matthew andSTFC Chief Executive Prof Keith Mason.09EC1060

Dr Arden Bement,Director, NationalScience Foundation,Arlington, USA, withDr Andrew Taylor atthe ISIS Second TargetStation during his visitin June. 09EC2196

▲ Dr Frances Saunders, ChiefExecutive, Defence Science &Technology Laboratory (left), visitedISIS in June with Prof Keith Mason,Dr Liz Towns-Andrews andDr Andrew Taylor (STFC). 09EC2110

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The thrill of delivering firstneutrons to the Second TargetStation last year has been morethan matched by the scientificcommissioning and earlyoperation of its instrument suite.

The first seven instrumentshave been completed – on time, onbudget, and to specification – andhave demonstrated performancecapabilities that are exceeding theexpectation of the instrumentscientists themselves!

This is a tremendousachievement. My thanks go to allwho have contributed to thesuccess of the TS-2 project: ISISstaff, the user community, externalcontractors and companies. Andwe must not forget those whohave kept ISIS operating at the topof its game delivering a world-leading programme while all thiswas happening. Tremendousindeed!

Whilst we rightly focus on thesuccess of the Second TargetStation, the main scientific deliveryfrom ISIS still rests with theefficient and effective operation ofthe existing target. This targetstation, with its fully developedinstrument suite, highlysophisticated sample environmentequipment and dedicated usersupport teams, has set the standardto which the new sources beingdeveloped elsewhere aspire. Inaddition, the Second Target Stationinstrument suite representsinnovation not yet beingcontemplated anywhere in theworld. Taken as an entity, ISIS is,and is destined to remain for someconsiderable time, the world’spremier pulsed neutron facility.

As we introduce newinstruments, we also say ‘goodbye’to old friends – the HETspectrometer, a flagship ISIS

instrument for 24 years, finallyclosed as the new choppermachine Merlin (with aperformance some 30 timesgreater) came online. And Prisma,the pioneering single crystalspectrometer developed throughour Italian collaborations, also sawits last experiment.

Beyond ISIS itself we can lookforward to developments on thewider Harwell campus that willfurther feed ISIS science. TheResearch Complex at Harwellopens its doors at the end of theyear to foster experimentalprogrammes in support of ISIS,Diamond and the Laser Facilities atRAL, and to attract new sciencecapabilities and develop newpartnerships.

The ISIS user programme is fullyaligned with the developing STFCstrategy and delivers ‘impact’ in allsenses of the word: impact throughthe science programme, throughinnovation, inspiration, thenurturing of skills, attractinginward investment to the HarwellCampus and underpinning

economic well-being byaddressing key science-ledgovernment challenges.

These are difficult times forthe economy and we recognisethat pragmatic short termbudget savings needed to bemade. Nevertheless we are

confident that a proper evaluationof STFC’s priorities will soon restorethe ISIS user programme to anappropriate level of operation.

FOREW

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to remain for some considerable time,premier pulsed neutron facility.

Foreword

▲ John Webster and Jeff Penfold (ISIS)studying data from the Inter reflectometerduring the first experiment on the SecondTarget Station. 09EC2086

▲ Laurent Chapon and Pascal Manuel(ISIS) pleased with first data from Wish.09EC2794

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A year around ISIS

▼ Tony Moore and Jim Brassington from BNSNuclear Services, formally ALSTEC, hand overthe Second Target Station building to ISISdirector Dr Andrew Taylor in April. Alsopresent were ISIS staff Harry Jones and ZoeBowden, and BNS site representative FredGuttridge. 09EC1592

Dr Brian Bowsher,Managing Director,National PhysicalLaboratory, touringthe Second TargetStation in June.09EC2604

▲ In March, Professor LucianoMaiani, President of the NationalResearch Council of Italy,inaugurated the Nimrodinstrument on the Second TargetStation. He is seen here with ProfCarla Andreani (University ofRome Tor Vergata) viewingarchaeological artefacts beingstudied on Engin-X. 09EC1122

▲ Danish Scienceand TechnologyInstitute membersvisiting ISIS in June:Inge Maerkedahl(Director General)Johnny Mogensen(Head of Division),Morten Scharff(Special Advisor)and John RennerHansen (Neils BohrInstitute, Universityof Copenhagen).09EC2306

Secondary school teachers attending the ‘Living in a Materials World’ teacherweekend in June learning about ISIS with Chris Frost and Martyn Bull (ISIS).09EC2472

▲ Dr AnanthaDasannacharyavisiting ISIS inSeptember.

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Oxford UniversityHeads of Departmentwere shown around theSecond Target Station inDecember by STFC ChiefExecutive Prof KeithMason. 08EC4851

▼ Prof Steven Cowley(Director, UKAEACulham, left) and MrMartin Cox (AssistantDirector, Operations,UKAEA Culham) viewingTS-2 instruments in July.09EC2914

▲ March saw studentsattending the ParticlePhysics Masterclassvisiting ISIS and learningabout TS-2. 09EC1236

▲ Prof Michael Steiner, CEO, Hahn-MeitnerInstitute, Germany (left) and his appointedsuccessor Prof Anke Pyzalla (second fromright) visiting ISIS in November with RobertMcGreevy, Andrew Taylor and UschiSteigenberger (ISIS). 08EC4552

▼ The ISIS Second Target Station wasone of the first facility projects toreceive European constructionfunding. The EU project teammembers visited ISIS for their finalmeeting in March. 09EC1590

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Highlights of ISIS science

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Section 1Highlights of ISIS science

The advanced facilities provided byISIS enable world-class research to beperformed by scientists from aroundthe world together with facility staff.Academic and industrial applicationsof the intense neutron and muonbeams encompass a very broad rangeof science areas. Presented in thefollowing pages are brief summariesof recent science highlights.

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Organic spin valvesopen up to neutrons

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Electronic devices that utiliseatomic-level spins – as opposed tocharge – hold unique prospects forfuture technology. They promise low-power logic, possibly at the quantumlevel, and the combination on the samechip of communication, logic andmemory elements. When such spintronicdevices include use of organic materials,which have low manufacturing costs andare mechanically flexible, there is considerablefurther potential for extending the scope thatthese devices have. This may lead to an entirelynew generation of spin-enabled electronics.However, the mechanisms behind spin injectionand transport in organic materials are not wellknown, as there is a severe lack of suitableexperimental techniques. Using spin polarisedneutron reflectivity, we have imaged the injectedspin polarisation and its transport away from a

buried interface within a fully functional andrealistic device. The results highlight the uniquepotential of the technique to reveal themechanisms that limit the spin coherence withindevices, especially in those involving organicmaterials. Specifically, it can enable bulk andinterface-related spin decoherence phenomenato be differentiated.

Spintronics, technologies based on the use of theelectron spin as opposed to conventional charge-based electronics, has seen enormous recentdevelopment. In the mid-nineties it wasproposed that a spin-polarised current ofelectrons would be able to rotate itsmagnetisation, removing the need for appliedmagnetic fields. This has been demonstrated –however, the primary hurdle for making use ofthese devices is the prohibitively high switchingcurrent densities required. An alternative is touse a spin-spiral material, such as holmium.Holmium is ferromagnetic, but the moments

rotate from one plane to the next in a spiralfashion. In devices, the entire spin-spiral can beemployed in the switching, thereby lowering thenecessary current densities. Using polarisedneutron reflectometry we have been able tostudy the temperature and layer thicknessdependence of the spin-spiral in films only 25atomic layers thick. Such information is essentialto produce optimised spin-spiral devices.

(a) A schematic of a Ho based spin-spiral device. (b) Temperature dependence of the magnetic Bragg peakfrom a 50 nm Ho epitaxial film.

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Nanoscale spin-spirals to aid magnetic switching

AJ Drew (Queen MaryUniversity of London),L Schulz (University ofFribourg), S Langridge(ISIS)

Contact:

Dr Alan Drew,A.J.Drew@qmul.ac.uk

Further reading:

AJ Drew et al., NatureMaterials 8 (2009) 109

A spintronic device of the sort already used in hard driveread heads and magnetic memory: the spin valve. A spinpolarised current is injected from a magnetic layer (green)into a non-magnetic spacer layer (yellow), where the spinpolarisation is reduced as the current flows until it finallyreaches a second magnetic layer (blue). Current flowdepends on the spin alignment through the device.

J Witt, A Aziz, M Blamire(Cambridge University),R Fan, C Kinane,T Charlton, S Langridge(ISIS)

Contact:

James Witt,jdsw2@cam.ac.uk

Further reading:

O Wessely et al., PhysRev B 79 (2009) 104433

Materials for advancedelectronics

• Polymer thin film surface

• Organic interfaces: polymer interdiffusion

• Organic/inorganic interface: roughness, reactivity

– +

QUASIELASTIC NEUTRON SCATTERING• backbone and side-chain motion and vibrations, phase transitions

NEUTRON DIFFRACTION• structure

INELASTIC NEUTRON SCATTERING• phonon density of states

• nanoparticles, nanorods, aggregates

SMALL ANGLENEUTRON

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NEUTRONREFLECTOMETRY

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Nanoscale propertiesof organic solar cell polymers

Muons probe charge transport in organic semiconductors

Conjugated polymers have been intensivelystudied since it was demonstrated that theycould behave as semiconductors. The ability touse these polymers to produce organic lightemitting diodes (OLEDs) and solar cells (OSCs)has created great expectations. Our neutrondiffraction and quasielastic scatteringexperiments performed on the Osirisspectrometer are the initial stage of a programintended to investigate the structure anddynamics of the most widely used conjugatedpolymers – the poly-3-alkyl-thiophenes. Theadded functional groups along the conductingbackbone provide solubility, improving the abilityto process the polymers. Nevertheless, theirstructure has to be controlled and their dynamicsunderstood in order to avoid hindering thecharge carrier motion that provides the basis fortheir usefulness in devices. We havedemonstrated the coexistence of amorphous and

crystalline phases, determined their melting andcrystallisation temperatures and providedevidence of a low temperature glass transition.This information, characterisation of thestructure and dynamics at the nanoscale, iscrucial to achieve the production of higherperformance organic solar cells.

Electronic devices based on organicsemiconductors such as Alq3 (tris[8-hydroxy-quinoline] aluminium) are revolutionisingelectroluminescent displays and large-areaelectronics. These organics are economicallyfavourable, can be easily processed in largeareas, have tuneable electronic properties, andare simple to grow into high quality thin films.

Even though charge transport in such organicconductors is fundamental to their operation,many of its mechanisms are still only poorlyunderstood. Progress in this area may be pivotalto utilising these materials to their fullest extent.

Implanted muons provide a powerful localprobe for studying the dynamics of mobile spins.Muon spin relaxation studies at ISIS have beenused to investigate charge carrier motion in Alq3as a function of temperature. The chargemobilities obtained in this way are significantlylarger than those obtained from direct transportmeasurements in polycrystalline films and thusprovide an estimate for the intrinsic upper limit

for the mobility that might beachievable in high quality bulk

material.

AJ Drew (University ofFribourg, Switzerland),FL Pratt (ISIS), NA Morley(University of Sheffield),P Desai (Queen Mary,University of London),R Scheuermann (PSI,Switzerland)

Contact:

Dr AJ Drew,a.j.drew@qmul.ac.uk

Dr FL Prattfrancis.pratt@stfc.ac.uk

Further reading:

AJ Drew, FL Pratt et al,Phys Rev Lett 100 (2008)116601

A Urbina, J Padilla(University of Cartagena,Spain), F Batallán,C Díaz-Paniagua (ICMM-CSIC, Spain),V García Sakai (ISIS)

Contact:

Dr A Urbina,antonio.urbina@upct.es

Further reading:

A Urbina et al., Phys RevB 78 (2008) 045420

Diagram of an organic solar cell showing where neutronscattering experiments can improve our understanding ofthe device structure.

The propeller-shaped molecules of Alq3,which are used as an active constituent oforganic light emitting diode (OLED) displays.

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From compasses to iPods, magnets are the basisof many technological applications. Ourunderstanding of magnetism is based around theidea of atomic-level spins and the interactionsbetween them. Positive interactions result in aferromagnet with all spins aligned, whereasnegative interactions (antiferromagnetic, AF)between spins give rise to more complicatedmagnets. AF spins located on a two dimensional(2-D) square produce an arrangement withalternating spins. However, it’s not possible forAF spins on the vertices of triangles to alignthemselves so that all of their interactions withtheir neighbours are satisfied. In this case thesystem is said to be ‘frustrated’. An example of afrustrated 2-D magnet, named after a Japaneseweaving technique, is the kagome lattice. In realsystems, 2-D kagome layers (KL) are coupledtogether through other layers that tend to breakthe frustration. It is generally thought that thebest way to keep the KL frustrated is to decouplethe layers to reduce these interlayer interactions.

Using a combination of neutron scatteringand computer simulations on a kagome likesystem YBaCo4O7, we show that in fact, strongcoupling between the KL can help to keep themfrustrated. Our model also introduces a newmagnetic entity, a trigonal bipyramid, where thesum of the basal spins is opposite to the sum ofthe apex spins.

Frustration occurs when it is not possible tosatisfy all interactions between atoms. Asdescribed in the article above, a magnetic atommight want its spin direction to be misalignedwith that of a neighbouring atom (if theinteractions are antiferromagnetic). But for somearrangements of atoms, misalignment with oneneighbour prevents misalignment with another –producing frustration. Frustration plays animportant role in a diverse range of physics, frommagnetism to protein folding. Pyrochlores –magnetic materials with atoms arranged in away that leads to frustration – are fascinating asby changing one atom the frustration behaviourchanges, culminating in properties such as a ‘spinliquid’, ‘spin glass’ or ‘spin ice’.

The frustration in pyrochlore Tb2Sn2O7 haspreviously led some to believe it exhibits a novelstate of magnetism in which the magnetisationdirection reverses multiple times a second. Thisis not how a permanent magnet normallybehaves. We tested the behaviour using muonsimplanted into silver in front of the sample(rather than into the sample itself). If the samplebehaved like a permanent magnet, its field lineswould penetrate the silver and be detectable by

the muons. This is indeed what is revealed – sothat Tb2Sn2O7 does in fact behave like apermanent magnet below its transitiontemperature of 0.87K.

An oscillatory signal in the muon data is a clear indicationof static internal magnetic fields in Tb2Sn2O7. The insetshows the temperature depence of the internal fieldbelow the transition.

An outsider’s view: a novel muon study of frustration

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P Manuel, LC Chapon(ISIS), PG Radaelli(Oxford University),JF Mitchell, H Zheng(Argonne NationalLaboratory, USA)

Contact:

Dr P Manuel,Pascal.Manuel@stfc.ac.uk

LC Chapon,Laurent.Chapon@stfc.ac.uk

Further reading:

P Manuel, LC Chapon etal., Phys Rev Lett 103(2009) 037202

SR Giblin,JDM Champion (ISIS),HD Zhou and CR Wiebe(Florida State University,USA), JS Gardner (NIST,USA), I Terry (DurhamUniversity), S Calder,T Fennell, ST Bramwell(University CollegeLondon)

Contact:

Dr Sean Giblin,sean.giblin@stfc.ac.uk

Further reading:

SR Giblin et al., PhysRev Let 101 (2008)237201

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Magnetic diffusemaps, data andsimulation, fromYBaCo4O7 intwo scatteringplanes.

Competing interactions:studies of frustration

The trigonal bipyramid: a new building blockfor making frustrated magnets

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Merlin’s magic reveals quantummagnet behaviour

A dimerised quantum antiferromagnet is asystem in which quantum atomic spins arestrongly coupled into pairs or dimers withonly weak interactions between the dimers.The lowest energy state of such a system isa spin singlet (S=0), and this is separatedfrom the S=1 excited state by an energy gap.Because these dimers have integer spins,they have been observed to form an unusualquantum state at very low temperatures,called a Bose-Einstein Condensate, in whichall the particles are identical and in thelowest energy state of the system.

We investigated the magnetic properties of arecently discovered dimerised antiferromagnet,Sr3Cr2O8. The magnetic chromium ions arearranged on frustrated triangular bilayers and thedominant intra-bilayer interaction couples theminto dimers. A structural distortion removes thefrustration giving rise to spatially anisotropicinter-dimer interactions and resulting in threetwinned domains. The magnetic behaviour can

be studied in detail using single crystal samplesand a neutron spectrometer such as Merlin. Thedata confirm the structural distortion and enablethe magnetic interactions to be characterised indetail.

The spin-chain systems with general formulaA’3ABO6 have been attracting considerableattention in recent years as they offer thepossibility of probing several phenomena in asingle family of materials: geometricalfrustration, the behaviour of linear (Ising) chainsof magnetic spins, and ferroelectricity(spontaneous electric polarisation of a crystal).Among these compounds, Sr3NiRhO6 andSr3NiPtO6 exhibit interesting properties, havingmagnetic (Ni2+, Rh4+) and nonmagnetic (Pt4+)ions. Sr3NiRhO6 shows a complex magneticground state below 40K, while Sr3NiPtO6 remainsparamagnetic (spin-liquid-like) down to mKtemperatures. The crystal structure has Ni and Rh(or Pt) ions surrounded by six oxygens, formingdistorted trigonal-prisms and octahedrarespectively, that are connected to form 1D-chains. Inelastic neutron scattering on HET hasprovided direct information on the nature of themagnetic ground state. Data from Sr3NiRhO6indicate the importance of intersite interactions,whereas that from Sr3NiPtO6 may suggest asingle ion type of response.

Inelastic neutron scattering data from Sr3NiRhO6 andSr3NiPtO6 at 5K.

Fundamental magnetic properties of spin-chain systems

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DL Quintero-Castro,B Lake, EM Wheeler,ATMN Islam (HelmholtzZentrum Berlin,Germany), T Guidi (ISIS)

Contact:

DL Quintero-Castro,diana.quintero_castro@helmholtz-berlin.de

Further reading:

DL Quintero-Castro etal., arXiv:0909.3941v2,accepted for Phys Rev B

DT Adroja (ISIS),S Rayaprol (UGC-DAECSR, India), AD Hillier,M Telling (ISIS),EV Sampathkumaran(TIFR, India)

Contact:

Dr DT Adroja,Devashibhai.adroja@stfc.ac.uk

Further reading:

DT Adroja at el, to besubmitted to Phys Rev B

Neutron scattering data from Merlin from Sr3Cr2O8 in thelow temperature phase showing three dispersive magnonmodes.

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Structural investigations oftechnologically-relevant materials

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Sorting out the structureof multiferroic BiFeO3

Multiferroics aretechnologically-important materialswhich simultaneouslyexhibit electric order(alignment of electricdipoles in an electricfield) and magnetic order(alignment of magnetic spins in a magnetic field).This makes them potentially useful in devicessuch as random access memories, sensors andactuators. BiFeO3 is the most widely studiedmultiferroic as both the magnetic and electricordering occur at room temperature. The roomtemperature structure of BiFeO3 (α-phase) hasbeen well established as rhombohedral. Howeverthe transition away from electric ordering at hightemperatures (ferroelectric, α, to paraelectric, β,transition around 820-830°C) is coupled with achange in structural symmetry. The exact natureof the β-phase has been a subject of muchdispute with many different symmetriesreported. We used high resolution neutron

diffraction to investigate the β-phase with theaim of resolving these discrepancies. We wereable to clearly demonstrate that this phase isorthorhombic, ruling out some of the previouslysuggested models, and subsequently present thefirst full crystallographic model.

A variety of interesting and potentiallyuseful materials are produced when aperovskite crystal structure is distorted bythe presence of dopant atoms. Examplesinclude ferroelectrics, which show a spontaneouselectric polarisation (analogous toferromagnetism), ferroelastics (which showspontaneous strain) or materials – multiferroics –which show a combination of magnetic, electricor elastic behaviour. Of importance for theproperties and behaviour of such materials is thesize of the strain field around individual dopantatoms. One method of measuring this is todetermine the extent to which a material’stransition temperature remains independent ofdopant concentration for a suitable phasetransition. In principle the transition temperaturewill not change from that of the pure phase untilthe strain fields around individual impurity atomsstart to overlap. We have used HRPD to makeprecise measurements of the monoclinic toorthorhombic transition occurring in La-dopedPrAlO3 at about 150 K. We find this temperatureis unchanged to a La dopant level of about

1.6%, and infer strain fields of order 1.6-1.8 pmdiameter. This appears to be a characteristiclength scale for strain relaxation aroundimpurities in oxide perovskites.

Dopant atoms strain perovskites

α-BiFeO3RhombohedralFerroelectric

β-BiFeO3OrthorhombicParaelectric

Change in Fe positionin FeO6 octahedra

820-830°C

820-830°C

MA Carpenter,CJ Howard, REA McKnight(Cambridge University),BJ Kennedy, Q Zhou(Sydney University),KS Knight (ISIS)

Contact:

Prof MA Carpenter,mc43@esc.cam.ac.uk

Further reading:

MA Carpenter et al.,Phys Rev B 80 (2009)214101

DC Arnold, FD Morrison,P Lightfoot (University ofSt Andrews), KS Knight(ISIS)

Contact:

Prof Phil Lightfoot,pl@st-andrews.ac.uk

Further reading:

DC Arnold et al, PhysRev Lett 102 (2009)027602

Temperature of the monoclinic to orthorhombic transitionas a function of La dopant content in (Pr,La)AlO3. This istemperature-independent to about 1.6% La. Inset:structure of PrAlO3.

Schematic representation of the α- and β-phases ofBiFeO3 showing the change in structural symmetry fromrhombohedral to orthorhombic at the ferroelectric-paraelectric phase transition.

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Negative thermal expansionin porous frameworks

Negative thermal expansion (NTE), orcontraction upon heating, is of fundamentalscientific interest and may find applications inprecision engineering. Understanding themechanisms for NTE may allow tuning of thebehaviour by modification of the atomic-levelstructures through which it is produced. Aprincipal cause of NTE is transverse atomic andmolecular vibrations – vibrations that are atright angles to the atomic or molecular bonds.Such vibrations are often low in energy, makingthem difficult to model and therefore identify.However, the Tosca spectrometer can now berun with its chopper stopped during the onepulse in five that goes to the ISIS Second TargetStation, enabling collection of the lower energyregion of the vibrational spectrum.

NTE is being noted increasingly in metal-organic framework materials, which have beenstudied principally for applications such as gasstorage. Using Tosca we have found a uniqueand relatively complex mechanism for NTE inone such framework, Cu3(1,3,5-

benzenetricarboxylate)2. We find NTE arises fromrelief of geometric frustration through motionsof its dicopper benzoate unit, which distortsfrom square-prismatic towards the antiprismaticconfiguration on heating.

Materials with low-dimensional structures (e.g.2-D or layered materials such as graphene, high-temperature superconductors) are importantprecisely because low dimensionality often leadsto unusual and useful physical properties. Nickelcyanide, Ni(CN)2, is a material with a layer-likestructure that shows the unusual phenomenonof negative thermal expansion. This means thatthe dimensions of its square-grid-like layersdecrease with increasing temperature, in contrastto most materials which expand as thetemperature is raised. A combination of neutronscattering and X-ray diffraction has been used toshow that the crystal structure of this materialactually exhibits long-range structural order inonly two dimensions, with no true periodicityperpendicular to its grid-like layers. This lack ofperiodicity reflects the weakness of theinteractions between layers. Because of this, thesquare-grid layers can vibrate very easily andessentially independently of one another, andthis in turn gives rise to its negative thermalexpansion behaviour.

Disordered stacking arrangement in Ni(CN)2. Weakinteractions between square-grid layers allow largeamplitude vibrations that cause the layer dimensions toshrink with increasing temperature.

VK Peterson, GJ Kearley(ANSTO, Australia),Y Wu (Sydney University,Australia), AJ Ramirez-Cuesta (ISIS), CJ Kepert(Sydney University,Australia)

Contact:

Dr Vanessa Peterson,Vanessa.Peterson@ansto.gov.au

Further reading:

VK Peterson et al.,submitted.

AL Goodwin, MT Dove(Cambridge University),SJ Hibble, AM Chippindale,AH Pohl (ReadingUniversity), AC Hannon(ISIS)

Contact:

Dr AL Goodwin,alg44@cam.ac.uk

Further reading:

AL Goodwin et al. Phys.Rev. B (submitted)

Two parts order, one part disorder: negative thermal expansion in Ni(CN)2

0 20 40 60 80 100 120

Energy transfer (cm-1)

0.6

0.4

0.2Inte

nsit

y (a

rb. u

nits

)Spectra (Tosca) at 100 K (red) and 20 K (blue) forCu3(1,3,5-benzenetricarboxylate)2. Low energy featuresarise from the dicopper benzoate unit (inset along Cu-Cu)which changes from square-prismatic (left) to distorted(right).

14

Applications of complexmolecules

ISIS 2009H

IGH

LIGH

TSO

F ISIS SCIEN

CE

Nano-structures in surfactantmixtures revealed

In many commonplace surfactant-basedformulations (comprising ionic/nonionicsurfactant mixtures) the addition ofcosurfactants such as straight-chainalkanols and more complex alcoholstructures (such as perfumes) can havean impact upon the structure and stability of thesolution. Recently we have used Small AngleNeutron Scattering (SANS) to study the impact ofa range of straight-chain alkanols on the phasebehaviour and microstructure of a di-alkyl chaincationic (DHDAB) and non-ionic (C12E12)surfactant mixture.

In the absence of alcohol the DHDAB/C12E12mixture exhibits a rich structural evolution withcomposition – from small globular micelles forC12E12-rich compositions to large polydispersebilamellar or multilamellar vesicles for DHDAB-rich compositions. The addition of the largeralkanols (dodecanol and hexadecanol) results inmicelles and vesicles coexisting, and to vesiclesoccurring at solution compositions progressivelyless rich in DHDAB.

Most notable, however, is the observationthat the smaller alkanols (octanol and decanol)produce a transition from large polydispersebilamellar or multilamellar vesicles to very smallmonodisperse unilamellar vesicles, or nano-vesicles.

These results highlight the importance ofSANS in elucidating these remarkable nano-structures. These structures offer great potentialfor the formulation of systems in which it isimportant to maintain a high degree of fluidityand transport.

The study of interfaces in the fields of bio- andnanoscience, especially of interfaces betweenartificial and biological materials, is oftremendous importance. Oligo(ethylene glycol)(OEG) and poly(ethylene glycol) (PEG)monolayers have biotechnological applicationssuch as biosensing, bio-compatibility (e.g. ofimplants) and in supporting model membranes. Ithas been found that these monolayers are

resistant to irreversible protein adsorption,although the underlying physicochemicalmechanisms for this are still under discussion.We have studied the protein density profile atthe solid/liquid interface in order to obtaininformation about the interactions between OEGlayers and proteins. Neutron reflection resultsreveal an oscillatory density profile for theprotein solution immediately above the OEGlayer. This indicates that the proteins reach theproximity of the OEG layer, but are preventedfrom adsorbing irreversibly, by, for instance, astrongly bound water layer. The net effect of saltwas also studied and appears to be small,although charges may play a more subtle role inthe complex balance of forces within thisintricate system.

Protein density profile obtained from data fitting (blueline) of an OEG self-assembled monolayer (SAM) incontact with a 15 wt % bovine serum albuminprotein/D2O solution at 25 °C. The cartoon shows asnapshot of the corresponding protein layering at theinterface.

Exploring protein-resistant surfaces

0.0 0.2 0.4 0.6 0.8 1.0

DHDAB/C12E12 composition (mole fraction nonionic)

Lv/Lsv

LvL1

L1

Lsv/L1Lv/Lsv

Lsv

0

20

40

60

80

Alc

ohol

con

cent

rati

on (m

M)

Lv/L1L1/Lv

J Penfold (ISIS, OxfordUniversity), I Tucker(Unilever), RK Thomas,R Bradbury (OxfordUniversity), I Grillo (ILL)

Contact:

Prof J Penfold,Jeff.Penfold@stfc.ac.uk

Further reading:

J Penfold et al., Langmuir24 (2008) 12209;I Tucker et al, Langmuir25 (2009) 7674

MWA Skoda,JRP Webster (ISIS),F Schreiber (TübingenUniversity, Germany),RMJ Jacobs (OxfordUniversity), M Wolff (ILL, France), R Dahint,D Schwendel, M Grunze(Heidelberg University,Germany)

Contact:

Dr MWA Skoda,Maximilian.Skoda@stfc.ac.uk

Further reading:

MWA Skoda et al.,Langmuir 25 (2009)4056

The effects of octanol addition to DHDAB/C12E12surfactant mixtures, showing the different nano-structures formed.

oscillating protein density

OEG SAM

Au

15

HIG

HLIG

HTS

OF ISIS SC

IENC

EISIS 2009

Dynamics of nanoparticlesfor drug delivery

Nano- and micro-particlesthat are composed ofsaccharide (sugar-like)and lipid (moleculessuch as fats and oils)components can beproduced for potentialapplications as highly-biocompatible drugcarriers. A detailed understanding of particle-solvent interactions is of key importance in orderto tailor their characteristics for delivering drugswith specific chemical properties. For example,lecithin (a commercial mixture of different lipids)and chitosan (a positively chargedpolysaccharide) can be used to producenanoparticles able to encapsulate lipophilic (fat-soluble) drugs with lower water solubility.

Using the Iris spectrometer we haveinvestigated the local dynamics oflecithin/chitosan nanoparticles, and the effect ofisopropylmiristate (IPM), a lipophilic additive

commonly used to improve drug loadingefficiency. The data indicate that IPM, which isfluid at room temperature, increases the mobilityof the lipids with respect to pure lipid/saccharidenanoparticles by about three times. Thismicroscopic scenario is reflected in themacroscopic kinetics of drug release: the amountof released drug in the presence of IPM is about3 times higher than that of the samenanoparticles without IPM.

Polymeric microgels consist of nanometer-sizedspheres. The spaces inside the spheres can befilled with a pharmacologically-active material –a drug – suspended in water. Such microgels arebiocompatible, and so they have promisingapplications as injectable drug-delivery systems.Pharmacological activity, however, is onlypreserved if the drug is embedded in the properenvironment. The behaviour of the water and thedesign of the microsphere are key to providingsuch an environment. PVA/p(MA-co-NiPAAm)porous microgels are good candidates forcontrolled drug delivery since the microspheres’

volume depends upon temperature – so bodytemperature can be used as a trigger for drugdelivery. Furthermore, the drug release propertiesare strongly dependent upon the diffusivebehaviour of the water. It is therefore necessaryto characterise how water diffuses within themicrogel spheres using quasi-elastic neutronscattering (QENS) in order to evaluate thediffusion characteristics of the drug itself. QENShas allowed quantitative water diffusion rates tobe determined above, and below, the volumephase transition in one particular thermo-responsive microgel.

Water diffusion in drug delivery microgels

15 20 25 30

Temperature (°C)

(b)(a) (c)

ΔE (µeV)

Ave

rage

Dh

(µm

)

S (Q

,ω)

35 40 45 50

1.0

1.2

1.4Heating

Cooling

1.6

1.8

-200 -100 0 100 200

0.01

0

0.02

0.02

0.04

0.05

0.06

SV Ghugare, E Chiessi,G Paradossi (Universitàdi Roma Tor Vergata,Italy), MTF Telling (ISIS)

Contact:

Prof G Paradossi,paradossi@stc.uniroma2.it

Further reading:

SV Ghugare et al.,Biomacromolecules 10(2009) 1589

Y Gerelli, MT Di Bari,A Deriu, F Cavatorta(Università di Parma,Dipartimento di Fisica,and CNR, Italy),S Barbieri, F Sonvico(Università di Parma,DipartimentoFarmaceutico, Italy),V García-Sakai (ISIS)

Contact:

Prof A Deriu,Antonio.Deriu@fis.unipr.it

Further reading:

MT Di Bari et al., ChemPhys (2008) 239

(a) Confocal micrograph ofmicrogels, (b) Microspherediameter vs. temperature,(c) QENS experiment onhydrated microgels at roomtemperature: red dots,experimental data; blackline, total fit; blue line,polymer elasticcontribution; green line,bound water; orange line,free water.

Multilayer structure oflecithin/chitosan nanoparticles(schematic view). The orangearrow indicates a pathway forthe diffusion/release of drugmolecules.

16

Superconductivity and magnetism

ISIS 2009H

IGH

LIGH

TSO

F ISIS SCIEN

CE

Symmetry breakingin superconductor LaNiC2

A ‘symmetry’ is a property of a system whichmeans that the system behaves in the same wayeven though it has undergone a change. Forexample, a square looks the same when it hasbeen turned through 90°. The concept ofsymmetry is very important in physics, as is theidea of symmetry breaking, in which a system nolonger obeys a particular symmetry.Superconductivity provides a paradigm forsymmetry breaking, and in some superconductorsa variety of symmetries can be broken. Forexample, in cuprate high-temperaturesuperconductors, which have a layered structurewith planes made of square CuO2 ‘plaquettes’,the 90° rotation symmetry of the plaquettes isbroken on entering the superconducting state. Aneven more exotic possibility is failure of time-reversal symmetry in the superconducting state.This can be detected through an increase in themuon spin relaxation rate produced by thespontaneous onset of magnetic fields below Tc(such as in Sr2RuO4).

Non-centrosymmetric superconductors –materials whose crystal structure has no central

symmetry point – are particularly interesting asthe way the electrons in the material pair up inthe superconducting state can take unusualforms. One example of a non-centrosymmetricsuperconductor is LaNiC2 (critical temperatureTc=2.7K). We have shown that the muon spinrelaxation rate in zero applied field increases asthe material is cooled through the transition.This is the first direct proof of broken time-reversal symmetry in any non-centrosymmetricsuperconductor.

Recently, a new iron-based infinite-layerantiferromagnetic insulator SrFeO2 (spin S=2)was produced. The FeO4 square-planararrangement in this material is very rare, becausealmost all iron compounds have been known toadopt three-dimensional local environmentssuch as FeO4 tetrahedron and FeO6 octahedron.This unprecedented arrangement gives rise toseveral unexpected structural and physicalproperties, including a high antiferromagnetictransition temperature (473 K), stability of thenovel structure and a pressure-induced transitioninto an intermediate spin state (S=1)accompanied by an insulator-to-metal transition.

To better understand this behaviour, we studiedthe magnetic excitations by inelastic neutronscattering. The results demonstrate that out-of-plane interactions are comparable to the in-plane interactions, in contrast to the cuprate(high temperature superconductor) layeredcompounds which have the same structure. It istherefore considered that this strong out-of-plane bonding together with in-plane bonding,explains the high transition temperature,structural stability, and intermediate spin state.

The unusual properties of SrFeO2

0 2

Temperature (K)

Zero field cooled

λ (µ

s-1 )

0.020

0.025

0.030

0.035

b

c

a

0 1 2 3

Wavenumber Q (Å-1)

T=5K

Ener

gy (m

eV)

Inte

nsit

y(m

barn

meV

-1 s

r-1

per

Fe)

4 50

20

40

60

80

E=45 meV

1.7 2.1 2.5Wavenumber Q (Å-1)

Inte

grat

ed in

tens

ity

(a.u

.)

2.9

12

10

8

6

4

2

0

10030

20

10

0

Fe2+

Sr2+

O2-

a

cb

(a)

(b)

FeO2 plane

FeO2 plane

AD Hillier, J Quintanilla(ISIS), R Cywinski(University ofHuddersfield)

Contact:

Dr Adrian Hillier,adrian.hillier@stfc.ac.uk

Dr Jorge Quintanilla,jorge.quintanilla@stfc.ac.uk

Further reading:

AD Hillier et al., PhysRev Lett 102 (2009)117007

K Tomiyasu (TohokuUniversity, Japan),H Kageyama,Y Tsujimoto, T Watanabe,K Yoshimura (KyotoUniversity, Japan),JW Taylor (ISIS), A Llobet,F Trouw (LANSCE, USA),K Kakurai (JAEA, Japan),K Yamada (TohokuUniversity, Japan)

Contact:

Dr K Tomiyasu,tomiyasu@m.tains.tohoku.ac.jp

Crystal structure of LaNiC2 and temperature dependenceof its electronic relaxation rate, λ, showing magneticfields appearing at the superconducting criticaltemperature (dashed line).

(a) Crystal and magneticstructure of SrFeO2. (b)Inelastic neutronscattering intensitydistribution in (Q,E) spacemeasured at 5 K.

17

HIG

HLIG

HTS

OF ISIS SC

IENC

EISIS 2009

Bonding and magnetismin cuprates

The most sensitive tests of models for themagnetic interactions in materials come fromdetailed measurements of the magneticfluctuations. Inelastic neutron scattering directlyyields such data. The information can beseparated into two parts: one part based on thespin density, and another which containsinformation on the spin-spin interactions.

The two components have beenunambiguously separated in the one-dimensionalcuprate chains in Sr2CuO3. The strength of themagnetic interactions in the cuprates arises fromthe strong mixing (hybridisation) of the copperelectron orbitals with those of the oxygen atomswhich lie on the line joining adjacent coppersites. Strong copper-oxygen hybridisation willalter the spin density from its normally assumed

form in cuprates. This effect has generally beenignored in the analysis of high temperaturecuprate superconductors – yet this experimentshowed that it fully accounts for a threefolddiscrepancy in intensity between theory andexperiment in a simple cuprate where the theoryshould otherwise be exact.

The recent discovery of superconductivity inseveral iron- and arsenic-based compounds withcritical temperatures (TC) as high as 55K hascaused great excitement because they are thefirst non-copper-based high-TC superconductors.Just like the cuprate superconductors, they areformed by doping a layered parent material, andthere is strong evidence that magnetism has acentral role in the mechanism responsible for thesuperconductivity. There are, however, manydifferences, and researchers are using a gamut ofexperimental probes to unravel the origins of thesuperconductivity in these materials.

Experiments performed at ISIS are making asignificant impact. Muon measurements fromSmFeAsO1-xFx showed enhanced magneticfluctuations near the superconducting transition,and have revealed a region of coexistingsuperconductivity and iron magnetism. Theexistence of a magnetic resonance that appears

only in the superconducting phase ofBa0.6K0.4Fe2As2, one of another family of ironpnictides, and which is strongly reminiscent of thecuprate superconductors, was discovered onMerlin. The bandwidth of the spin fluctuations ofparent materials BaFe2As2 and CaFe2As2 havebeen measured on Merlin and Maps, revealingexcitations that extend to almost 200 meV. Suchmeasurements help in enabling a detailed modelof the magnetic behaviour to be produced. Finally,examples of structural studies are those on theoxygen-free iron pnictides LiFeAs and NaFeAs,which show superconductivity without doping.

Structure of LiFeAs (Pitcher et al); spin waves in CaFe2As2from magnetic exchange parameters measured on Merlin(Zhao et al); phase diagram of SmFeAsO1-xFx (Drew et al).

Iron pnictide superconductors: the impact of ISIS

0

0

1

2

1

20 0.10 0.20

F doping

TcTmagTsTSm

Tem

pera

ture

(K)

0.30

E (meV)

H (r.l.u.)

K (r.l.u.)

200

100

0

20

40

60

80

100

120

140

Staticmagnetism Superconductivity

A Walters (UCL and ISIS),TG Perring (ISIS andUCL), IA Zaliznyak(Brookhaven NationalLaboratory, USA)

Contact:

Toby Perring,toby.perring@stfc.ac.uk

Igor Zaliznyak,zaliznyak@bnl.gov

Further reading:

AC Walters et al.,Nature Physics (2009)doi 10.1038/nphys1405

Further reading:

A Christianson et al.,Nature 456 (2008) 930;RA Ewings et al., PhysRev B 78 (2008)220501(R); J Zhao et al.,Nature Physics 5 (2009)555; S Diallo et al., PhysRev Lett 102 (2009)187206; AJ Drew et al.,Nature Materials 8(2009) 310; MJ Pitcheret al., Chem Comm.2008 5918; DR Parker etal., Chem Comm (2009)2189

Copper ions (centres of the square plaquettes) formisolated chains in Sr2CuO3. The plots show calculated spindensity isosurface (left) and that for an isolated Cu d-orbital.

18

A variety of technologies – man-made and natural!

ISIS 2009H

IGH

LIGH

TSO

F ISIS SCIEN

CE

Catalysts revealed

Heterogeneous catalysis (catalysis where thecatalyst is in a different phase from the reactants– e.g. a solid catalyst and gaseous reactants) is akey economic driver in advanced nations. It isintegral to processes that range from crude oilrefining to fine chemical and pharmaceuticalproduction. Knowledge of the adsorbed specieson the surface of a heterogeneous catalyst is anessential component in understanding andoptimising a catalyst’s performance. Realcatalysts are generally nanocrystalline and thereare no experimental methods available forstructure determination of hydrogenousadsorbed species on such materials. We haveused neutron diffraction to show that it ispossible to obtain structural information foradsorbed hydrogenous species on real catalystsas opposed to idealised systems under ultra-highvacuum. Bond distances are directly obtainablefrom the experimental data and the methodworks at room temperature in the presence of

1 bar of reactive gas. The method is completelygeneral: it is applicable to any heterogeneouscatalyst whether amorphous or nanocrystalline,a metal or an oxide.

Spiders and insects have achieved what manyindustries and labs yearn to accomplish: thecontrolled assembly in water of large proteinsinto high performance fibres, all at ambienttemperature and pressure.

The formation of silk fibres by both spidersand silkworms is characterised by a conversionof disordered proteins to sheet structures (knownas β-sheets), followed by assembly into fibres.

It has been hypothesised that the interplay ofwater and silk proteins’ structural flexibility is keyto this transition. To test this hypothesis, we haveused quasi-elastic neutron scattering to investigatethe effect of hydration on silk protein dynamics.

During the experiment we monitoredsimultaneously the evolution of structure β-sheet crystallinity) and polymer chaindynamics with increasing temperatures. Wefound that low and high hydration levels preventstructural conversion, whereas intermediatewater content promotes β-sheet conversion.

The results suggest that a clever control oflocal fluctuation may be the key to enablingand/or inhibiting silk protein conversion andconsequently their assembly into fibres.

(a) Effect of increased hydration on the bulk motion(mean square displacement) of silk proteins films. (b)Neutron diffraction spectrum taken before (black) andafter (red) conformational change. The Bragg reflection at4.3 Å is evidence of regular spacing between the strandsof the protein sheet structures.

Spinning a story: silk at the molecular level

P Albers (AQura,Germany), SF Parker,DT Bowron, S Imberti,AK Soper, K Refson (ISIS)

Contact:

Dr SF Parker,stewart.parker@stfc.ac.uk

Further reading:

SF Parker et al, AngewChemie, submitted.

C Dicko, I Diddens(Oxford University),AE Terry, MTF Telling(ISIS), F Vollrath (OxfordUniversity)

Contact:

Dr Cedric Dicko,Cedric.dicko@zoo.ox.ac.uk

Further reading:

C Dicko et al.,Biomacromolecules 9(2008) 216

-250 -200 -150 -100 -50 0 50 100

Temperature (°C)

d (Å)

<u2

>A

rbit

rary

inte

nsit

y

0

0.05

0.10

0.15

0.20

Silk humidSilk intermediateSilk dry

(a)

(b)

2.5 3.0 3.5 4.0 4.5 5.0 5.5

25

30

35

40

0 1 2

Distance (Å)3 4

-0.1

0.0

0.1

ΔD

(R)

0.2

Determination using Sandals of the surface structure ofhydrogen adsorbed on Raney nickel, a commonly usedhydrogenation catalyst. The arrows highlight the Ni–Hdistance of 1.68 Å and the H·····H distance of 2.54 Å inboth the experimental data (blue) and an ab initiocalculation (red).

19

HIG

HLIG

HTS

OF ISIS SC

IENC

EISIS 2009

How do molecular crystals form?

How does the ordering in a crystal arise from theinteractions present? Solving the structure showswhat the structure is, but not how it arises. Suchinformation is crucial in trying to predict crystalstructure from the chemistry of the molecule, along-held aim in pharmaceutical research. Theinfluence of a molecule on the positions of itsneighbours results in broad scattering features ina neutron diffraction pattern known as diffusescattering. By modelling this scattering it ispossible to determine the key molecularinteractions and cooperative molecular motionsand how these lead to the ordering of themolecules. We used diffuse scattering measuredon SXD to examine the intermolecularinteractions in deuterated para-terphenyl, C18D14(D means the hydrogen has been replaced by itsheavier isotope, deuterium). It was found thatintramolecular and intermolecular interactions,and the molecules themselves, can be thought ofas acting as nanoscale mechanical linkages.

This work shows that we can use the analysis ofdiffuse scattering to build up a picture of howmolecular interactions lead to molecularordering.

In April 2009 the Front End Test Stand (FETS)came to life when the ion source produced itsfirst beam. FETS is being developed as a newhigh power injector for the particle acceleratorsof the future. It will produce a perfectly chopped50 Hz ,60 mA, H– beam at 3 MeV with a 10%duty factor. Its applications are many and includeISIS upgrades, a neutrino factory and nuclearwaste transmutation.

FETS is a collaborationbetween STFC, ImperialCollege, Warwick University,The University of the BasqueCountry and Tekniker. Itconsists of a high current H–

ion source, a three-solenoidmagnetic Low Energy BeamTransport (LEBT), a 324 MHz,3 MeV, 4-vane RadioFrequency Quadrupole(RFQ), a very fast beamchopper and acomprehensive suite ofdiagnostics.

The ion source and laser diagnostics havebeen commissioned, and the LEBT will now beinstalled, followed by the RFQ and chopper.

Members of the FETS collaboration after the first beamwas produced.

Driving future accelerators: first beam for the FETS project at ISIS

DJ Goossens (AustralianNational University),MJ Gutmann (ISIS)

Contact:

DJ Goossens,goossens@rsc.anu.edu.au

Further reading:

DJ Goossens andMJ Gutmann, Phys RevLett 102 (2009) 015505

M Bates, MA Clarke-Gayther, DC Faircloth,DJS Findlay, T Knott,SR Lawrie, AP Letchford,M Perkins, P Romano,M Westall, M Whitehead,P Wise, T Wood (ISIS),FJ Bermejo (Bilbao, Spain),J Lucas (Elytt Energy,Madrid, Spain), J Alonso,R Enparantza (FundaciónTekniker, Elbr, Spain),SMH Al Sari, S Jolly,A Kurup, DA Lee,P Savage (ImperialLondon), J Pasternak,JK Pozimski (ImperialCollege London, ISIS),C Gabor, C Plostinar(ASTeC), JJ Back (WarwickUniversity)

Contact:

Dr Dan Faircloth,dan.faircloth@stfc.ac.uk

Further reading:

DC Faircloth et al.,Proceedings of PAC09Vancouver, April 2009

(a)

(b)

Maps of diffuse scattering in the (a) hk0 and (b) h 12l planesof para-terphenyl. Key features that relate to themolecular ordering have been highlighted.

20

ISIS users at work

ISIS 2009ISIS

USERS AT W

ORK

▲ Xiubo Zhao, Donghui Jia and FangPan (Manchester University) lookingat their Surf data during studies ofthe effect of hydrophobic chainlength on the interfacial structure ofpeptide surfactants. 09EC2736

Lorna Dougan (Leeds University)loading her sample for Sandalsstudies of hydrogen bonding inglycerol at low temperatures.09EC2771

▲ Craig Brown (NIST, USA) preparing to study hydrogeninteractions in metal-organic framework structures onTosca. 09EC2738

▼ Nikolay Vasiler (Lancaster University) at ISIS during hisneutron reflectometry studies of a 3He layer adsorbed onto liquid 4He on Crisp. 09EC2732

▲ Helena Alberto and Joao PedroDuarte (Coimbra University,Portugal) preparing the EMU muonspectrometer to investigatephthalocyanine organicsemiconductors. 09EC2746

▼

21

ISISU

SERS AT WO

RKISIS 2009

Stefan Knupfer (Heriot WattUniversity) preparing his sample forresidual stress characterisation oflaser-formed aluminium plates onEngin-X. 09EC2780

▲ Neil Hamilton, Andrew McFarlaneand Ian Silverwood (GlasgowUniversity) using MAPS to investigatereactions relevant to Fischer-Tropschcatalysis used for hydrocarbonproduction. 09EC2742

▲ Fsolt Gercis, Alex Barcza, Karl Sandeman and Rantej Bali(Imperial College London andUniversity of Cambridge) usingGem to study giantmagnetostriction in CoMnSi.09EC2739

Alessia Giuliani (Universitàdegli Studi Roma Tre, Italy)using Sandals for structuralcharacterisation of waterconfined in an MCM silicamatrix. 09EC2758

Sue Kilcoyne(Salford University)loading a sample onMuSR for studies ofmoment stability andspin fluctuations inferromagnetic Au4V.09EC2774

▼

▲

▲

22

ISIS 2009D

EVELO

PMEN

TSA

ND

EVEN

TS

Developments and events

23

DEV

ELOPM

ENTS

AN

D EV

ENTS

ISIS 2009

Section 2Developments and events

Development at ISIS is a continuousprocess, driven in response to the changingneeds of the user community and tomaintain ISIS as a world-class neutron andmuon source. Evolution of existinginstruments and construction of new ones,together with advances in neutron andmuon techniques, provide freshopportunities for materials investigations.

The past year has seen first experiments onSecond Target Station instruments, a verysignificant project achievement. Othertechnique and instrument developments toenable new science are also described,together with developments of theaccelerator and target systems.

Also highlighted are some of the manytraining and education activities run by ISISover the past year – from courses andworkshops for the user community toprojects run with schools and professionaldevelopment of facility staff.

24

Second Target Stationinstruments shine!

This year has seenfirst science beingdone on SecondTarget Stationinstruments. Andthe instruments aremore than living upto expectations!

ISIS 2009SECO

ND

TARG

ET STATIO

N IN

STRUM

ENTS SH

INE!

λ (n

m)

-2.0 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0Coil current (A)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

▼ Nick Webb, Rob Dalgliesh and RichardColeman (ISIS) with Offspec. 08EC4980Inset: Offspec spin-echo data from a gratingsample.

Inter science: the first Second Target Stationexperiment

Bob Thomas (OxfordUniversity) using theInter reflectometerduring the firstexperiment on theSecond Target Station.09EC2092

25

On 26 May 2009 Inter opened itsdoors to the first TS-2 users: JeffPenfold (ISIS) and Robert Thomas(Oxford).

Surfactant and polymer-surfactant mixtures canspontaneously form multilayerstructures at interfaces. Suchsystems are relevant to areas suchas soft lubrication, encapsulation,surface delivery and retention, andin understanding bio-lubrication(for example, lung surfactants).

This experiment used the powerof Inter to explore the kinetics offormation and dissolution of suchmultilayer structures. A speciallydesigned trough allowed thedisassembly of the surfacestructure to be followed as itprogressed in real time.

Inter enabled measurements tobe made at time intervals as shortas two minutes (with sub-minutemeasurements predicted for thefuture).

These results demonstrate theability to follow the kinetics ofsuch processes and open up anexciting new area of science thathas been hitherto inaccessible.

SECON

D TA

RGET STA

TION

INSTRU

MEN

TS SHIN

E!ISIS 2009

Refl

ecti

vity

0.05 0.1Momentum transfer Q (Å-1)

0.2

10-5

10-4

10-3

Det

ecto

r ch

anne

l

200 400 600 800 1000Time channel

50

-7

-6

-5

-4

-3

-2

-1

100

150

200

OffspecOffspec has successfullydemonstrated several of its modesof operation including spin-echosmall angle neutron scattering andspin-echo resolved grazing incidencescattering. The complex series ofspin manipulation (precession)devices which have been developedat TU Delft are working well andhave allowed Offspec to accesslength scales that were previouslyunobtainable in traditionalreflectometry. Commissioning of theremaining modes is making strongprogress alongside the start of theuser programme.

Polref Polref is now into its commissioningprogramme. The reflectometer incorporatesa polariser guide field and spin analyser formagnetic studies. This will be complementedby the imminent arrival of a threedimensional 2 T vector cryomagnet.

Inter reflectivity data from a 2 mM sodiumdodecyl benzene sulfonate (anionicsurfactant) solution in 2 mM CaCl2. Thecharacteristic Bragg scattering associatedwith surface multilayers can be seen,together with its decrease in visibility as thesurface structure disassembles towards asurface monolayer.

Inset: spontaneous formation at an interfaceof a multilayer structure by a polymer-surfactant mixture. Courtesy Jennie Tucker of J T Designs

View of the Polref spin analysingsystem, with Polref commissioningdata from a Ni on Si line gratingas inset.

26

Second Target Stationinstruments shine!

Sans2dFirst neutrons were delivered to the Sans2d sampleposition at the end of March and then on 30 May, to themain detectors in the 13m long, 3.25m diameter vacuumtank. Results are very encouraging and suggest that theincrease in flux over the existing Loq instrument is asexpected. As a first user experiment, Prof Rob Richardson(Bristol) has studied the temperature dependence of liquidcrystalline polymer Bragg peaks. The data demonstratethe extremely wide simultaneous Q range available onSans2d with the two 1m square detectors.

WishThe Wish instrument opened its shutter for the first timeat the end of March, and has run with a liquid methanemoderator in the following cycles. Wish has beenproducing high-quality data from the start, with thedoubly-focusing elliptical guide generating the expectedhigh count rate. The detector array on one side of theinstrument is fully operational, with the 100,000 pixels,each with 5,000 time bins, generating 1.6 Gb of data perrun. Calibration of the detector linear positions iscurrently underway and is the final milestone before theuser program starts. A 14 T magnet has been deliveredand is soon to be tested on the instrument.

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a) First diffraction pattern obtained on Wish, from a Si sample with theliquid methane moderator. b) Debye-Scherrer cones on the cylindricaldetector array. c) First experiment with a single crystal of BaMnF4(sample courtesy of Dr. Bombardi, Diamond Light Source).

Initial Sans2d data from a liquid crystalline polymer.

View of the two detectors inthe Sans2d vacuum tank.

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LETLET is a chopper spectrometer with π steradians of detector coverage that is almost gap-free by virtue of usingthe world’s first 4 m long position-sensitive detectors. A complex chopper system involving 7 disks ensures themaximum flux with a clean beam and full control of the energy resolution. LET opened its shutter for neutronsfor the first time on the 5 August. Initial measurements show a neutron flux which is close to that predicted bysimulations. Results from the detectors are excellent with a 20 mm position resolution. Over the coming monthsthe remaining chopper housings will be put in place and more detectors added.

John Hogg (ALSTEC) working inside the LET vacuum tank. The frames that can be seen on the back will support a wall of 4 m long detectors.08EC4125

The Nimrod diffractometer has begun commissioning.Eighteen ZnS scintillator neutron detectors arecurrently installed at scattering angles 5°-40°, and alow angle bank of 756 detectors cover the angle range0.5°-2°. Initial results are extremely encouraging, withdata being observed which arguably gives Nimrod thewidest Q range accessible in a single experiment ofany diffractometer in the world.

Normalised diffraction data measured on Nimrod for severalamorphous silicas with a range of pore sizes, compared to pure silicaglass. The very large rise in scattering of the porous silicas at low Qcompared to pure silica is caused by their different pore structurescombined with surface scattering effects at the lowest Q values.

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As well as largerinstrumentdevelopments,advances in techniquesor in otherexperimentalequipment also enablenew science to bedone using neutronsand muons at ISIS.

New science from instrument and technique advances

Making supercritical CO2 thicker

ISIS now has the capability to make simultaneous neutron and Ramanscattering measurements at temperatures between 1.5 and 450 K. Ramanmeasurements with a resolution of 1-4 cm-1 can be made over a widewavelength range (100-3200 cm-1)at the same time as a variety ofneutron scattering measurements.The new equipment has been usedfor inelastic neutron scattering andneutron diffraction in conjunctionwith Raman for studies of theglobular protein lysozyme (MAAdams et al, Applied Spectroscopy63 (2009) 727). 500 1,000 1,500

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A new facility based on neutron resonance capture analysis (NRCA) and neutronresonance transmission (NRT) has been installed at ISIS. This is part of the EUAncient Charm project, which aims to develop science research techniques forcultural heritage objects. NRCA and NRT use epithermal neutrons for non-destructive bulk analysis and for mapping of elements in archaeological objects.The equipment can potentially be usedalso for cross section measurements ofreference materials and nuclear materials.This work is a collaboration between GGorini and E Perelli Cippo (Milano-Bicocca,Italy), P Schillebeeckx (IRMM Geel,Belgium), and W Kockelmann andE Schooneveld (ISIS).

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A new Thar pressure cell has been used to great effect onLoq. The improved efficiency of the cell has allowedEastoe et al., (Bristol), to study designer, low-costhydrocarbon surfactants as fluid modifiers for supercriticalcarbon dioxide (sc-CO2). Small angle neutron scatteringhas shown these surfactants form hydrated reversemicelles in sc-CO2 which could be used to unlock the fullpotential of CO2 as a green solvent (MJ Hollanby et al.,Angew Chem Int Ed 48 (2009) 4993).

Simultaneous neutron and Raman scattering

Spectroscopic neutron analysis facility for archaeological objects

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Sarah Rogers (ISIS) preparing the new Loq pressure cell. 08EC2300The graph shows small angle scattering profiles of dry (blue circles)and hydrated micelles (yellow circles) stabilised in sc-CO2 by thesurfactant TC14. The scattering obtained (triangles) when using thesurfactant AOT4 is also shown for comparison. The inset shows aschematic representation of a hydrated reverse micelle in sc-CO2.

▼ Mark Adams and Stewart Parker (ISIS)setting up the Raman spectrometer forsimultaneous neutron measurements.09EC1880

The graph shows inelastic neutronscattering spectra of drylysozyme at (a) 293 K and(b) 10K and forcomparison (c) theRaman spectrum at10 K. The spectra arevertically offset forclarity.

The recent development of a compactvariable temperature insert for the Paris-Edinburgh pressure cell has allowed study ofthe high-pressure, high-temperaturestructural behaviour of the widely usedexplosive RDX. The structures of three formsof this material have been characterised forthe first time. Information obtained underthe extreme conditions typical of thoseexperienced during explosive decompositionis very important for modelling theperformance and characteristics of energeticmaterials (Prof C. Pulham, Edinburgh, andDr W Marshall, ISIS).

Putting the squeeze on energetic materials

The Paris-Edinburgh pressure cellequipped with the compact variable-temperature insert. The cell allowedobservation of the molecularconformation change when the alpha-form of RDX is transformed into theepsilon-form at high pressure (5 GPa)and temperature (500 K).

A polarised 3He cell hasbeen developed at ISIS forneutron spin flipping andanalysis. The 3He analyserproduces a better signal-to-noise ratio compared with asupermirror analyser for off-specular reflectivity data.Here we see a comparisonbetween polarised neutronscattering data taken onCrisp with the 3He cell andwith a supermirror analyserfrom a 2.5μm pitch Nigrating.

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X-ray diffractionfor disorderedmaterialsThe ISIS Disordered Materials Groupare now running a laboratory X-raydiffractometer, optimised forstructural studies of liquids, glassesand disordered crystals. The aim is toprovide X-ray diffraction data whichwill complement the data obtained

Detectors, computing and electronicsfor instrument developmentsNew instrument developmentsprovide a variety of challenges forthe ISIS Detector, Computing andElectronics groups.

For example, the new TS-2reflectometers have complexmotion control environments andrequire many motors to be movedprecisely and in harmony foroptimal experimental conditions.Control software has had to bedeveloped, using the NationalInstruments LabVIEW package.

A flow-throughquartz cell with gasflow control systemA flow-through quartz gas cell, togetherwith its complementary flow control andmonitoring system, has been developed byISIS in collaboration with ChalmersUniversity of Technology, Sweden. Thisequipment allows neutron powderdiffraction data to be collected onsamples at temperatures up to around1300 K when exposed to mixtures of O2,Ar, CO2 and CO. For example, the cell hasbeen used to probe thecrystal structure of CeO2-δ,which has applications insolid oxide fuel cells, as afunction of oxygen partialpressure.

Hifi is a new high-field muon spectrometer incommissioning at ISIS. This year has seencompletion of all major project elements,including delivery of the main 5T magnet(seen here being installed). First experimentsare scheduled for the end of 2009. 09EC2912

New science from instrument and technique advances

▲ Freddie Akeroyd (ISIS) developing dataacquisition software for ISIS instruments.08EC4166

The flow through quartzgas cell, together with theevolution of the neutronpowder diffractionpattern of CeO2-δmeasured at 1273K ondecreasing oxygen partialpressure (S Hull et al.,J Sol Stat Chem (2009)).

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on the group’s neutron diffractometers, Gem,Nimrod and Sandals, by virtue of the differentcontrasts for the two radiations. Currently thediffractometer is nearing the end ofa period of scientificcommissioning, after whichit will be available forapproved disorderedmaterials experimentsby ISIS users.

Polaris upgradeA major upgrade programme for the Polarisdiffractometer is currently in progress. This project,funded by STFC with contributions from Spanish andSwedish partners, will provide increases in count rateof between 4x and 20x (depending on the scatteringangle), coupled with significant improvements to theinstrumental resolution at backscattering angles.Installation of the new instrument is planned for 2010.New sample environment equipment is also beingdeveloped, with funding from the Swedish researchcouncil, including in-situ cells for studies ofelectrochemical processes and time-resolvedinvestigations of samples under controlled atmospheres.

The Wish instrument has been a different sort ofchallenge. Its 389,125 pixels were too numerousfor a single data acquisition crate and so asystem for parallel access to acquisitioncrates was developed. The data volumesand memory requirements involvedwere also reaching the limits for32bit operating systems, so a 64bitversion of the acquisitionsoftware has been developed.

The first operational detectorpanel for the Wish instrument aftertesting, with members of the ISISdetector group involved in itsproduction: Nigel Rhodes,Davide Raspino, ErikSchooneveld and MattNorth. 08EC4976

▲ One of the newPolaris detectorbanks, with aschematic of thecompleteinstrument.

Nattapol Laorodphan (Warwick University)preparing the new X-ray diffractometer. 09EC2792

Kathryn Baker(ISIS) working onexperimentcontrol softwarefor Inter. 08EC4175

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Accelerator andTarget developments

Higher beam currents at ISIS!Sustained beam currents of 230 μA have beenproduced during ISIS run cycles this year, meaning thatISIS can deliver the same number of protons to TS-1whilst also supplying TS-2. The secret is reducingbeam loss in the synchrotron.

The performance of the ISIS accelerators is limited by the amountof beam that is lost during the acceleration cycle. Simulation studies(top) can be compared with measured (bottom) beam loss in thesynchrotron to better understand the causes of beam loss.

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▲ The three beamline choppers for Wishready for installation, with team Mike Brind,Paul Chorley, Erik Johnson, Peter Galsworthyand Adam Davis (ISIS). 09EC1003

Robin Burridge (ISIS) inspectinga newly-installed cabinet ofradiation monitors for TS-1’sservices area. The monitor headsare positioned around the servicestrolley to detect any changes inbackground levels and tohighlight any fluctuations withinthe D20 water cooling circuitsduring operation. 09EC2045

▼ The Second Target Station target, reflector andmoderator assembly being prepared. 08EC3270

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▲ The ISIS synchrotron dual harmonic system – which consistsof four new accelerating cavities inserted into the accelerator –enables beam intensity to be increased by reducing protonbeam loss. The figure shows beam loss with and without thedual harmonic system in operation.

A dual harmonic accelerating cavity in theISIS synchrotron. 09EC1467

Dan Faircloth (ISIS) inspectsISIS ion sources. An ion sourcetypically lasts 20 to 30 daysbefore needing to be replaced,and a collection of tensources, which are made atISIS, is kept ready to be used.08EC4248

▲ ISIS Duty Officer Tom Noonekeeping a watchful eye onaccelerator parameters. 08EC4205

Final preparations being made on the newtungsten neutron target and reflectorassembly prior to its first operational run inMay. This work was undertaken within theremote handling cell via two pairs ofmaster/slave manipulator arms positionedeither side of the target and moderatorassembly. 09EC2037

▲ Mike Ruddle (ISIS) in front of new buffertanks for the first target station cryogenicmoderators. Each has a capacity of 2000 l.Five are used to hold methane following thedaily transfer, with the sixth for any gasvented from the hydrogen system. 09EC2030

Steve West (ISIS)inspecting thenew synchrotronmain magnetpower supplychokes duringinstallation inMay. 09EC2456

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A farewell to old friends!As new TS-1 and TS-2 instruments come on-line, ISIS bidsfarewell to instruments that are being replaced by thenext generation of spectrometers and diffractometers.This year saw final beam on HET and Prisma after manyyears of sterling service.

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Young engineers help ISIS beam monitoringAs part of the Engineering Education Scheme (England), theaccelerator diagnostics section worked with ateam of A-Level students from Kennet School,Thatcham, to build a new calibration systemfor the ISIS split electrode positionmonitors. The new system usesstepper motors to move a copperpipe carrying a signal around themonitor. It has significantlydecreased the time it takes tocalibrate a monitor as historicallythis has been done manuallywithout the aid of motors.

Students from Kennet School with the newsplit electrode position monitors. 09EC1932

ISIS neutron training courseThe annual ISIS neutron training course took placein February. This course is designed to providepractical experience of setting up and runningneutron scattering experiments on a wide variety ofinstruments at ISIS for researchers new to neutrontechniques. This year 24 participants came from UKuniversities – mainly postgraduate students andsome post-docs. After an initial day of talks, theparticipants conducted real neutron experimentsand then learnt data analysis techniques. Judgingfrom the course feedback, the training was well-appreciated by all the participants – although manyof them felt that the course was too short! You cannever get enough of a good thing.

▲ Aziz Daoud-Aladine (left) supervises Philip Merchant (UCL)loading a single crystal sample on SXD. (left to right) Chris Lester(Bristol), Dan Porter (Royal Holloway), Pabitra Biswas (Warwick)and Dean Whittaker (Bath) look on. 09EC2222

Professor Keith McEwen and Dr HelenWalker (University College London) andDevashibhai Adroja(ISIS) explored thecrystal field levelsin the rare earthtetraboridesduring the finalexperiment onHET in October.08EC4348

▼ (left to right) Pascal Manuel (ISIS), Carla Andreani (University of RomeTor Vergata, Italy), Uschi Steigenberger, Martyn Bull and Steve Payne(ISIS) celebrate Prisma’s successes following the final experiment on theinstrument. 08EC5089

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▼ ISIS held an open morning in August to enable staff and contractors to bringfriends and family to see the new Second Target Station building and to learnabout the facility. Here, Chris Frost (ISIS)is wowing visitors with sciencedemonstrations. 08EC3812

Delegates at the joint Daresbury Laboratory and Rutherford AppletonLaboratory Accelerator workshop held at RAL in January. 09EC1954

▲ The 3rd Empirical Potential Structure Refinement Workshop was organised by the ISIS DisorderedMaterials Group at RAL and Cosener’s House in April. 09EC2601

▲ ISIS staff were involved in an exhibition at the Royal Society on‘Accelerators everywhere, from the big bang to curing cancer’. From leftto right: Riccardo Bartolini (Diamond and JAI), Phil Burrows (JAI), Rolf-Dieter Heuer (Director General of CERN), Emmanuel Tsesmelis (CERN),Suzie Sheehy (JAI) and John Thomason (ISIS).

▲ Keith Refson (CSED, STFC) demonstrating software during thecomputational methods workshop. 08EC4543

Workshop in computationalmethods for the exploitationof vibrational spectraThis workshop was run at RAL by ISIS in November2008 and attended by 29 participants. Its aims wereto show how computational methods can be usedfor the exploitation of vibrational spectra in studiesof molecular motions and dynamics. The course waslargely practical and involved exploring theapplications of state-of-the-art software(Gaussian03, DMOL3, CASTEP). Half of theparticipants were not regular neutron users, andinterest in the workshop was high.

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▲ ‘Other People’s Business’ events are a good way for STFC staff to learn about what goes on in other parts of the organisation. Here, John Thomason(left) is showing a group around the ISIS synchrotron. 09EC1026

ISIS has made the news in a number ofways this year! This includes a varietyof specialised press – for example,Plant Engineer magazine featured anarticle on the ‘extreme plant’ operatedroutinely by ISIS; ISIS Engineers HannaFikremarium, Chris Benson and SeanHiggins featured in ProfessionalEngineering, published by the Instituteof Mechanical Engineering; and theISIS timing and control systems werefeatured in Pinpoint, the magazine forthe Location and Timing KnowledgeTransfer Network. Facility DirectorAndrew Taylor has featured in a PublicLife article in the Daily Telegraph, andbeen interviewed about the Second

Target Station project on Radio 4’s‘Today’ programme. ‘Metro’ newspaperdescribed ISIS as a ‘21st CenturyWonderland’ in their feature article inMay!

A year around ISIS

▲ Studies of the role ofhydroxybenzoate in surfactantself assembly. Neutronscattering with deuteriumlabelling by the OxfordIsotope Facility has shownthat the ortho form ofhydroxybenzoate is partiallylocated in the hydrophobicregion of the surfactantinterface (left), whereas thepara hydroxybenzoate is inthe hydrated head groupregion (right). J Penfold et al.,Langmuir 20 (2004) 8054.

The Oxford Isotope Facility is funded by STFC and is based in the Physical andTheoretical Chemistry Laboratory in Oxford. It aims to provide deuterium labelledmaterials for the UK neutron scattering community for experiments at ISIS, ILL andelsewhere.

Contrast manipulation, by H/D isotopic substitution, is the main feature thatmakes neutron scattering an attractive and unique tool for the study of soft matter.Recent examples include a detailed study of the effects of hydroxybenzoate on theself assembly of surfactant CTAB. Deuterium labelling enabled the locations of thehydroxybenzoate at the surfactant interface to be deduced.

The Oxford Isotope Facility provides small molecule deuteration, materials such asfatty acids, alcohols, bromoalkanes, and a wide range of surfactants. Further detailscan be obtained from Jeff Penfold at ISIS (jeff.penold@stfc.ac.uk) or Bob Thomas atOxford (robert.thomas@chem.ox.ac.uk).

Oxford Isotope Facility

▼ Dr Martyn Bull, Head of ISISCommunications, being interviewed by sciencejournalists visiting ISIS in July. 09EC2503

ISIS in the media

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ISIS PeopleCongratulations are due to a varietyof ISIS staff this year. Tim Broome,wh