annual report 2007 forschungs-neutronenquelle heinz maier ... · 5 – 7 february 2007:...

ANNUAL REPORT 2007Forschungs-NeutronenquelleHeinz Maier-Leibnitz (FRM II)

Title image: View on the FRM and FRM II on the “Lange nacht der Wissenschaften”

Contents iii

Contents

Directors’ report 2

The year in pictures 4

I Instrumentation 9

1 Central services and reactor 101.1 Detector and electronics lab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.2 HELIOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.3 Sample environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.4 Reduced enrichment for the FRM II core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2 Diffraction 222.1 SPODI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.2 HEIDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.3 POLI-HEIDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.4 RESI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292.5 KWS2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312.6 STRESS-SPEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332.7 REFSANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362.8 NREX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3 Inelastic scattering 413.1 J-NSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413.2 MIRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443.3 PANDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463.4 SPHERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483.5 RESEDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503.6 DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523.7 PUMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.8 TOFTOF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4 Nuclear physics and applied science 614.1 Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614.2 MEPHISTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.3 PGAA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664.4 MEDAPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694.5 NEPOMUC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

II Scientific highlights 73

5 Soft matter 745.1 Separation of coherent and spin-incoherent scattering by polarization analysis . . . . . . . . . . . . . 745.2 Time-of-flight grazing incidence small angle neutron scattering . . . . . . . . . . . . . . . . . . . . . . 76

6 Condensed matter 786.1 Magnetization in ferromagnetic EuO thin films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 786.2 Examination of rat lungs by neutron computed micro tomography . . . . . . . . . . . . . . . . . . . . 806.3 Thermal expansion under extreme conditions at TRISP . . . . . . . . . . . . . . . . . . . . . . . . . . 82

iv Contents

6.4 Investigation of embedded submono-layers in Al using positron annihilation . . . . . . . . . . . . . . 84

III Facts and figures 86

7 Facts 877.1 User office and public relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 877.2 "Fortgeschrittenenpraktikum" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907.3 11th JCNS Laboratory course on neutron scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907.4 Industrial activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917.5 Biannual workshop at Burg Rothenfels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917.6 PLEPS workshop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

8 People 958.1 Committees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958.2 Staff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1018.3 Partner institutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

9 Figures 1069.1 FRM II in the Press . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1069.2 Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Imprint 113

Contents 1

2 Directors’ report

Directors’ report

In 2007 - the 3rd year of itsroutine operation - the Forschungs-Neutronenquelle Heinz Maier-Leibnitz(FRM II) operated for 233 days withfull power (20 MWatt). The originallyenvisaged 5 reactor cycles could notyet be reached, due to a failure of apump in the D2O moderator systemwhich occurred in the course of the10th reactor cycle right at the begin-ning of the year. The repair of thatpump required the painstaking open-ing of the D2O circuit. But with theenthusiastic commitment of our staffand help from the hot workshop ofKernkraftwerk Isar FRM II was able torestart with the 11th reactor cycle ontime.In early spring 2007 the east build-

ing with its large second neutronguide hall was finished and the JülichCentre for Neutron Sciences (JCNS)moved into its offices and labs on topof the guide hall. This all together wascelebrated in an inauguration eventon 9th of May 2007. Step by stepthe first instruments of the JCNS wentinto operation and typical gains in per-formance by factors 10 to 100 areachieved, compared with their per-formance at DIDO, FZ-Jülich. In thiscase gain in performance is definedby increase in flux at the detectortimes increase in resolution. This gainis the result of both, higher flux of theneutron guides at FRM II and a so-phisticated upgrade of each of theinstruments. Two proposal rounds forthe JCNS instruments took alreadyplace in 2007.With its instrumentation for nuclear

and particle physics FRM II partici-pates actively in the excellence clus-ter "Structure and Origin of the Uni-verse". On the other hand the excel-lence cluster is heavily engaged in therealisation of the Ultra Cold NeutronSource at the FRM II.In July 2007 the Federal Ministry

for Education and Science (BMBF) re-newed its engagement in funding in-struments at FRM II. PUMA, SPODI,polarized HEIDI and biological sam-ple environment at RefSANS whichcontinue to be under the patronageof BMBF. Also further funds for threemore instruments or upgrades wereallocated, such as POWTEX, KOM-PASS and automatic sample set-upat StressSpec. The universities incharge of the BMBF instruments areUniversität Göttingen, TU Darmstadt,RWTH Aachen, LMU Munich, Univer-sität zu Köln and TU Clausthal. Someof them are even engaged in severalinstruments.So in 2007, for the first time, lab-

oratory courses for the advancedsemesters of the study of physics atthe Physics Department took place atselected instruments of FRM II. Dur-ing each course a 24-hour hands-on-training on a particular instrumentwas practiced with subsequent evalu-ation of the results.Similar training was conducted

within the annually organized neutronschool of the FZ-Jüich, where duringa one week crash course about 40PhD students from all over Europelearnt the essentials of neutron scat-tering and which was completed by aone week training at the instrumentsinstalled at FRM II.In early 2007 FRM II got the

approval for treating tumors byfast neutron irradiation from theBavarian State Authority for Envi-ronment Protection (Landesamt fürUmweltschutz). This was subse-quently executed by the irradiationof the first patient, sent from TUM’sown clinic. The typical treatment ofa tumor is up to 5 irradiations, eachtreatment taking 60 - 90 seconds ofirradiation time.On October 31, 1957 the

Forschungsreaktor München, bet-

ter known as Atomic Egg, producedits first neutrons. The Atomic Egg be-came Germany’s first nuclear facility.It became the seed of what is now-a-days Germany’s largest campus forscience and engineering. On 31st ofOctober 2007 we celebrated the 50thanniversary of that event by a collo-quium "50 years of neutron researchat Garching - and its future". Beingjust three weeks in office the BavarianMinister President Dr. Günther Beck-stein emphasized the importance ofthe Neutron Research Source HeinzMaier-Leibnitz for the scientific andeconomic development of Bavariaand highlighted its role as a contri-bution of Germany to the EuropeanResearch Area. He renewed the com-mitment of the Bavarian Free State forits largest research facility with greatenthusiasm. "Neutrons are light",with these words Prof. Dr. Dr. h.c.mult. Wolfgang Herrmann, Presidentof the TUM, explained the uniquepotential of science with neutrons.He welcomed FZ-Jülich, which hadtaken in use its new outstation "JülichCenter for Neutron Sciences" at theFRM II short time before. Dr. WaltherHohlefelder, member of the board ofthe electricity producer E.ON spokeabout "The Future of Nuclear Powerin Europe and Germany", a futureclearly decided for Europe, but lessevidently for Germany. In his speech"The neutron, in nuclear and particlephysics" Prof. Dr. Schreckenbach,former Technical Director of FRM II,delivered insight into the beauty offundamental physics with neutrons.These neutrons are a powerful toolfor engineering science and were im-pressively demonstrated by the talk"Industrial research with neutrons" ofProf. Dr. Richard Wagner, Director ofthe Institute Laue Langevin. The col-loquium was finished by an outlookof Prof. Bernhard Keimer, MPI for

Directors’ report 3

Solid State Research on "Correlatedelectron systems, on the way to newmaterials".Obviously FRM II did very well in

2007. So the Bavarian nuclear reg-ulatory authority made a Christmasgift to FRM II. On 19th of December2007 FRM II was authorized to useits single compact core for 60 days,instead of 52 days. In fact this is afurther proof of the extremely conser-vative and reliable design of the FRMII fuel element. The decision itself hasconsiderable impact onto the futureoperation of FRM II. About one fuelelement less is needed per year andconsequently the work load of chang-ing the fuel element is reduced in addi-tion to the reduced nuclear transportsand amount of spent fuel. Also an-nual operating costs will be reducedby maintaining the availability of theneutron source.Further progress has been

achieved in developing high densityfuels for future use in FRM II. Largefuel plates made of UMo particlesembedded in an Al matrix and withan Uranium density of 8g Ucm3 wereirradiated to neutron fluences exceed-

ing the burn-up at FRM II by 50%. Aconservative swelling of these fuelplates at low and medium burn-up isfollowed by a critical increase of thefuel plates thickness for high burn-up.Clearly further R & D has to be donebefore such a fuel can be used inhigh performance research reactors.However, these and other tests haveshown the way to pursuit.Altogether 20 beam hole instru-

ments have been operating by theend of 2007. Another 10 instrumentsare under construction. Finances forthe new instruments are mainly com-ing from FRM II, JCNS and BMBF, butalso from the universities engaged. Aprominent example is the contributionof the excellence cluster "Structureand Origin of the Universe" for theimplementation of the Ultra Cold Neu-tron Source (UCN). As the last ofthese new instruments the UCN willbe taken in operation in 2012.

Excellent science is done at the in-struments of FRM II. An example formany of them is the experiment con-ducted by Christian Pfleiderer, (Sci-ence 316, 1871 (2007)). By means

of resonant spin echo techniques hewas able to measure changes in lat-tice parameters with a 10−6 preci-sion. Part of the beauty of this exper-iment is that this can be done underextreme sample conditions like Mil-likelvin temperatures or high pressureand there is hope to ameliorate theprecision to a 10−7 level.With deepest sympathy we have

to report about the sudden death ofGuido Engelke, former AdministrativeDirector. He passed away on 4 March2008 on a trip through Namibia. InDecember 1994 Mr. Guido Engelkestarted working for FRM II as projectsupervisor. From 1st of January 2002until December 2006 he filled the posi-tion of Administrative Director of FRMII. From the very beginning Mr. En-gelke was in charge of the licensingprocess and the construction of theneutron source. His experience ac-quired during many years world-wideas well as his hard work and dedica-tion were essential for the success-ful commissioning of FRM II. We willcontinue to honour the memory of Mr.Guido Engelke.

Klaus Seebach Winfried Petry Ingo Neuhaus

4 The year in pictures

The year in pictures

22 January 07: Students from the German-French Lycée Jean Renoirin Munich enjoy their visit at the neutron research source (photo: UllaBaumgart).

5 – 7 February 2007: Fortgeschrittenen-Praktikum (Hands-on trainingfor advanced students): Students from the TU Physics Departmentduring the theoretical part of the course together with Prof. Schre-ckenbach, one of the speakers.

9 May 07: Inauguration ceremony of the new East Building providinglabs and offices for staff of JCNS and GKSS: The rainy weather couldnot spoil the cheerful atmosphere of that day.


9 May 07: From right to left: Prof. Dr.-Ing. Th. Hugues, the responsiblearchitect; Mr. Solbrig, Mayor of the town of Garching; Dr. IngoNeuhaus and G. Engelke, Technical respectively former AdministrativeDirector FRM II; Mr. H. Mayer, responsible Building Director, BATUM;Prof. Dr. h.c. mult. Wolfgang A. Herrmann, President of TechnischeUniversität München; Dr. R. Koepke, BMBF; Prof. Dr. Winfried Petryand Dr. Klaus Seebach, Scientific respectively Administrative Directorof FRM II.

9 May 07: Happy about the new premises for the Jülich Centre forNeutron Science (JCNS) – Prof. Dr. Th. Brückel, head of JCNS,(together with Prof. Petry) and Dr. Alexander Ioffe, head of theoutstation JCNS at FRM II.

23 May 07: The spent fuel unit is moved into the neutralization pool.


3 – 14 September 07: Attendees of the 11th JCNS Laboratory Courseorganized jointly by JCNS and FRM II in front of the Jülich neutronspin echo spectrometer (J-NSE).

27 September 07: “Reading in unusual places” – In the neutron guidehall of FRM II the well-known German novelist Asta Scheib readchapters from her book “Sei froh, dass Du lebst” describing feelingsand life in Germany in the fifties and sixties.

27 September 07: Tunes of the postwar period played by the group“Garchinger Pfeiffer” made memories come back.


08 October 2007: The IAEA offers a variety of career chances to sci-entists, explained Catherine Monzel, responsible for recruitment andstaff development at IAEA, during her speech on aims and tasks ofInternational Atomic Energy Agency.

13 October 2007: Open Doors in 2007 - The Long Night of Scienceattracts a large number of persons interested in guided tours andtopics related to FRM II.

13 October 2007: Radioprotection staff is explaining the tools theyneed to fulfil their tasks.


13 October 2007: Dr. Tobias Unruh is showing round children andyouth – a unique opportunity at the Open Doors.

30 October 07: 1st user meeting at FRM II - Scientific discussions ina relaxed atmosphere: Dr. Peter Geltenbort, ILL Grenoble, togetherwith Prof. Böni, Dr. Georgii and Dr. Zeitelhack, FRM II respectivelyPhysics (clockwise).

31 October 07: On a beautiful autumn day the campus of Garchingcelebrated the 50th anniversary of it’s first neutrons with a colloquium“50 years of research with neutrons at Garching and its future”. Dr.Günther Beckstein, Minister President of Bavaria and the President ofTechnische Universität München, Prof. Dr. h. c. mult. W.A. Herrmann,in front of the Atomic Egg, the symbol for the commencement ofneutron research in Germany.

Part I

Instrumentation

10 1 Central services and reactor

1 Central services and reactor

1.1 Detector and electronics lab

I. Defendi1, C. Hesse1, M. Panradl1, T. Schöffel1, K. Zeitelhack1

1ZWE FRM II, TU München

Beside the standard activities con-cerning service and maintenance ofthe detectors installed at the scientificinstruments, two outstanding new de-tector projects distinguished our ac-tivities in 2007. In the following sec-tions we will report on the devel-opment of the new SANS1 detec-tor presently under construction andthe first beam test results of a read-out system for 320×320 individualchannels of a fast, medium resolutionMWPC developed in the frameworkof the NMI3-JRA2 (MILAND) project.

The SANS1 Detector

The new small-angle scattering in-strument SANS1 presently being in-stalled in the neutron guide hall willbe equipped with a 2D-position sen-sitive detector with 1×1m2 activearea, 8mm×8mm position resolutionand 1MHz global count rate capa-bility. Similar to the D22 detector atILL, the detector consists of a lineararray of 1m long position sensitive3He-detectors of type Reuter Stokes

Figure 1.1: Prototype detector consistingof 8 PSDs mounted at TREFF duringthe PSD8+ readout system test

P4-0341-201 (length L = 1m, diame-ter d = 8mm, pHe = 15bar) mountedinside the evacuated flight tube.The individual detectors will be

readout by the PSD8+ readout sys-tem for position sensitive proportionalcounters developed by mesytec[1]. Itconsists of 16 MSPD-8+ front endmodules mounted inside the flighttube which are connected via bus sig-nals to 2MCPD-8+modules mountedin the counting house. In November2007, we performed first system testswith a set of prototype readout mod-ules at our test beam facility TREFFusing a prototype detector consistingof 8 PSDs shown in Figure 1.1.The PSD8+ system used has been

specifically adapted to the P4-0341-201 PSDs and features a shapingtime constant τ = 1.0µs. In Figure 1.2the pulse height spectra of λ = 4.7Åneutrons recorded at TREFF are de-picted as a function of the PSD an-ode voltage. Even at highest oper-ation voltage the detectors allow anefficient separation of neutrons fromgammas.

Figure 1.2: Neutron pulse height spectra for various anode voltage settings recordedwith a P4-0341-201 PSD read out by the PSD8+ system

It was the main intention of the testto study the performance of the pro-totype detector system in terms ofposition resolution, linearity and ho-mogeneity. The PSDs were scannedalong the tube axis with a λ = 4.7Åneutron beam which was collimatedby a slit system resulting in an intrinsicbeam width of d ≈ 0.7mm. For eachbeam position the position spectrumwas fitted using a Gaussian distribu-tion and a linear fit was used for po-sition calibration. Figure 1.3 shows aplot of the measured beam positionversus the real beam position for 7illuminated PSDs.For a representative PSD, Figure

1.4 shows the resulting position reso-lution (FWHM) at five beam positionsalong the detector axis for variousoperating voltage settings. It revealsthe symmetrical shape expected fromtheory and clearly surpasses the per-formance required for SANS1 (∆x <8mm).

1 Central services and reactor 11

Figure 1.3: Measured beam position versus real beam position for 7 illuminated PSDs

Figure 1.4: Position resolution (FWHM) along the detector axis for various anodevoltage settings

Meanwhile all 128 PSDs of theSANS1 detector have been deliveredand were successfully tested in ameasurement campaign at TREFF interms of homogeneity, active lengthand position resolution.

MILAND signal processingelectronics

The NMI3-JRA2 (MILAND) project isdedicated to the development of afast, high resolution (∆x ≈ 1mm) 2D-neutron detector based on a MWPCwith 320×320 individual channel read-out. Based on the layout alreadypresented in[2] we built a 128×128

Figure 1.5: Position resolution (FWHM) of the MILAND detector (orthogonal to theanodes) for two different algorithms of position determination

channel prototype of the correspond-ing signal processing electronics. InSeptember 2007, a first system testwas performed with the MILAND pro-totype detector[3] mounted at theILL beam station CT2. A collimatedbeam of λ = 2.5Å neutrons was usedto study the achievable resolution inthe direction orthogonal to the anodewires using different algorithms forthe position determination based ona Time-over-Threshold (ToT) measure-ment. Figure 1.5 shows the result fora fine scan along 2mm covering 2anode wires with the position resolu-tion coming close to the envisagedperformance. At present the seriesproduction of all modules required tofully equip the MILAND detector is inprogress.[1] Fa. mesytec; Germany. http://

www.mesytec.com.

[2] Defendi, I., et al. FRM-II annualreport 2006, 8–9.

[3] Guerard, B., et al. NMI3-JRA2 an-nual report 2006, (2006).


1.2 HELIOS – polarized 3He gas for neutron instrumentation

S. Masalovich1, O. Lykhvar1, G. Borchert1, W. Petry1,2

1ZWE FRM II, TU München2Physik-Department E13, TU München

HELIOS, the optical pumping facil-ity, provides the ability of a large-scaleproduction of a dense spin-polarized3He gas at FRM II. The use of polar-ized 3He gas is of significant impor-tance in many research areas wherepolarized gas is considered as a sub-ject or a tool in investigations. In par-ticular, it makes a great impact on theinstrumentation for neutron polariza-tion and polarization analysis sincepolarized nuclei of helium-3 possessvery high spin-dependent neutron ab-sorption efficiency over a wide rangeof neutron energies. Neutron spin fil-ters (NSF) based on a dense hyper-polarized 3He gas may compete inpolarization efficiency with commondevices such as magnetized singlecrystals or supermirrors [1]. Althoughthese other methods are rather sim-ple in operation, their applicationsare strongly limited by the accept-able neutron energy and the allowedrange of scattering angles. In con-trast, broadband neutron spin filterscan be built to a predetermined sizeand shape in such a way that they willmeet just about all practical needs(see Fig.1.6).About sixty NSF cells have been

filled with polarized 3He gas in theyear 2007. More than half of themwere used in neutron experiments,while the other part served for test-

Figure 1.6: NSF cells at FRM II: for com-mon use and instrument-oriented

ing of NSF cells and magnetostaticcavities.

Magnetostatic cavity

Magnetostatic cavity is an importantunit used to hold the polarized 3HeNSF in a homogeneous guiding mag-netic field and to screen the polarizedgas against environmental magneticfield at a neutron instrument. Gener-ally, the relaxation rate of a gas po-larization in a NSF cell may be repre-sented as a sum:

1T1

=1

Tcell+

1Tmag

Here T1 is the total relaxation time,Tcell – the relaxation time related tothe cell (relaxation due to interactionswith the cell walls and due to dipole-dipole interactions) and Tmag – the re-laxation time related to the gradientof the magnetic field over the cell vol-ume. The last term can be writtenas

1Tmag [h]

=1.7 ·104

p [bar]

(∇|~B⊥|

B0

1[cm]

)2

where p is the gas pressure, B0 refersto the mean value of a holding mag-netic field and B⊥ – to the componentof the magnetic field normal to B0.It follows then that the field gradientless than 3 · 10−4cm−1 is required toassure Tmag ≥ 500h in a 1 bar pressurecell. Magnetostatic cavities aimed toprovide such a homogeneous mag-netic field have been developed inmany groups working with polarizedgas (see, for example, [2]). Typicallythey are based on an accurate de-sign with a fixed geometry of a cav-ity and on an assumption about thevalue and space distribution of the en-vironmental magnetic field at a neu-tron instrument. Actually, the last as-sumption brings about a free parame-ter in the design, which often cannot

be evaluated in advance. As a result,the field gradients over the cell vol-ume may differ significantly at differ-ent instruments. The other solutionwould be to build a cavity with ex-cessive screening factor and henceheavy and/or large.We have proposed and developed

a new approach in designing a mag-netostatic cavity. This approach isalso based on an accurate design of acavity capable to provide a highly uni-form magnetic field. However, somemagnetic components of the cav-ity are not fixed and can be movedand/or tilted. This additional move-ment can be used to perform a cor-rection (tuning) of a magnetic field,if necessary. Of particular interest isthe ability to tune an internal magneticfield in the presence of an inhomoge-neous external field, which is usuallythe case at a neutron instrument withpolarization analysis. Such TUneableMagnetostatic cavity (TUM-box) hasbeen designed and built by the Neu-tron Optics group at FRM II (Fig.1.7).Fig.1.8 shows the effect of tuning

on the homogeneity of the holdingfield in the presence of a local exter-nal magnetic source.

Figure 1.7: TUneable Magnetostatic cavity(TUM-box)


50 45 40 35 30 25 200.00030

0.00035

0.00040

0.00045

0.00050

0.00055

0.00060

0.00065

0.00070

Tuning

Mag

netic

fiel

d gr

adie

nt (r

elat

ive)

[1/

cm]

Distance to magnetic source [cm]

Figure 1.8: Effect of tuning in the presenceof an external magnetic source. Boldcircles – measured gradient of the hold-ing field averaged over the cell volume(10× 10× 10cm). The dashed curve isonly an eye-guiding line

It is clearly seen in Fig.1.8 that thefield gradient over the cell volumeincreases as the distance betweenthe TUM-box and external source de-creases. After the gradient has beendoubled the additional tuning was ap-plied to bring the gradient down tothe required value. This proves theability to tune a holding field at a neu-tron instrument. The first TUM-boxwas used successfully in experimentsat FRM II.

0.01 0.02 0.03 0.040

100

200

300 Hemoglobin D2O solution

250 mg/ml

Inte

nsi

ty (a.u

.)

Q,A-1

non spin-flip

spin-flip

Figure 1.9: Corrected spin-flip and non spin-flip components of the small angle scat-tered beam resolved with a 3He NSF analyzer. Results are reproduced from [3].

Experiments with neutrons

Because of a failure of one of ourlasers, the mean value of a 3He gaspolarization in NSF cells reached only71% instead of 76%. Neverthelesssuch a polarization was still goodenough to perform neutron experi-ments. As an example, Fig.1.9 showsthe result of the first SANS measure-ments on a protein sample with po-larization analysis based on the useof a 3He NSF, performed at the MIRAinstrument [3].Polarization analysis provides the

ability to resolve spin-flip and nonspin-flip components of the scatteredbeam, which can be used to dis-tinguish coherent nuclear scatteringfrom spin-incoherent nuclear scatter-ing [4].Neutron imaging with polarization

analysis is another example of suc-cessful implementation of a 3He NSF.This is based on the fact that a 3HeNSF does not disturb straight-lineneutron trajectories and hence anyimaging system with polarization anal-ysis can profit from the use of a3He NSF. Such type of measurements

have been performed at the instru-ment RESEDA with the aim of map-ping the beam polarization over theentire beam cross section (see sec-tion 2.7).An opaque spin filter [5] has been

used successfully in many experi-ments at FRM II. Such a filter almostcompletely suppresses the transmis-sion of one spin component of a neu-tron beam while another spin com-ponent has noticeable, even if verylow, transmission. This filter pos-sesses practically 100% analyzing ef-ficiency and can be implemented inaccurate measurements of beam po-larization. The opaque spin filter wasused, for example, at the instrumentMIRA for testing the new V-shapedpolarizer (2.5 m long) designed andconstructed for the new SANS instru-ment at FRM II [6].

2×1 NSF

An alternative to an opaque spin filteris a new proposed 2× 1 NSF [7] ca-pable to provide a very accurate num-ber of a beam polarization for a widerange of NSF parameters. The geom-etry of such NSF might be, for exam-ple, a rectangular cell with two sidessized 2:1 (2×1 NSF) (see Fig.1.10).In this method the transmission of

the neutron beam with initial polariza-tion and with reversed one (the spin-flipper is either OFF or ON) is mea-sured alternately along two sides ofthe same cell. Calculations show thatthe uncertainties in either 3He gas po-larization or cell opacity do not affectthe accuracy of the measured neu-tron polarization and this accuracyis mostly limited by statistical errors.Experimental test of this method isplanned for 2008.[1] Cussen, L., Goossens, D., Hicks,

T. Nucl.Instr.Meth., A440, (2000),409.

[2] Petoukhov, A., Guillard, V., An-dersen, K., Bourgeat-Lami, E.,Chung, R., Humblot, H., Jullien,D., Lelièvre-Berna, E., Soldner,T., Tasset, F., Thomas, M.Nucl.Instr.Meth., A560, (2006),480.


[3] Gaspar, A., Doster, W., Appavou,M.-S., Busch, S., Diehl, M.,Häußler, W., Georgii, G., Masa-lovich, S. Report on FRM II ex-periment 665.

[4] Gentile, T., Jones, G., Thompson,A., Barker, J., Glinka, C., Ham-mouda, B., Lynn, J. J.Appl.Cryst.,33, (2000), 771.

[5] Zimmer, O., Müller, T., Hautle, P.,Heil, W., Humblot, H. Phys.Lett.,B455, (1999), 62.

[6] Gilles, R., Ostermann, A., et al. Tobe published.

[7] Masalovich, S. Nucl.Instr.Meth.,A581, (2007), 791.

Figure 1.10: 2×1 NSF at FRM II

1.3 Sample environment

J. Peters1, H. Kolb1, A. Schmidt1, A. Pscheidt1, J. Wenzlaff1, P. Biber11ZWE FRM II, TU München

In addition to instrument support inroutine operation considerable workwas done to improve the handlingand availability of sample environ-ment equipment. Now all closedcycle cryostats (CC) and the cryo-gen free 7,5 T magnet (CCM) areequipped with rotary feedthrough toallow maximum movability. In 2007the CCM was operated for the firsttime on the instruments REFSANS,N-REX+, MIRA and SPODI resultingin considerable effort to integrate themagnet into the instrument set up.A rotatable test bar fitting into our

closed cycle cryostat (CCR) was de-veloped and tested, being one alter-ative for sample rotation. The designof our 3He- and dilution inserts wasre-engineered to decrease possibil-ity of failure and facilitate adaptationto diverse experimental needs (e.g.feedthrough of capillaries, additionalwiring etc.). The first cryogen free di-

lution insert was tested successfullyreaching a base temperature of 42mK. Unfortunately a cross over leakoccurred in the unit. The problem willbe fixed in early 2008.The FRM II gas pressure genera-

tor was operated successfully in ahigh pressure, high temperature ex-periment on TOFTOF. The PLC con-trolled pressure generator provides amaximum pressure of 10 kbar and al-lows automation of pressure profileoperation and remote control.By reason of a strong request for

larger sample tube diameters a newCCR was developed in cooperationwith VeriCold Technologies GmbH.The cryostat provides a sample tubeof 80mm diameter; all other dimen-sions are almost unchanged.In the field of high temperatures,

the second generation of our hightemperature furnace (HTF) rack isnow available. The rack is more pow-

erful (400 A heater current) with amodular electronics design for oper-ation of a DC power supply alterna-tively. A new HTF sample holder al-lows in situ vertical and rotational ad-justment.


Figure 1.11: 10kbar gas generator

1.4 Reduced enrichment for the FRM II core

W. Petry 1, H. Breitkreutz1, K. Böning1, R. Hengstler1, R. Jungwirth1, A. Röhrmoser1, W. Schmid1, P. Boul-court2, A. Chabre 2, S. Dubois2, P. Lemoine2, Ch. Jarousse3, J.L. Falgoux3, S. van den Berghe4, A. Leenaers4

1ZWE FRM II, TU München2CEA Saclay, Gif-sur-Yvette, France3AREVA-CERCA, Romans & Lyon, France4SCK-CEN, Institute for Nuclear Materials Science, Mol, Belgium

The collaborationCEA-CERCA-TUM

In 2003 the Technische UniversitätMünchen (TUM) launched a programfor the development of high densityfuel for research reactors with highestneutron flux. Principally this gain indensity can then be used to reducethe enrichment of the fuel. Still a sin-gle compact core like that of FRM IIcan for physical reasons not be re-placed by a compact core of Ura-nium enriched to less than 20 %(LEU).However, reduction to medium enrich-ment (MEU) is conceivable [1]. In acollaboration with the French Com-missariat à l’Energie Atomique (CEA)and the company AREVA with its di-visions NP and CERCA different met-

allurgical and methodological optionsare persecuted: i) irradiation of fullsize fuel plates made of UMo alloyparticles dissolved in an Al matrix withan AlFeNi cladding, ii) tests of modi-fied UMo alloys in various dispersionsby heavy ion irradiation, iii) develop-ment of manufacturing processes forfull size UMo monolithic foils includ-ing cladding, iv) calculation of theneutronics and thermohydraulics ofpossible high density fuel elementsfor the high flux reactor FRM II. Forthe purpose of post irradiation exam-inations (PIE) of the irradiated UMofuel plates the Belgium Institute forNuclear Materials Sciences SCKCENjoined this collaboration. v) Further,the irradiation tests for the qualifica-tion of the currently used U3Si2 dis-

perse fuel have been re-evaluated.Detailed progress reports concerningi) - iv) can be found in the proceed-ings of the International Conferenceon Research Reactors Fuel Manage-ment RRFM [2, 3, 4, 5, 6], whereasthe re-evaluation of the tests of thepresent fuel used for FRM II has beenpublished in [7]. In the following sum-maries of the present progress statesare given.

Irradiation of full size fuelplates made of UMo alloyparticles dispersed in an Almatrix

Six large fuel plates with UMo alloyparticles dissolved in an Al matrix had


been produced. The UMo powderwas produced by means of grinding.An Uranium enrichment of 50% hasbeen chosen and the Mo content inthe UMo alloy has been set to 8 wt%.The Uranium density was set to nomi-nal 7 gU/cm3 for two of the test plates(No. 700x), the others were producedwith a density of 8 gU/cm3 (No. 800x).Further two of the test plates with adensity of 8 gU/cm3 (No. 850x) weredispersed in Al containing 2 wt% of Si.Irradiation at the MTR reactor OSIRISat CEA-Saclay started in Sept. 2005and most of the plates were irradiatedfor a total of 5 reactor cycles, whereasone plate was irradiated for a total ofseven cycles. The four plates withnominal 8 gU/cm3 density were dis-tributed into two irradiation devices(core position 11 & 17). The plateswith 7 gU/cm3 were not inserted inthe core and served as a reserve. Theneutron spectra were rather identicalfor both positions, since they are attwo similar edges of the OSIRIS core.Measurements of the swelling weredone in situ mechanically after eachcycle. In the course of the irradiationone of the plates with density of 8gU/cm3 had to be replaced by a plateof 7 gU/cm3 due to technical reasons.The last irradiation cycle ended March2007.Fig. 1.12 summarizes the swelling

at the hot spot of all irradiated IRIS-TUM plates. The following is easilyperceived: i) All plates retain the fis-sion products even at highest burn-up. ii) Swelling is minimal during thefirst 2 irradiation cycles, most prob-ably due to the consumption of thebuild-in porosity of about 8 vol.%.iii) A more or less linear increase upto a fission density of about 2.0×1021cm−3 is followed by a steeperand steeper increase in the courseof adding up fission densities. iv)Plates with Si addition (850x) showa reduced swelling when comparedto those without Si addition.In comparison to other full size

tests with UMo dispersive fuel it isobserved: i) The swelling is higherthan in IRIS-1 (also ground powder)[8]or IRIS-3 (atomized powder) [9], pre-sumably because of the higher heat

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Figure 1.12: Comparison of the swelling at the hot spot of all IRIS-TUM plates. Forcomparison the maximum swelling observed for other full plate irradiation programsare also shown as there were IRIS-1 (ground powder), IRIS-3 (atomized powder)and IRIS-U2Si2 (ρ = 3 gU/cm3) [7].

load and subsequent higher temper-atures during the IRIS-TUM irradia-tion. ii) The "best" UMo plate withSi addition swells at a the target FDof 2.3× 1021cm−3 by 22 %, which isclearly more than the silicide fuel witha density ρ = 3 gU/cm3.After about 1 year of cooling time

the plates 8002 and 8503, both irra-diated during the first 5 cycles, couldbe transported to CEA-Cadarache,where small samples have been cutout from the top corner and alongthe maximum flux plane (mfp) of themeat zone. These have been trans-ported to SCKCEN, Mol, Belgium,where the samples have been pre-pared metallographically, and opticaland scanning electron microscope ex-aminations have been performed inhot cells. Fig. 1.13 (top) shows op-tical microscopy images of samplestaken from the top end of the meatzone, i.e. a region of lower fissiondensity. The shredded shape of theground powder particles is clearly dis-cernable. Dark lines within the UMoparticles are presumably oxidized lay-ers formed during the fabrication pro-

cess. In the top-right image the Siprecipitates in the Al meat are vis-ible. In both samples an interdiffu-sion layer, known to be rich in Al, hasbeen formed around the UMo parti-cles. Scanning electron microscopypictures with larger magnification -not shown here - show the distribu-tion of the fission gas bubbles withinthe UMo particles mainly along grainboundaries. No fission gas bubblesare observed in the interdiffusion layer.The bottom part of Fig. 1.13 displaysthe average thickness of the interdif-fusion layer measured along the mfp.Data have been grouped into 3 zones:thickness of the interdiffusion layer atthe interface between cladding andmeat, separately for the top and bot-tom interface (top and bottom with re-spect to the sample orientation) andin the centre of the meat. This inter-diffusion layer forms during irradia-tion and is suspected to be relatedto the break-away swelling observedin previous irradiation tests of UMofuel plates like IRIS-2 and FUTURE[8].


Figure 1.13: Top: Optical microscopy images of samples taken from the top end ofplate 8002 (left) and 8503 (right) where the flux and fission densities are at about 2

3of the corresponding maximum flux plane (mfp) values. Bottom: Measured meanthickness of the Al rich interdiffusion layer along the mfp for three different positions:at the top interface between meat and cladding, in the middle of the meat layer andat the bottom interface between meat and cladding.

The post irradiation examinations(PIEs) of plates 8002 and 8503 willbe continued, in particular electronprobe micro-analysis is planned. Fur-ther, plates 8501 and 7003 with higherfission densities are awaiting theirtransport to hot cells, once their ra-diation level has lowered to tolerablevalues. A few preliminary conclusionscan already be drawn at the actualstate: i) In the mfp the matrix mate-rial is consumed to a very high extent.ii) From the metallurgical preparationof samples along the mfp it can bederived that the irradiated meat be-comes extremely brittle, that meanshas a high tendency for developingcracks. iii) The interdiffusion layer is- if at all - only slightly reduced in thesamples containing additional Si. iv)For the irradiation doses achieved inplate 8503 and 8002 the fission bub-bles are accommodated in the UMoparticles mainly along grain bound-aries.

Summary/Outlook

For the first time large UMo disper-sion fuel plates have been irradiatedup to meat fission densities as highas 3.2×1021cm−3 or to a LEU equiv-alent burn-up of 88 % - and at highheat load of 260W/cm2. No failure ofthe first barrier - the cladding - hasbeen observed, even at a thicknessincrease of 323 (which correspondsto 66% of "swelling"). Large build-in porosity delays the onset of lin-ear swelling. During the irradiation,a period of almost linear increase ofthickness is followed by a steeper,non linear increase of thickness. Inthe most favourable case this non-linear increase begins at about 2.0×1021cm−3, in the case of no additionalSi at lower fission densities. The be-ginning of this nonlinear increase canbe seen most clearly in the time andspatial dependence of the swelling.Fuel with Si added to the Al matrixswells a little less than that without

Si additive. The microscope imagesfrom samples of plate 8503 and 8002yet do not give a clear indication whythis is the case. Growth of the interdif-fusion layer is - if at all - only slightlyhindered by addition of Si.The progress achieved in this irra-

diation campaign is dominantly as-cribed to the usage of ground pow-der. Why does ground powder showa more controlled swelling than atom-ized powder? A final answer has towait for more detailed PIEs, as theyare in progress. Certainly the groundparticles have a defect density ordersof magnitude higher than that of at-omized particles. This higher defectdensity - and we explicitly include oxi-dation and additional impurities - formseeds for the nucleation of mediumlarge fission bubbles, which again pre-vents diffusion of fission gases intothe interdiffusion layer.In spite of the progress reported

here, we are still far away from highdensity fuel (ρ ≥ 8 gU/cm3) whichwithstands the high irradiation dosesand rates as they occur in research re-actors with highest neutron fluxes likeFRM II. Also the best behaving fuelplate 8501 is far away from satisfyingsafety criteria as they are achieved inthe present U3Si2 fuel. For instance,it has to be examined, how UMo fuelbehaves under higher heat load be-cause it is to suspect, that irradia-tion at higher temperature in the UMograins will enhance diffusivity of thefission products. Fig. 1.12 gives a firsthint on that. Both, IRIS-1 and IRIS-3 show less swelling than IRIS-TUM,and in both cases the temperature inthe UMo grain has been much lower.Therefore, TUM and its partners

aim at future irradiation of large scaleUMo dispersed test plates at heatloads in the order of 400 W/cm2. Fur-ther it seems to be unrealistic to pro-duce ground powder with 50% en-richment on an industrial scale as nec-essary to produce the annual needsof FRM II fuel element production [10].Therefore we have to come back toatomized powder, but now with dif-ferent metallurgical treatment like ox-idization, addition of diffusion block-


ers like Si in Al and/or modified defectstructure.

Tests of modified UMoalloys in various dispersionsby heavy ion irradiation

During in-pile irradiation of fuel platesmade of UMo particles dissolved inAl matrix, growth of an undesired in-terdiffusion layer (IDL) has been ob-served - see chapter 1.4. It has beenshown that bombardment of nuclearfuel specimens with heavy ions pro-duces effects comparable to thoseafter in-pile irradiation [11]. Especiallythe growth of an IDL around UMo par-ticles inside an aluminium matrix hasbeen observed after bombardmentwith I-127. It has been shown thatthis IDL is comparable to the one ob-served after in-pile irradiation [12]. Wecontinued bombardment of UMo/Aldispersion fuel at Maier-Leibnitz Lab-oratory in Garching.The samples contain atomized

U10Mo inside a pure aluminium ma-trix. All samples were cut out of mini-plates provided by Argonne NationalLab and polished before irradiation.Sample size was 3 times7.6mm2 ×300µm. We used I-127 at 80MeV forthe irradiation simulating a typical fis-sion product. The incident angle be-tween the ion beam and the samplesurface was 60°. The size of the beamspot was ∼ 3× 3mm2. The sampletemperature was monitored during ir-radiation by a thermocouple and didnot exceed 100°C. The irradiationshave been carried out under a vac-uum of ∼ 1× 10−7mbar. The total in-tegral fluency was ∼ 1×1017ions/cm2.The penetration depth of 80MeV I-127ions in UMo is ∼ 6.5µm respectively∼ 16.5µm in Al. This results in an iondensity of at least 1.6× 1021ions/cm3

in UMo and 6× 1020ions/cm3 in Al.Due to the energy deposition profileof heavy ions entering matter, theion impact is even larger in certaindepths. This means, that at least thefinal fission density of FRM II (2.1×1021fissions/cm3) has been reached[13].After the irradiation light micro-

scope and scanning electron micro-scope pictures were taken. Also aqualitative and quantitative analysisof the isotope distribution at certainpoints of the sample was performedusing EDX technique.Optical inspection revealed that a

large IDL has grown around the UMoparticles inside the area hit by the ionbeam. Electron microscopy showsa large, asymmetric IDL around ev-ery UMo particle hit by the ion beam(Fig. 1.14). No IDL was found aroundUMo particles which had not been hitby the ion beam.By local EDX it has been found

that the composition of the IDL is alu-minium rich and approximately thesame in all examined positions (∼20at%U,∼ 3at%Mo,∼77at%Al). Thecomposition of the unaffected UMocore (Fig.1.14) and of the unirradiatedUMo grain did not change.

Conclusion and outlook

For the first time UMo/Al sampleshave been irradiated by heavy ionsup to a fluency which correspondsto fission densities typically reachedduring the burn up of such fuel in re-search reactors. SEM pictures andEDX data have been taken on sev-eral points on the sample. It has beenfound, that the composition of the IDL(∼ 20at%U, ∼ 3at%Mo, ∼77at%Al)does not change significantly on dif-ferent positions on the irradiated area.The composition of the IDL is in goodagreement with values found after in-pile irradiation tests [14].It is planned to examine the crys-

tal phases contained in the IDL us-ing XRD. Further heavy-ion bombard-ment experiments are scheduled incollaboration with CEA-Cadarache (H.Palancher, E. Welcomme).

Figure 1.14: SEM image of UMo grainswhich were directly hit by the ion beam.The incident beam direction is markedin the pictures. A large, asymmetric IDLaround a remaining UMo core is visible.The asymmetry of the IDL is associatedto the direction of the incident beam.EDX measurements have been taken atthe marked positions.

Manufacturing processesfor full size UMo monolithicfoils

Monolithic UMo foils allow densitiesaround 15 gU/cm3. It is thereforea promising alternative to disperseUMo-Al fuel for converting high fluxresearch reactors to lower enrichment.Unfortunately it is not possible so farto produce full size fuel plates on anindustrial scale from monolithic UMo,because the demanding mechanicaland metallurgical properties of thematerials to be used make commonprocessing techniques hardly applica-ble [15, 16].A new approach to solve this prob-

lem is the use of DC-magnetron sput-tering [17]. Sputtering is a commonlyused process for growing metal layerson a micrometer or sub-micrometer


scale on different substrates. Thesputter deposited layers provide ex-cellent substrate adhesion and highdensity. In contrast to thermal vac-uum deposition methods the sput-tering process will not change thecomposition of the deposited materi-als, because it is independent of thevapour pressure of the materials be-ing used.We intend using this technique in a

first step to grow a massive full sizemeat layer of UMo. In a second step,sputtering will be used to cover themeat layer with several ten microm-eters of Al or other materials as pre-cladding. The resulting UMo / Al sand-wich structure will then be further pro-cessed by common and more eco-nomic welding, rolling or hot pressingtechniques to finalize the Al claddingand thus to produce a full size fuelplate.For this purpose a DC magnetron

sputtering facility was built. The di-mensions of the apparatus were cho-sen to enable the production of sam-ples with a size of 700×65mm2 whichcorresponds to the size requirementsof the currently used FRM II fuelplates.In preliminary tests the deposition

of different surrogate metals (Cu, Al,Zn) and alloys (brass, stainless steel)on Al and stainless steel substratesfor process pressures between 1×10−3 and 1 mbar were studied. Asmost important limiting factors for thedeposition rate and therefore for theprocess speed we identified the heatremoval from the target and the max-imum voltage provided by the DC-power supply. In about 40 hours wesucceeded to deposit Cu layers with athickness of up to 1300µm (Fig. 1.15a).The deposits had an elasticity andstrength that was similar to bulk ma-terial. However, the layers showed agradient in thickness from centre tothe edges of up to 50% of the max-imum in length and of up to 20% inwidth.Finally we produced multilayer

structures to show the feasibility ofour two step production procedurementioned in the first paragraph. Wewere able to produce a multilayer

Figure 1.15: a) Sputtered sheet of Cu with a thickness of 1300µm and a size of700x65mm2. (b) Sputtered multilayer foil from Cu with Al cladding, size 700×65mm2.(c) Microscopy image of a cross section of the multilayer structure shown in (b).Here the inner Cu layer has a thickness of 200µm, the Al cladding has on one side athickness of 15µm and on the other side a thickness of 25µm.

structure of 300 µm thick Cu cov-ered by 40 µm of Al (Fig. 1.15b&c).Again the deposits were as stable asfoils made from bulk material. TheAl cladding showed a good adhesionto the Cu layer. Thickness gradientsoccurred as expected.

Conclusion and outlook

Our tests demonstrate that it is pos-sible to deposit different metals andalloys as blank sheets and foils of700× 65mm2 size and several hun-dred micrometers thickness by DC-magnetron sputtering. We alsoshowed, that it is possible to cladthis structures in a second step withseveral tens of micrometers of Al us-ing sputtering. We plan to repeatthe sputter process to fabricate blanksheets of depleted UMo and cladthem with AlFeNi.

Re-evaluation of the tests ofthe present U3Si2 fuel usedfor FRM II

In the course of the licensing proce-dure of the FRM II, extensive test irra-diations have been performed to qual-ify the U3Si2−Al dispersion fuel witha high density of highly enriched ura-nium (93 wt% of 235U) up to very highfission densities [7].

Two of the three FRM II type fuelplates used in the irradiation testscontained U3Si2−Al dispersion fuelwith HEU densities of 3.0 gU/cm3 or1.5 gU/cm3, and one plate two adja-cent zones of either density ("mixedplate"). They were irradiated in theFrench MTR reactors SILOE andOSIRIS in the years before 2002. Thelocal plate thickness was measuredalong the plates during interruptionsof the irradiation. The maximum fis-sion density obtained in the U3Si2fuel particles FDP was 14×1021 f /cm3

and 11× 1021 f /cm3 in the 1.5gU/cm3

and 3.0gU/cm3 fuel zones, respec-tively. In the course of the irradia-tions the plate thickness increasedmonotonously and approximately lin-early, leading to a maximum platethickness swelling of 14 % and 21 %and a corresponding volume increaseof the fuel particles of 81 % and 106%, respectively.

As an example, Fig. 1.16 showsa micrograph of the specimen withFDP = 12× 1021 f /cm3. Since in ev-ery fission an uranium atom is con-verted into two fission fragments thevolume of the fuel particles increases,in this case by about 70 %. The as-fabricated porosity (VP = 0.95 %) hasdisappeared, but many small pores(bubbles) have been produced dur-ing irradiation to accommodate thegaseous fission fragments. In Fig.


1.16 most of these "fission gas bub-bles" have a diameter of below 2µmwith only a few larger ones. The veryuniform distribution of small gas bub-bles that show no tendency to in-terlink is the reason for the stableswelling behaviour of U3Si2 [18, 19,20]. The interdiffusion layer whichbuilds up at the surface of the par-ticles is about 6−10µm wide.Fig. 1.17 demonstrates that the

swelling of the fuel particles PS,which is independent of the uraniumdensity in the U3Si2-Al fuel meat, isa monotonous and well predictablefunction of FDP over this very largerange. It is clear that the swelling isa uniform function of the fission den-sity - without any indication of a rapidincrease which would have been re-lated to a build up and interlinkageof very large gas bubbles in the fuelparticles ultimately leading to exces-sive swelling (pillowing) and failure ofthe fuel plate. This uniform behaviourof PS also excludes any build up oflarger pores in the Al matrix of the fuelsince such an effect would be misin-terpreted as a particle swelling.In conclusion it is evident that

U3Si2−Al dispersion fuel - under re-alistic operating conditions and fornot too high uranium densities so thatthere is always sufficient matrix alu-minium available in the fuel meat -represents an excellent fuel for beingused in high performance researchreactors up to very high fission den-sities, fission rates and fuel tempera-tures.

Figure 1.16: Micrograph of the specimen with an uranium density of 1.5gU/cm3 anda fission density of 12× 1021 f /cm3 in the U3Si2 particles to 1.6× 1021 f /cm3in themeat. This examination has been performed in the hot cell laboratories of the CEAGrenoble [7, 11]

.

Figure 1.17: Increase of the volume of the U3Si2 fuel particles (PS) as a function of thefission density in the particles (FDP). This is a comprehensive plot of all irradiations.The unknown as-fabricated porosity VP has been adjusted for each curve of theOSIRIS experiments to yield an initially smooth relationship. Shown are the data forthe OSIRIS homogeneous plate and the OSIRIS mixed plate, all with 3.0gU/cm3, aswell as the data of the OSIRIS mixed plate and the SILOE results, all with 1.5gU/cm3.The straight line represents a fit of all our data with a slope of 6.86×10−21%cm3/ f .Also shown are the ANL data of ref. [18, 21] as obtained from a HEU sample with1.7gU/cm3. .


[1] Röhrmoser, A., Petry, W., Wi-eschalla, N. Transactions ofRRFM 2005, Budapest, Hungary,(2005).

[2] Röhrmoser, A., Petry, W., Boul-court, P., Chabre, A., Dubois,S., Lemoine, P., Jarousse, C.,Falgoux, J., van den Berghe,S., Leenaers, A. Transactionsof RRFM 2008, Hamburg, Ger-many, (2008).

[3] Jungwirth, R., Petry, W., Schmid,W., Beck, L., Bergmaier, A. Trans-actions of RRFM 2008, Hamburg,Germany, (2008).

[4] Schmid, W., Jungwirth, R., Petry,W., Böni, P., Beck, L. Transac-tions of RRFM 2008, Hamburg,Germany, (2008).

[5] Jarousse, C., Lemoine, P., Boul-court, P., Petry, W., Röhrmoser,A. Transactions of RRFM 2007,Lyon, France, (2007).

[6] Röhrmoser, A., Petry, W. Trans-actions of RRFM 2006, Sofia,Bulgaria, (2006).

[7] Böning, K., Petry, W. Journal ofNuclear Materials. Submitted.

[8] Lemoine, P., Snelgrove, J.,Arkhangelsky, N., Alvarez, L.

Transactions of RRFM 2005, Mu-nich, Germany, (2005).

[9] Lemoine, P., Anselmet, M.,Dubois, S. Transactions ofRRFM 2008, Hamburg, Ger-many, (2008).

[10] Communication by AREVA-CERCA, .

[11] Walker, D. Journal of nuclear ma-terials, 37, (1970), 48 – 58.

[12] Wieschalla, N., Bergmaier, A.,Böni, P., Böning, K., Dollinger,G., Grossmann, R., Petry, W.,Röhrmoser, A., Schneider, J.Journal of nuclear materials, 357,(2006), 191 – 197.

[13] Wieschalla, N. Out-of-pile ex-amination of the high densityU-MoAl dispersion fuel. Ph.D.thesis, Technische UniversitätMünchen, Germany (2006).

[14] Leenars, A., den Berghe, S. V.,Koonen, E., Jarousse, C., Huet,F., Trotabas, M., Boyard, M., Guil-lot, S., Sannen, L., Verwerft, M.Journal of nuclear materials, 335,(2004), 39–47.

[15] Jarousse, C. Transaction ofRRFM 2008, Hamburg, Ger-many, (2008).

[16] Clark, C. R. RETR, Chicago,USA, (2003).

[17] Wieschalla, N., Böni, P. Newmanufacturing technique for U-Mo monolithic. Patent referenceno. DE 10 2005 055 692 (2005).

[18] Safety evaluation report relatedto the evaluation of low-enrichedUranium-Silicide dispersion fuelfor use in non-power reactors(July 1988).

[19] Hofman, G., Snelgrove, J. InCahn, R., Haasen, P., Kramer,E., editors, Volume 10 A NuclearMaterials, chapter Dispersion Fu-els (VCH Weinheim, 1994).

[20] Hofman, G., Copeland, G., Snel-grove, J. Oak Ridge Na-tional Laboratory (ORNL), re-port ORNL/TM-13061, (August1995).

[21] Copeland, G. Private commu-nication (July 2000) as basedon the report by J.L. Snelgroveet al.: Evaluation of ExistingTechnology Base for CandidateFuels for the HWR-NPR, re-port ANL/NPR-93/002, February1993.

22 2 Diffraction

2 Diffraction

2.1 SPODI

M. Hoelzel1, A. Senyshyn1, H. Boysen2, W. Schmahl2, S. Park2, H. Ehrenberg3, H. Fuess1

1Technische Universität Darmstadt, Material- und Geowissenschaften, Darmstadt2Ludwig-Maximilians-Universität, Depart. für Geo- und Umweltwissenschaften, München3Leibniz-Institut für Festkörper- und Werkstoffforschung, Dresden

Instrument developmentand sample environment

During the year 2007 a new softwarehas been developed to make the datatreatment (i.e. the derivation of diffrac-tion patterns from the two dimen-sional raw data) more user friendlyand efficient. In particular, new al-gorithms have been implemented toovercome asymmetry effects causedby the smearing of Debye-Scherrercones along the vertical directions atlow scattering angles. Thus, high res-olution and good profile shapes canbe achieved even when the full detec-tor height of 300 mm is used.New devices of sample environ-

ment have been set into operationand successfully applied in user ex-periments. The 3He insert of theclosed-cycle refrigerator has beenused for the first time in a user experi-ment to investigate magnetic scatter-ing at 500 mK. The closed cycle re-frigerator was also successfully usedin the cryofurnace mode (currently be-low 450 K) in the framework of userexperiments. The high-temperaturevacuum furnace was used in powderdiffraction experiments at 1775 °C.The mirror furnace (LMU) has beenset into operation and applied in auser experiment for high-temperaturediffraction experiments in air. After itscommissioning, the 7.5 Tesla verticalmagnet has been successfully com-missioned in frame of a user exper-iment, where evolution of magneticstructure has been studied as a func-tion of magnetic field (up to 3 Tesla)and temperature.

User service

The Structure Powder Diffractome-ter SPODI was highly overbooked inthe 2007 proposal rounds. Althoughnot much time was used for instru-mentation and maintenance in 2007,overload factors higher than 3 (5thproposal round) and even 4 (6th pro-posal round) have been reached. Be-sides the regular user service, sev-eral days of beamtime have been pro-vided for industrial applications. Thediffractometer SPODI has also partici-pated in the practical neutron scatter-ing course organised by Jülich Centrefor Neutron Science.Various investigations in the frame

of user service have been publishedduring year 2007. To our knowledge,11 publications based on the resultsfrom structure powder diffractometerSPODI exist in the literature. In the fol-lowing, two selected examples of sci-entific highlights from the year 2007,both describing Li diffusion in solids,are illustrated in detail.

Example: S. Park, Li motions inlithosilicates

Li motion in dehydrated microp-orous RUB-29 (Cs14Li42Si72O172)-typelithosilicates as potential Li-cationicconductors has been studied usinghigh-resolution neutron diffraction atSPODI in conjunction with impedancespectroscopy. These materials incor-porate lithium not only in spaciouschannel sites, but also in denselypacked Li2O-layers in the framework(Figure 1), providing new conditionsfor hosting mobile lithiums. One of

the motivations for developing mi-croporous conductors is that "sim-ple" ion-exchange processes can beperformed in order to manipulatethe structures for fast ionic conduc-tion. Characteristically, a moder-ate direct current (DC) conductivityvalue of 2∼ 6× 10−5 S·cm−1 at 873K in RUB-29 can be enhanced dra-matically through Na-exchange pro-cesses. Na-exchanged RUB-29 pos-sesses 100-times higher overall con-ductivity values between 3.2×10−3

and 7×10−3 S·cm−1, depending onthe content of Na. A careful eval-uation of impedance spectra com-bined with Rietveld analysis of neu-tron powder diffraction data of de-hydrated Na-RUB-29 and RUB-29agree with that the fast relaxationprocesses can be due to fast dy-namic disorder of both Li+ withinLi2O-layers and Na+ (or Cs+ beforeNa+-exchanging) within most porousintersections of 10MR-channels [1].The conductivity values of Na-RUB-29 materials reach in the highest re-gion ever observed in zeolitic cationicconductors. On the other hand, tofind optimal structural basis for theLi-ionic conduction which is not af-fected by water molecules, we haveinvestigated pseudo-microporous Li-bearing silicates, such as the milarite-family. Among them, sugilite andsogdianite contains chains of LiO4-tetraheda und AO6-octahedra with A= Fe3+ and Zr4+, respectively. Resultsfrom Rietveld analysis of diffractionpatterns collected at T = 300 - 1273K can explain the presence of low-frequency relaxations in impedancespectra measured perpendicular to

2 Diffraction 23

Figure 2.1: Calculated (line) and measured (circles) neutron powder diffraction patternof sogdianite at 1273 K. The upper and lower tick marks indicate reflections ofsogdianite and the Nb-can, respectively. The lower curve shows the differencebetween the observed and calculated data. The refined structure of sogdianite withanisotropic atomic displacements (ADP) ellipsoids at 1273 K is displayed in inset,emphasizing large ADP at Li sites.

the c-axis of a single crystal of sog-dianite as a consequence of the siteexchange of Li between tetrahedraland octahedral sites.Even higher conductivity values of

s = 2.2× 10−4 S·cm−1 at 913 K and1.9×10−3 S·cm−1 at 1093 K were de-termined with a plate of massive poly-crystalline crystals of sugilite. To ex-plain the structural reasons a set ofdiffraction patterns at T = 293-923 Kwas collected in the last period andnow Rietveld analysis is in progress.For exploring Li-ionic conductors wehave studied with SPODI data on dy-namic motions in kunzite (pink spo-dumen) and a synthetic lithosilicateLi2SiO5, as well [2]. Rietveld analy-sis revealed strong anisotropic atomicdisplacements at Li sites in both ma-terials. The Li-dynamic motions inboth lithium silicates can be mainlyresponsible for cationic conductiv-ity determined by impedance. Com-pared to RUB-29, the overall site ex-change processes in these materialshave to overcome pretty high activa-

tion energy barriers of 1∼1.5 eV. Thepresence of densely packed layers ofedge-sharing LiO4-tetrahedra, whichis unique to the topology of RUB-29,may be a better option for providingpath ways for fast Li conduction.

Example: H. Ehrenberg, Li ionbatteries

Precise structural data have beenobtained from a simultaneously Ri-etveld refinement of high-resolutionneutron and X-ray powder diffractiondata for the three phases LiCoPO4,LizCoPO4 with a specific intermedi-ate Li content z=0.6(1) and CoPO4,which are obtained by electrochem-ical Li-extraction from LiCoPO4 [3].All three phases are isostructural andisosymmetric, which implies first or-der transitions between these phases.The same collinear antiferromagneticstructures with magnetic momentsnearly parallel to the [010] direc-tion are observed for LiCoPO4 andLizCoPO4, but with a significantlyhigher Néel temperature of 76 K for

the latter compound in comparisonwith 23 K for LiCoPO4.Olivine-type CoPO4 was prepared

from LiCoPO4 by delithiation, and itsphysical properties were investigatedfor the first time. An antiferromag-netic arrangement along the [100] di-rection is observed for CoPO4 with anadditional weak ferromagnetic com-ponent along the [001] direction (mag-netic space group Pn′m′a and Tc=45K).The easy axes and the magnetic

exchange interactions between Co-ions change dramatically with theCo2+ ↔Co3+ transition. A continu-ous change of the formal oxidationstate of a transition element by elec-trochemical Li-extraction and a quasi-continuous in−situ observation of theresulting magnetic structure by neu-tron diffraction appear feasible.

Outlook: developments oninstrument and sampleenvironment

In the frame of the "Verbund-förderung" of the "Bundesministeriumfür Bildung und Forschung" upgradesof the Structure Powder Diffractome-ter SPODI are funded. In Jan-uary 2008 the installation of a newmonochromator focusing unit will becarried out to improve the neutron fluxand flexibility of the instrument.At present various developments

on sample environment are underway: automatic sample changer, ap-paratus for in− situ gas charging ofsamples (in particular: catalysts andframework materials), improved pos-sibilities for experiments under me-chanical stress, a sample stick forthe closed-cycle refrigerator to enableexperiments under hydrogen atmo-sphere, devices for in− situ analysisof Li-ion batteries etc.

24 2 Diffraction

Figure 2.2: Neutron diffraction pattern of "Li0.2CoPO4" at 5 K, measured data as redpoints, calculated profile in black and the corresponding difference curve in blue atthe bottom of each figure. The lines of green marks indicate the calculated posi-tions of allowed reflections. The narrow excluded regions are due to contributionsfrom the cryostat. The line of reflection marks belong from top to bottom to thenuclear contributions from LiCoPO4 and LizCoPO4, the magnetic reflections fromLiCoPO4 and LizCoPO4 and the nuclear and magnetic peaks from CoPO4. Magneticstructures of LiCoPO4 and CoPO4 are shown in left and right insets respectively.

[1] Park, S.-H., Senyshyn, A., Paul-mann, C. J. Solid State Chem.,180, (2007), 3366–3380.

[2] Park, S.-H. FRM-II experimentalreport Nr 698.

[3] Ehrenberg, H., Bramnik, N.,Senyshyn, A., Fuess, H. In prepa-ration.

2.2 HEiDi – Single crystal diffractometer with hot neutrons

M. Meven1, V. Hutanu2, G. Heger21ZWEFRM II, TU München2Institut für Kristallographie, RWTH Aachen

Introduction

HEiDi is one of the two single crystaldiffractometers at the neutron sourceHeinz Maier-Leibnitz (FRM II). It isplaced at beam line SR9B in the ex-perimental hall of the reactor buildingand uses the hot source (fig. 2.3). Theinstrument is a collaboration betweenthe RWTH Aachen (Institut für Kristal-lographie) and the TU München (ZWEFRM II).HEiDi covers a broad range of sci-

entific cases in the area of structural

research on single crystals in the fol-lowing fields of interest:

• Structure analysis (harmonicand anharmonic MSD (meansquare displacements), hydro-gen bonds, molecular disorder).

• Investigation of magnetic order-ing (magnetic structures, spindensity).

• Structural and magnetic phasetransitions.

The use of the hot source (graphitecylinder at T(20MW)=2300 K) at beamline SR9 yields a remarkable increaseof the neutron flux in the range

Figure 2.3: Overview of HEiDi

2 Diffraction 25

Figure 2.4: Gain factor of hot source at SR9

between 0.6 Å and 0.4 Å with a gainfactor about eight (fig. 2.4).Diffraction experiments that focus

on structural and magnetic detailsprofit significantly from the accessto a very large reciprocal space(Q = |~Q| = sinΘmax/λ ) with Q > 1.5 at0.55 Å. Other advantages are the

• reduction of extinction effectsof large and very perfect singlecrystals and the

• reduction of absorption effectsin compounds with highly ab-sorbing elements like samariumor gadolinium.

To our knowledge there exists onlyone other neutron single crystaldiffractometer worldwide (D9 at ILL)with these unique capabilities. Detailsof the instrument and its applicationswere presented in 2007 on the

• annual meeting of the DGK inBremen [1],

• the 4th European conference onneutron scattering in Lund [2],

• the first user meeting at FRM IIand

• Neutron News [3].

Use of sample environment

Low temperature environment

The closed cycle cryostat of HEiDireaches a minimum temperature ofabout 2.2 K. This and its reliabilitymake the cryostat very attractive fordetailed investigations on magnetismand other structural properties at lowtemperatures. The movability of thecryostat in the Eulerian cradle wascontinuously improved in the last year.The tilt range of the χ axis was suc-cessfully extended to χmin =−380 andχmax = +910 while the φ range coversa complete sample rotation (fig. 2.5).Thus in comparison to room tem-

perature experiments the observationof reciprocal space at low tempera-ture is not significantly limited and al-lows the collection of complete Braggdata sets. More than 65 percent ofusers beam time were used for exper-iments with this sample environment.

Figure 2.5: Cryostat in cradle with rotatingconnectors

High temperature environment

The air cooled furnace (fig. 2.6) wasused for two high temperature experi-ments around T =1100 K. At the endof 2007, after two third of the secondHT experiment the niobium shieldingof the furnace was damaged (proba-bly due to a vacuum leak). In com-bination with some other repairs andimprovements the furnace might beavailable at the second half of 2008.Simultaneously, developments for

a mirror furnace are in progress. Thisfurnace is designed to have a largebeam window for use in the Euleriancradles of HEiDi and RESI and allows

Figure 2.6: Large (top) and small (bottom)furnace in Eulerian cradle

26 2 Diffraction

temperatures up to almost 2000 K.Thus, it is very likely that this furnacewill replace the air cooled furnace in2008.Experiments with slightly increased

temperatures up to about 420 K canstill be performed with a small furnacedeveloped at the Institut für Kristallo-graphie, RWTH Aachen (fig. 2.6).In 2007 only about 8 percent of

users’ beam time were given for HTexperiments. The total number of HTproposals and requested beam timefor this kind of experiments is signif-icantly higher (about a factor of two).There is no doubt that our efforts toimprove the temperature ranges ofour single crystal furnaces are manda-tory to meet the needs of those of ourusers who wish to do structural inves-tigations at high temperatures.

Use of beam time

In 2007 both proposal rounds weresignificantly overbooked concerninguser experiments on HEiDi with fac-tors between 2 and 3. Typical scien-tific cases of the external proposalswere

• magnetic superstructures at lowtemperatures,

• order/disorder phase transitionsat low and high temperatures,

• ionic conductors and• local disorder or vacancies,esp.of H bonds.

Eleven external proposals (of aboutsubmitted twenty ones) were ac-cepted and accomplished at HEiDiwith altogether 165 days. Thus, morethan 71% of the complete beam timeof HEiDi could be given to externalusers in 2007. The average valueof 15 days for each proposal seemsquite large on the first sight. But onthe other hand most of these propos-als contained measurements of Braggdata sets at two or more different tem-peratures and large Q ranges up toQ = 1.2.Additionally, some time was spent

to• check crystal orientations andhomogeneities of samples thatwere used for experiments on

other instruments at FRM II, es-pecially the triple axes spec-trometers,

• and to perform practicalcourses for the

– Advanced practical coursefor physicist students atthe TU München and the

– JCNS Neutron course ofthe ForschungszentrumJülich

and finally for tests of new compo-nents of the new single crystal instru-ment for 3D polarisation analysis atFRM II - Poli-HEiDi (see 2.3).Two of the most remarkable propos-

als in 2007 focused on multiferroics,compounds that undergo a variety ofmagnetic (and sometimes additionallystructural) phase transitions.GdCuO3 (Proposal 684, J. Voigt, A.

Möchel) is a compound of the multi-ferroics family that contains the highlyabsorbing element Gd. For thermalneutrons the large absorption crosssection of Gd of about σ(λ = 1.8Å) =49700 barn makes it impossible toget any neutron diffraction data atall. The absorption coefficient aboutµ(λ = 1.8Å) = 873 Å

−1yields a trans-

mission of T = 10−57 for a reasonablylarge sample (cube with 1 to 2 mmlength per edge).

Figure 2.7: Bragg reflection of GdMnO3 measured on HEiDi

Only by using the short wave-lengths of HEiDi the absorption co-efficient drops down to a reasonablevalue of µ(λ = 0.55 Å) = 12.7 barn.The transmission of 16% at this wave-length allowed the collection of twoBragg data sets at room temperatureand low temperature with reasonablestatistics. A typical Bragg reflectionof this experiment is shown in Figure2.7.DyMnO3 (Proposal 1449, D. Ar-

gyriou, N. Aliouane [4]) is anothercompound of the multiferroics fam-ily. A possible structural phase tran-sition at low temperature should re-sult in slightly different oxygen bondlengths. To clarify the situation rel-ative accuracies better than 10−4

for the bond lengths values wererequested to make possible struc-tural changes visible. This ambitiousgoal was achieved by using the shortwavelength of HEiDi to measure twoBragg data sets (each one with about3000 Bragg reflections) up to Q = 1.2above and below the possible phasetransition.

2 Diffraction 27

Outlook

In 2007 the neutron single crystaldiffractometer HEiDi has proven to bean extremely valuable “working horse”for a variety of detailed structural andmagnetic investigations.The low temperature sample envi-

ronment fulfils the needs of our usersand needs only minor improvements.The high temperature sample environ-ment will undergo some substantialimprovements in 2008 to allow high

temperature experiments significantlyabove 1000 K, e.g. for investigationson ionic conductors.Furthermore we wish to establish

a collaboration with the Fakultät fürMaschinenwesen of the TU Münchento improve the speed and flexibility ofdata collection at HEiDi by optimizingthe controller design.[1] Sazonov, A., Meven, M., Heger,

G. In Jahrestagung der DeutschenGesellschaft für Kristallographiein Bremen, 5.-9. March, 010–05

(2007).

[2] Meven, M. In ECNS Lund, 25.-29.June, T038 (2007).

[3] M. Meven, G. H., V. Hutanu. Neu-tron News, 18, Issue 2, (2007), 19.

[4] Aliouane, N., Argyriou, D.,Strempfer, J., Zegkinoglou, I.,Landsgesell, S., v. Zimmermann,M. Phys. Rev. B, 73, (2006),020102.

2.3 Polarisation investigator POLl-HEiDi at SR 9 - the advances of theproject

V. Hutanu1,2, M. Meven2, G. Heger11Institut für Kristallographie, RWTH Aachen2ZWE FRM II, TU München

Introduction

Polarised neutron diffraction is oneof the most important tools to de-termine magnetic structures. One-dimensional neutron polarisation anal-ysis is used to determine the direc-tions of magnetic moments. In ad-dition, recently developed sphericalneutron polarimetry (SNP) is very use-ful to investigate complicated mag-netic structures in detail [1, 2, 3].For instance, the non-diagonal termsof polarisation matrices measured inSNP give us important information onchiralities and magnetic domains ofmagnetic structures.The new polarised neutron diffrac-

tometer POLI-HEiDi – currently un-der construction on neutron beam9 (SR 9) – is dedicated to investi-gate complex magnetic structures bymeans of SNP. Two zero-field po-larimeters, the Cryopad and the Mu-PAD, are available for this task andcould be used with the new instru-ment. Our project is carried out by theInstitut für Kristallographie of RWTHAachen with financial support of theBMBF. The successful realisation andtest of the numerous components ofthis new polarised instrument in 2005and 2006 [4, 5] assured further finan-cial support for this project through

the BMBF for the next future (2007-2010). A number of important newparts and components for the po-larised neutron diffractometer POLI-HEiDi were built and partially testedin 2007. In this report we will presentthese new components. For 2008the commissioning of the most im-portant components like the detector-analyser unit Decpol, the zero-fieldsample environment Cryopad as wellas the controlling electronics for thesample table are planned. Also sometest experiments with all componentsassembled in the new instrument willbe done.

3He spin filter cells

Based on the successful tests of130mm long filter cells for the shortwavelength neutrons [4, 5] a numberof new filter cells made of quartz glasswere produced in collaboration withthe HELIOS team. The practising ofcell handling and use shows that themost delicate part of the Cs coatedfilter cells are their refilling valves. Onthe one hand they should be perfectlytight to high vacuum (up to 10−8 mbar,reached in the cell during the prepa-ration procedure). On the other handthey should be tight at high pressure

(up to 3bar working pressure duringuse). Our experience shows that tradi-tionally used glass vacuum stopcockssealed with vacuum grease do not al-ways work reliably, especially for mul-tiple refilling at high pressure. More-over their handling needs special care.Therefore, the search for alternativetypes of refilling valves and their in-tegration in the cell design was animportant issue in our spin filter celldevelopment.Different types of greasefree valves

were tested in the cells Heidi 3 andHeidi 4. Figure 2.8 shows a photo-graph of the cell Heidi 4.1.

Figure 2.8: Spin filter cell Heidi 4.1 madeof quartz glass and Cs coated inside.J. Young type greaseless high vacuumstopcock is used in the edge geometry.

28 2 Diffraction

The bodies of the cell have thesame dimensions for all Heidi typecells (136mm outer length, 60mmdiam.). A high vacuum Teflon ringsealed angle stopcock (productionJ. Young Ltd.) was connected to thecell. The valve was made of borosil-icate glass. For this reason, a seal-ing ring adapter from quartz glass toborosilicate glass was inserted be-tween the cell body and the valve.This greaseless construction success-fully withstands high and low pressuretests and now will be the subject tofurther investigations regarding relax-ation characteristics.

Figure 2.9: Main coil of the Decpol duringthe magnetic field test measurements.

Figure 2.10: Decpol after arriving fromworkshop. In the open detector dooron the left a single tube detector will behoused inside the blue shielding. Theconstruction with the mobile detectorallows an easy change of the 3He anal-yser cells inside the magnetic chamber.

Detector-analyser deviceDecpol

The idea to combine a single tubeneutron detector and a 3He spin fil-ter cell used as polarisation analyserin the same housing was for the firsttime realised in the Institute Laue-Langevin (ILL) Grenoble [6]. The de-vice was called Decpol. Starting fromthe original ILL design we realised in2007 a modified version of Decpol.This new Decpol was optimised to beused together with the Heidi type filtercells. In comparison to the ILL designit is more compact, has a differentpassive cooling system for the cor-rection coils and uses boron dopedPE for the detector screening. Theresults of the field homogeneity mea-surements inside the magnetic cham-ber are in good agreement with previ-ously calculated values. Power sup-plies suitable for operation with theDecpol were purchased. The optimi-sation of the coil current ratios as wellas the final commissioning of the newDecpol is planned for the first reactorcycle in 2008 (10b). Figure 2.9 showsthe main coil of the Decpol duringtest measurements before the final as-sembling, situated in the 3D magneticfield mapping device. Figure 2.10presents the assembled Decpol. Theopen door shown in this picture offersthe possibility for a quick change ofthe filter cell.

Non-magnetic sample table

After about one year delay in deliv-ery, at the end of 2007, we man-aged to receive the sample table forour new polarised diffractometer fromFa. Huber Diffraktionstechnik GmbH.Figure 2.11 shows the non-magneticsupport unit during the acceptancetest at the producer before shipment.The sample table includes a massivebasal plate for the stability of thewhole instrument. The upper surfaceof the plate is hardened and servesas a support for the wheels fixed onthe bottom part of the detector arm.The basal plate has three pairs of airpads (design and production FRM II)

that are adjustable in height. A Huber440 turn table is used for the move-ment of the detector arm (2theta cir-cle). A Huber 430 turn table is usedfor the sample rotation (omega circle).A fixed plate between the two turntables serves as support for the po-larisation analysis devices as well asfor other instrumentation, e.g. a mag-net. On the top of the omega circlea 2-direction tilting table with a man-ual flat turn table (partially circle chi,and phi) is mounted. The availabletilting angle in the both perpendiculardirections is ±5.

Polarisation manipulationdevices

In cooperation with the ILL in theframework of our project two socalled nutators wre realized in 2007(see figure 2.12). These devices usethe precession of the magnetic mo-ment of the neutron in an externalmagnetic field for adiabatic transi-tion from axial polarisation (along thebeam path) to transversal polarisation(in-plane perpendicular to the beampropagation direction). Moreover themechanical rotation of the nutatorsaround the beam direction axis per-mits the orientation of the

Figure 2.11: Non-magnetic sample tablefor the new diffractometer POLI-HEiDiduring the acceptance tests.

2 Diffraction 29

Figure 2.12: Adiabatical spin rotators fromthe axial to the transversal direction re-garding the beam propagation direction(nutators) fixed on their mechanical turntables.

transversal polarisation vector to anydirection between 0 and 360 inthe plane perpendicular to the beam.Therefore, these devices are used forthe orientation of the polarisation vec-tor of the incident and the scatteredbeam in the direction of the requiredprojection of the scattering vector dur-ing 3D polarisation analysis experi-ments. A nutator consists of threemagnetic coils fixed in the weak ferro-

magnetic material body. Two of thesecoils are connected to polar piecesof special form in order to produce ahomogeneous transversal magneticfield in the region of the polarised neu-tron beam path. The third coil is po-sitioned axially to the beam and as-sures an adiabatic coupling betweenthe transversal field and the axially po-larised neutrons. Bipolar power sup-plies suitable for the nutator operationwere also procured.

Acknowledgements

We are thankful to S. Masalovich andA. Lykhvar from Neutron Optics groupof FRM II for the cooperation in thecell preparation. We are also thankfulto J. Fink and F. Tralmer from the con-struction department of FRM II for thework on Decpol and nutators.This work is supported by the

German Federal Ministry for Educa-tion and Science (BMBF) through theprojects 03HE6AA3 and 03HE7AAC.

[1] Tasset, F., Brown, P., Lelievre-Berna, E., Roberts, T., Pujol, S., Al-libon, J., Bourgeat-Lami, E. Phys-ica B, 267-268, (1999), 69.

[2] Brown, P., Crangle, J., Neumann,K., Smith, J., Ziebeck, K. J. Phys:Cond. Matter, 9, (1997), 4729.

[3] Brown, P., Forsyth, J., Tasset, F.J. Phys: Cond. Matter, 10, (1998),663.

[4] Hutanu, V., Meven, M., Heger, G.Progresses in the development ofthe polarized neutron diffractome-ter POLI-HEiDi. Technical report,Annual report 2006 FRM II, TUMünchen (2007).

[5] Hutanu, V., Meven, M., Heger, G.Physica B, 397, (2007), 135–137.

[6] Lelievre-Berna, E. Advances inNeutron Scattering Instrumenta-tion, I. Anderson & B. Guerard, Ed-itors, Proceedings of SPIE, 4785,(2002), 112–125.

2.4 RESI – The single crystal diffractometer

B. Pedersen1, G. Seidl1, W. Klein1, W. Scherer2, F. Frey3

1ZWE FRM II, TU München2Inst. f. Physik, Universität Augsburg3Sektion Kristallographie, GeoDepartment, LMU München

During 2007 RESI was operatingroutinely. The use of further sampleenvironment was successfully imple-mented, including use of the He-3 in-sert for diffraction experiments downto 500mK.To improve the performance of the

instrument, we are currently design-ing a focussing secondary neutronguide. This guide will reduce the spotsize on the detector for large crystals,thus increasing the (spatial) resolutionfor these samples.

Sample Environment

During the last year, the sample envi-ronment available for RESI has beenimproved. The closed cycle refrig-erator is now equipped with rotating

connector for the high pressure lines,which enables full 360° phi-rotationand much freer chi-motion.The FRM II He-3 insert was suc-

cessfully used in a number of exper-iments on magnetic structures, ex-tending the temperature range downto 500 mK. Here the large area detec-tor allows data collection with a singlerotation axis. Thanks to the flexiblesoftware design, it was even possibleto implement a temperature cyclingmeasurement, where each image wasmeasured at 500mK and 3K immedi-ately after each other.For high temperature experiments,

the FRM II mirror furnace has beenadopted to the Eulerian craddle.Compared to the standard high tem-perature furnace, this setup yields

much lower background and an im-provement in accessible reciprocalspace.

30 2 Diffraction

Figure 2.13: RESI in the Eulerian craddle setup, equipped with a closed-cycle refriger-ator

2 Diffraction 31

2.5 KWS-2 Small-angle neutron diffractometer of JCNS at FRM II

A. Radulescu1, H. Frielinghaus1, V. Pipich1, P. Busch1, V. Ossovyi1, T. Kohnke1, A. Ioffe1, D. Schwahn2,M. Heiderich2, U. Bünten2, R. Hanslik3, K. Dahlhoff3, G. Hansen3, G. Kemmerling4, R. Engels4, H. Kleines4,D. Richter1,21JCNS, Jülich Centre for Neutron Science, outstation at FRM II2IFF-5,Research Centre Jülich3ZAT, Research Centre Jülich4ZEL, Research Centre Jülich

The KWS-2 small-angle neutrondiffractometer was moved from theJülich reactor FRJ-2 to the Munich re-actor FRM II in 2006. The instrumentis now positioned at the end of thevertically "S-shaped" neutron guideNL3a-o. During the reconstructionphase the instrument was upgradedaiming at its optimization either forhigh intensity or for high resolutionmodes. Due to these upgrades, thepositioning of the instrument in theFRM II neutron guide hall and theparticular beam characteristics, someconstituent parts of KWS-2 were sub-ject to major changes.The first change is concerned with

the increase of the beam size from30x30 mm2 to 50x50 mm2. The in-strument was equipped with a newsystem of neutron guides (18 pieces

Figure 2.14: The neutron flux at KWS-2 measured at the sample position for the reactorpower of 20MW and cold neutron source filling of 10.5 l (with 30x30 mm 2 entranceaperture).

x 1m length, with a m=1.3 NiMo-Tinonmagnetic coating). New collima-tion apertures have been installed: 5variable apertures made of ceramic10B, which allow either symmetric orslit-like opening with sizes between1x1 and 50x50 mm2 (placed at 2, 4,8, 14 and 20m before the sample po-sition) and 14 fixed 10B coated aper-tures having a size of 50x50mm2. Thecombination of the larger beam sizewith the old collimation housing re-quired a new design of the workingprinciple and automatic control of thenew guide-aperture system: distinctcarriers for the neutron guides andapertures allowing them to move in-dependently from each other in or outof the beam have been installed.Another major change is caused by

the high neutron flux delivered by

the FRM II reactor: a massive com-bined lead and boron shielding wasinstalled around the velocity selec-tor and the collimation housing in or-der to keep the level of γ and neu-tron background within the limits re-quired by the radioprotection regula-tions. Optimization, adjustment andtest of the new collimation systemand shielding was carried out in thefirst half of 2007. The velocity selectorwas calibrated using standard sam-ples (opal and silver behenate [1, 2]);the neutron flux at the sample posi-tion was measured for different wave-lengths and collimation lengths us-ing monitors and was calibrated bygold foils activation measurements(Fig.2.14). For the nominal filling ofthe FRM II cold source (13 l) KWS-2has a flux very close (30% lower) tothat of the world leading SANS instru-ment - the D22 at the ILL, Grenoble.

Figure 2.15: View of the KWS-2 SANS in-strument at FRM II (summer 2007); onthe right side the open collimation hous-ing of KWS-1 SANS instrument can beseen.

32 2 Diffraction

Figure 2.16: The scattering pattern of silica particles in a mixed ethanol/water solventmeasured over the nominal Q-range of KWS-2 by using 2 sample-to-detector dis-tances (2m and 8m) and 2 wavelengths, 6 and 19 Å ; the collimation length was inall cases 8m.

Because the presently availablespace in the FRM II guide hall per-mits only the installation of a 14 mlong detector tube (Fig. 2.15), KWS-2 was set up in a temporary, shorterconfiguration. The installation of thecomplete, 20 m long detector hous-ing will be possible only after joiningthe FRM II guide hall with the FRM-1ring laboratory in the year 2008.The shorter version of the detec-

tion system (allowing for a maxi-mal sample-to-detector distance of8m) implied that, in order to coverthe nominal Q-range (0.002 - 0.2Å−1), two wavelengths must be used,namely 6Å and 19Å . As an exam-ple, the results obtained on the sys-tem of silica particles in mixed proto-nated/deuterated ethanol/water sol-vent [3] are presented in Fig. 2.16:the experimental data obtained with

these two wavelengths were cor-rected for the scattering from emptycell and detector sensitivity, cali-brated in absolute units using a stan-dard sample and radially averaged inorder to deliver the scattering crosssection of this system.The KWS-2 instrument became op-

erational in the short version at thebeginning of September 2007 when itwas opened for internal and externalusers.

Figure 2.17: The upgrades permitting the high-resolution operation mode of KWS-2:parabolic lenses (left) and high-resolution detector (right).

Further upgrading of KWS-2 wascontinued in the second half of 2007in parallel with the user program:the optical focusing elements (MgF2parabolic lenses, Fig.2.17, left) wereimplemented within the end segmentof the collimation system towards thesample position and a "small" high-resolution detector (spatial resolutionof about 1x1 mm2) was installed infront of the conventional detector (Fig.2.17), right). The high-resolution de-tector can be moved to any posi-tion covered by the large detectorand used in combination with thelenses allowing us to cover the Q-range down to 2x10−4ÅThe test andoptimization of the focusing opera-tional mode and the high-resolutiondetector are currently in progress.[1] Graetsch, H., Ibel, K.

Phys.Chem.Minerals, 24, (1997),102.

[2] Keiderling, U., Gilles, R., Wieden-mann, A. J.Appl.Cryst., 32, (1999),456.

[3] Kohlbrecher, J., Buitenhuis,J., Meier, G., Lettinga, M.J.Chem.Phys, 125, (2006),44715.

2 Diffraction 33

2.6 STRESS-SPEC Materials science diffractometer

M. Hofmann 1, U. Garbe 2, G.A. Seidl 1, J. Rebelo Kornmeier3, J. Repper 1, U. Wasmuth 4, R.C. Wimpory 3,C. Krempaszky5, R. Schneider3, C. Randau6, H.G. Brokmeier2,61ZWE FRM II, TU München2GKSS, Geesthacht3BENSC, Hahn-Meitner-Institut, Berlin4UTG, TU München5CDL, WKM, TU München6TU Clausthal, Clausthal-Zellerfeld

Introduction

During the last year the materials sci-ence diffractometer STRESS-SPEC[1] operated without major difficul-ties. A total of 23 user experimentshave been conducted during this year.They covered a wide area of appli-cations in materials science rangingfor instance from kinetic measure-ments in ausferritic steel (M. Bam-berger, Technion, Israel) or residualstresses in integral structures withadhesively bonded crack retarders(D. Liljedhal, Open University, UK)to texture measurements in archeo-logical relevant Mesopotamine seals(D. Visser, Netherlands). For more de-tails the reader is referred to the Ex-perimental Reports section.

-4 -3 -2 -1 0 1 2 3 4

2x103

4x103

6x103

Inte

nsity

[Cou

nts/

30s]

Position [mm]

Figure 2.18: Measured intensity on scanning a 1 mm steel pin through the gaugevolume as a function of position of the center of the pin.

The following sections will reviewrecent hardware developments andgive a brief overview on current in-house research projects.

New hardware

The following hardware develop-ments are now available for routineuse at STRESS-SPEC:

• Top-view camera system forsample alignment

• 1/4- circle Eulerian cradle forsamples up to about 30 kg

• Radial collimatorThe new radial collimator acquiredfrom JJ-Xray, Denmark arrived thisyear and first tests with neutrons werecarried out. The measured gauge

width of the collimator is FWHM =2.05(1) mm (see figure 2.18) and itslong focusing distance of about 200mm leaves enough space for samplemovement even for larger specimens.The advantages of the radial collima-tor compared to the conventional slitsystem are a sharper definition of thegauge volume independent of the dis-tance between sample and collimatorand the reduction of peak clipping ef-fects in measurements close to thesurface of samples.

Science

This section will give some detailsfrom two current in-house researchprojects concerned with "Influence ofmicro stresses on the residual stressanalysis with neutron diffraction" (J.Repper, FRM II, DFG PE-580/7-1) and"Optimisation of Composite Castingsby Means of Neutron Measurements"(U. Wasmuth, UTG, DFG-PE 580/2).

Influence of microstructuralparameters on macro residualstress analysis

Mechanical and thermal treatmentsduring the manufacturing process in-evitably cause the accumulation ofresidual stresses in parts consistingof materials with complex microstruc-ture (e.g. high performance mul-tiphase Ni- or Ti-alloys). Neutrondiffraction is particularly well suitedto determine residual stress distribu-tions within the bulk of the compo-nent.The analysis of residual stresses

from diffraction data, however, canbe strongly influenced by inhomo-geneities of microstructural parame-

34 2 Diffraction

ters (texture, grain size, distribution ofprecipitates, phase composition). Wewere able to show this influence bymeans of a simple sample geometry(flat disc shaped IN718 specimen, di-ameter = 100 mm) where process rel-evant boundary conditions allow us topredict the stress distribution in oneprinciple - here axial - direction [2].For the determination of the resid-

ual stress distribution in the IN718forged pancake it was not possible tocut a reference sample from the speci-men itself as the pancake will be usedfor further experiments. In this casea reference value was calculated onthe basis of mechanical equilibriumassuming the axial stresses to vanish.This assumption is valid in case of thinplate-like components of constantthickness with a thermo-mechanicaltreatment which is symmetrical to themid-plane of the disc and homoge-nous and isotropic with respect tothe in-plane coordinates [3]. Mechan-ical equilibrium then yields that thestress in thickness direction is zero.Taking this into account it could beshown that the calculated reference

0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5

-600

-400

-200

0

200

400

600

Measuring depth x [mm]

hoop radial axial radial/hoop model

Res

idua

l Stre

ss

[MP

a]

Figure 2.19: Residual stress distribution in the three principal axes hoop, radial andaxial plotted against measuring depth x across the thickness of an IN718 disc(dashed lines indicate the position of the surfaces of the disc). The black lineshows the stress distribution in the radial and hoop direction predicted by a simplesemi-analytical model [2, 3].

value varies across the thickness ofthe pancake [2]. This stems from in-homogeneities in the microstructurecaused by the manufacturing pro-cess (forging and quenching). Thetemperature of regions near the sur-face decreases faster than the interiorof the pancake during the quench-ing. This leads in addition to straingradients to changes in the chem-ical composition of the matrix overthe thickness of the pancake. There-fore, each measuring point necessi-tates its own reference value to obtainthe true macroscopic stress. Figure2.19 shows the resulting stress dis-tribution through the thickness of thepancake. The residual stresses de-rived from the experiment show goodquantitative agreement with the pre-dictions of a simple semi-analyticalthermo-mechanical model based onthe work of Landau et al. [4] eluci-dating the transient thermal stressesduring quenching.For a detailed understanding of the

relations between stresses (macro-scopic and microscopic stresses aswell) and microstructural parameters

further experiments (e.g. tensile tests,relaxation tests) are planned.

Optimisation of compositecastings

Composite casting is mainly usedto produce composite engine blockswith in-cast liners. Due to differentthermal expansion of the casting ma-terial and the material of the insertresidual stresses occur during solidi-fication. These residual stresses canreduce fatigue strength and lead todistortions of the part. They canbe minimised by constructive mea-sures. Casting simulation is a suitablemethod to predict residual stressesand distortions and thus to optimisedesign of parts. To improve the accu-racy of stress simulations simple com-posite test castings were designed(see figure 2.20) and characterisedby neutron diffraction experiments onSTRESS-SPEC [5]. In order to vali-date the experimentally derived resid-ual stresses the balance of total axialforce(2.1)

F totalax =

∫φ

∫rσax(r,φ) r dr dφ = 0

perpendicular to the ring area Awas verified at center position z=0(see Figure 2.20). Because of sym-metry the stress function σax(r,φ) de-pends only on the radius r. The steelring and the aluminium ring forceswere calculated individually in accor-dance to eq. (2.1). Calculated axialforces of 51.9 kN in the aluminiumring and -50.1 kN in the steel ring areadequate results to satisfy stress bal-ance. Axial and hoop stresses ob-tained by strain gauge methods at sur-faces are on the same level as neutrondiffraction measurements and verifythe neutron data additionally [4].

2 Diffraction 35

Figure 2.20: Test specimen consisting of ainner steel ring and an outer aluminiumcasting, (left) photograph with straingauges for stress measurements, (right)sketch with dimensions and polar coor-dinate system.

The residual stress simulation wascarried out using mechanical param-eters of [6, 7]. The start tempera-ture of aluminium and steel was setto solidus temperature (TS = 479°C).The 0.2% proof stress and tensilestrength parameters have been deter-mined experimentally. The simulatedstresses proofed to be three timeshigher compared to the experimen-tal reference as the material model inthe mechanical simulation does notinclude stress relaxation processesduring solidification. In general stressrelaxation depends strongly on tem-perature, stress level and time [8]. Es-pecially composite casting processesare influenced by stress relaxation,as stresses are formed even at hightemperatures due to different thermalexpansion coefficients of materials.In our case stress relaxation was

24 26 28 30 32 34 36 38-300

-250

-200

-150

-100

-50

0

50

100

hoop radial axial

Res

idua

l Stre

ss

[MP

a]

Radius r [mm]

Figure 2.21: Residual stress distribution in the three principal axes hoop, radial andaxial plotted against measuring depth x across the radius of the composite casting.The coloured lines are results from the simulation as discussed in text. The verticaldotted lines in the graph adumbrates the position of the steel ring.

implemented to the mechanical simu-lation introducing an effective thermalstrain term

(2.2) εth,eff = εth− εsr

with thermal strain εth and relaxationstrain εsr. The simulation model in-cludes stress relaxation depending onthe stress level while neglecting tem-perature and time dependence. UsingTaguchi methods [9] the stress simu-lations were optimised based on theexperimentally derived hoop stresses.Optimised relaxation to thermal strainratios ranging form 0.357 to 0.367fit both the level and shape of thestress curves (see figure 2.21). Dueto fraction processes during solidifi-cation the experimentally determinedaxial stresses are lower than the sim-ulated stress. Nevertheless the op-timised simulation shows sufficientagreement with the neutron diffrac-tion data of the investigated test spec-imen.However, the simulation has to be

extended by a universal temperatureand a time dependent stress relax-ation model. As stress relaxation datais difficult to determine experimentallyat high temperatures, in-situ strainmeasurements using neutron diffrac-tion will be carried out during the so-lidification process of the specimenin the near future. The experimental

results could then be used to verifyuniversal relaxation models in castingsimulations.[1] Hofmann, M., Kornmeier, J. R.,

Garbe, U., Wimpory, R., Rep-per, J., Seidl, G., Brokmeier, H.,Schneider, R. Neutron News, 18(4), (2007), 27–30.

[2] Repper, J., Hofmann, M., Krem-paszky, C., Petry, W., Werner, E.Mat. Sci. Forum, (accepted 2007).

[3] Krempaszky, C., Werner, E.,Stockinger, M. Proceedings ofthe Sixth International Special Em-phasis Symposium on Superal-loys 718, 625, 706 and Derivatives,527.

[4] Landau, H., Weiner, J., Zwicky, E.J. Appl. Mech., 27, (1960), 297–302.

[5] Wasmuth, U., Meier, L., Hofmann,M., Mühlbauer, M., Stege, V., Hoff-mann, H. Annals of the CIRP, (sub-mitted 2008).

[6] Hutchings, M. Taylor & Francis,(2005).

[7] Bäckerud, L. SolidificationCharacteristics of AluminiumAlloys, Vols. 2-3, (1990),Afs/Skanaluminium.

[8] M.F. Ashby, H. J. Springer-Verlag,(1986).

[9] Funkenbusch, P. Marcel Dekker,(2005).

36 2 Diffraction

2.7 Integration of a new sample goniometer and a further double discchopper (SC-2) in the ToF-neutron reflectometer REFSANS

R. Kampmann1, M. Haese-Seiller1, J.-F. Moulin1, V. Kudryashov2, B. Nickel4, E. Sackmann3, A. Schreyer11GKSS Forschungszentrum, Geesthacht2Petersburg Nuclear Physics Institute, Russian Federation3Physik-Department E22, TU München4LMU München

New sample goniometer atREFSANS

REFSANS has been designed as anovel ToF neutron reflectometer [1, 2]for comprehensive analyses of sur-faces and interfaces. A new sam-ple goniometer could be purchasedin 2007 to enable samples inside oflarge and heavy (up to 200 kg) environ-ments to be analysed at REFSANS.The goniometer comprises x-, y- andz-translation tables, one rotation ta-ble and two cradles (Fig. 2.22). Thedistance from the symmetry centreof the cradles to their upper surfaceamounts to 300mm.

Slave-chopper-2

SC-2 was installed in the beam guidechamber of REFSANS in January2007. The SC-2 discs-5 and -6

Figure 2.22: Sample goniometer of REF-SANS with a sample aligned in thebeam.

have one large window (W5,0 and W6,0)with an opening of 120° and 5 smallwindows with openings of only 1°(W5,1 . . . W5,5: Fig. 2.23a; disc-5) and3°, 1°, 2°, 1° and 5° (W6,1 . . . W6,5:Fig. 2.23b; disc-6). The angular sep-aration between the closing sides ofthe small windows of both discs is10° whereas the gap between the firstsmall and the 120° window amountsto 20°. The linear table is installedin REFSANS vertically and the beampasses SC-2 to the right of the axis ifviewed in beam direction. This corre-sponds to a beam position above theaxis in Fig. 2.23a and 2.23b.SC-2 can be used in different op-

eration modes by adequate settingof the phases of disc-5 and disc-6.For reflectometry and GISANS mea-surements the phases may be setsuch that SC-2 opens only one win-dow with an angular width between 0°and 120° in order to define the wave-length range to be used for an experi-ment. In the calibration mode usuallyup to 11 small windows with widthsbetween 1° and 5° are adjusted suchthat only neutrons of various wave-lengths λi can pass through SC-2. Inthe inelastic mode only one or a fewsmall windows are opened for inelas-

W5,0

W5,1

W5,5

disc-5

a)

W6,0

W6,1

W6,5

b)

disc-6

Figure 2.23: Views of SC-2 with rotation drive and linear table in beam direction(Fig. 2.23a) and against it (Fig. 2.23b). The yellow arrows indicate the rotationdirection, the green bar indicates the beam area.

tic measurements. Furthermore, forreflectivity measurements with a verybroad wavelength range SC-2 will notbe rotated and the beam penetratesits windows. These different oper-ation modes lead to the unconven-tional design of discs-5 and -6.

High precision neutronreflectometry at REFSANS

High resolution reflectometry needsprecise measurements of both the in-cidence angle and the wavelength.The incidence angle can accuratelybe measured at REFSANS by meansof the high spatial resolution of the2D-detector (FWHM ≈ 2mm in verti-cal direction [3]) and the long distanceof up to ≈ 12m which can be set be-tween the sample and the detector.The installation of SC-2 allows of

performing accurate λ -calibrations.Those measurements are performedby setting discs-5 and -6 of SC-2such that only intensity peaks aretransmitted. An example of a primarybeam and calibration measurementas performed in the frame of measure-ments for proposal 1542 is shown inFig. 2.24: The continuous spectrumin Fig. 2.24a represents the primary

2 Diffraction 37

beam measurement with non rotatingdiscs-5 and -6 and a sample detec-tor distance of 6697mm (REFSANS-parameter table=6m). At short flighttimes (t < 35ms) the spectrum reflectsthe cold spectrum of neutron guideNG-2b. After ≈ 35ms the transmis-sion of the chopper decreases moreand more and vanishes at ≈ 70ms.This results from the window set-ting of the Master-Chopper (MC) andSlave-Chopper-1 (SC-1) for this mea-surement.After the primary beam measure-

ment SC-2 was started and thephases of discs-5 and -6 were setsuch that the small window peaksformed by disc-6 were observed withflight times t6,i < 30ms and those fromdisc-5 at t5,i > 40ms. A further calibra-tion peak (t5,6 ≈ 37ms) is formed bythe large windows of disc-5 and -6.

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

0 20 40 60 80 100flight time [ms]

netto

cou

nt ra

te [1

/s]

primary beam / 3calibration table=6m

a)

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

0 20 40 60 80 100flight time [ms]

netto

cou

nt ra

te [1

/s]

calibration table=1mcalibration table=11m

b)

Figure 2.24: Primary beam measurement and λ -calibration at REFSANS. Measurementof the primary beam was performed with non rotating SC-2 at table = 6m corre-sponding to a sample detector distance of 6697mm (Fig. 2.24a). The λ -calibrationwas performed by running SC-2 in calibration mode and setting the detector totable = 1m, 6m and 11m 2.24a and Fig. 2.24b.

Afterwards the calibration peakswere measured at further distancesbetween the sample and the detectorcorresponding to differences in flightlength of ±5m (Fig. 2.24b). The timedifferences of the peak positions areused to determine the velocity andthus the wavelength of the neutrons.It is pointed out that these measure-ments can be performed in short mea-suring time, they lead to a very pre-cise lambda-calibration for a set ofvery different wavelengths.

Such calibration measurements byuse of SC-2 significantly improved thereconstruction of reflectivity curvesbecause the flight time at REFSANSdepends not only on the wavelengthbut also on the openings of the win-dows of the MC and SC-1 (γMC andγSC−1) and further on the phase shiftbetween the closing of MC and the

opening of SC-1 (δMC,SC−1). This re-sults from the fact that γMC, γSC−1and δMC,SC−1 define both the positionand the starting time of the neutronpackages in dependence of the wave-length. After putting SC-2 into op-eration these parameters are deter-mined from lambda-calibrations by fit-ting the observed peak arrival timesto the chopper settings.The neutron reflectivity of a film

from an implant coating with cellmembrane mimics exemplifies theperformance of REFSANS for highprecision reflectometry (proposal1542). Firstly, the reflectivity from ametallic Ti-alloy (Ti-6Al-4V; 100nm)sputtered onto a Si wafer was mea-sured at REFSANS. Measurementswere performed at different incidenceangles as indicated in Fig. 2.25.Afterwards the metallic film wascoated with POPE (Palmitoyl-OleoylPhosphatidyl-Ethanolamine). Signifi-cant changes of the reflectivity curvewere observed after ageing of thePOPE and adhesion of proteins (fetalbovine serum, containing 3− 4.5gProtein / dl; see Fig. 2.25).

Use of REFSANS in 2007

REFSANS could not be used for userproposals to the expected extend.This was due to technical reasons re-sulting from faulty soft- and hardwaresystems controlling the neutron op-tics and the choppers. A strong re-duction in staff members from Aprilto November 2007 made running ofREFSANS further difficult. Neverthe-less, REFSANS has been improvedtechnically and measurements in theframe of exciting internal and exter-nal proposals could successively beperformed.

Acknowledgements

The great contribution of the technicaldepartment of GKSS to constructingand manufacturing of REFSANS com-ponents is gratefully acknowledged.The development of REFSANS hasbeen supported by the German Fed-eral Ministry of Education, Research

38 2 Diffraction

and Technology (BMBF) under con-tracts 03-KA5FRM-1 and 03-KAE8X-3.

References

[1] Kampmann, R., Haese-Seiller, M.,Marmotti, M., Burmester, J., De-riglazov, V., Syromiatnikov, V.,Okorokov, A., Frisius, F., Tristl, M.,Sackmann, E. Applied Physics A,74, (2002), 249–251.

[2] Kampmann, R., Haese-Seiller, M.,Kudryashov, V., Deriglazov, V.,Tristl, M., Daniel, C., Toperverg, B.,Schreyer, A., Sackmann, E. Phys-ica B, 350, (2004), e763–e766.

[3] Kampmann, R., Marmotti, M.,Haese-Seiller, M., Kudryashov, V.

Nuclear Instruments and MethodsA, 529, (2004), 342–347.

1E-07

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E+00

0 0,05 0,1 0,15 0,2 0,25 0,3momentum transfer [1/Å]

refle

ctiv

ity

without POPE (3.034°)

without POPE (0.534°)

without POPE (3.034°; low-lambda-res.)

with POPE and proteins (3.034°)

Figure 2.25: Implant coating with cell membrane mimics: Reflectivity curves withoutPOPE phospholipid (see text) and with POPE and proteins are shown (proposal1542: F. Feyerabend et al.).

2.8 N-REX+ – The neutron / x-ray contrast reflectometer with spin-echooption

A. Rühm1, M. Major1, M. Nülle1, J. Franke1, J. Major1, H. Dosch1

1Max-Planck-Institut für Metallforschung, Stuttgart

Status

During the year 2007 first user exper-iments have been conducted at theneutron/X-ray contrast reflectometerwith spin-echo option, N-REX+ [1, 2].Fields covered were soft matter re-search (interfaces, membranes), mag-netism in superconductors, and wear-resistant coatings. We also contin-ued our research on the dewettingof polymer films and further exploredthe advantages of the novel SERGISmethod for this purpose (Spin-EchoResolved Grazing Incidence Scatter-ing, see [3]). In this context, newtriangular spin-echo coils (collabora-tion with Roger Pynn, Indiana Univer-sity at Bloomington, USA) have beentested for the first time as an alterna-tive to resonance coils. In addition,further instrument operation modes(PNR, SANS, and GISANS) have beeninstalled and applied for the first time,alongside with conventional neutron

Figure 2.26: N-REX+ in SERGIS mode with triangular spin-echo coils. Inset: Detailedview of a pair of triangular-shaped spin-echo coils. The coils can be water-cooledand air-cooled with additional ventilators (not shown). Currently coil sets with45/45 and 30/60 angles are available.

2 Diffraction 39

reflectometry, neutron/X-ray contrastvariation, and the SERGIS technique[3], which had already been utilized inthe year before. As an example, wedescribe in the following two sectionsthe results of a SERGIS and a PNRexperiment conducted in 2007.

Spin-echo resolved grazingincidence scattering

Fig. 2.26 shows N-REX+ in SERGISmode with triangular spin-echo coils(one coil pair is shown enlarged in

Figure 2.27: Top row: Detector images of the GISANS signal of an optical grating (alu-minum 1"×1", 3600 lines/mm), left column: resonance coils, right column: trianglecoils. The intense horizontal streak at the bottom is the primary beam, the featureon top is the GISANS signal from the sample. The red and blue regions of interest(ROI) are centered on the Yoneda scattering feature [4, 5] and the total scattering,respectively, where the latter also includes specular contributions. The black ROIcentered on the primary beam was used to obtain a reference signal. Middle row:SERGIS data sets obtained from the red and blue ROI as a function of spin-echolength lSE. The total counting time per displayed data point was 24-65 minutes (leftcolumn) and 80 minutes (right column), respectively. Bottom row: Comparison ofSERGIS data obtained from the Yoneda ROI (red curves) and the total scattering(blue curves) with resonance and triangular spin-echo coils, respectively. In case ofthe red ROI (Yoneda intensity), which is the more reasonable choice, even details ofthe scattering length density profile in between two grating lines are reproducedvery consistently for the two coil variants.

the inset). The two images at thetop of Fig. 2.27 show detector im-ages on which the primary beam andthe GISANS signal from an opticalgrating can be discerned (left: ex-periment with resonance spin-echocoils, right: experiment with triangu-lar spin-echo coils). The correspond-ing SERGIS data sets as obtainedfrom the GISANS signal are plottedin the graphs below the detector im-ages and compared with each otherin the bottom row of Fig. 2.27. Overallthe two data sets are well consistentwith each other.In the case of reso-

nance spin-echo coils, the achievablespin-echo length is (at the same staticcurrent setting) two times larger thanin the case of triangular coils with45/45 angles. On the other hand,the triangular spin-echo coils providea better resolution at smaller spin-echo lengths, and as an option, tri-angular coils with 30/60 angles arenow also available at N-REX+, whichcan compensate the lost factor of 2.

Polarized neutronreflectometry

The two images in Fig. 2.28 showN-REX+ during a polarized neutronreflectometry (PNR) experiment em-ploying a 7.5 Tesla magnet providedby FRM II (collaboration with Prof.Wolfgang Donner, University of Hous-ton, USA, now Technische Univer-sität Darmstadt). The superconduct-ing NbTi/Nb multilayer sample wascooled to 2.5 K in a cryostat, andthe influence of magnetic fields upto 6 Tesla on the magnetic structureof the sample was investigated. Forthese experiments we used neutronswith a wavelength of 5.5 Å. The ini-tial vertical neutron beam polarisationwas preserved at about 80% whenpassing the magnet, which pointsto negligible depolarisation in spiteof the symmetrical construction ofthe magnet. Nevertheless the ex-pected small difference between thereflectivity curves of spin-up and spin-down neutrons (shown in Fig. 2.28)could not be verified very clearly, pre-sumably due to problems with thealignment of the sample in the cryo-stat, which is very critical in thiscase. It is planned to improve thealigment capabilities inside or outsidethe cryostat for future experiments.A slight asymmetry between spin-upand spin-down reflectivity was ob-servable, however. The associatedmaximum in the polarization movesto higher angles (larger momentumtransfers) upon increasing the appliedmagnetic field from 3 T to 5 T (seebottom row of Fig. 2.29). This wouldhint at a compression of the flux linelattice at larger magnetic field.

40 2 Diffraction

Figure 2.28: N-REX+ in polarized neutronreflectometry (PNR) mode. The big 7.5Tesla magnet and a compatible cryo-stat were supplied by FRM II.

Figure 2.29: Neutron reflectivity curves and corresponding polarization values mea-sured on a superconducting NbTi/Nb multilayer (black: spin-up neutrons, red:spin-down neutrons, the final spin state after reflection was not analyzed). A slightpeak-shift was expected between the two curves (see main text). The experimen-tal data on the left and right were measured at a magnetic field of 3 T and 5 T,respectively. The total counting time per displayed data point was 5-25 minutes.

[1] Rühm, A., Wildgruber, U., Franke,J., Major, J., Dosch, H. In: Neu-tron Reflectometry, A Probe forMaterials Surfaces, Proceedingsof a Technical Meeting organizedby the International Atomic EnergyAgency and held in Vienna, 16-20 August 2004, Vienna, Austria,161–175.

[2] Teixeira, S. C. M., Zaccai, G.,Ankner, J., Bellissent-Funel, M. C.,Bewley, R., Blakeley, M. P., Cal-low, P., Coates, L., Dahint, R., Dal-gliesh, R., Dencher, N. A., Forsyth,

V. T., Fragneto, G., Frick, B.,Gilles, R., Gutberlet, T., Haertlein,M., Hauß, T., Häußler, W., Heller,W. T., Herwig, K., Holderer, O., Ju-ranyi, F., Kampmann, R., Knott,R., Krueger, S., Langan, P., Lech-ner, R. E., Lynn, G., Majkrzak, C.,May, R. P., Meilleur, F., Mo, Y.,Mortensen, K., Myles, D. A. A., Na-tali, F., Neylon, C., Niimura, N., Ol-livier, J., Ostermann, A., Peters, J.,Pieper, J., Rühm, A., Schwahn, D.,Shibata, K., Soper, A. K., Strässle,T., Suzuki, J., Tanaka, I., Tehei,M., Timmins, P., Torikai, N., Unruh,

T., Urban, V., Vavrin, R., Weiss,K. Chemical Physics, 345, (2008),131–151.

[3] Major, J., Dosch, H., Felcher, G. P.,Habicht, K., Keller, T., te Velthuis,S. G. E., Vorobiev, A., Wahl, M.Physica B, 336, (2003), 8–15.

[4] Yoneda, Y. Phys. Rev., 131, (1963),2010.

[5] Sinha, S. K., Sirota, E. B., Garoff,S., Stanley, H. B. Phys. Rev. B, 38,(1988), 2297.

3 Inelastic scattering 41

3 Inelastic scattering

3.1 J-NSE: Performance and first experiments

O. Holderer1, M. Monkenbusch1, R. Schätzler1, N. Arend1, G. Borchert2, C. Breunig2, K. Zeitelhack2,W. Westerhausen3, H. Kleines4, M. Wagener4, F. Suxdorf4, M. Drochner41JCNS, Research Centre Jülich, outstation at FRM II2ZWE FRM II, TU München3ZAT, Research Centre Jülich4ZEL, Research Centre Jülich

Introduction

The neutron spin-echo instrument, J-NSE, has been moved from the FRJ-2in Jülich to the guide hall of the newFRM II reactor. In order to supply anintense beam of polarized neutronsat the assigned new position of theinstrument, a neutron guide systemhad to be designed and built to trans-port neutrons from the available par-tial beamwindow of the neutron guideNL2 at the wall of the guide hall to theproper spectrometer. Polarization ofthe short wavelengths is achieved ina bent section with a m=3 FeSi mul-tilayer coating. Due to the total re-flection of FeSi, longer wavelengthspass unpolarized and an additionalshort polarizer at the entrance of theinstrument is required. For a neutronwavelength band of 10% FWHM cen-tered at 7Å a flux of 1×107/cm2s atthe sample has been achieved.

The polarizing neutron guidesystem

Neutron spin echo (NSE) spec-troscopy provides the highest reso-lution (corresponding down to a fewnano eV) in inelastic neutron scatter-ing [1, 2], with applications in thestudy of slow dynamics of soft mat-ter systems as e.g. polymer melts ormicro-emulsions, or in paramagneticscattering (spin glasses). The normal-ized intermediate scattering functionis measured in terms of polarizationloss of the scattered neutrons. As

input the instrument accepts a polar-ized beam with a wide velocity distri-bution and thereby yields the neces-sary scattering intensity.The Jülich NSE spectrometer (J-

NSE) had been installed in the neu-tron guide hall of the Jülich researchreactor FRJ-2 [3].With the end-of-operation of the

FRJ-2 reactor the instrument (see fig.3.1) has been technically updated andtransferred to the FRM II in Garch-ing supplying a considerably higherneutron flux. The neutrons from theFRM II cold source have to be po-larized and transported efficiently

Figure 3.1: View on the J-NSE instrument at the FRMII.

to the J-NSE instrument. The dedi-cated neutron guide system which isdescribed here is designed to servethis purpose.At the new position at the FRM II,

the J-NSE is connected to a dedi-cated fraction of the neutron guideNL2, i.e. NL2a-o.Using a mechanical velocity selec-

tor included into the guide sectionit is possible to use wavelengths λ

between 4.5 and 19 Å. This givesan enormous increase in the dy-namic range of the spin echo spectro-meter, since the intermediate scatter-ing function depends on the Fourier

42 3 Inelastic scattering

time t with t ∝∫|B|dl λ 3, where the

first factor, the field integral∫|B|dl

alone allows for a 1:103 variation.The neutron guide NL2a-o sepa-

rates by a bent part of 8 m lengthinside the radiation shielding case-mate from the neighboring NL2 sec-tion that leads to the time-of-flightspectrometer TOF-TOF. The radius ofcurvature is 160 m which on the oneside yields sufficient distance fromthe TOF-TOF feeding guide at the po-sition of the instrument and on theother hand polarizes the beam in therange from λ=2.5...8 Å by reflectionfrom a m=3 (spin-up) and m=0.65(spin-down) FeSi multilayer producedby T. Krist, NOB. The m-value de-notes the ratio of the total reflectionangle compared with that from a plainNi coating as reference. Due to thehigh primary flux at the curved sectiona coating containing cobalt was dis-carded because the long term buildupof considerable 60Co activation. Be-cause of the unpolarized total reflec-tion of FeSi below m=0.65 the longerwavelengths λ =8...16 Å need an ad-ditional short polarizer at the entranceof the actual NSE instrument. Afterthe bent section a mechanical selec-tor (which currently limits the wave-length to λ ≥4.5Å) is inserted, fol-lowed by 10 m of tapered 58Ni cov-ered guide which ends with a crosssection of 60×60 mm2. The NSE-spectrometer uses only a limited di-vergence of the neutron beam, sincethe sample position is approximately3.5 m behind the end of the neutronguide. A supermirror (NiTi) coating in-stead of 58Ni would mainly increasethe flux with high divergence and istherefore not necessary in our case,which also simplifies the shielding ofthe neutron guide.The additional long wavelength po-

larizer consists of a 60 cm long pieceof neutron guide with 2 separatingwalls, the reflecting guide surface andboth sides of the walls are coveredwith an m=3 FeSi multilayer (SwissNeutronics). For the short wavelengthconfiguration, this polarizer acts asa simple piece of neutron guide. Itfollows directly the last part of the58Ni-Guide. For polarizing the long

wavelengths, the whole NSE spectro-meter needs to be turned by Θ = 4

and the long wavelength polarizer ismoved to an angle of Θ/2 = 2. Thisleads to a reflection at the polarizingwalls and to a deviation of the beamof 4.The initial bent section after the

NL2a-o separation is embedded intoa vertical guide and magnetizationfield > 30 mT which is generatedby NbFeB magnet columns betweensoft iron plates on top and below theguide. After the bent section withFeSi multilayer coating the field is re-duced to 6mT. On a 1 m section be-fore the selector the vertical field isturned smoothly into the longitudinaldirection by a solenoid around theneutron guide. That way the neutronspins and hence the beam polariza-tion follows the field direction adiabat-ically. The selector is surrounded bya solenoid to preserve the polariza-tion during the neutron passage. Thesubsequent 10 m of neutron guideare surrounded by a coil with about 2turns/cm which yields B=2.5 mT at acurrent of 10A. Finally, the additionalpolarizer for long wavelengths is sur-

Figure 3.2: Flux at the sample position as function of wavelength setting of the selec-tor. Open symbols correspond to straight configuration of the spectrometer withinactive secondary polarizer, solid symbols show result from the 40 setting withactive polarizer.

rounded by a solenoid able to sustain5 mT and to create a (once in a whileneeded) magnetizing field of 30 mTduring a few seconds.The flux at the end of the neutron

guide, i.e. at the entrance of theNSE spectrometer, has been mea-sured by gold-foil activation. Thewavelength band is defined by themechanical velocity selector (10 %FWHM). Short wavelengths are suffi-ciently polarized, whereas the longerwavelengths need an additional po-larizer. Thus beyond 12Å the goldfoil activation detects the sum of bothspin directions. The flux at the endof the guide ranges from polarized4.5 ×107/cm2s for wavelength shorterthan λ = 7 Å down to 1×107/cm2s atλ =16 Å. The wavelengths beyond 9-10Å are insufficiently polarized andneed the additional polarizer. On thenon-guided path of ' 3.5m betweenneutron guide exit and sample posi-tion the larger divergence of the longwavelength neutrons leads to a con-siderable dilution effect on the flux atthe sample position.A reduction of the flipping ratio with

increasing wavelength results from


the total reflection of both spin com-ponents. The additional polarizer isused at a fixed deviation angle of 4.For λ = 8 Å the flipping ratio is sig-nificantly enhanced by the polarizer(from below 7 to above 25), however,the angluar acceptance there is notfully developed to the desired valuedue to limitation of m. On the otherhand at 19Å the total reflection edge(m=0.6) of the polarizer starts to con-tribute.The flux at the sample position

was measured with a calibrated beammonitor. All correction elements andflippers in the beam path were in-stalled.Considering the polarization the

flux obtained in the straight configu-ration may be used up to 8 to 9 Å be-yond that the 4°configuration with ac-tive polarizer needs to be employed.The wavelength dependence of

the flux at the sample position isillustrated in figure 3.2 for the sit-uation without extra polarizer (us-able for λ ≤ 9 Å) and with po-larizer (usable for λ ≥ 8 Å). AMaxwell spectrum emitted from asmall source is expected to delivera flux Φ0 λ−5 exp(−h2/(2mnλ 2kBT )),since the wavelength band is pre-pared by a selector with constant rela-tive width, i.e. ∆λ ∝ λ the λ−5 depen-dence is mitigated to Φ ∝ λ−4. Theflux at the sample for 7 Å matchesthat of the ILL instrument IN15, how-ever, the decrease at longer wave-length is steeper for the J-NSE. Thelatter effect has still to be understood.

First experiments

First experiments have been carriedout with different setups. The “shorty”option (a spin echo setup with a set ofsmall main precession coils betweenthe main precession coils and thesample position) together with wave-lengths of 5 Å allowed for measur-ing with Fourier times ≥ 4 ps. Thestandard setup with λ = 8 Å hasbeen used for comparison with exper-iments performed at the DIDO reac-tor in Jülich. First experiments havebeen performed also at longer wave-lengths (12.8 Å) to access Fouriertimes of ∼ 70 ns. For experiments

at large field integrals and hence highFourier times, the resolution of thespectrometer needs to be further im-proved and development is going onto achieve this with better correctioncoils in each arm. In Figure 3.3, twospin echo groups recorded at differ-ent setups are presented (top) as wellas the intermediate scattering func-tion of a polymer solution at q=0.81/nm, showing Zimm dynamics.

Conclusion

In summary the flux a the new posi-tion of the J-NSE at the FRM II yields15 times the flux at 8Å that was ob-tained at the old position in the FRJ-2 guide hall. In addition, the flexi-bility to choose 4.5 ≤ λ ≤ 19Å hasbeen gained by the combined effectof the new reactor source and the tai-lored neutron guide system. First

Figure 3.3: Spin echos measured at 5 Å and 12 Å (top) and S(q,τ ) from a polymersolution measured at 8 Å.

experiments have been performed onthe relocated spectrometer. Develop-ment is going on for improving theresolution at large field integrals. Fur-ther details may be found in ref. [4].[1] Mezei, F., editor. volume 128

of Lecture Notes in Physics(Springer, Berlin, Heidelberg, NewYork, 1980).

[2] Mezei, F., Pappas, C., Gutberlet,T., editors. volume 601 of LectureNotes in Physics (Springer, Berlin,Heidelberg, New York, 203).

[3] Monkenbusch, M., et al. Nucl.Instr. & Methods In Physics Re-search A, 301–323.

[4] Holderer, O., et al. Nucl. Instr. &Methods In Physics Research A.In press.


3.2 MIRA – The beam line for very cold neutrons at the FRM II

R. Georgii1, M. Ay2, P. Böni3, R. Gähler4, C. Grünzweig2, Ph. Jüttner1, T. Hils3, A. Mantwill1, S. Mühlbauer1,R. Schwikowski11ZWE FRM II, TU München2Laboratory for Neutron Scattering ETHZ & PSI,Switzerland3Physics Department E21, TU München4Institut Laue Langevin, Grenoble, France

MIRA is a versatile instrument forvery cold neutrons (VCN) using neu-trons with a wavelength λ > 8 Å. Theflux at the sample position is 5 · 105

neutrons/(cm2 s) unpolarised. It issituated at the cold neutron guideNL6b in the neutron guide hall of theFRM II. As the instrument set-up canbe changed quickly, MIRA is ideallysuited as a testing platform for real-izing new instrumental set-ups andideas. In particular, MIRA is unique inits possibilities of combining differentneutron scattering methods as:

• Polarized or non-polarized re-flectometry.

• Spherical polarimetry• Polarized or non-polarizedsmall angle scattering (SANS).

• Classical NRSE (Neutron Reso-nance Spin Echo) setup as wellas using the MIEZE principle.

Figure 3.4: MIRA and the secondmonochromator shielding

Status

In 2007 year MIRA was again suc-cessfully operated for 5 reactor cy-cles. In total, 16 external and 18 in-ternal proposals, several test and ser-vice measurements were performed.Several measurements for diplomatheses were finished using mainlydata from MIRA. A total of 2 weekswas devoted to the Fortgeschrittenen-praktikum of the Physics Departmentfor 35 students in total.Currently the upgrade of MIRA to

shorter wavelengths is in progress.The goal is to use neutrons with wave-lengths between 3 Å and 6 Å from theneutron guide NL 6a (beam area 120 x60 mm2) using a PG monochromator.Having neutrons with a wavelengthcloser to the maximum of the coldflux, having the PG monochromatorwith a higher reflectivity as the currentmultilayer monochromator and usingalso a vertical focusing monochroma-tor, MIRA will then show an significantincrease the intensity. This year thenew monochromator shielding has al-ready been integrated in the guide NL6a (see Figure 3.5) and all prepara-tions for installing the new option inJanuary 2008 have been taken.

Multiple small angle neutronscattering (MSANS): A newtwo-dimensional ultrasmallangle neutron scatteringtechnique

Small angle neutron scattering (SANS)is a powerful technique for studyingthe structure of materials with lateralcorrelation lengths in the range ofabout 0.6 nm up to about 600 nm.This corresponds to a q-range of 1Å−1 to 10−3 Å−1. Measuring correla-tion lengths in the micrometer range

being of high interest for the researchon biological samples, polymers, col-loid systems, cements, micro-porousmedia leads to unacceptable lossesin intensity by a factor 104 using thestandard SANS technique. With thenew MSANS technique we can over-come the intensity problem. Themethod is based on two 2D-multi-hole Cd-apertures one placed at thefront end of the collimator of a com-mon SANS instrument and the otherclose to the sample (Fig. 3.6 ).By choosing the proper MSANS ge-

ometry, individual diffraction patternsare superimposed leading to a largegain in intensity. Using MSANS asan option for SANS beam lines, theq-resolution can be increased to 10−5

Å−1 without dramatically sacrificingintensity. The first demonstration ex-periment of the MSANS technique [1]was performed at the diffractometerbeam line MIRA, where we alreadyobtained a q-resolution of 3 ·10−4 Å−1.Fig. 3.7 shows a section of the de-tector image of a gadolinium (Gd) ab-sorption grating with a period of 2µm.Fig. 3.8(a) shows the detector im-

age from a silicon phase grating witha period of 2 µm. The large gain inintensity is clearly visible in Fig. 3.8(c).

Figure 3.5: A close-up of the monochro-mator shielding


2 m

Si

Gd

2 m

Si

Gd

neutron source

entrance multihole aperture (Me)

sample multihole aperture (Ms)

imagedetector

sample

L2

L1

ae,s

de,s

ae,s

de,s

z

x

y

ad

Figure 3.6: Schematic experimental setup of the MSANS option showing the 2D en-trance multi hole aperture (Me) with a lattice constant ae and hole diameter de, andthe 2D sample multi hole aperture (Ms) with lattice constant as and hole diameter ds.Using appropriate values ae= 5 mm, as= 2.5 mm and L1 = L2 = 2.6 m, the individualbeams superimpose on the detector on a grid with the lattice constant ad = 5.

Recently, a similar experiment hasbeen performed using D11 at the Insti-tute Laue-Langevin, where a gratingwith a pitch of 17 µm was resolvedusing the MSANS technique.[1] Grünzweig, C., et al. Appl. Phys.

Lett., 91, (2007), 203504.

Figure 3.7: Section of an MSANS detectorimage of a 2 µm period Gd absorptiongrating.

Figure 3.8: MSANS data of Si phase grating with a period of 2 µm. (a) Detectorimage. (b) Profiles along the y-axis through one hole pattern without sample in thebeam (green box in (a)). The orange box in (a) showing the diffraction pattern ofa 1D phase grating. (c) Section plot along the y-axis of 16 individual summed updiffraction patterns (red box in (a)).


3.3 PANDA– report from the FRM II cold TAS

P. Link1, A. Schneidewind2, D. Etzdorf1, M. Loewenhaupt21ZWE FRM II, TU München2Institut für Festkörperphysik, Technische Universität Dresden

Introduction

The second year of routine operationon PANDA was governed by majorimprovements of the instrumental per-formance as well as the extension ofthe useable palette of sample environ-ments. Here we report in detail aboutthe final performance of the double fo-cusing PG monochromator evaluatedin January 2007 and the tests of theHeusler monochromator and analyzerat the end of the year. Together withthe FRM II sample environment groupand also external users the variety ofsample environments used on PANDAwas extended by high pressure cells,a low temperature cryostat, the FRMII high temperature furnace (HTF) andthe 7.5 T vertical field magnet. This al-together has been achieved besidesa continuous heavy load of externaluser experiments.

Figure 3.9: Constant–Q scan at Q = (2.2,2.2,0) of a 0.8 cm3 Pb s.c. for the differ-ent foci modes of the PG002 monochromator. The inset shows the wave vectordependance of the gain factor for the three focusing modes.

Progress of instrumentalperformance

Double focusing PGmonochromator

In January 2007 the improved focus-ing drives of the PG monochroma-tor have been commissioned and ex-tensively tested. Allowing for an in-dependent automated adjustment ofboth, the vertical focus and the hori-zontal focus drive depending on themonochromator take-off angle, inelas-tic measurements using the fully fo-cused set-up with the highest avail-able intensity are possible. Fig. 3.9shows exemplarily constant Q scansof a transverse acoustic phonon ofa 0.8 cm3 Pb single crystal at Q=(2.2,2.2,0) for the different focus-ing modes of the PG monochroma-tor keeping the analyzer unchangedat k f =2.57Å−1 with a 6 cm PG filteron k f . Rather impressive the over-all gain in intensity by one order of

magnitude while keeping the energyresolution almost unchanged. The in-set of the figure reports the wave vec-tor dependence of the gain factor forthe three different foci modes with re-spect to the flat monochromator set-up obtained from scans having a 3Hemonitor mounted on the sample po-sition with a 1 cm2 aperture in frontof it. While the horizontal focus alonegives a rather constant gain of almosta factor of 2, the vertical focus gainfactor varies from 2 to 5 with increas-ing wave vectors. This variation is dueto the increasing active monochroma-tor surface for decreasing scatteringangles.

Polarized neutron set-up withHeusler monochromator andanalyzer

In December 2007 we could for thefirst time introduce both, the Heuslermonochromator and analyzer to thePANDA set-up. The monochromatorchange was done remote controlled(keeping the shielding closed) usingthe foreseen monochromator changer.Adiabatic spin-flipper’s before and af-ter the sample position and guidefield elements along the neutron flightpath have been mounted. In a firststep the currents for the compensa-tion field and for the flip field of thespin-flippers were adjusted to valuesappropriate for the selected neutronwavelength using the direct beam (nosample). Fig. 3.10 displays a typicalscan of the spin-flippers flip-field cur-rent, using already the optimal com-pensation field at a neutron wave vec-tor of 1.64 Å−1 and a PG filter in thebeam; the line is a fit to a cosine func-tion. In the following we show theresults of a number of tests that havebeen performed. Fig. 3.11 a) showsthe non spin-flip (nsf) and spin-flip (sf)intensities of a nuclear Bragg peak ofthe Pb single crystal. From the pictureone may directly


Figure 3.10: Exemplary data of the polarized neutron set-up: Direct beam intensityvarying with the spin-flippers flip field current at optimal compensation current.

Figure 3.11: Test scans using the PANDA polarized neutron set-up with P ⊥ Q: a) nonspin-flip and spin-flip scattering of the Q=(2,0,0) nuclear Bragg peak of Pb b) nonspin-flip and spin-flip scattering of the Vanadium standard.

read the flipping ratio being in theorder of 40, resulting in a beam po-larization of about 0.95. The Vana-dium sample also (Fig.3.11 b) ex-hibits the expected 2:1 ratio of thesf versus the nsf intensity arisingfrom nuclear-spin incoherent scatter-ing. In total the commissioning of theHeusler monochromator and analyzerhas been a full success enabling usnow to perform polarized neutron ex-

periments. The next step will be tointroduce Helmholtz coils at the sam-ple space to perform longitudinal po-larization analysis or a MuPad / Cry-opad set-up for full 3D polarizationanalysis.

Sample environment

The PANDA instrument faces an im-portant demand of particular sample

environments from our users. Theoverload factor for beam-time usingthe 14.5 T vertical cryomagnet is con-tinuously 2-3. Besides this low tem-peratures (T < 1.5 K) make up an im-portant issue for the requested beam-time. Therefore, a Variox cryostat hasbeen purchased by FRM II in 2007 tobe used together with the TU Dres-den Kelvinox dilution cryostat. Aftera successful commissioning (see Fig.:3.12) the Kelvinox has been success-fully used for three experiments onPANDA and one experiment on TRISP.The attained base temperature var-ied between 30 mK and 60 mK forthe different runs. In 2007 we alsoused for the first time the FRM II 7.5 Tvertical magnet. Although having alower maximum field this magnet isan attractive alternative as it allowsfor larger sample diameters and doesnot need cryogenic liquids for coolingmaking the operation on the beameasier. The FRM II standard high tem-perature furnace (HTF) had been oper-ated during one user experiment com-pleting the usable palette of temper-ature devices on PANDA. Concern-ing high pressures there were two ex-periments where our users broughtWcWhan type pressure cells to per-form experiments at pressures up to15 kbar.

Figure 3.12: The PANDA instrument run-ning with the Variox / Kelvinox cryostatcombination.


3.4 First productive experiments on the new backscattering spectrometerSPHERES

J. Wuttke 1, G. J. Schneider1, L. C. Pardo Soto1,2, M. Prager 3, Q. Shi 4, A. Budwig 5, G. Hansen 5, A. Ioffe 1,H. Kämmerling5, F.-J. Kayser6, H. Kolb 7, A. Nebel 1, V. Ossovyi 1, H. Schneider1, P. P. Stronciwilk1, D. Richter 31JCNS, outstation at FRM II, Research Centre Jülich2Grup de Caracterització de Materials, Departament de Física i Enginyeria Nuclear, Universitat Politècnica deCatalunya, Barcelona3IFF, Research Centre Jülich4Afdelingen for Materialeforskning, Forskningscenter Risø, Danmarks Tekniske Universitet, Roskilde5ZAT, Research Centre Jülich6ZEL, Research Centre Jülich,7ZWE FRM II, TU München

Status

Commissioning of SPHERES is ap-proaching the final stage. By the endof 2006, we had demonstrated in prin-ciple that the instrument will producecompetitive spectra. By the end of2007, stability and performance haveimproved to the point where produc-tive experiments are becoming rou-tine. The signal-to-noise ratio wasincreased from 165:1 to 330:1. Weaspire to obtain the permanent oper-ation permit in the first half of 2008.The instrument is now open for regu-lar user proposals.

Technical upgrades

Initially, test experiments were ham-pered by instabilities of vital compo-nents, namely the neutron velocity se-lector and the phase-space transformchopper. These problems being un-derstood and solved, all subsystemsof SPHERES are now running stablefor entire reactor cycles.A cryostat, lent by FRM II, was

adapted to the detector geometryof SPHERES. Accessible tempera-ture ranges are now 4. . . 330 K and10. . . 550 K, depending on configura-tion.Software development continued

throughout the year. Computer con-trol has been extended to the Dopplerdrive. Basic spectrometer operationis now possible through a graphicuser interface. Measurements canbe scripted. The beam shutter andother safety-critical components arecontrolled by a SPS.

Neutronic improvements

Extensive tests were performed, aim-ing at a better understanding of theremaining neutronic noise. We tem-porarily divided primary and sec-ondary spectrometer by a huge boronrubber barrier, and we moved neutrondetectors around to localise leakages.In the event, we improved the shield-ing around the primary beam path,especially around the monochroma-tor, and around the exit channel of thechopper.In measurements on a standard

scatterer (without sample environ-ment), we achieved a signal-to-noiseratio of 330:1 in the large-angle de-tectors (Fig. 3.13). At least a third

Figure 3.13: Resolution function of the large-angle detectors.

of the remaining noise is caused byfast neutrons that are created in the6Li absorbers in the chopper. As an-ticipated in the last report, replacingthese absorbers by boron ceramicsis a major effort. We are currentlyinstalling a purpose-built lifting gearthat will give us access to the chopperwheel. As there is no way to balancethe activated wheel, it is necessaryto build a new one. It is foreseen totransfer the PG crystals from the oldto the new wheel in summer 2008. Bythis measure alone, we will reach asignal-to-noise ratio of 500:1.Commissioning of the five small-

angle detectors just started. After firstimprovements of the neutronic shield-ing, we obtained signal-to-noise ra-


tios between 50:1 and 100:1; the en-ergy resolution (fwhm) lies betweena good 0.93 µeV and an unaccept-able 2.3 µeV. It might be necessaryto rethink the analyser and detectorgeometry before substantial progresscan be made.

Productive experiments

In the last three reactor cycles of2007, we performed an increasingnumber of test experiments. Theseexperiments provided us invaluableguidance in preparing for routine op-eration. At the same time, they pro-duced full-fledged results. First ex-perimental reports from satisfied testusers have arrived.Rotational dynamics and quantum

tunneling were studied in several com-pounds. Measurements on methylx-anthines, a biologically importantclass of molecules, were used to con-clude a study that was begun onthe old Jülich backscattering spectro-meter BSS [1]. In theophylline, a dou-blet tunneling band is observed at15.1µeV and 17.5µeV (Fig. 3.14).

Figure 3.14: Spectrum of anhydrous theophylline at 3K. Based on the crystal structure,the broad tunneling peak could be interpreted as an unresolved doublet of equalintensities [1].

This is in agreement with the roomtemperature crystal structure, imply-ing that no phase transition occurswith cooling. In caffeine, orientationaldisorder leads to a 2.7µeV broad dis-tribution of tunneling bands aroundthe elastic line.To characterize the temperature

dependence of quasielastic scatter-ing, we went beyond the elastic(“fixed-window”) scans customarilymeasured in neutron backscattering.Given the high flux at SPHERES, itwould be a waste of measuring timeto restrict temperature scans to theelastic channel. Instead, during tem-perature ramps we measure a rapidsuccession of inelastic spectra. Afterthe event, we integrate over appropri-ate energy windows to obtain elasticand inelastic scattering as function oftemperature.Such inelastic temperature scans

are particularly useful in localising dy-namic phase transitions. Fig. 3.15shows a striking example: the rotationof ammonia in Mg(NH3)6Cl2 under-goes a transition at 140 K. This tran-sition shows up much more clearly in

Figure 3.15: Inelastic and elastic scatter-ing from Mg(NH3)6Cl2 as function oftemperature. Note the phase transi-tion at 140 K which shows up muchmore clearly in the inelastic than in theelastic signal. From a “friendly-user”experiment of Shi, Jacobsen, Vegge,Lefmann from Risø.

the inelastic than in the elastic scat-tering intensity.Some Freon compounds form a

plastic phase in which the moleculessit in a regular lattice, but rotate moreor less freely. This phase has anexceptionally high fragility. Abovethe glass transition, there is anotherdynamic phase transition at about130K. Above this transition, we see arapid increase of quasielastic broad-ening, which we attribute to jumpsbetween trans and gauche conforma-tions (Fig. 3.16).[1] Prager, M., Pawlukojc, A., Wis-

chnewski, A., Wuttke, J. J. Chem.Phys., 127, (2007), 214509.


Figure 3.16: In the plastic phase of freon, conformational jumps lead to quasielasticbroadening.

3.5 Replacement of the neutron guide and a new polarizer at RESEDA

Wolfgang Häußler1,2, Mathias Sandhofer1, Reinhard Schwikowski2, Andreas Mantwill1, Peter Böni11Physics Department E21, TU München2ZWE FRM II, TU München

One major challenge in 2007 atthe Resonance Spin Echo (NRSE)Spectrometer RESEDA has been thereplacement of the neutron guide.The old, polarizing neutron guide NL5had to be removed, due to non-tolerable activation of its magneticsupermirror layers. The new neutronguide NL5 consists of glass furnishedwith non-magnetic NiTi supermirrors.As a consequence, the neutron beamis not any more polarized, and a su-permirror cavity fixed at the very endof the guide is used now as polarizer.Fig. 3.17 shows an image of this po-

larizing cavity, being 2 m in length andoptimized for neutron wavelengths of5-8Å. A strong magnetic field pro-duced by permanent magnets and

iron plates around the polarizer pro-vides sufficient magnetization of themagnetic supermirror layers. In or-der to maintain sufficiently strongmagnetic field strength along thewhole polarizer, several measureswere taken. The beam shutter at theend of the neutron guide, having be-fore partly covered the glasswalls ofthe polarizer, had to be exchangedby a smaller, but nevertheless equallyefficient shutter, because more spacewas needed for the iron plates of theguide field. The number of magnetswas increased, in order to reach afield strength of about 400 G.The instrument was moved on air

pads about 80 cm aside the neutronguide, so that the polarization could

be measured directly behind the po-larizing cavity, before the neutrons tra-verse the instrument. After some im-provements, the biggest ones being adiaphragm, suppressing unpolarisedneutrons at larger divergence anglesand increased field strength at theend of the polarizer, the polarizationreached a mean value over the wholebeam cross section of 88 % at neu-tron wavelength 6 Å.Fig. 3.18 shows a false color im-

age of the polarization data acquiredby means of a polarization measure-ment setup, consisting of two spinflippers, the 3He cell (kindly providedby the FRM II - He3 group, Dr. Masa-lovich and O. Lykhvar) used as an-alyzer and the detectors. For fast


Figure 3.17: The new polarizing cavity(length 2 m), which is now mounted atthe end of the neutron guide NL5, infront of RESEDA.

tuning of the spin flippers, we useda standard 3He counter. For the fi-nal measurements providing spatialresolved polarization data, we used aCCD camera equipped with a neutronsensitive scintillator. By four measure-ment steps, this setup allows to deter-mine both the flip efficiency of bothflippers and the "true" beam polariza-tion.In order to detect eventual depo-

larization effects in the first spectro-meter arm of RESEDA, RESEDA hasbeen moved back to the neutronguide, and the polarization measure-ment setup described above wasmoved behind the first spectrometerarm.While moving RESEDA aside and

back, it turned out that the air padsworked only partially. The air is

pressed through two circular, concen-tric air gaps for being able to movethe instrument easily on an air layer.Imperfect precision of the concen-tric rings, manufactured out of alu-minum, leads to unequally distributedair pressure. The air pads are par-tially stuck to the floor, when all airpads are simultaneously activated, sothat the available air pressure is de-creased slightly. In order to avoidsimilar problems in future, construc-tion of improved air pads has beenstarted in mid 2007. Nevertheless,the instrument was positioned backand aligned according to the neutronbeam.The very first polarization tests

show, that the polarization is notequally distributed within the neutronbeam behind the first arm of RESEDA.Fig. 3.19 shows a false color image ofthe polarization distribution. Improv-ing the polarization will be continuedduring the first cycle in 2008.Last but not least, big effort in au-

tumn 2007 was put into the place-ment of the new RESEDA user cabin.Subsequently, after having been puton place, the security installations ofthe cabin had to be put to place, espe-cially on the top of the cabin, where abig part of the electrics and electron-ics is placed now. Moving the elec-tronics there has been a major task inlate 2007, and will be continued andfinished in early 2008.Then, also the NRSE coils, which

have been supplied with motorizedgoniometers and rotation tables inearly 2007, in order to provide fastand efficient positioning of the coils,will be put into operation again. Hav-ing finished the polarization measure-ments, we will start then with spinecho test measurements, employingthe NRSE coils together with new

NSE coils put into operation also inearly 2007, used for measurements atsmall spin echo times.

Figure 3.18: False color contour plot ofthe polarization measured directly be-hind the new polarizer at the end ofNL5. The polarization reaches the max-imum value 92 %, the mean value is88 %.

Figure 3.19: False color image of the re-sult of the very first polarization test.The polarization measurement setupwas placed behind the first spectro-meter arm of RESEDA. The polarizationshows some heterogeneity of not yetknown origin.


3.6 DNS - An instrument for unraveling complex magnetic correlations viapolarization analysis

Y. Su 1,2, W. Schweika 2, R. Mittal 1,2, E. Küssel 2, F. Gossen 1,2, B. Schmitz 2, K. Bussmann 2, M. Skrobucha 3,M. Hölzle1,2, H. Schneider1,2, R. Möller4, M. Wagener4, A. Ioffe1,2, Th. Brückel1,21Jülich Centre for Neutron Science2IFF, Forschungszentrum Jülich3ZAT, Forschungszentrum Jülich4ZEL, Forschungszentrum Jülich

The construction of the new polar-ized time-of-flight spectrometer DNSat FRM II has reached the first mile-stone with the delivery of the first neu-trons and intense polarized neutronbeams in September of 2007. Shortlyafter the starting of the instrumentcommissioning with polarized neu-trons in the diffraction mode in the lastreactor cycle, DNS has been steadilyproducing sound experimental resultsto unravel complex magnetic corre-lations in a wide range of emergentmaterials via polarization analysis.DNS is a new cold neutron multi-

detector time-of-flight spectrometerwith both longitudinal and vector po-larization analysis at FRM II. This al-lows the unambiguous separation ofnuclear coherent, spin incoherent andmagnetic scattering contributions si-multaneously over a large range ofscattering Q- and E-resolution. DNSis therefore ideal for the vector Q and

Figure 3.20: The new DNS at FRM II

energy transfer E. With its compactsize DNS is optimized as a high inten-sity instrument with medium investi-gations of magnetic, lattice and pola-ronic correlations in many frustratedmagnets and highly correlated elec-trons. With its unique combinationof single-crystal time-of-flight spec-troscopy and polarization analysis,DNS is also complimentary to manymodern polarized cold neutron triple-axis spectrometers.The relocation of major compo-

nents from FZ Jülich and the con-struction of the new DNS at FRMII have started in 2006. The firstphase of this project is to imple-ment the diffraction mode with po-larized neutrons. Soon after the in-stallation of the double-focusing py-rolytic graphite monochromator andsecondary spectrometer in the sum-mer (as shown in Fig.3.20), the firstneutrons and intense polarized neu-tron beam were delivered to DNSin September. Newly constructedpolarizer and polarization analyzers,

Figure 3.21: First polarized neutrons at the new DNS demonstrating the high flippingratio of 50 achieved

both using m = 3 Schärpf bender-type focusing supermirrors, performextremely well. A polarized neu-tron flux as high as 5 x 106 n/s/cm2

has been achieved at the neutronwavelength with 4.74 Å. The polar-ization rate of the incident neutronbeams is nearly 96%, as shown inFig.3.21. The expanded analyserbank over a 2θ range of 120 degreeshas largely improved the measure-ment efficiency. The radiation shield-ing at both monochromator housingand secondary spectrometer has alsobeen improved. The radiation back-ground at the DNS measurement areahas met the strict requirement im-posed by the radiation protection reg-ulations. This paves the way for thefirst commissioning experiments.In the last reactor cycle of 2007, a

number of polarized neutron exper-iments on both powder and single-crystal samples have been success-fully undertaken at DNS. One typicalapplication of polarization analysis onpowder samples at DNS is to sep-


Figure 3.22: Investigations of the mag-netic structure of MnNCN via powderneutron diffraction. (a) and (b): puremagnetic and nuclear coherent scat-tering, respectively determined at DNSwith polarization analysis. (c): formerdata from SV-7 without polarizationanalysis

arate magnetic scattering from nu-clear coherent and spin incoherentscattering on antiferromagnets andparamagnets via XYZ-method. Highpolarized flux and the improved effi-ciency on polarization analysis allowus to obtain high quality data on theinvestigation of the magnetic struc-ture of manganese carbodiimide (Mn-NCN) powder, as shown in Fig.3.22.In comparison to the old data takenwith non-polarized neutron powderdiffraction at the dedicated powderdiffractomter SV-7 at FRJ-2, the DNSdata is much superior. It provides thecomprehensive information on mag-netic reflections and their temperaturedependence.

Another typical application is tomap out the reciprocal space togetherwith polarization analysis on singlecrystal samples. Intensive testing ex-periments on various Kagome spinsystems, pyrochlore spin ice and per-ovskite CMR manganites have beencarried out. The routines for thedata treatment have also been imple-mented. Some types of very pecu-liar magnetic correlations due to highgeometrical frustrations and strongelectronic correlations have been re-vealed from these new experimentswith polarization analysis. One suchexample is the observation of therod-like paramagnetic diffuse scatter-ing in the so-called cooperative Jahn-Teller distorted regime on highly cor-related CMR manganites, as shownin Fig.3.23. This rod-like diffuse fea-ture is a clear indication of the pres-ence of strongly anisotropic magneticexchange interactions due to orbitalordering.

Figure 3.23: Paramagnetic diffuse scattering at 220 K measured on a large singlecrystal of La0.875Sr0.125MnO3 via polarization analysis

The successful commissioning of

DNS with intense polarized neutronsin the diffraction mode and subse-quent successful applications haveproven capabilities of DNS as anunique instrument with polarizationanalysis. However, the full poten-tial of DNS can only be realized afterthe completion of the second phaseof the DNS project - installations ofa massive position sensitive detec-tor bank and high-performance dou-ble chopper system. These two newcomponents are expected to be inoperation before the end of 2008.In collaboration with the Institute

of Inorganic Chemistry of RWTHAachen, we would like to thankManuel Krott and Andreas Houbenfor permitting us to use the MnMCNdata taken both from DNS and SV-7.


3.7 PUMA – the thermal triple axis spectrometer

K. Hradil1, R. A. Mole2, H. Gibhardt1, M. Gründel1, F. Güthoff1, J. Leist1, N. Jünke1, J. Neuhaus2, G. Eckold 1

1Inst. f. Physikal. Chemie, Universität Göttingen2ZWE FRM II, TU München

Over the last year PUMA in its ba-sic detector version has assignedaround 150 days to 10 different ex-ternal user groups (for the results seeexperimental reports of FRM II). Be-side the external measurements theinstrument characterisation was con-tinued and technical advances madewith the implementation of some newdevices. The stroboscopic measur-ing technique to investigate the realtime behaviour of excitations in de-pendence of external fields (temper-ature, electrical fields) is now avail-able also for the user community. Ad-ditionally, first successful test mea-surements were performed using afocussing guide in front of the sam-ple.

Stroboscopic measuringtechnique - real timeinvestigations of excitations

Inelastic neutron scattering techniqueprovides information about the micro-scopic dynamics of solids. Investiga-tions on a real time scale within ex-ternal fields (temperature, pressure,magnetic/electrical fields) yields themicroscopic information of relaxationprocesses (phase transitions, domainorder/disorder processes, decompo-

start

cycle

accumulation

channel advance0 8192time channel

trigger signal (external/internal)

delayvariable

accumulationvariable

(1microsecond - serveral seconds)

external field(temperature,electrical field, ...)

Figure 3.24: schematic time diagram of the stroboscopic technique

sition processes). The time scales ofthese types of processes are normallymuch smaller than the time neededto perform an inelastic measuringscan (measuring times are typicallyin the range of seconds or minutesper point), even on high flux instru-ments. Such long measuring timesmean conventionally inelastic neutronscattering is not suitable for real-timeexperiments. A method to combinereal time resolution together with in-elastic neutron scattering using a stro-boscopic measuring technique wasdeveloped by our group for the triple-axis spectrometer UNIDAS in Jülich inthe early 1990’s [1]. Fig. 3.24 showsa schematic time diagram of the stro-boscopic technique. By cycling thesample in an external field, the scat-tered intensity is not only detected asa function of momentum and energytransfer but also sorted within timechannels. Measuring for several cy-cles provides the necessary countingstatistics for analysing the individualtime channels. Therefore, the repeata-bility of the processes is a necessarycondition for the application of thetechnique. The basics of the mea-surement protocol are as follows: theinstrument is periodically checked tosee if the positioning step has fin-

ished. A trigger signal then controlsboth the start of the counter card andthe sample environment. This triggercan be given from an external sourceor produced from an internal clock ofthe card. The time resolved counterboard in use was developed by theFRM II detector group. The data ac-cumulation takes place in eight 1-dimensional arrays with 8192 chan-nels. For internal triggering the timebase can be defined in such a waythat the time channels are definedfrommicroseconds up to serveral sec-onds. In case of external triggeringthe time channel is defined by a wavefunction generator.This technique was recently im-

plemented within the spectrometerelectronics of PUMA and providesthe possibility to analyse excitations

Figure 3.25: Furnace for fast temperaturechanges (5K/s) for the time-resolvedmeasurements. The crystal is heatedby a heating wire which is mountedaround an aluminum cyclinder placedaround the sample. The fast coolingis supported by air presse flow on thealuminum cyclinder controlled by theheat power supply.


Figure 3.26: Time dependent charac-teristics of the temperature jumps(370/670K) investigating demixing pro-cesses within the system NaBr/AgBr

within relaxation processes on atimescale down to microseconds.The technique described above isstrongly dependent on the ability tocontrol the external field on the sam-ple in a very precise way as well as as-suring the reproducibility. In Fig. 3.25a furnace is shown to cycle the tem-perature between 300 and 670K. Thecooling rate is about 10K/s using airpressure cooling. The requirementconcerning the control of the temper-ature for a sucessful time-resolvedmeasurement is shown in Fig. 3.26where the temperature is logged forthis experiment. Using this equip-

Figure 3.27: Time evolution of the q = [0.40 0] phonon within the Ag0.22Na0.78Brsystem for a temperature change from670K to 370K

ment we performed a time-resolvedmeasurement of a demixing processwithin the system Ag0.22Na0.78Br fol-lowing an transvers acoustic phononin the temerature range of 370K/670K.In Fig 3.27 a TA phonon for thefully mixed phase at 670 K and thetime evolution within 2 hours is rep-resented. Already shortly after de-creasing temperature (145 s) a clearsplitting into two peaks can be ob-served synonymous with a demixingin a AgBr and NaBr phase.

Inelastic measurements onsmall crystals - focussingguide test

The weak interaction of neutrons withcondensed matter typically restrictsthe investigations to large sampleswith dimensions of the order of cubiccentimeters. There are many areasof scientific interest, where it wouldbe advantageous to use TAS tech-niques, however, this is often pro-hibited because of the difficulty ofgrowing large, high quality single crys-tals. Topics of interest range fromtypical TAS applications such as su-perconducting materials with variousdoping levels, but also extend to ex-amples such as biomolecules andmolecular materials, where TAS meth-ods are very infrequently used dueto the problems with crystal growth.Furthermore, certain sample environ-ment such as pressure cells also

Figure 3.28: Photograph of the elliptical guide on the primary beam path of PUMA

restricts the size of the sample al-lowed. To overcome this problemwith sample size on TAS instrumentswe have been investigating the useof supermirror focusing guides [2],to generate a very small but intensebeam spot at the sample positionof the thermal three axis instrumentPUMA.The guide used has a length of 500

mm and has been described previ-ously [3]. The guide was installedon PUMA between the monochroma-tor and the sample (fig. 3.28). In thefirst instance we used a neutron CCDcamera to both correctly align theguide and to analyze the shape andintensity of the beam at the sampleposition. These measurements, alongwith Monte-Carlo simulations of theprofile are shown in Fig. 3.29. Both,measurement and simulations showthat the beam has a FWHM of approx-imately 2 mm in the horizontal direc-tion and 8 mm in the vertical direction.Such a profile is ideal for studyingsamples with mm dimensions, unlikethe conventional PUMA profile wherethe primary beam has dimensions ofroughly 25 mm in the horizontal di-rection and 28 mm in the vertical di-rection and any adjustment for sam-ple size is done by adjustable, neu-tron absorbing slits. The CCD cam-era images also revealed that usingthe guide results in a very low back-ground.We performed sucessful test ex-


periments on quartz samples withthe guide and in the conventionalfocussed monochromator setting ofPUMA. In both cases the PG(002)monochromator and analyser wasused. Due to the guide entrancedimensions and the horizontally flatmonochromator only neutrons com-ing from one of the 117 monochroma-tor crystals are guided to the sampleposition for the guide configuration. Adirect comparison between the con-ventional PUMA configuration and theguide (Fig. 3.30) shows that we canmeasure a sample with a volume thatis 250 times smaller than the origi-nal crystal, with a low backgroundand improved energy resolution. Fur-ther tests, experiments and simula-tions are ongoing so that these guidescan be used routinely on PUMA in thefuture. Ultimatively guides designedand optimised for PUMA will be man-ufactured and offered to users as apossible setup.

Conclusion

In conclusion both new techniquesintroduced to the instrument will al-low new and exciting experimentsto be performed. The stroboscopictechnique together with challengingsample environment allows the ex-ploration of real time relaxation pro-cesses (phase transitions, domain or-der/disorder processes, decomposi-tion processes). Using elliptic guideswill open triple axis spectrometers fortiny crystals or sample environmentswith limited accepting volumns, whilestill having excellent energy resolu-tion.[1] Eckold, G. Nucl. Instr. and Meth-

ods, A289, (1990), 221–230.

[2] Schanzer, C., Böni, P., Filges,U. Nucl. Inst. and Meth. A, 529,(2006), 63–68.

[3] Mühlbauer, S., Stadlbauer, M.,Böni, P., Schanzer, C., Stahn, J.,Filges, U. Physica B, 385-386,(2006), 1247–1249.

-0,0050 -0,0025 0,0000 0,0025 0,0050

Inte

nsity

/ ar

b. u

nits

distance / mm

Figure 3.29: Horizontal beam profile measured with a delCAM neutron CCD camera.Red: Simulation of the horizontal beam profile.

0

1000

2000

3000

4000

5000

6000

7000

8000

puma.opj

TA phonon(-0.9 2.0 0)

20 mm * 20 mm * 5 mm, V = 2000 mm3

neut

rons

/ 10

.4 s

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.00

20

40

60

80

100

120

140

neut

rons

/ 72

.9 s

Energy (THz)

SiO2: 2 mm * 2 mm * 2 mm, V = 8 mm3

Figure 3.30: Top: Normal PUMA configuration, bottom: Same measurement using thefocusing guide with a sample that is 250 times smaller.


3.8 Quasielastic and inelastic neutron scattering experiments at thetime-of-flight spectrometer TOFTOF

C. Smuda1, S. Busch1, G. Gemmecker2, T. Unruh1

1ZWE FRM II, TU München2Bayerisches NMR-Zentrum, Chemie Department, TU München

Introduction

During 2007 the multi–chopper time–of–flight spectrometer TOFTOF [1]was in full user operation. Therefore,only minor optimizations of the instru-ment were carried out. The most im-portant improvement is the installa-tion of an automatic gas handling sys-tem for the sample chamber, which al-lows to flush the whole chamber withargon gas. By this way the air scat-tering inside the chamber could bereduced leading to a further reduc-tion of the already extreme low back-ground of the spectrometer. This lowbackground can exemplarily be ob-served in the high resolution measure-ment recently recorded at TOFTOFwith an incident neutronwavelengthof 14 Å (cf. Fig. 3.31). The presentedraw data have not been corrected forbackground. In this measurement itcould also be demonstrated that evenwith a resolution of 4 µeV a signal tonoise ratio better than 104 could beachieved in the vicinity of the elasticline.

Figure 3.31: Methyl tunneling in pentafluorotoluene (graphic formula displayed in theinset) at 5 K measured with a resolution of 4 µeV obtained with neutrons of wave-length λ = 14 Å, chopper frequency of 16.000 rpm and frame overlap reductionratio 8 (recording time: 14 h).

In the following sections of this re-port some exemplary results of theinhouse research at TOFTOF in 2007are briefly summarized.

Rotational dynamics ofmethyl groups inpentafluorotoluene andpentafluoroanisole

Almost half of the hydrogen atomsin the oligoisoprene derivative coen-zyme Q10 are bound to methyl groups.For a detailed evaluation of QENSspectra obtained from TOFTOF mea-surements of liquid Q10, it is essen-tial to know the scattering contribu-tion of these methyl group hydro-gen atoms to the quasielastic inten-sity [2]. Up to now the rotation ofmethyl groups in liquids of organicmolecules is scarcely investigated.Therefore it is of special and gen-eral interest to characterize methylgroup rotation in the solid as wellas in the liquid state. The aim of

Figure 3.32: Structural formulae ofpentafluoroanisole (left) and pentaflu-orotoluene (right).

the investigations is to find a prefer-ably universally applicable model forthe description of the QENS of methylgroups in liquids of small organicmolecules.Pentafluoroanisole and pentafluoro-

toluene were investigated as modelcompounds (cf. Fig. 3.32) in the liquidand solid state.QENS spectra of solid pentafluo-

roanisole could satisfactorily be mod-elled by a scattering function S(Q,ω)which comprises only one Lorentzianfunction, whereas the dynamics ofmethyl groups in solid pentafluo-rotoluene could only be describedby a combination of two Lorentzianfunctions indicating two differenttypes of methyl groups. The ob-tained linewidths for the compoundsin the solid state are displayed inFig. 3.33 [3].As the methyl group dynamics

is a thermally activated process, itshows an Arrhenius behaviour inthe solid state for both compounds,whereas in the liquid state it wasfound that the frequency of themethyl group rotation is independentof temperature. The used modelfor data analysis includes not onlythe methyl group rotation but alsolong-range diffusion and isotropic ro-tational diffusion of the molecule


Figure 3.33: Arrhenius plot of half widths at half maximum (HWHM) Γ obtained frombest fits for the two non-equivalent methyl group in polycrystalline pentafluoro-toluene (PFT) and pentafluoroanisole (PFA), respectively. The solid lines representbests fits to the Arrhenius equation yielding activation energies of 6.4 kJ/mol forPFA and 2.74 kJ/mol and 0.96 kJ/mol for the two different types of methyl groups inthe lattice of PFT, respectively.

S(Q,ω) = SMethyl(Q,ω)⊗STrans(Q,ω)⊗SIRD(Q,ω)

and describes the experimental dataperfectly. Evaluation of the QENSspectra without consideration of themethyl group rotation results in worsefits. The long-range diffusion ofthe molecules in the liquid phasecould for all investigated tempera-tures clearly be separated from theinternal motions. Diffusion constantsextracted from the model are com-parable to PFG-NMR diffusion coeffi-cients. The temperature dependenceof the obtained Q independent rota-tional diffusion constants can be de-scribed by the Arrhenius equation.The Q independent HWHM for themethyl group rotation was determinedto be about 1 meV for pentafluoro-toluene as well as pentafluoroanisole.

Self-diffusionmeasurements ofmedium-chain molecules

It could be demonstrated in [4]that QENS is best suited for in-vestigations on molecular self-diffusion inside nanosized dropletsdispersed in another liquid. How-ever, by measurements of the

self-diffusion coefficients of the oligo-isoprene derivative coenzyme Q10in nanosized droplets and in thebulk, respectively, at the time-of-flightspectrometer TOFTOF discrepanciesto the PFG-NMR diffusion constantsof more than one order of magnitudehave been found [2]. In order to studythis effect more systematically QENSmeasurements on a series of differentmedium-chain n-alkanes was per-formed with the aim to understandthe influence of the chain length ofthe molecules to their diffusivities.For data evaluation, different mod-

els for the dynamic structure factorS(Q,ω) were used to extract diffusionconstants: (i) sum of two Lorentzianfunctions, (ii) convolution of long-range diffusion and isotropic rota-tional motion, and (iii) convolution oflong-range diffusion and diffusion in-side a sphere. The experimental datacould be described by each of thethree models and it turned out thatthe determined diffusion constantsare independent of the applied model.The derived diffusion constants werecompared with values obtained byPFG-NMR [5].

Figure 3.34: Diffusion constants of n-alkanes determined by QENS at 110Cas a function of the molecular weight incomparison with PFG-NMR values [5].

One main result is that with increas-ing chain length the ratio of the QENSdiffusion coefficient to the PFG-NMRdiffusion coefficient increases [6]. Theincrease of this ratio can easily be rec-ognized when plotting an isotherm ofthe diffusion constants of different n-alkanes on a double logarithmic scaleas it is demonstrated in Fig. 3.34 for110C.The discrepancies of the diffusion

constants determined by the two dif-ferent methods might be due to (i) achange of the diffusion mechanismon a nm length scale for molecules ofmedium-chain length or to (ii) contri-butions of internal motions.Further efforts with respect to data

evaluation have to be made in orderto find the true reason for the ob-served discrepancies of the QENSand NMR results. Some more exper-imental information will be obtainedby neutron spin-echo measurements,which are in progress to determine theQ dependence of the diffusion con-stants at low Q-values. In addition thestudy is intended to be extended onother medium-chain molecules likeoligomers of polyoxyethylene, fattyacids, alky alcohols or silicon oils.

Dynamics of phospholipidsin stabilizing monolayers

Many modern drugs are not water-soluble. To facilitate their intravenousapplicability, a drug carrier has to


be employed. Dispersions of lipidnanoparticles stabilized by dimyris-toylphosphatidylcholine (DMPC) arepromising candidates. It has beenshown that not only the drug releaserate but also the storage stability ofthese systems highly depends on theproperties of the stabilizer [7, 8, 9].These properties were investigatedi. a. by SAXS [10], revealing that thestructure of the monolayer is clearlydistinct from what one would expectfrom the well-known structure of bi-layers: It is thinner and the peaks inthe electron density profile are lesspronounced.A series of experiments aiming to

determine the dynamic characteris-tics of DMPC-monolayers is plannedat TOFTOF. A major goal is to link themolecular dynamics with the before-mentioned properties like storage sta-bility. First experiments were donecomparing the picosecond-dynamicsin a dispersion of vesicles, servingas model for phospholipid bilayers,which had a diameter of ≈ 40nm(PCS z-average) with the one of a sta-bilizing phospholipid monolayer in anemulsion of deuterated hexadecanein D2O (diameter ≈ 57nm). The maindifficulty in these measurements isthe low content of phospholipid, be-ing only 1.3weight% of the sample inthe beam.

-0.2 -0.1 0 0.1 0.20

0.25

0.5

0.75

1

ω [meV]

S(Q

,ω)/

S(Q

,0)

0 1 2 30

20

40

60

Q2 [Å−2]

HWHM

[µeV

]

Figure 3.35: Left: Spectra of vanadium (innermost), vesicles, and emulsion (outermost)after background subtraction as described in the text plotted versus energy transferat a momentum transfer of 1Å−1. It is visible that the quasielastic broadening ofthe central line is larger in the case of the emulsion (phospholipid monolayer). Right:The linewidth of the narrow component of a two-Lorentzian fit plotted versus thesquared momentum transfer Q2. The one steming from the monolayer is aboutdouble the one of the bilayer.

The part of the sample spectra dueto scattering from D2O and possi-bly hexadecane molecules has to besubtracted. Then the quasielasticbroadening caused by the dynamicsof DMPC becomes visible which isdepicted in figure 3.35 along with theinstrumental resolution, determinedby the measurement of a vanadiumstandard. The broadening caused bythe dynamics of DMPC in a mono-layer is clearly larger, indicating fasterdynamics.To determine the type of dynam-

ics, the spectra were fitted with asimple model consisting of a sum oftwo Lorentzians, which can roughlybe assigned to diffusion of the DMPCmolecules (narrow component) andinternal motions of the DMPC (broadcomponent). As both, water and hex-adecane, are faster than the phospho-lipids, their dynamics does not influ-ence the line width of the narrow com-ponent even if the subtraction wasnon-ideal but would only be visible inthe broad component. The width ofthe narrow component shows a lin-earish dependence of Q2 (confer tofigure 3.35) which is a sign for non-local diffusive motions. The diffusioncoefficient of DMPC is proportionalto the slope and therefore in a mono-layer about two times the one in abilayer.

The looser molecular arrangementof the phospholipid molecules in themonolayer [10] can intuitively be cor-related with the increase of diffusionaldynamics. This will be investigatedmore thoroughly. Currently, we tryto find a more elaborated method tosubtract the contributions of D2O andhexadecane to the spectra so thatthe broad component can be evalu-ated more reliably. Furthermore, ex-periments investigating the influenceof stabilizing co-emulgators on thephospholipid dynamics are planned.

The TOFTOF team

The TOFTOF team (cf. Fig. 3.36) islooking forward to seeing you per-forming your forthcoming experimentat FRM II.[1] Unruh, T., Neuhaus, J., Petry,

W. Nucl. Instr. Methods A, 580,(2007), 1414–1422.

[2] Smuda, C., Gemmecker, G.,Bunjes, H., Unruh, T. FRM II An-nual Report, 84–86.

[3] Smuda, C., Gemmecker, G., Un-ruh, T. J. Phys. Chem., (submit-ted).

[4] Unruh, T., Smuda, C., Gem-mecker, G., Bunjes, H. MRSQENS 2006 Conf. Proc., 137–145.

[5] von Meerwall, E., Beckman, S.,Jang, J., Mattice, W. L. J. Chem.Phys., 108, (1998), 4299.

[6] Smuda, C., Gemmecker, G., Un-ruh, T. Langmuir, (in prep.).

[7] Westesen, K., Siekmann, B. Int.J. Pharm., 151, (1997), 35.

[8] Bunjes, H., Koch, M. H. J., West-esen, K. J. Pharm. Sci., 92,(2003), 1509.

[9] Bunjes, H., Steiniger, F., Richter,W. Langmuir, 23, (2007), 4005.

[10] Unruh, T. J. Appl. Cryst., 40,(2007), 1008.


Figure 3.36: The TOFTOF team in front ofthe flight chamber of the spectrometer(from left to right): Christoph Smuda,Tobias Unruh, Sebastian Busch, Win-fried Petry, Jandal Ringe, ReinholdFuner, Jürgen Neuhaus and RaffaelJahrstorfer.

4 Nuclear physics and applied science 61

4 Nuclear physics and applied science

4.1 Irradiation facilities

X. Li1, H. Gerstenberg1, J. Favoli1, V. Loder1, J. Molch1, A. Richter1, H. Schulz1


General

The irradiation service of the FRM IIcontinued its routine operation suc-cessfully during the five reactor op-eration cycles in 2007. Altogethermore than 500 irradiations were car-ried out for different research projectsand commercial purposes on our facil-ities. The 1000th irradiation since thestarting up of FRM II was achieved inNovember 2007. Table 4.1 shows theirradiation batches on each system.Our service could extend in manycountries in 3 continents. A big jumpin this year was the installation of thefinal automatic silicon doping systemwhich went into a routine productionphase after the successful commis-sioning controlled by TÜV at the be-ginning of this year. The silicon dop-ing became the main part of the irra-diation service and amounted almostto the half of total number of irradia-tions in 2007. Four tons silicon ingotswith broad range of target resistivi-ties from 1050 Ωcm till 22 Ωcm wereirradiated. Beside this big commer-cial service, irradiation of samples fornuclear medicine and geological dat-ing was arranged at the second placewith about 100 batches. In 2007 Webegan some works of neutron acti-vation analysis for scientific research,application in industry and educationaim. Some important and interestingprojects supported by our irradiationsystems are described in the follow-ing text.

Table 4.1: Irradiation batches at the FRM II in 2007position PRA KBA SDA SDA1 RS total

irradiation No. 122 42 225 113 2 504

Production of isotopes forthe nuclear medicine

An interesting project for the nuclearpharmacy is the optimization of aneffective production of the radioac-tive isotope 177Lu, which may helpcreate the first successful radiophar-maceutical for solid tumors. 177Luemits a low beta energy, which re-duces radiation side effects and pro-duces a tissue-penetration range ap-propriate for smaller tumors. As abonus, 177Lu emits gamma radiation,which allows physicians to also use itfor both imaging and therapeutic pur-poses. In order to prepare the 177Lu,two production ways are tested in theinstitute for radiochemistry of the TUMünchen. One is direct neutron acti-vation of enriched 176Lu. The resultsof a series of test irradiation in thelast years showed that the produc-tion throughput of this way is high butthe co-produced long-lived isotope177mLu (T1/2=161d) causes a big disad-vantage. The other indirect way is theproduction of 177Lu via the nuclear re-action 176Y b(n,γ )176Y b(β−)→177Lu. No177mLu is produced in the decay chain[1]. After a long time irradiation of asample of 176Y b with 9 days on thecapsule irradiation system (KBA) inOctober 2007 and a successful sepa-ration of Yb/Lu, a first effective label-ing of 177Lu on some bio moleculeswas obtained. This new and more ef-fective way to prepare 177Lu will be

optimized and test irradiations are go-ing on.The goal of the project BetaMo

supported by the Bavarian sciencefoundation is the development of ra-dioactive implants for a possible ap-plication in the medicine, above allfor the wound healing process afterinflammations and operative proce-dures. Suitable radioactive radiationcan have positive influence on thehealing process. Samples made ofPEEK foil or copper-wire containingphosphorus were irradiated with dif-ferent irradiation durations on our cap-sule irradiation system to producethe pure beta-ray source 32P for thephysics department of the LMU andcooperating clinics. The calculationof the actual radiation dose of the im-plants in the hospital was based onthe information of the neutron flux de-termined by measuring the activity ofa co-irradiated Au-wire in each irra-diation in order to guarantee an un-certainty limit of 5% on the sampleactivity calculation as required. Theneutron flux determination was per-formed at the FRM II after the irradia-tion of the samples.After a first successful irradiation

of tungsten in the high flux irradia-tion position in the control rod of theFRM II during the 8th reactor cyclein 2006, two following samples en-riched to 99.9% in 186W were irradi-ated during an entire reactor cycle in2007 for the production of 188Re via adouble neutron capture reaction withthermal neutrons: 186W (n,γ) →187

W (n,γ) →188 W (β−)(T1/2 = 69d) →188Re(T1/2 = 17h) . The samples wereloaded before the reactor was startedand unloaded after the reactor wasshut down, i.e. after completion of 52-

62 4 Nuclear physics and applied science

days. 188Re emits beta particles (Emax= 2.12 MeV ) having an ideal range forintravascular brachytherapy and cer-tain cancer brachytherapies. It canbe usually extracted for medical ap-plications by a so-called 188W/188Regenerator.

Irradiations for the fissiontrack dating

About 100 apatite samples from dif-ferent geological institutes were irra-diated in our irradiation channels in2007 for the fission track dating of ge-ological substances. This method isa radiometric dating technique basedon analysis of the damage trails, ortracks, left by fission fragments incertain uranium bearing minerals andglasses. The number of tracks corre-lates directly with the age of the sam-ple and the uranium content. To deter-mine the uranium content the sampleis annealed by heating and exposedto a barrage of thermal neutrons [2].Due to the high uranium content in thegeological samples, the samples areusually irradiated in the position SDA-1 with a relatively low neutron fluencebetween 1×1015 and 1×1016 (cm−2),which was achieved within few min-utes. In several cases standard neu-tron flux monitors (Au/Co) were irradi-ated simultaneously with the samplesand analyzed separately, in order toobtain the information about the localneutron fluxes within the sample sets,which typically consist of more than10 single disc-shaped samples.

Measurements of γ-dosagein spent fuel units

In order to use the very strong gammaradiation in the spent fuel elementsas a supplementary irradiation sourceat FRM II, two measurements with45 min and 2 h irradiation time re-spectively were performed to studythe dose rate in the central positionof a spent fuel element. Figure 4.1shows the measurement device in aspent fuel unit. Special dosimetersmade of small pieces of radiation-sensitive material which change color

when irradiated were used. By mea-suring the amount of color-change bymeans of a spectrophotometer, thetotal dosage can be calculated. Be-cause almost no neutrons exist inspent fuel, what is a big advantagein comparison to our other irradiationpositions with high neutron dose term,the gamma radiation dose could behere determined clearly without anyinterference. The radiation-induceddarkening of our samples was mea-sured at the Jülich research center.Some results are shown in Table 4.2.

Figure 4.1: dose measurement in a spent fuel unit.

Table 4.2: radiation dose in spent fuels at FRM IIdosimeter source cooling

time (d)radiationtime (min)

dose rate(kGy/h)

HL 255 321 FRM II - 012 212 45 16.2HL 255 323 FRM II - 012 214 120 16.1HL 255 325 FRM II - 012 214 120 14.9

Neutron activation analysis(NAA) at FRM II

As well known, the neutron activa-tion analysis (NAA) is a very preciseanalysis method for determination oftrace elements. Very low concentra-tion down to ppb- and ppt-level canbe measured under favorable condi-tions. Samples for scientific researchprojects, industrial applications andpurposes of education were analyzedvia NAA directly at FRM II in 2007.To mention but a few, trace ele-


ments in samples of silicon nano pel-lets with diameter of 10 nm from theWalter-Schottky-Institute, in pure sil-icon wafers from Infineon AG andin different color pigments were an-alyzed. Impurity could be determineddown to the ppb-level in the very puresemiconductor materials. Differentconcentrations of silicon in the nanoparticles depending on the produc-tion procedure were determined alsoby using NAA.The analysis of the color materials

can help the art historians getting in-formation about the background ofthe paintings and a possible relation-ship between the colors. Up to 20elements could be determined in thesamples by using k0 multi-elementanalysis method after one single ir-radiation. Another interesting workwas an analysis work of 2 meteoritesfrom a museum in Nördlingen withinthe framework of a laboratory train-ing course. High concentration ofmetal elements, above all of elementsin the iron-platinum-group was deter-mined in both samples. The remark-ably high concentration of iridium ofalmost 1 ppm indicates the extrater-

Figure 4.2: trace elements determined in a meteorite. Ir concentration is about 100times higher than in the earth’s crust.

restrial background of our samples.Iridium is notable for its significance

in the determination of the probablecause of the extinction, by a mete-orite strike, of the dinosaurs. Figure4.2 shows analysis result of a mete-orite.

Silicon doping facility (SDA)

The silicon doping for commercial pur-poses had already begun by usinga prototype facility (SDA-opt) at theend of 2005. In 2006 almost 3 tonssilicon ingots were irradiated. In Jan-uary 2007 the final silicon doping fa-cility offering a semi automatic opera-tion was completely installed at FRMII. After a successful commissioningprogram containing about 30 tests,the doping system was verified byTÜV and the regulatory authority. InMarch the silicon doping service suc-ceeded in being ISO9001:2000 certi-fied by TÜV Süd Management ServiceGmbH. It went into a routine produc-tion phase in the following 3 reactorcycles. About 4 tons silicon ingotswere doped during this time. Thedemand increases drastically.We en-

tered into a business relationship with5 companies from Europe and Asia.Already on the prototype facility, a

special nickel absorber was mountedon the outside of the irradiation con-tainer and tested in order to reducethe axial inhomogeneity of the neu-tron flux density at the irradiation po-sition to a value below 5% as requiredby most industrial clients. Basedon the earlier flux measurements,the special absorber shape was con-structed and optimized by means ofMonte Carlo calculations. The dis-tribution of local neutron flux in thenew system was monitored by mea-suring the activity of gold standardslocated in different positions withinthe ingot with a total length of 500mm. The result of the measurementis shown in Figure 4.3. New calibra-tion factors for the calculation of dop-ing time were optimized again underthe new conditions. Based on ourneutron flux measurements and somefeedbacks about the doping qualityfrom our clients, we are sure, that thenew nickel absorber layer in our dop-ing system was correctly constructedand coated on the liner pipe.The doping results show that the

compliance with the target resistiv-ity and the axial resistivity variationis less than 4 ∼ 5%. The radial varia-tion is below 3∼ 4% and seems to becompletely hidden in measurementnoise. With the new calibration fac-tors, which connect the irradiationdose and the target resistivity, theconditions of the doping specifica-tions for target resistivities from 22Ωcm up to even 1050 Ωcm can befulfilled very well. Worthy of mentionis the doping of ingots with high tar-get resistivities, because the dopingtime is short, usually between 20 and30 minutes. The influence of time un-certainty during drive-in and drive-outis here significantly higher than in thecase of lower target resistivities. Onthe other hand, the radiation damagecaused by the fast neutron-inducedreactions has more influence in theingots with higher target resistivitiesthan with lower. Due to the very purethermal flux in our position, this effectis minimized effectively. The doping


results show that the lifetime of freeelectrons in the doped ingots is high,around 400-700 msec, what meanslow content of irradiation defects.Most of the ingots have diameters

of 4, 5 and 6 inches. 3 batches of 8inches ingots were irradiated in 2007.The effect of self shielding in radialdirection was analyzed and is shownin Figure 4.4. Generally the startingmaterial was n-type Si exhibiting a re-sistivity of several thousand Ωcm butalso some p-type prior-doped ingotswere doped at FRM II. We are con-fident to increase our throughput intwo shifts operation considerably in2008.[1] Dvorakova, Z. Production and

chemical processing of 177Lu fornuclear medicine at the Munich re-search reactor FRM-II. Ph.D. the-sis, TU München (2007).

[2] Glasmacher, U., Wagner, G.,Puchkov, V. Techonophysics, 354,(2002), 25–48.

Figure 4.3: neutron flux profile in a 6 inches ingot behind the new nickel absorber liner.

Figure 4.4: relative radial resistivity deviation within an 8 inches ingot.


4.2 Particle physics at the cold neutron beam facility MEPHISTO

J. Klenke1, H. Abele2, S. Mironov3, H.-F. Wirth2, O. Zimmer3,21ZWE FRM II, TU München2Physik-Department E18, TU München3Institute Laue-Langevin, Grenoble

Motivation

Particle physics with neutrons is insome respect a description of low en-ergy physics experimentation. Exper-iments with neutrons fit in a greaterfield of precision measurements com-prising cold or ultracold neutrons,cold or ultracold ions or atoms, pro-tons, electrons, and their antiparticles.These experiments have obtained anextreme level of sensitivity and pre-cision. Although it is difficult to de-termine an exact range, basic ques-tions - relating the standard modelof particle physics to cosmology andother areas of physics and astronomy- come into reach for low energy ex-perimentation, where tiny signs fromcorresponding effects are detectable,but remain so far and in the futuremostly unaccessible for high-energyaccelerator experiments. Therefore,due to their extreme precision, low-energy experiments can be sensitiveto processes occuring at much higherenergies than accessed with today’saccelerators. The experiments pro-vide the zero-energy values of thestandard model, improve its internalconsistency and define the point ofdeparture for new physics.

Figure 4.5: The polariser (blue) during thebuild up of the lead shielding

Status

The work at the beamline MEPHISTOin the year 2007 was splitted in twomain parts. The first part was concen-trating on Helimephisto, a new sourceof ultracold neutrons extracted fromthe cold MEPHISTO beam, the sec-ond part was the improvement of thebeam line by testing a new remov-able polariser and the refurbishmentof parts of the neutron guide system.

Helimephisto

During the first half year of 2007the experiments with the setup He-limephisto proceeded before it wasmoved to the ILL. Helimephisto isthe prototype of a superthermalsource for ultracold neutrons (UCN).Incoming cold neutrons were down-scattered in superfluid 4He (below1.3 K) to UCN energies (below 170neV). Last tests with a new coating

Figure 4.6: Comparison between the transmissive spectra of the polarised and unpo-larised beam

in the liquid 4He chamber were doneto improve the ultracold neutron den-sity. The experiment showed forthe first time that it is possible toextract UCN with a high efficiencyfrom a 4He converter. The exper-iment itself is reported in detail inthe Ref. [1]. The main idea for theexperiment is to use a phonon ex-citation in liquid 4He to slow downneutrons with a wavelength around 9Å. Therefore the experiment neededan accurate knowledge of the neu-tron spectra, especially at λ=9 Å.Former measurements were alreadydone [2] at the neutron guide NL1,but only at the position of the NRex+

monochromator, which is situated 5.7m away from the sample volume fac-ing upwards to the cold source. Forthe measurements the same time-of-flight (TOF) spectrometer was usedas in [2]. The spectrometer need acomplete radiation shielding whichhad to be build up, because former


measurements took advantage of theNRex+ monochromator housing. Itwas measured the integral flux (viagold-foil activation) and the shape ofthe spectrum (via the TOF spectro-meter). These informations allow amore precise analysis of the data fromHelimephisto.In a first step the beam was charac-

terised as before for the Helimephistoexperiment but without the long colli-mation tubes after the neutron guide.

Goldfoil activation and shape of thespectrum were taken at this positiondirect behind the neutron guide. Af-ter that the polariser was inserted andthe transmission spectrum of the po-lariser was measured. The two spec-tra were shown in Fig. 4.6. The newpolariser will be part of the experimen-tal equipment offered by FRM II for allusers.During the end the of the year the

first 2 m of neutron guide between

the gap for the NRex+ monochro-mator and the experiment shutter ofMEPHISTO were exchanged.The authors kindly appreciate the

effort of the students M.Aßmann andM.Helmecke working on the experi-ments at MEPHISTO.[1] Zimmer, O., et al. Phys.Rev.Lett.,

99, (2007), 104801.

[2] K.Zeitelhack, et al. Nuclear Instru-ments and Methods in Physics Re-search A, 560, (2006), 444–453.

4.3 PGAA – Prompt gamma activation analysis

P. Kudejova1,2, G. Meierhofer3, L. Canella2, K. Zeitelhack4, R. Schulze1, J. Jolie1, A. Türler21Inst. für Kernphysik, Universität zu Köln2Inst. für Radiochemie, TU München3Physikalisches Inst., Universität Tübingen4ZWE FRM II, TU München

General

In April 2007, first cold neutrons flewthrough the neutron guide NL4b dedi-cated to Prompt Gamma-Ray Activa-tion Analysis (PGAA) instrument. Therest of the year 2007 was used totest and characterize the instrumentand to work on the proper shielding.We measured the intensity and neu-tron spectrum of the cold neutron fluxat the first exit window of the guide.Further on, we used a tomographycamera and made radiographs of thebeam at different positions from theexit window of the neutron guide. Fi-nally, we have measured first samplesand analysed the PGAA spectra.

Introduction

Prompt Gamma-Ray Activation Anal-ysis is a nuclear analytical techniqueusing the (n,γ ) reaction to determinethe elemental (or chemical) composi-tion of various samples. PGAA de-termines the major, minor and traceelements in the entire volume of thesample non-destructively, thereforeit is a preferred method for small ar-chaeological objects as well as forother valuable samples.In general, PGAA is an effective

technique for the quantitative determi-nation of H, B, Na, Cl, K, Sc, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, As, Se, Br, Sr, Mo,Ag, Cd, In, Xe, Cs, Hf, Ta, Re, Os, Pt,Au, Hg, Nd, Sm, Eu, Gd, Dy, Er and U.The limits of detection for these ele-ments is in range between 1 ng/g forGd and 100 µg/g for Ti. PGAA canalso detect practically all the other el-ements, but with limits of detectionalready of the order of hundreds ofµg/g up to units of percent ( e.g. forC, N, O, F, Sn, Pb and Bi).

Experimental

The PGAA instrument is shown in

Figure 4.7: The flexible PGAA set-up with two detector positions: one is dedicatedfor standard PGAA measurements (left), another is exchangeable between pairspectrometer and PGAI detector (right).

Figure 4.7. The prompt γ-rays aredetected by a Compton-suppressedspectrometer, which consists of acentral HPGe detector inserted into aBGO scintillator annulus and operat-ing in anti-coincidence mode with it.In Figure 4.7, there are two positionsfor the detectors available and willserve for different applications: stan-dard PGAA, position sensitive PGAA- called PGA-Imaging (PGAI) and fora Pair Spectrometer, which measuresonly prompt γ-rays of higher energies(above 2 MeV).In November 2007, we tested the

PGAA acquisition system on medical


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Figure 4.8: First PGAA spectra were taken on medical samples with simple chemicalcomposition - mostly H, Cl and Fe are presented, in one of them Boron (P2-sample)occurs as well.

samples with relatively simple com-position. The task was to determine,if there is boron inside or not. Pre-liminary results show boron in somesamples, one example is presentedin Figure 4.8.Nevertheless, we will yield reliable

quantitative results not sooner thanthorough measurements and analysisare performed. This task is alreadyplanned for the first half of the year2008.

Neutron flux at NL4b

The NL4b neutron guide is about 51 mlong, with a curvature of 390 m. Be-cause of the strong curvature of theguide the neutron flux is not homoge-neous - the intensity at the left part(following the n-flux) is higher than theright part of the guide. To homoge-nize the neutron beam and to yieldmore intensity, the last 6.9 m were de-signed to be straight and ellipticallytapered. To have more flexibility forthe PGAA measurements, the ellipti-cal guide was divided into two parts,first of them 5.8 m long.

Intensity

In April 2007, the neutron flux at theexit window of the 5800 mm longelliptical guide was measured. Us-ing a set of 6 round pieces of goldfoils (11 mm in diameter), we cov-ered an area of 25 mm×51 mm. Us-ing the mean neutron wavelengthof about 6.7 Å(1.83 meV), we mea-sured an average neutron intensityof 6.0×109 n/cm2s. This neutronflux intensity corresponds to about2.2×1010 n/cm2s of thermal equiva-lent neutron flux.Due to the elliptical shape, the fo-

cus of the beam is not at the exit ofthe guide but about 30-35 cm fromthe first exit window (5.8 m of the el-liptical guide). According to the sim-ulations - while taken into consider-ation the real flux measurements -the neutron flux intensity of the fo-cused beam at the distance of 35 cmshould be about 7.3×109 n/cm2s withuseful dimensions of 14 mm×38 mm.With an additional 1.1 m of the focus-ing elliptical "nose", the intensity inthe focal point about 9 cm far fromits exit window should reach even

2.0×1010 n/cm2s with useful area ofabout 4 mm×11 mm.

Mean wavelength

To measure the mean neutron wave-length at NL4b, we have used a com-pact Time-Of-Flight spectrometerconstructed specially at FRM II forthese purposes [1]. Its external diam-eters are about 1000 mm×600 mmwith the aim to fit to most of the beamguides. We have scanned the neu-tron flux in horizontal direction about30 cm far from the exit window be-tween -2 and + 2 with a step of0.5 to determine not only the neu-tron mean wavelength, but also thedivergence curve. The acquired dataare only partially analysed and themean wavelength has a preliminaryvalue of about 6.7 Å, corresponding toan average neutron energy of 1.8 meV.More details to these measurementscan be found in the diploma thesis ofG. Meierhofer [2].

2D images

Due to the high intensity of the neu-tron flux, the 2D profiles of the

Figure 4.9: 2D-image of the neutron beamobtained by the DEL CCD Camera at35 cm distance from the first exit win-dow (after 5.8 m of the elliptical guide).


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Figure 4.10: Vertical profiles of the 2D images at different distances from the neutronguide exit window. For the distance at 35 cm given by Figure 4.9, the profile isgrayed.

n-beam could be measured only witha flux reduced to about 6% of the fullneutron intensity. The average inten-sity measured at the exit of the guidewas 3.6×108 n/cm2s.One example of the 2D images

measured at the distance of 35 cmfrom the neutron guide exit windowis presented in Figure 4.9. The darkspot in the bottom right corner of the2D image is an optical effect in the

lens system of the DEL camera de-veloped at FRM II. The shutter timeof the camera was set to 2-3 s be-cause the intensity of the beam wason the camera’s upper limit. The ver-tical profiles of the neutron beam atdifferent distances from the exit win-dow are presented in Figure 4.10 anddescribed in the reference [3]. For thePGAA measurements, we will select

a homogeneous part of the n-beamintensity with an appropriate aperture.

Outlook

The very next task is to follow up thecommissioning of the PGAA instru-ment and to come to routine opera-tion. We will start to measure samplesof scientifc interest in the next reac-tor cycle. We will characterize theneutron flux at the second exit win-dow, using the extendable ellipticallyfocusing guide of 1.1 m length. TheHPGe detectors need a proper effi-ciency calibration before we can startaccurate sample analysis. Further itis necessary to decrease the beambackground to achieve the expectedlimits of detection by the measure-ments.[1] Zeitelhack, K., Schanzer, C., Kas-

tenmüller, A., Röhrmoser, A.,Daniel, C., Franke, J., Gutsmiedl,E., Kudryashov, V., Maier, D.,Päthe, D., Petry, W., Schöffel, T.,Schreckenbach, K., Urban, A.,Wildgruber, U. NIM A, 560, (2006),444–453.

[2] Meierhofer, G. Diploma thesis.Graz University of Technology,Austria (2007).

[3] Kudejova, P., Meierhofer, G., Zeit-elhack, K., Jolie, J., Schulze, R.,Türler, A., Materna, T. JRNC. Inpress.


4.4 Fission neutron source - MEDAPP

F. M. Wagner1, A. Kastenmüller1, H. Breitkreutz1, B. Loeper-Kabasakal1, J. Kummermehr21ZWE FRM II, TU München2Strahlenbiologisches Institut der Universität München

The irradiation facility

Fig. 4.11 shows a plan view of thebeam SR10. It is supplied by unmod-erated fission neutrons which are gen-erated in a pair of uranium converterplates near to the entrance of thebeam. The spectrum was adaptedto the medical requirements by beamfilters consisting of lead and boratedepoxy resin [1].

Determination of neutronfluence data

The total flux was measured byhelp of a method which was orig-inally developed for the spectrum-independent determination of thesource strength of neutron emitters.The source would be placed in thecentre of a water bath which con-tains thermal neutron absorbers,

8

Figure 4.11: Horizontal section of the irradiation facility: 1 Compact reactor core inthe centre of the D2O moderator tank (diameter 2.5 m); 2 thermal-to-fast neutronconverter plates; 3 beam tube with four revolving shutter drums; 4 cavern containingthe shutter motors, filters, light projection, and beam monitor chambers; 5 multi leafcollimator (MLC); 6 patient couch; 7 beam dump.

e.g., gold. If the bath is so big thatthe neutrons are fully thermalized, thetotal activation of the probes is a mea-sure for the total fluence. At the SR10instead of the radioactive source, abeam channel from the surface to thecentre of the bath was inserted intothe phantom the influence of whichhad to be corrected with respect tothe efflux. Fig.4.12 shows the 200-l-water phantom furnished with goldprobes in one quadrant around thebeam axis (it is the phantom used forthe standard dosimetry, too). The to-tal neutron flux of the beam was de-termined to be 3.2·108 s-1cm-2; thisvalue is in line with other experimen-tal assessments. The neutron energyspectrum was determined by reso-nance and threshold foil activation [2].The effective cross sections were ad-justed by help of MCNP simulationsof the spectrum.

Figure 4.12: Phantom with gold probes[2].

The result is the expected fissionspectrum with an addition of epither-mal neutrons, see Fig. 4.13. A trans-mission calculation applied to thespectrum at the entrance of the beamtube confirms the MCNP simulationsand shows that neutrons once scat-tered do not any more contribute tothe flux at the irradiation site. Theweak thermal peak is mainly the resultof scattering in the collimator; there-fore the transmission calculation ofthe filtered source spectrum does notshow thermal neutrons.The experimental determinations

of the fluence and doses showedthat the simulations using MCNP 4C2overestimated the total fluence by afactor of 1.3. The most probablereason is that this version does nottake into account any delayed effectsby activation or fission products likeXe-135 with 2.65·106 barn thermalcapture cross section. The form ofthe calculated spectrum, however, isnot biased. For the same reason,the contribution of all activation prod-ucts is not calculated so that the totalgamma dose rate is underestimated.This was shown by measurement ofthe gamma dose during the first sec-onds rate after fast shut down of thereactor. The new version MCNPX2.6 Beta does take into account allthese delayed effects, but is still to betested.


Figure 4.13: Neutron spectrum free in air. Dots: MCNP simulation, full line: Transmis-sion calculation

Patient therapy

The permission of the patient ther-apy was issued in February 2007 byBayerisches Landesamt für Umwelt.On the basis of a three dimensionaldosimetry of the water phantom forall relevant collimations (S. Kampfer,Klinikum r. d. Isar), the first medicalirradiation was performed on June 11,2007. The patients were treated withsingle doses of 1.5 to 2 Gy, by 3 to 4(1-6) fractions, 1 to 4 fields per patient.In total, 80 fields have been irradi-ated. 12 patients were treated withina combined photon/neutron therapy,4 patients got neutrons only (pre-irradiation was more than 3 monthsbefore).With curative intention, the treat-

ment was carried out on 6 patients.They had no further tumor lesions.Their diagnoses were: 3 adenoidcystic carcinoma (ACC) of salivaryglands, 1 lymph node and 1 skinmetastasis of squamous cell carci-noma (SCC) and 1 skin metastasisof malignant melanoma. One patienthad bone metastases of breast can-cer, while the neutron therapy of the

chest wall was indicated in locally cu-rative intention. For all these patientsit is to early to give a statement aboutefficacy. The acute side effects werewithin the expected range.The other 9 patients got neutron

therapy for palliation: 3 extended skinmetastases of breast cancer, 2 locallyadvanced recurrences of ACC, 2 ex-tended cervical lymph node metas-tases of SCC, 1 multiple skin metas-tases of malignant melanoma, and1 locally advanced angiosarcoma ofthe chest wall. The palliative effec-tiveness became apparent in visibleregression of tumor lesions (e.g. ma-lignant melanoma), in more mobilityof the jaw joint for better eating andspeaking (ACC) or in less bleedingand secretion of ulcerous tumor le-sions (SCC).

Preclinical screening of thebiological effectiveness ofthe therapeutic beam

In order to render a sound radiobio-logical basis to the clinical applica-tion of fission neutron radiation, a pi-lot study into the Relative BiologicalEffectiveness, RBE, was performed

[3]. As a simplified in vitro tumormodel epithelial megacolonies gen-erated from human squamous cellcarcinoma line UTSCC5 (a) were em-ployed. The hallmark of this systemis that the cells are in close intercel-lular contact before, during and af-ter the irradiation. Furthermore, thetreatment effects can be quantifiedby in situ endpoints such as clonal ex-pansion of surviving cells, colony re-growth delay, and permanent colonycontrol (cure). The dose dependenceof permanent control to single dose ir-radiation was performed in a polyethy-lene phantom at the depths of 0, 3,and 6 cm, and compared to a refer-ence beam of 300 kV X-rays is shownin Fig. 4.14. The typical sigmoiddose-cure curves have been analyzedaccording to the generally acceptedlinear-quadratic model of cell survivalS:

−ln(S) = αD+βD2

with D = energy dose. RBE valuescan be read off directly as dose ratiosat the mean tumor cure probability(TCP) of 0.5; values estimated by sta-tistical analysis are listed in Table 4.3.The RBE varies mainly with the ra-

tio of photon to neutron dose whichdepends on the depth in the phantom;these results should also be descrip-tive of the situation in patients. By as-suming a common coefficient β of thequadratic dose term, the dependenceof RBE was also calculated as a func-tion of dose (Fig. 6). Extrapolation toan infinitesimally small dose rendersthe maximum RBE, equivalent to theratio of the linear dose coefficients forfission radiation and X-rays, α f /αx.As can be expected from the physi-

cal properties and the complexity offission radiation, the RBE undergoessubstantial variation with depth in tis-sue and dose employed. The ratherbig RBE at clinical doses per fraction(1 to 2 Gy) was also confirmed by mul-tifractionated single cell survival ex-periments (colony formation assay).Compared with other neutron

sources used for patient treatment,the fission neutron beam at FRM IIis highly efficient. The pronounced


decrease of the RBE with depth asa consequence of the drop of theneutron-to-gamma ratio has to betaken into account in treatment plan-ning. In suitable situations it mayeven be advantageous in sparinghealthy tissue underlying superficialtumours, e.g. the irradiation of breastwall metastases of mammary cancer.The investigations have been per-

formed in partial fulfilment of a masterthesis by V. Magaddino (University ofNaples, Italy). This project was con-ducted within the course “EuropeanMaster of Science in Radiation Biol-ogy” under the auspices of the Univer-sity College London (Prof. K.-R. Trott),and in co-operation with the Radiobi-ological Institute of the University ofMunich, LMU (Dr. J. Kummermehr).[1] Kampfer, S., Wagner, F., Löper-

Kabasakal, B., Kneschaurek, P.Strahlenther. Onkol., 183 (Son-dernr. 1), (2007), 72.

[2] Breitkreutz, H. Spektrale Charak-terisierung des Spaltneutronen-strahls der Neutronentherapiean-lage MEDAPP am FRM II. Mas-ter’s thesis, Fakultät für PhysikE13 (2007).

[3] Magaddino, V., Wagner, F., Kum-mermehr, J. ExperimentelleStrahlentherapie und KlinischeStrahlenbiologie, 16, (2007), 129–131.

Dose n+ [Gy ]

0 5 10 15 20 25

TCP

0.0

0.2

0.4

0.6

0.8

1.0

X-raysFRM-0FRM-3FRM-6

62d post irradiation

Dose n+ [Gy]

0 2 4 6 8 10 12 14 16 18

RB

E

1

2

3

4

5

6

FRM-0FRM-3FRM-6

Data TCP 62d

Figure 4.14: (left) Mean tumour cure probability(TCP) vs. dose at depths 0 cm (red), 3cm (green), and 6 cm (blue) in a PE phantom; black: TCP of 300 kV X-rays. (right)Relative biological effectiveness vs. single dose at depths 0, 3, and 6 cm (denotedby FRM0, FRM3, and FRM6, respectively.)

Table 4.3: Summary of RBE, α , and RBEmax derived from the data in Figures 1 and 2.

FRM-0 FRM-3 FRM-6 300 kV X-rays

RBE(TCP=0.5)

1.95 ± 0.044 1.82 ± 0.048 1.61 ± 0.036 -

α [Gy-1] 0.84 ± 0.11 0.76 ± 0.09 0.62 ± 0.08 0.17RBEmax 5.10 4.62 3.76 -

4.5 The positron beam facility NEPOMUC and instrumentation for positronphysics

Christoph Hugenschmidt1,2, Benjamin Löwe2, Jakob Mayer2, Philip Pikart2, Christian Piochacz1, ReinhardRepper1, Martin Stadlbauer1, Klaus Schreckenbach2, Werner Egger3, Gottfried Kögel3, Peter Sperr3, Gün-ther Dollinger31ZWE FRM-II, Technische Universität München2Physik Department E21, Technische Universität München3LRT2, Universität der Bundeswehr München, Neubiberg

The low-energy positronbeam of high intensity atNEPOMUC

In 2007 various experiments were per-formed at the high intensity positronbeam facility at NEPOMUC –NEutron

induced POsitron source MUniCh–which delivers up to 5 ·108 moderatedpositrons per second at a kinetic en-ergy of 1 keV. A new positron remod-eration unit, which is operated witha W(100) single crystal in back reflec-tion geometry, has been implementedin order to improve the beam bril-

liance. At present, the primary beamenergy is 1 keV, and the beam energyof the remoderated beam is set to20 eV. A longitudinal magnetic guidefield of 5-7mT is applied for positronbeam guidance, and the beam diam-eter amounts typically to 2.5-4mm. A


survey of recent positron beam exper-iments can be found in [1].

Experiments at NEPOMUC

The present status of NEPOMUCand the spectrometers connected tothe positron beam facility are shownFig. 4.15.The set-up of the coincident

Doppler-broadening spectrometer(CDBS) was improved which now al-lows coincident measurements withinshorter data acquisition times (<6 hper spectrum), and the backgrounddue to small-angle Compton scatter-ing of annihiliation quanta in the sam-ple was reduced to a minimum. Thisspectrometer is routinely operatedup to a beam energy of 30 keV witha beam diameter focused to about1mm onto the sample in order to al-low spatially resolved defect studies.In addition, a cryostat allows tempera-ture dependent measurements downto 76K. Various experiments havebeen performed in order to investi-gate crystal defects and the chemicalsurrounding at open-volume defects:e.g.: ion-irradiated metals and Mg-based alloys [2], defects in Al-basedalloys after mechanical load, metalliclayered systems.At the positron annihilation induced

Auger-electron spectrometer (PAES)for surface studies we succeeded torecord PAE-spectra within only 1 hacquisition time, which is about twoorders of magnitude lower than inlab-beam based experiments. TheAuger-yield and the surface selectiv-ity of PAES at Cu-covered surfacesof single crystalline silicon were de-termined and compared with conven-tional EAES [3]. At the end of 2007a new electron energy analyzer withhigher efficiency was installed whichis currently set into operation.The pulsed low-energy positron

system (PLEPS), which was previ-ously running with a 22Na-basedbeam at the UniBW, was transferredto the FRM II. First positron life-time measurements have been per-formed with positron energies be-

tween 0.5 and 20 keV. The results ofthis unique spectrometer are promis-ing for lifetime experiments withmono-energetic positrons: An ac-quisition time of only 3min lead to2.5 · 106 counts in the lifetime spec-trum, the overall timing resolution is240ps, and the peak-to-backgroundratio is better than 3 ·104 [4].Two additional experimental se-

tups were installed at the multi-purpose beam port: The appara-tus for the production of the nega-tively charged positronium (Ps−) (de-veloped at the Max-Planck-Institutefor nuclear physics [5].) allowed tomeasure the Ps−-decay rate with su-perior signal-to-noise ratio. These ex-periments will be continued in 2008with reduced systematic errors andhigh statistics.Another apparatus was connected

to the beam line for the investiga-tion of positron moderation in a gas-filled drift chamber. Inelastic positron-nitrogen scattering, positron coolingefficiency, energy and intensity lossmechanisms were quantified in orderto estimate the moderation efficiencyof this device [6].

Figure 4.15: The positron spectrometers at the positron beam facility NEPOMUCat FRM II: CDB spectrometer (TUM), PAES-facility (TUM), apparatus for Ps−-production (MPI nuclear physics, Heidelberg), and the pulsed-beam facility PLEPS(UniBW München).

[1] Hugenschmidt, C., et al. Appl.Surf. Sci,, (in press, avialable on-line).

[2] Stadlbauer, M., Hugenschmidt, C.,Schreckenbach, K., Böni, P. Phys-ical Review B (Condensed Mat-ter and Materials Physics), 76(17),(2007), 174104.

[3] Hugenschmidt, C., Mayer, J.,Schreckenbach, K. Surf. Sci., 601,(2007), 2459–2466.

[4] P.Sperr, Egger, W., Kögel, G.,Dollinger, G., Repper, R., Hugen-schmidt, C. Appl. Surf. Sci., (inpress, available online).

[5] Fleischer, F., Degreif, K., Gwinner,G., Lestinsky, M., Liechtenstein,V., Plenge, F., Schwalm, D. Phys.Rev. Lett., 96, (2006), 063401.

[6] Löwe, B., et al. Appl. Surf. Sci., (inpress, available online).

Part II

Scientific highlights

74 5 Soft matter

5 Soft matter

5.1 Separation of coherent and spin-incoherent neutron scattering fromprotein samples by polarization analysis

A.M. Gaspar1,2, W. Doster2, M.-S. Appavou2, S. Busch2, M. Diehl2, W. Häussler1,3, R. Georgii1,3, S. Masa-lovich1

1ZWE FRM II, TU München2Physik-Department E13, TU München3Physik-Department E21, TU München

We explored the possibility to per-form polarization analysis to experi-mentally separate coherent and spin-incoherent nuclear scattering pro-cesses, from a representative set ofsamples of interest for protein studies.Such a method [1, 2] had so far lim-ited application in the study of amor-phous materials [3, 4, 5], despite ofthe relevance of the information thatit provides. For instance, it allowsfor the experimental determination ofthe coherent structure factor Scoh(Q)of materials containing a significantamount of hydrogen atoms, such asproteins, uncontaminated by the enor-mous incoherent background. Knowl-edge of the relative importance of thecoherent and incoherent terms at dif-ferent Q values is also a pre-requisitefor the interpretation of dynamicalneutron scattering experiments, per-formed at instruments in which thetotal dynamic structure factor is mea-sured, as is generally the case of neu-tron time-of-flight and backscatteringinstruments.The experiments performed rely on

the principle that using a polarizedincident neutron beam and countingseparately neutrons scattered withand without spin-flip, a separationof the coherent from spin-incoherentnuclear scattering processes can beachieved. This is because only 1/3 ofthe spin-incoherent scattering eventsfrom a sample with random nuclearpolarization are without spin flip (theother 2/3 being with spin flip), whileall the coherent nuclear scattering

events correspond to scattering with-out spin flip [6].Hence from INSF = Icoh + 1/3 Iinc,

ISF = 2/3 Iinc one directly obtainsIcoh = INSF−1/2 ISF, Iinc = 3/2 ISF. Itshould be noted however that in prac-tice, the scattered intensities needto be corrected for a total finite flip-ping ratio, accumulating the effect ofthe imperfections in the spin analy-sis and manipulation components

0.01 0.02 0.03 0.040

100

200

300 Hemoglobin D2O solution

250 mg/ml

Inte

nsi

ty (a.u

.)

Q,A-1

non spin-flip

spin-flip

Figure 5.1: Small-angle scattering intensities of neutrons scattered with and withoutspin flip from a concentrated solution of hemoglobin in D2O. Results obtained atthe MIRA instrument at the FRM II.

of the instrument (see e.g. [2]). Figure5.1 illustrates how this separation wassuccessfully achieved at the MIRA in-strument at the FRM II, over the small-angle scattering region of a concen-trated hemoglobin solution.A more complete set of static scat-

tering measurements was obtainedon different samples of myoglobin (indry powder, hydrated powder, andin deuterated solutions of different

5 Soft matter 75

0.0 0.4 0.8 1.2 1.6 2.0 2.40.0

0.2

0.4

0.6

0.8

1.0

coherent

Myoglobin

dry powder

Fra

ctio

n o

f S

ca

tte

rin

g

Q,A-1

MIRA data

incoherent

D7 data

0.0 0.4 0.8 1.2 1.6 2.0 2.40.0

0.2

0.4

0.6

0.8

1.0

D7 data

Myoglobin

hydrated powder

incoherent

coherent

fra

ctio

n o

f sca

tte

rin

g

Q,A-1

0.0 0.4 0.8 1.2 1.6 2.0 2.40.0

0.2

0.4

0.6

0.8

1.0

RESEDA data

MIR

A d

ata

Myoglobin D2O

solution 100mg/ml

coherent

incoherent

Fra

ctio

n o

f sca

tte

rin

g e

vents

Q,A-1 0.0 0.4 0.8 1.2 1.6 2.0 2.4

0.0

0.2

0.4

0.6

0.8

1.0Myoglobin D

2O

solution 25 mg/ml

D7 data

coherent

incoherent

Fra

ctio

n o

f scatt

eri

ng e

ve

nts

Q,A-1

0.0 0.4 0.8 1.2 1.6 2.0 2.40.0

0.2

0.4

0.6

0.8

1.0

coherent

incoherent

D7 data

Myoglobin D2O

solution 10 mg/ml

Fra

ctio

n o

f scatt

erin

g e

ve

nts

Q,A-1

0.0 0.4 0.8 1.2 1.6 2.0 2.40.0

0.2

0.4

0.6

0.8

1.0Myoglobin D

2O

solution 2 mg/ml

D7 data

coherent

incoherent

Fra

ctio

n o

f sca

tte

rin

g e

ve

rnts

Q,A-1

Figure 5.2: Fractions of the total scattering corresponding to coherent and to spin-incoherent events, obtained for the differentmyoglobin samples investigated. Analyzer rocking scan of the primary beam.

76 5 Soft matter

concentrations), combining data fromthe MIRA and RESEDA instrumentsat the FRM II with data from the D7instrument at the ILL, thereby cover-ing a wide Q range, from the small(0.005 < Q < 0.05 Å−1) to the wide an-gle region (up to ∼ 2.5 Å−1). Resultsallowed obtaining quantitative infor-mation on the fractions of coherentand spin-incoherent scattering, whichis displayed in figure 5.2 for the dif-ferent myoglobin samples. From thisfigure it is possible to conclude thatfor the powder samples, for Q valuesabove 0.3 Å−1, the static incoherentterm represents more than 80% of thesignal and that, for Q > 0.9 Å−1, thecoherent and incoherent terms con-verge to the coherent and incoherentfractions of the total cross section.This is not the case for the proteinsolutions. Only at high protein con-centrations (say >100 mg/ml), andespecially if the analysis can be re-

stricted to 0.4 < Q < 1.2 Å−1, we mayalso assume a dominating incoherentcontribution of approximately 80% ofthe total scattering.Otherwise, as in the case of the

more diluted solutions, the coherentand incoherent scattering contribu-tions appear similarly important, evenwith interchangeable predominance.These results are particularly rel-

evant to the interpretation of time-of-flight or backscattering results ob-tained on protein solutions, or on anyother liquid or soft matter system, forwhich the structure factor changessignificantly over the Q region gener-ally investigated. Since the dynam-ical correlations at the origin of thecoherent and incoherent parts of thespectra are not the same [7, 8], inter-pretation of the spectra requires ap-propriate consideration of these twoterms and of their relative importance.

A.M. Gaspar acknowledges the Por-

tuguese Science and Technology Foun-dation (FCT) for support in the form ofa post-doc grant SFRH / BDP / 17571 /2004

[1] Moon, R. M., Riste, T., Koehler, W. C.Phys. Rev., 181, (1969), 920.

[2] Schaerpf, O. Physica B, 182, (1982),376–388.

[3] Dore, J. C., Clarke, J. H., Wenzel, J. T.Nucl. Instr. & Meth., 138, (1976), 317–319.

[4] Gabrys, B. J. Physica B, 267-268,(1999), 122–130.

[5] Gabrys, B. J., Zajac, W., Schaerpf, O.Physica B, 301, (2001), 69–77.

[6] Hicks, T. J. Adv. Phys., 45, (1996),243–248.

[7] Skoeld, K. Phys. Rev. Lett., 19, (1967),1023–1025.

[8] Bee, M. Quasielastic Neutron Scatter-ing (Adam Hilger, 1988).

5.2 Time-of-flight grazing incidence small angle neutron scattering

P. Müller-Buschbaum1, J.-F. Moulin2, V. Kudryashov2, M. Haese-Seiller2, R. Kampmann2

1ZWE FRM II, TU München2GKSS Forschungszentrum, Geesthacht

Polymers with controlled nanoscalemorphologies continue to be of con-siderable interest for a wide rangeof applications in electronics, opto-electronics, photonics, sensors, anddrug delivery. In particular, nanos-tructured polymer films allow for newproperties, which are mainly basedon surface effects and a size reduc-tion down to a regime in which a char-acteristic length scale of a physicalphenomenon becomes comparablewith the typical length scale of thenanostructure. In many applicationspolymers are favoured because manyof them are transparent, compliant,and biocompatible and/or biodegrad-able. Moreover, polymer devices areinexpensive and disposable, which ishighly desirable for cost-effective ap-plications.In addition to a real space im-

age of surface structures, a mean-ingful statistical analysis is advan-

tageously performed with scatteringtechniques. Synchrotron radiationbased grazing incidence small an-gle X-ray scattering (GISAXS) turnedout to be a powerful advanced scat-tering technique to probe nanostruc-tured polymer films. Similar to AFMa large interval of length scales be-tween molecular and mesoscopicones is detectable with this surfacesensitive scattering method. Whilewith AFM only surface topographiesare accessible, with GISAXS in ad-dition the buried structure is probed.Due to the larger area probed byGISAXS, this technique provides datahaving a much higher statistical qual-ity than AFM. However, contrast be-tween different components building-up nanostructures might be small andconsequently, the possibility of tun-ing contrasts, which is possible by(partial) deuteration in case of neu-tron scattering, can be extremely ad-

vantageous. Thus neutron surfacescattering as analytical technique isa very successful technique. Usingneutrons instead of x-rays in combina-tion with the grazing incidence smallangle scattering geometry results ingrazing incidence small angle neutronscattering (GISANS). As compared toGISAXS measurements based on syn-chrotron radiation, experiments us-ing neutrons are still very rare. Sofar all GISANS experiments were per-formed with a monochromatic neu-tron beam. These single wavelengthexperiments are typically very timeconsuming in case several different in-cident angles are probed. Within thisarticle we report on a new approach,combining GISANS with the time-offlight mode (TOF). TOF mode allowsfor a specular and off-specular scat-tering experiment, in which neutronswith a broad range of wavelengths areused simultaneously and recorded as

5 Soft matter 77

a function of their respective times offlight. Such white beam experimentsare impossible with x-ray beams dueto the immediate radiation damageto the sensitive (bio-) polymer struc-ture. Due to the different interaction,neutron scattering experiments over-come all problems related to radia-tion damage and are thus a uniqueprobe to detect radiation sensitive sur-face structures. So far TOF-modebased surface sensitive neutron scat-tering experiments were restricted toneutron reflectivity and standard off-specular scattering.To demonstrate the possibilities of

the new analytical technique TOF-GISANS we focus on a simple poly-mer nanostructure. The model sys-tem consists of an arrangement ofsmall droplets, called nano-dots, con-taining a deuterated homopolymerwhichi prepared on top of a solid sup-port [1]. Historically, a comparablepolymer nano-dot sample was usedas model system for the first GISANSexperiments as well [2]. Thus thenanostructure is accessible with AFMand single wavelength GISANS mea-surements exist, which allows for adetailed evaluation of a TOF-GISANSexperiment.The presented experiments were

carried out at the REFSANS beamlineat the neutron research source HeinzMaier-Leibnitz (FRM II). The total in-tensity, integrated over all TOF chan-nels, and hence over all wavelengthsis strongly dominated by the chan-nels with highest intensity. However,the wavelength integration is equiv-alent to a strong smearing, becauseat individual wavelengths the detec-tor pixels cover different qyqz-areas.

Figure 5.3: Selection of twelve 2d intensities measured simultaneously in the TOF-GISANS experiment. The corresponding mean wavelengths are a) 0.50, b) 0.55, c)0.61, d) 0.68, e) 0.75, f) 0.82, g) 0.91, h) 1.00, i) 1.11, j) 1.22, k) 1.35 and l) 1.48 nm.The intensity is shown on a logarithmic scale represented by colours following theEOS2 palette (white= low and black= high intensity). Taken from [3].

Thus for a quantitative analysis onlythe 2d intensities related to individ-ual TOF channels are suited. In fig-ure 5.3 the 2d intensity distributionsat 12 TOF channels is shown for afixed number of effective pixels. Dueto the different wavelengths each 2dintensity in figure 5.3 corresponds toa different (qy, qz)-range. Thus each2d image in figure 5.3 is equivalentto the GISANS signal obtainable in astandard GISANS set-up [4] for thewavelength of the TOF channel.

Figure 5.3 shows the anisotropy ofall observed scattering patterns. Dif-ferent main features are already deter-mined right from the two-dimensionalimages: The intense specular re-

flected peak, the Yoneda peak (whichposition depends on the related wave-length) and the splitting of the diffusescattering into two strong Bragg-rods.The Yoneda peak is located at the po-sition of the critical angle αc. [3][1] Müller-Buschbaum, P., et al. J.

Phys. Condens. Matter, 17, (2005),S363.

[2] Müller-Buschbaum, P., et al. PhysChem Chem Phys, 1, (1999),3857.

[3] Müller-Buschbaum, P., et al. Sub-mitted.

[4] Müller-Buschbaum, P., et al. Phys-ica B, 283, (2000), 53.

78 6 Condensed matter

6 Condensed matter

6.1 Field and temperature dependence of the magnetization inferromagnetic EuO thin films

S. Mühlbauer1, P. Böni2, R. Georgii1, A. Schmehl3, D.G. Schlom3, J. Mannhart41ZWE FRM II, TU München2Physics Department E21, TU München3Department of Materials Science and Engineering, Pennsylvania State University, Pennsylvania, USA4Experimentalphysik VI, Institut für Physik, Universität Augsburg

Introduction

The ferromagnetic semiconductorEuO is the only known binary ox-ide that can be grown in a thermo-dynamically stable form in contactwith silicon. The conductivity canbe matched to the conductivity ofsilicon by introducing oxygen vacan-cies, which is a key necessity forcoherent spin injection in spintronicdevices. Therefore, heterostructurescomposed of Si and EuO may beused as model systems for study-ing applications of devices in thefield of spintronics, where besides thecharge, the spin degree of freedomis also used to control the flow ofconduction electrons. Recently, it be-came possible to grow epitaxial filmsof EuO1−x on Si with spin polarizationabove 90 percent. The direct integra-tion of EuO with Si will allow the fabri-cation of model systems for studyingdevices in the field of spintronics.[1]While the magnetization of EuO

grown on YAlO3 has been measuredby means of a superconducting quan-tum interference device (SQUID) yield-ing a saturation moment µsat = 6.7µBper Eu atom and a coercive fieldHc = 60 Oe at 5K , the magnetic mo-ment of EuO1−x grown on Si has notyet been determined. The reason be-ing that the large and rather elusivesamples are supposed to be usedfor additional bulk measurements andshould therefore not be reduced insize for measuring the magnetizationwith a SQUID. Moreover, bulk mea-

surements would not provide informa-tion on the re-orientation process ofthe domains, a property that is of im-portance for device applications.In order to non-destructively deter-

mine the magnetic properties of thinfilms of EuO on Si, we have measuredthe critical angle of reflection by usingpolarized neutrons. The results con-firm that the magnetic moment in thefilms is consistent with the bulk value.In addition, we show that the changeof magnetization is not caused by re-population of domains but by domainrotation.

Qk

i kf

M

Flipper 1Polarizer

Flipper 2

Analyser

Detector

B

Bg

2

Figure 6.1: Schematics of the polarized neutron reflectometer MIRA. The incomingneutrons ki are elastically reflected by the sample. Q designates the momentumtransfer. The polarization of the neutron beam is selected by means of spin flippersbefore and after the sample. The polarization of the neutrons follows adiabaticallythe direction of the guide field Bg. This setup allows the measurement of the fourcross-sections I++, I−−, I−+ and I+−

Experimental details

The EuO1−x films were deposited byreactive molecular beam epitaxy onthermally cleaned (001) Si and (110)YAlO3 and have been protected in situagainst degradation when exposed toair by a 130 Å thick capping layer ofSi or other materials. X-ray diffrac-tion scans showed that the struc-tural properties were of exceptionallyhigh quality, comparable to single-crystalline EuO.The reflectivity measurements were

performed on the beam line for very

6 Condensed matter 79

cold neutrons MIRA. The sample wasmounted inside a closed cycle cryo-stat on a flat aluminium holder. Amagnetic field was applied parallel tothe incident neutron beam with wave-length λ = 9.7±0.05Å and parallelto the sample surface, as sketchedin figure 6.1. As the magnetic field isalso guiding the neutron polarization,P is therefore parallel or antiparallel tothe sample and perpendicular to Q.The amplitude of the magnetic mo-

ments can be determined by twomeans: i) either by conducting mea-surements up to reasonably large qand fitting the data with a bilayermodel that includes the EuO and thecapping layer or by ii) determining theangle of total reflection. Due to thelow intensity of the beam line MIRAwe have chosen method ii) that is alsoused for the characterization of super-mirrors. The reflection profiles I++,I+−, I−+, I−− were measured by per-forming Θ−2Θ scans with fixed initialwavevector ki for temperatures 6K≤ T ≤ 71K in magnetic fields B=0Oe,125Oe and 250Oe.

Results and discussion

The obtained results can be summa-rized as follows: Figure 6.2 shows atypical reflectivity profile of the EuOsample recorded at 6K and fieldsB=0Oe, B=125Oe and B=250Oe.The direct beam is visible around 0.Due to footprint effects, the plateauof total reflection for I++ is reached atroughly 0.011 Å−1, while I−− showsno total reflection. Due to the limitedlength of the sample, the total reflec-tion plateau does not reach the fulldirect beam intensity. The critical an-gle of total reflection was determinedat 50 percent reflectivity, normalizedto the plateau of total reflection. Thedata has been corrected for a finitebeam polarization of 92%.The observed lack of spin-flip in-

tensity for B=125Oe and B= 50Oeshows, that the magnetization of theEuO is strictly parallel to the ap-plied magnetic field, whereas thedata recorded at B=0Oe clearly ex-hibits spin-flip scattering. This

Figure 6.2: Reflectivity profile of EuO on Si (001), T=6K, B= 0Oe, 125Oe and 250Oe,full polarization analysis. The crosstalk between the individual channels due to finitebeam polarization and flipper efficiencies has been corrected. The pronouncedpeak on the left hand side identifies the un-scattered direct beam, the dip betweenthe plateau of total reflection and direct beam is due to foot-print effects on thesmall sample. The critical angle of total reflection was determined at 50 percentreflectivity normalized on the total reflection plateau. Both spin-flip cross-sectionsI+− and I−+ vanish for B=125Oe and B=250Oe while the data for B=0Oe showsspin flip scattering.

demonstrates, that the change ofmagnetization is caused by domainrotation and not repopulation, rulingout B ‖M.In figure 6.3, the temperature and

field dependence of the critical angleof total reflection for I++ and I−− isshown. The merging of the criticalangles for T = Tc = 69K, where theferromagnetism of the sample van-ishes, is obvious. M(T ) qualitativelyexhibits the expected decrease withincreasing temperature. A slight shiftof the ferromagnetic to paramagnetictransition to higher temperatures forincreasing magnetic field is visible,due to the field induced smearingof the ferromagnetic phase transition.The observed increasing magnetiza-tion with increasing field of the EuOlayer is due to domain reorientation indirection of the external applied mag-netic field.Two independent features of the

measured reflectivity data can beused to verify the obtained values forΘc:

The direct beam direction, definingΘc = 0 has been used for performingan absolute calibration of Θc. Thisyields a value bmag(Eu2+) = 1.78±0.19· 10−12 cm for T=6.5K and B=250Oe,which is within 6.5 percent of theliterature value (blit(Eu2+) = 1.904 ·10−12 cm).

To crosscheck these results, the ob-tained data has also been normalizedto the angle of total reflection of thenuclear contribution of bnuc(Eu2+) andbnuc(O), obtained above Tc, whereno magnetic contribution is present,giving identical results for bmag(Eu2+).With bmag = ( γr0

2 )g f (Q)S and ( γr02 ) =

0.2695 ·10−12 cm a magnetic momentµsat = 6.6±0.7 µB is obtained per Euatom, which is consistent with resultsfrom bulk single crystals.

Conclusion

By measuring the critical angle of to-tal reflection with polarized neutronreflectometry, we demonstrated thatthe saturation moment of EuO grownepitaxially on Si (001) matches the


moment of EuO grown on YAlO3 asmeasured using a SQUID, withoutthe need of cutting the samples intosmall pieces. The observed magneticmoment of the EuO1−x layers agreesvery well with values from bulk sin-gle crystals, proving the extraordinaryhigh quality of the samples, whereasearlier measurements on EuO layersshowed a reduced magnetic moment.The samples clearly show a well de-fined ferromagnetic transition at Tc=69K. Thus, EuO1−x, matched to theconductivity of silicon and grown epi-taxially on silicon may be broadlyused for spintronic devices within thewell established Si-based technology.

Furthermore, the ability of polarizedneutron reflectometry being sensitiveto the orientation of the magnetic mo-ment in the sample proves, that do-main reorientation and not repopula-tion is responsible for the process ofmagnetization.[1] Schmehl, A., et al. Nature Materi-

als, 6, (2007), 882 – 887.

Figure 6.3: Temperature dependence of the critical angle of total reflection of EuO onSi (001) for different temperatures from 6K ≤T≤ 71K and different applied magneticfields B=0, 125 and 250Oe; For T=Tc, the magnetic contribution vanishes. Theclear field dependence indicates domain repopulation for increasing external fieldsin direction of the applied external field.

6.2 Examination of rat lungs by neutron computed micro tomography

B. Schillinger1,2, Andrew Comerford3, Elbio Calzada1,2, Josef Guttmann4, Robert Metzke3, MartinMühlbauer1,2, Hanna Runck 4, Matthias Schneider4, Michael Schulz 1,2, Claudius Stahl 4, Lena Wiechert 3,Wolfgang Wall31ZWE FRM II, TU München2Physics Department E21, TU München3Chair for Computational Mechanics,TU München4Department of Anesthesiology and Critical Care Medicine, University of Freiburg

Abstract

By means of a thinned scintillationscreen and a high resolution opticalsystem an effective resolution in theorder of 30-40 µm is achieved at theANTARES facility for neutron imaging.This setup was used to gather struc-tural information of freshly extractedrat lungs. The aim of the measure-ment is the development of a numeri-cal lung model for improvement of ar-tificial respiration in human medicinein hospitals.

Introduction

Patients who need artificial respira-tion in hospital over several days of-ten suffer lung damages because therespiration pressure cannot be setwith sufficient precision due to insuf-ficient knowledge about the exactcomposition of the lung. The chairfor computational mechanics of TUMünchen aims to develop a numericalmodel of a lung in order to simulatepressure and air flow in the branchingof the air vessels. As it turned out,the structure of the lung is known inprinciple, but not in detail, and very lit-tle is known about the actual branch-

ing and diameters of the pulmonaryair passages. As the volume of thelung consists mostly of air, with verythin air and blood vessels, normal X-ray examinations deliver insufficientcontrast of the tissue to image thestructure of the lung. Neutron imag-ing delivers a high contrast of the hy-drogen content in the tissue and wassuccessfully employed to deliver 3Dimages of the lung structure.

Experimental setup

Since neutron imaging employs a par-allel beam, there is no inherent mag-nification of the sample, and the im-


age resolution is limited to the ac-tual detector resolution. ANTARESused a thinned scintillation screen(50µmthickness) and a ZEISS pla-nar high resolution lens on a 2048x 2048 pixel cooled CCD camera.With an effective pixel size of 20µm,the achieved resolution (due to blur-ring of the scintillation screen) wasestimated in the order of 30-40µm.Live laboratory rats were delivered tothe engineering faculty, were anaes-thetised and killed. The lungs wereextracted and sewn with their main airpipe onto on a plastic tube, then putinside an aluminium tube that bothsimulated the confinement of the ribcage and also fixated the lung againstmovement during the measurement.The lung was then inflated with 20-30mbar air pressure and mounted on arotation table in front of the detector.

Measurement

At this high resolution, the incidentneutron flux per pixel is very low. Oneprojection required between 13 and80 seconds exposure time, totallingin 2.5 to 9 hours for 400 projectionsfor the computed tomography. Ad-ditional experiments were conductedwith a Gadolinium containing contrastagent that was directly injected intothe main airway. Due to the capillaryforces, this contrast agent penetratedinto the finest air vessels.Fig. 6.4 shows one projection of a

lung confined in the Aluminium tube,fig. 6.5 shows a lung with addedGadolinium contrast agent. Fig. 6.6shows a lung that was taken outof the Aluminium container and hadconsecutively inflated to double itsoriginal volume. Fig. 6.7 shows athree-dimensional reconstruction ofa lung with the threshold set so highas to see only larger air vessels. Fig.6.8 shows another lung with a lowerthreshold level, showing many finevessels as well as apparently a majorblood vessel that branches towardsdifferent sections of the lung.Fig. 6.9 shows a lung filled with

Gadolinium contrast agent that haddissipated into the finest branches.

Since the liquid had followed gravityduring injection, the upper parts ofthe lung were not filled.

Conclusion

For the first time, neutron computedtomography has been used for thedetermination of the structure of lungtissue. The results will be employedin the development of a numericalmodel of a lung in order to improveclinical treatment of human patients.Further examinations are under way.

Figure 6.4: One projection of a lung con-fined in the Aluminium tube.

Figure 6.5: A lung with added Gadoliniumcontrast agent

Figure 6.6: A lung that was taken out ofthe Aluminium container and had con-secutively inflated to double its originalvolume.

Figure 6.7: A three-dimensional recon-struction of a lung with the thresholdset so high as to see only larger air ves-sels.


Figure 6.8: Another lung with a lowerthreshold level, showing many fine ves-sels as well as apparently a major bloodvessel that branches towards differentsections of the lung.

Figure 6.9: A lung filled with Gadoliniumcontrast agent that had dissipated intothe finest branches. Since the liquidhad followed gravity during injection,the upper parts of the lung were notfilled.

6.3 Thermal expansion under extreme conditions at TRISP

Christian Pfleiderer1, Peter Böni1, Thomas Keller2,3, Ulrich K. Rössler4, Achim Rosch5

1Physik-Department E21, TU München2Max-Planck-Institut für Festkörperforschung, Stuttgart3ZWE FRM II, TU München4IFW Dresden5Universität Köln

The resolution of conventional neu-tron and x-ray diffractometers islimited by the beam divergenceand monochromaticity. The Larmor-diffraction technique (LD) at TRISPsurpasses the resolution of conven-tional diffractometers by 1-2 ordersof magnitude and reaches in thepresent configuration ∆d/d ' 10−6.This makes possible the reexami-nation of a large number of promi-nent scientific questions in physics,chemistry, geoscience and engineer-ing through high-precision measure-ments of lattice parameters under ex-treme conditions like ultra-low or veryhigh temperatures, high hydrostatic

or uniaxial pressures and high electricfields.Here we report on a study of the

thermal expansion of the cubic metalMnSi under pressures up to 21kbarand temperatures down to 0.5K [1]at TRISP. MnSi attracted great in-terest because it is probably thebest candidate for a non-Fermi liquid(NFL) metallic state in a pure three-dimensional metal that is not sensitiveto a fine tuning of the underlying in-teractions [2, 3]. This possibility is in-ferred from an abrupt transition of thetemperature dependence of the resis-tivity from a well understood T 2 Fermiliquid behavior to a T 3/2 non-Fermiliquid behavior above pc = 14.6kbar.

The NFL resistivity is remarkably in-sensitive to pressure up to at least50kbar (∼ 3pc) [4, 5].The question whether the NFL re-

sistivity in MnSi is driven by a QCPor is the characteristic of a novelmetallic phase is settled by the ther-mal expansion data shown in Fig.6.10 and 6.11(b). (QCPs are de-fined as zero-temperature second-order phase transitions that are tunedby non-thermal control parameterssuch as hydrostatic pressure or mag-netic field). For the zero temperaturelimit the variation of the lattice spac-ing a2 shows expansion for p < p∗,while it shows contraction above pc(see phase diagram in Fig. 6.11(a)).


However, the change of sign is al-ready present for T > TC when TC issuppressed below ∼ 15K. Further, forpressures above pc the temperaturedependence of a2 remains essentiallyunchanged without any signature ofT0. This both rules out quantum crit-icality for Tc→ 0 at pc and a QCP forTC→ 0.Our results concerning the nature

of the phase diagram of MnSi showthat the transition at pc is first order,and the onset of partial order at T0(and thus p0) seen in neutron scatter-ing is clearly not related to a thermo-dynamic phase transition. This estab-lishes that the observed NFL behavioris not connected to a QCP. Instead,it is the characteristic of an extendedgenuine NFL state. More generally,this finding suggests that novel formsof order may be expected elsewherethan at quantum phase transitions.[1] Pfleiderer, C., Böni, P., Keller, T.,

ler, U. R., Rosch, A. Science, 326,(2007), 1871.

[2] Pfleiderer, C., Julian, S., Lon-zarich, G. Nature, 414, (2001),427.

[3] Pfleiderer, C. Physica B, 328,(2003), 100.

[4] Doiron-Leyraud, N., et al. Nature,425, (2003), 595.

[5] Pedrazzini, P., et al. Physica B,378-380, (2006), 165.

[6] Pfleiderer, C., et al. Phys. Rev. B,55, (1997), 8330.

[7] Pfleiderer, C., et al. Nature, 427,(2004), 227.

[8] Uemura, Y. J., et al. Nat. Phys., 3,(2007), 29.

Figure 6.10: Temperature dependence of magnetic and electronic contributions a2 ofthe lattice constant of MnSi at various pressures as obtained by Larmor diffraction atTRISP. The relative resolution obtained in this experiment is in the order of 1.6×10−6.The inset displays the lattice constant a at ambient pressure.

Figure 6.11: (A) Phase diagram of MnSi as a function of pressure. Data for TC arebased on the resistivity ρ and the ac susceptibility χ reported in [6]. T0 is basedon elastic neutron scattering [7]. The blue shading indicates the regime of Fermiliquid behaviour, where dark blue shading shows the regime of phase segregationseen in µ-SR [8]. The green shading represents the regime of NFL resistivity, wheredark green shading indicates the regime of partial order. The transition temperatureTC,L observed in the lattice constant by Larmor diffraction is in excellent agreementwith previous work. The crossover temperature TT E represents the appearanceof lattice contraction in a2 as measured by Larmor diffraction. (B) Extrapolatedzero-temperature variation of a2. The spontaneous magnetostriction varies veryweakly under pressure up to p∗ ∼ 12.5kbar before dropping distinctly and changingsign. It also varies very weakly above pc.


6.4 Investigation of embedded submono-layers in Al using positronannihilation

Christoph Hugenschmidt2,1, Philip Pikart1,2, Martin Stadlbauer1,2, Klaus Schreckenbach1,2

1Physics Department E21, Technical University Munich, 85747 Garching, Germany2ZWE FRM-II, Technical University Munich, 85747 Garching, Germany

In the presented work we demon-strate that metal layers in the sub-monolayer range embedded in a ma-trix are revealed with unprecedentedsensitivity by coincident Doppler-broadening spectroscopy (CDBS) ofthe positron annihilation using amono-energetic positron beam. Be-sides the application of a non-destructive technique, one aim hasbeen to reveal the elemental signa-ture of Sn of various thickness in theCDB-spectra in order to investigatethe positron trapping properties of theembedded Sn layer.A set of four layered samples was

prepared in an UHV-chamber: PureAl was evaporated onto water-cooledglass substrates (≥ 99.99%, thicknessof 5.5± 0.3 µm ). Afterwards, the Snlayer (≥ 99.999%) of various thicknessdSn (dSn = 0.10±0.03 nm, 1.60±0.1 nm,25±1nm, and 200±8nm) was evap-orated on top of the Al, which wasfinally by 200± 8nm Al. Annealed Aland annealed Sn serve as referencematerials. We performed calculationsof the Makhovian implantation profile(before diffusion) of the layered sam-ples in order to maximize the overlapof the positron distribution with theSn layer by variation of the kinetic en-ergy of the positrons. As a result ofthese calculations the kinetic energywas set to 6 keV for the three sam-ples with a Sn-thickness of 0.10 nm,1.6 nm, and 25nm, respectively, andto 15 keV for the others.The measurements were carried

out with the CDB-spectrometer [1] lo-cated at the high intensity positronsource NEPOMUC – NEutron inducedPOsitron source MUniCh [2]. Theraw data of the CDB-spectra are nor-malized to the same integrated inten-sity of the 511 keV photo-peak (fig-ure 6.12). Note the low backgroundleading to a peak-to-background ratioof better than 105. For a more detailed

view, all spectra have been divided bythe spectrum obtained for pure an-nealed Al in order to reveal the ele-ment specific contribution of Sn (fig-ure 6.13). The solid lines representleast-square fits of a linear combina-tion of the photon intensities recordedfor pure Sn and pure Al with only onefree fit parameter, which correspondsto the amount of positrons annihilat-ing in the Sn layer.The higher photon intensity for

larger electron momenta with increas-ing amounts of Sn is attributed tothe higher binding energy of the anni-hilating core electrons in Sn. Evenat an amount of 0.1 nm Sn belowthe 200nm Al coating, the photonintensity increases significantly for10 · 10−3m0c < pL < 25 · 10−3m0c. Thestrongly disproportional increase ofthe positron annihilation rate withcore electrons from Sn is interpretedas follows: After implantation, ther-malized positrons diffuse to the Al/Sn-interface, where they are efficientlytrapped in open-volume defects andhence could annihilate with localizedcore electrons of Sn atoms. Thenumber of those defects are ex-pected to be particularly large dueto the lattice mismatch at the Al/Sn-interface. On the other hand, thesmaller core annihilation probabilityfor positrons trapped in open volumedefects would lead to a lower pho-ton intensity in the high electron mo-mentum range than annihilation in theunperturbed Sn lattice. It is henceunlikely that defect trapping is solelyresponsible for the large enhance-ment of the Sn signature. The mainreason for the observed high anni-hilation rate in the Sn layer can beunderstood in terms of the elementspecific positron affinity: Due to themuch stronger positron affinity of Sncompared to that for Al, the Sn layercan be regarded as a well with a po-

tential depth of ∼ 3.2 eV. Therefore,positrons thermalized inside the Snlayer are repelled at the Sn/Al inter-face during their diffusion, and a cer-tain amount of those thermalized in Aldiffuse to the Sn layer where they areefficiently trapped inside the Sn layeror Sn clusters.With this experiment we demon-

strated that CDBS with mono-energetic positrons is clearly a verypowerful technique for the investiga-tion of thin layered structures that arehidden below coatings of hundredsof atomic layers. We envisage to in-vestigate layers of various elementsembedded in a matrix by CDBS as afunction of positron implantation en-ergy not only to reveal the elemen-tal information of the embedded layerbut also to determine its depth belowthe coating.[1] Stadlbauer, M., Hugenschmidt, C.,

Straßer, B., Schreckenbach, K.Appl. Surf. Sci., 252, (2006), 3269–3273.

[2] Hugenschmidt, C., Schrecken-bach, K., Stadlbauer, M., Straßer,B. Nucl. Instr. Meth. A, 554, (2005),384–391.


Figure 6.12: CDBS of the 511 keV annihilation line for pure Al, Sn, and the Al/Sn/Allayered samples.(normalized to same intensity).

Figure 6.13: Ratio curves of the photon intensities: All spectra (see fig. 6.12) aredivided by the Al reference spectrum. The uppermost curve shows the elementalsignature of Sn. (Details see text.)

Part III

Facts and figures

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7.1 User office and public relations

J. Neuhaus1, U. Kurz1, B. Tonin1


On May 9th 2007 the hand-over ofkeys of the new east building was cel-ebrated. About 150 visitors joined theparty welcomed by officials from TUMand the Forschungszentrum JülichGmbH - of which the Jülich Centre forNeutron Science occupies this build-ing as lodger of the second floor - toformer colleagues and friends fromneighboring and foreign institutes. Anight with movies in the huge and atthat time still empty east hall com-pleted the event.In autumn 2007 the Campus of

Garching celebrated its 50th anniver-sary. Everything started with thefirst neutrons at the Forschungsreak-tor München (FRM), the so-called“Atomic Egg” on October 31st 1957.Preparing the birthday activitiesstarted already in 2006. In a closecollaboration between the Technis-che Universität München, the Max-Planck-Institute for Plasma Physics,the European Southern Observatory(ESO) and the city of Garching severalactivities were organized.

Figure 7.1: Prof. Dr. Dr.h.c. mult. Wolf-gang A. Herrmann received the keys ofthe new east building from Mr. HeinrichMayer, responsible building director ofBaTUM.

The “Festveranstaltung” with pre-sentations from science and politicstook place on September 26th in thelecture hall of the Faculty for Engineer-ing in Garching. On this occasion theresigning prime minister Dr. EdmundStoiber pointed out the key role ofthe FRM and FRM II for the Garch-ing Campus. The national press andBavarian television responded wellto the long list of prominent speak-ers including the noble prize winnerProf. Dr. Theodor W. Hänsch and thepresident of the TUM, Prof. Dr. Dr.h.c.mult. Wolfgang A. Herrmann.This event was followed by the

“Long Night of Science” on Octo-ber 13th. Until midnight all institu-tions in Garching opened their doorsand attracted several thousands of

Figure 7.2: Prime minister Dr. Edmund Stoiber and president of the TUM, Prof. Dr. Dr.h.c.mult. Wolfgang A. Herrmann.

visitors. A panel discussion in thelecture hall of the Faculty for Engi-neering on “Von Garching nach Eu-ropa – Forschung im globalisiertenWettbewerb” opened the eveningevents. FRM II offered visitor toursthrough the reactor building as well asoverview talks in the Physics Depart-ment accompanied by presentationsof the radiation protection service andmovies presenting the research op-portunities at FRM II. The offer to visitFRM II was in great demand as usualand quickly fully booked. Altogether455 visitors toured the FRM II. Theguided tour included the view into thereactor hall and the presentation ofthe instruments in the experimentaland neutron guide hall.

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Figure 7.3: The Möbius strip symboliz-ing the interaction of the numerous re-search institutes at the campus andbetween the campus and the city ofGarching.

The “Long Night of Science” attractedespecially younger people to visit thescientific institutes. In the very begin-ning of the “Long Night” even veryyoung visitors were welcomed. Inparticular, children of staff membersgained insight in the work of their par-ents. Tobias Unruh, known for hisexpertise to explain difficult scientificsubjects to young pupils, deliveredfascinating insights into daily scien-tific work.On the occasion of the celebration

of the 50th anniversary of the Garch-ing Campus a new logo was created“Forschen in Garching”. The depictedMöbius strip symbolizes the interdisci-plinary research on a campus of manydifferent facilities.In addition to the program of the

individual institutes a competition forhigh school students was organized:“Das Unsichtbare sichtbar machen(Making the invisible visible)”. Theidea behind this contest was to bringtogether science and art classes fromschools and to create art objectswhich illustrate length and time scalesranging from sub-atomic particles upto the universe. The winner wasFranziska Ipfelkofer from the Donau-Gymnasium, Kehlheim.

Figure 7.4: The winner of the contest, Franziska Ipfelkofer, together with RaimundFries, deputy director of Donau-Gymnasium, Kelheim and Dr. Jürgen Neuhaus,FRM II.

Last but not least, at the anniver-sary day on October 31st the FRM IIand the Faculty of Physics organizeda colloquium, entitled “50 years ofresearch with neutrons in Garching– and its future”. There the newly ap-pointed prime minister Dr. GüntherBeckstein renewed the engagementof the Free State of Bavaria for theCampus Garching in general and inparticular for the Forschungsneutro-nenquelle Heinz Maier-Leibnitz.A very special event took place on

September 27th in the neutron guidehall of FRM II. The well known Munichwriter Asta Scheib read from her auto-biographical novel “Sei froh, dass dulebst”. This reading was part of a se-ries of performances entitled “Garch-ing liest”. Each event happened atanother special location. Certainlythe most unusual of all of them wasthe gallery of the neutron guide hall,where about 40 listeners found place.In addition to the literary pleasurethe music of the “Garchinger Pfeif-fer” guarantied for enjoyment. Theparticipants were impressed not onlyby the interesting presentation, but aswell by the unique ambience. The lo-cal organization was due to ChristophMorkel.

FRM II also participated at theGarchinger Herbsttage from Septem-ber 15th to 16th. Biannually theCity of Garching together with localcompanies organizes a trade showin the town center. Two years agothe FRM II displayed the research do-ing at our institute for the first time.This year a common booth was orga-nized together with the Max-Planck-Institute for Plasma Physics. The pub-lic has been informed about researchprojects of the two institutes for twodays.

Figure 7.5: The Bavarian prime minister Dr.Günther Beckstein during his speechon October 31st.

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Figure 7.6: Poster advertising the readingof Ms. Asta Scheib at FRM II.

Each autumn the University of Ap-plied Sciences Munich organizes ajob fair, especially for engineeringstudents. In order to attract youngengineers for scientific instrumenta-tion, Toni Kastenmüller and JürgenNeuhaus presented the employmentpossibilities at the FRM II. Amongmany traineeships, several open posi-tions for engineers in the area of civilengineering, physics engineering, me-chanical engineering and electro en-gineering were highlighted. As thejob fair mainly addresses students, anumber of internships could be ac-complished at the FRM II.By opening its doors to general

visitors FRM II helps to explain to agreater public the safety and useful-ness of nuclear technology. In 2007we welcomed a total of 2612 non sci-entific visitors, 526 of them were stu-dents and 522 were pupils from highschools. They were guided throughthe reactor building, could take a lookover the reactor hall from the visi-tors window at the sixth floor andpassed the experimental hall as wellas the gallery of the neutron guidehall. Concerning our scientific pro-gram two calls for proposals were

launched in 2007, as usual in Januaryand July. 509 experiments could beperformed within 2007 using the 234days of reactor operation. About 800scientists visited the FRM II for neu-tron and positron experiments. About60% of the beam time, distributedby the proposal procedure, were oc-cupied by scientists from Germany,32% came from European countriesand 8% from overseas. The distribu-tion of the beam time was reviewedby an international referee committee.In addition, the newly created JülichCentre for Neutron Science outsta-tion at FRM II of the Forschungszen-trum Jülich GmbH had two proposalrounds in 2007. 85 experiments wererealized at their instruments at FRMII.

Figure 7.7: Dr. Petra Nieckchen, Max-Planck-Institute for Plasma Physics, and Dr.Jürgen Neuhaus, FRM II at their booth at Gewerbeschau Garching.

Last but not least, in 2007 thefirst user meeting of the FRM II tookplace on 30th October. About 95participants followed the talks in thelecture hall of the Physics Depart-ment of LMU at Campus Garching.The presentations covered the widerange of scientific topics investigatedat FRM II. A Bavarian buffet sup-ported the long-lasting and interest-ing discussions on the scientific re-sults obtained. All instruments werepresented during the poster sessionwhich provided a detailed insightinto the experimental possibilities ofthe FRM II. Simultaneously, the firstPLEPS workshop was hold. The 40participants joined the poster sessionin the evening hours making the eventa marvellous success.

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7.2 "Fortgeschrittenenpraktikum" Neutron scattering at the FRM II

R. Georgii1, M. Hofmann1, M. Meven1, R. Mole1, K. Schrechenbach2, T. Unruh1

1ZWE FRM II, TU München2Physik Department E21, TU München

In the winter term 2006/07 the neu-tron scattering practical training ofstudents was started at the FRM II.Students in the 5th and 6th semesterfrom the physics department of theTU were participating in it as part oftheir "Fortgeschrittenenpraktikum".On five instruments, HEIDI, MIRA,

PUMA, Stress-Spec and TofToF, a to-tal of 35 students were participatingin 2007. After a half a day of intro-

duction in the technology of the FRMII and the theory of neutron scatter-ing, each student was participating intwo different experiments. The exper-iments were adopted from standardmeasurements typical for each of theinstruments and lasted a day each in-cluding night measurements. Duringthe experiments the students had thepossibility of a guided tour throughthe reactor. The results of the exper-

iments were then documented in ashort report by the students. Finally ashort colloquium based on this reporthad to be passed by the students.The response of the students,

which we tested with a short ques-tionnaire, was very enthusiastic. Themain highlight for them was the pos-sibility to work on "real" user experi-ments in normal operation contrary tolab experiments.

7.3 11th JCNS Laboratory course on neutron scattering

Th. Brückel1, G. Heger2, R. Zorn3

1Institute for scattering methods, Research Centre Jülich2Institute of Crystallography, RWTH Aachen3Institute for neutron scattering , Research Centre Jülich

September 3 - 14 the 11th JCNSLaboratory course on neutron scatter-ing was held by the Jülich Centre forNeutron Science. For the first time inthe history of the labcourse the lec-ture part and the experimental partwere held at different locations. Thelectures took place at Forschungszen-trum Jülich as in the past years andthe experiments were carried out atthe reactor FRM. The labcourse isopen for students of Physics, Chem-istry, and other natural sciences fromall around the world. It is part of thecurricula of the Universities of Aachenand Münster. The course was sup-ported by the Integrated Infrastruc-ture Initiative for Neutron Scatteringand Muon Spectroscopy (NMI3) andSoftComp, the European Network of

Excellence for Soft Matter Compos-ites. The neutron scattering courseconsists of one week of lectures andone week of hands-on training on theinstruments. The lectures encompassan introduction to neutron sources,into scattering theory and instrumen-tation. Furthermore, selected topicsof condensed matter research are pre-sented. The second week of the lab-course consisted of hands-on exper-iments at dedicated instruments atFRM II. Students performed on ex-periments at the backscattering in-strument SPHERES, the neutron re-flectometer TREFF, the Jülich neu-tron spin-echo spectrometer J-NSE,small and ultra-small angle scatteringat KWS-2 and KWS-3, single crys-tal and powder diffraction at HEIDI

and SPODI, polarisation analysis atDNS and triple-axis spectroscopy atPUMA. 47 students participated inthe labcourse. The students camefrom 13 countries in total of which10 belong to the EU. The participa-tion of female students was 43Thestudents experienced real life sci-entific work and atmosphere at theForschungszentrum Jülich as well asat the FRM II neutron facility. Theresponse was overwhelmingly posi-tive. The splitting of the locations wassurprisingly not seen as a burden al-though it implied a daylong bus tripfrom Jülich to Munich. Rather the stu-dents appreciated the possibility toget to know two major research cen-tres in Germany.

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7.4 Workshop – Neutrons for applied research in the field of materialdevelopment and material technology

R. Gilles1


On the invitation of the chair “Metal-lurgy of iron and steel” RWTH Aachen(Prof. Senk) a meeting was held inAachen on 19.10.2007. The work-shop was organized under the aus-pices of the Werkstoff-FORUM ofRWTH Aachen.After the introduction of Prof.

Heger (RWTH Aachen), the generalaspects of instrumentation using neu-trons for applied science were demon-strated by Prof. Petry (TU München).The other talks were focused on spe-cial instruments at FRM II or JCNSwhich are useful for material develop-ment and material technology.Burkhard Schillinger’s presentation

gave an overview about the variety ofobjects which could be x-rayed non-destructively with neutrons (motors,alloys, cochlea, lungs of a rat, piecesof wood etc.).Michael Hofmann reported on

strain measurements (for examplecrank, railroad tracks etc.) usingthe diffraction method to determinestress and texture.Hans Boysen focused his talk on

the different possibilities of sampleenvironment (high temperature, lowtemperature, tensile test machine)available at the structure powderdiffractometer SPODI.

Figure 7.8: Speakers of the workshop (from left to right): Burkhard Schillinger, MichaelHofmann, Ralph Gilles, Prof. Winfried Petry, Andrea Brings (manager of Werkstoff-Forum RWTH Aachen), Hans Boysen and Prof. Gernot Heger.

Ralph Gilles introduced the small-angle scattering method to character-ize on the nanometer scale for exam-ple precipitates of superalloys in situat high temperatures. Prof. Brückelgave an overview on the method ofneutron reflectometry on thin films,especially about their electric andmagnetic properties.

At the end of the workshop Prof.Petry, Prof. Heger and Prof. Brückelinformed the audience how to ap-ply and to prepare for beam time atthe FRM II. After excited discussionswith many people from the audiencein the poster session the speakersmet before leaving Aachen for a shortfarewell photo.

7.5 Biannual workshop at Burg Rothenfels

R. Georgii11ZWE FRM II, TU München

From Monday, 23.07 until Thursday,26.07.07 the 3rd workshop on neutronscattering of the FRM II took placeat Burg Rothenfels (see figure 7.9).60 participants from E21 and E13(Physics department, TU München),from the LMU, JCNS, GKSS and the

FRM II spent four days of intensediscussion in the pleasant surround-ing of Mainfranken (see figure 7.10). The program was very diverse andintense (see table 7.1 ) and includedan evening talk by Stefan Paul, E18,TU München about "Ultra Cold Neu-

trons". Half a day was devoted to ashort hiking tour in the beautiful land-scape around Burg Rothenfels.

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Figure 7.9: Burg Rothenfels

Figure 7.10: The participants of the workshop

7 Facts 93

Table 7.1: Summary of all talksAbul Kashem M. Magnetic nanoparticles in supported polymer structureAppavou M-S. Influence of pressure on the dynamics of Human hemoglobinBreitkreuz, H. Spektrale Charaktersierung des SpaltneutronenstrahlsDarko C. Thin films from crystalline diblock copolymersDoster W. Protein Diffusion in Biological CellsFrielinghaus, H. Tailormade Microemulsions with Polymer AdditivesGaspar A. Using polarized neutrons for the study of the dynamical structure of proteinsHugenschmidt, C. Positron annihilation spectroscopyIvanova R. Multicompartment polymeric hydrogels studied using SANSKaune G. GISAXS Investigation of Organic-Anorganic Nanostructures for PhotovoltaicsKeller, T. Introduction to Lamor diffractionKlein, W. Mo2B5 vs. Mo2B4 - Strukturlösung mit allen MittelnKudejova, P. PGAA and PGAI for the ANCIENT CHARM project and other applicationsKulkarni,A. Smart hydrogels from amphiphilic triblock copolymersLorenz, K. First measurements with the new multi filter at ANTARESLöwe, B. Beam brightness enhancement with a gas-moderatorMayer, J. Positron annihilation induced Auger-electron spectroscopyMehaddene, T. Dynamics of magnetic shape memory alloys investigated by inelastic neutron scatteringMetwalli Ali E. Water-vapor swelling response of thin casein filmsMoulin J.-F. In situ characterisation of a fluidic cellMüller-Buschbaum P. TOF-GISANS at REFSANSNickel, B. Reflectivity experiments on membranes and membrane associated protein layersNülle, M. Investigation of the dewetting of thin diblock copolymer filmsOstermann, A. Dynamical properties of the hydration shell of proteinsPapadakis C. The inner structure of thin block copolymer filmsPerlich J. Investigation of the solvent content in spin-coated thin polymer filmsPikart, Ph. Coincident Doppler-broadening sepctroscopy on Al-Sn-layersPipich, V. The diblock copolymer as an external field in A/B/A-B polymer mixturesRadulescu, A. Wide-Q SANS investigation of crystalline and semi-crystalline polymers in soloutionsRepper, J. Residual stress analysis on IN718 samplesRuderer M. Characterisation of semi-conducting polymer blend thin films for photovoltaic applicationsSazonov, A. Crystallographic and magnetic study of synthetic cobalt-olivineSchirmacher W. Theory of scattering from vibrational excitations of disordered solidsSchreckenbach, K. Production and lifetime determination of the negatively charged Positronium ionSmuda, Ch. QENS und PFG-NMR-Untersuchungen zur Diffusion in Schmelzen mittelkettiger MoleküleStüber S. Em levitation for time-of-flight spectroscopy - studying the dynamics of metallic meltsVisser,D. Ancients objects investigated with neutron beamsWang W. Swelling of Diblock and Triblock Copolymer Thin Hydrogel FilmsWudke, J. Erste Messungen und neue Perspektiven am Höchstfluss-Rückstreuspektrometer

SPHERESYang F. Hydrous silicates: structure and dynamicsZhenyu D. Time-resolved GISAXS on thin diblock copolymer films

94 7 Facts

7.6 PLEPS workshop and 2nd user-meeting at NEPOMUC

C. Hugenschmidt1, M. Hofmann1

1ZWE FRM II, TU München2Physik Department E21, TU München

In the winter term 2006/07 the neu-tron scattering practical training ofstudents was started at the FRM II.Students in the 5th and 6th semesterfrom the physics department of theTU were participating in it as part oftheir "Fortgeschrittenenpraktikum".This second user meeting at NEPO-

MUC/FRM II has been dedicatedto the pulsed low-energy positronsystem (PLEPS) which was trans-ferred from the University of theBundeswehr Munich (UniBwM) tothe FRM II. The one-day workshopat October 30th, 2007 at the Tech-nische Universität München (TUM)was organized by our positron groupat E21 and FRM II together with theresearch group of Prof. G. Dollingerat the institute for applied physicsand measurement technology of the

UniBwM.

The aim of the meeting was toadvertise the feasibility of positronlifetime measurements for defectspectroscopy with variable depthusing the PLEPS at the high inten-sity positron beam NEPOMUC. Atotal of 32 colleagues from all overEurope (France, Belgium, Finland,Hungary,...) attended the workshop.After welcome talks of Prof. W. Petryand Prof. G. Dollinger the positronbeam facility (C. Hugenschmidt) andthe PLEPS-apparatus (P. Sperr, W.Egger) were presented. The followingsessions consisted of 18 short oralcontributions concerning proposalsfor positron lifetime experiments. Theattendees presented a large varietyof experiments on defects in metals,

irradiated samples, free volume ofpolymers and membranes. In addi-tion we offered an extended guidedtour of FRM II with special emphasison the PLEPS apparatus and theother positron spectrometers locatedat NEPOMUC. In the evening theworkshop was closed at the postersession, where all experiments of theFRM II were presented, and we hada Bavarian "Brotzeit" together withthe colleagues of the FRM II usermeeting.

We gratefully acknowledge finan-cial support through NMI3 of the Euro-pean Community, by the TechnischeUniversität München and the team ofFRM II.

8 People 95

8 People

8.1 Committees

Strategierat FRM II

Chairman

Prof. Dr. Gernot HegerInstitut für KristallographieRWTH Aachen

Members

MRin Dr. Ulrike KirsteBayerisches Staatsministerium für Wissenschaft,Forschung und Kunst

Dr. Rainer KoepkeBundesministerium für Bildung und Forschung

Prof. Dr. Georg BüldtInstitut für Biologische InformationsverarbeitungForschungszentrum Jülich

Prof. Dr. DoschMax-Planck-Institut für MetallforschungStuttgart

Prof. Dr. Dieter RichterInstitut für FestkörperphysikForschungszentrum Jülich

Prof. Dr. Dirk SchwalmMax-Planck-Institut für KernphysikHeidelberg

Prof. Dr. Helmut SchwarzInstitute of ChemistryTechnische Universität Berlin

Prof. Dr. Dr. Michael WannenmacherRadiologische Klinik und PoliklinikAbteilung StrahlentherapieUniversität Heidelberg

Prof. Dr. Ewald WernerLehrstuhl für Werkstoffkunde und -mechanikTechnische Universität München

Prof. Dr.-Ing. Heinz VoggenreiterDirector of the Institute of Structure and DesignGerman Aerospace Center (DLR) Köln

Prof. Dr. Markus BradenPhysikalisches InstitutUniversität zu Köln

Honorary Members

MDgt i.R. Jürgen Großkreutz Prof. Dr. Tasso Springer

Guests

Prof. Dr. Dr. h.c. mult. Wolfgang A. HerrmannPräsidentTechnische Universität München

Dr.-Ing. Rainer KuchBeauftragter der HochschulleitungTechnische Universität München

96 8 People

Dr. Michael KlimkeReferent der HochschulleitungTechnische Universität München

Prof. Dr. Winfried PetryZWE FRM IITechnische Universität München

Dr. Ingo NeuhausZWE FRM IITechnische Universität München

Dr. Klaus SeebachZWE FRM IITechnische Universität München

Secretary

Dr. Jürgen NeuhausZWE FRM II

Instrumentation advisory board(Subcommittee of the Strategierat)

Chairman


Members

Prof. Dr. Dirk DubbersPhysikalisches InstitutUniversität Heidelberg

Prof. Dr. Michael GradzielskiInstitut für ChemieTechnische Universität Berlin

Prof. Dr. Rainer HockLehrstuhl für Kristallographie und StrukturphysikUniversität Erlangen

Prof. Dr. Werner KuhsGZG Abteilung KristallographieUniversität Göttingen

Prof. Dr. Stephan PaulPhysik Department E18Technische Universität München

Prof. Dr. Wolfgang SchererLehrstuhl für Chemische PhysikUniversität Augsburg

Prof. Dr. Wolfgang SchmahlDept. für Geo- und UmweltwissenschaftenLudwig-Maximilians-Universität MünchenDeputy of the Chairman

Dr. habil. Dieter SchwahnInstitut für FestkörperforschungForschungszentrum Jülich

Prof. Dr. Andreas TürlerInstitut für RadiochemieTechnische Universität München

Prof. Dr. Albrecht WiedenmannAbteilung SF3Hahn-Meitner-Institut Berlin

Dr. habil. Regine WillumeitGKSS Forschungszentrum Geesthacht

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Guests


Dr. Klaus FeldmannBEO-PFRForschungszentrum Jülich

MRin Dr. Ulrike KirsteBayerisches Staatsministerium für Wissenschaft,Forschung und Kunst

Prof. Dr. Gernot HegerInstitut für KristallographieRWTH Aachen

Dr. Jürgen NeuhausZWE FRM IITechnische Universität München




Secretary

Dr. Peter LinkZWE FRM II

Committee for industrial and medical use(Subcommittee of the Strategierat)

ChairmanProf. Dr.-Ing. Heinz VoggenreiterGerman Aerospace Center (DLR) Köln

Members

Automobile industryDr.-Ing. Rainer SimonBMW AG München

Dr.-Ing. Maik BrodaFord Forschungszentrum Aachen

Aerospace industryDr.-Ing. Rainer RauhAirbus Deutschland Bremen

Chemistry and environmentDr. Jens RiegerBASF AG Ludwigshafen

SecretaryDr. Ralph GillesZWE FRM II

98 8 People

Scientific committee - Evaluation of beamtime proposals(Subcommittee of the Strategierat)

ChairmanProf. Dr. Wolfgang SchererLehrstuhl für Chemische PhysikUniversität Augsburg

Members

Prof. Dr. John BanhartAbteilung Werkstoffe (SF3)Hahn-Meitner-Institut Berlin

Dr. Philippe BourgesLaboratoire Léon BrillouinCEA Saclay


Prof. Dr. Heinz-Günther BrokmeierInstitut für WerkstoffforschungGKSS - Forschungszentrum Geesthacht

Prof. Dr. Thomas BrückelInstitut für FestkörperforschungFZ-Jülich

Dr. Olwyn ByronInfection and ImmunityUniversity of Glasgow

PD Dr. Mechthild EnderleInstitut Laue LangevinGrenoble

Dr. Hermann HeumannMax-Planck-Institut für BiochemieMartinsried bei München

Prof. Dr. Jan JolieInstitute of Nuclear PhysicsUniversität zu Köln

Prof. Dr. Bernhard KeimerMax-Planck-Institut für FestkörperforschungStuttgart

Prof. Dr. Andreas MagerlLS für Kristallographie und StrukturphysikUniversität Erlangen

Prof. Dr. Karl MaierHelmholtz-Institut für Strahlen- und KernphysikUniversität Bonn

Dr. Joël MesotETH Zürich undPaul-Scherrer-Institut Villigen, Schweiz

Prof. Reinhard Dr. Krause-RehbergDepartment of PhysicsUniversität Halle

Dr. Stéphane LongevilleLaboratoire Léon BrillouinLaboratoire de la Diffusion NeutroniqueCEA Saclay

Prof. Dr. Andreas MeyerInstitut für Materialphysik im WeltraumDeutsches Zentrum für Luft- und Raumfahrt (DLR)Köln

Dr. Michael MonkenbuschInstitut für FestkörperforschungForschungszentrum Jülich

Prof. Dr. Werner PaulusStructures et Propriétés de la MatièreUniversité de Rennes 1

Prof. Dr.-Ing. Anke PyzallaMax-Planck-Institut für EisenforschungDüsseldorf

Prof. Dr. Joachim RädlerFakultät für PhysikLudwig-Maximilians-Universität München

Prof. Dr. Günther RothInstitut für KristallographieRWTH Aachen

Prof. Dr. Michael RuckInstitut für Anorganische ChemieTechnische Universität Dresden

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Prof. Dr. Wolfgang SchmahlDep. für Geo- und UmweltwissenschaftenLudwig-Maximilians-Universität München

Prof. Dr. Bernd StühnInstitut für FestkörperphysikTechnische Universität Darmstadt

Prof. Dr. Monika Willert-PoradaLehrstuhl für WerkstoffverarbeitungUniversität Bayreuth

Scientific secretaries

Dr. Jürgen NeuhausZWE FRM II

Dr. Christoph HugenschmidtZWE FRM II

Dr. Peter LinkZWE FRM II

Dr. Martin MevenZWE FRM II

Dr. Tobias UnruhZWE FRM II

TUM Advisory board

Chairman

Prof. Dr. Ewald WernerLehrstuhl für Werkstoffkunde und -mechanikTechnische Universität München

Members

Prof. Dr. Peter BöniPhysik Department E21Technische Universität München

Prof. Dr. Andreas TürlerInstitut für RadiochemieTechnische Universität München

Prof. Dr. Markus Schwaigerrepresented by Prof. Dr. Senekowitsch-SchmidtkeNuklearmedizinische Klinik und PoliklinikKlinikum Rechts der IsarTechnische Universität München

Prof. Dr. Bernhard WolfHeinz Nixdorf-Lehrstuhl für medizinische ElektronikTechnische Universität München

Prof. Dr. Arne SkerraLehrstuhl für Biologische ChemieTechnische Universität München

Guests



100 8 People



Scientific steering committee

Chairman


Members

Dr. Hans BoysenSektion KristallographieLudwig-Maximilians-Universität München

Prof. Dr. Bernhard KeimerMax-Planck-Institut für Festkörperforschung Stuttgart

Prof. Dr. Dieter RichterJülich Centre for Neutron ScienceForschungszentrum Jülich

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8.2 Staff

Board of directors of ZWE FRM II

Scientific directorProf. Dr. W. Petry

Technical directorDr. Ingo Neuhaus

Administrative directorDr. K. Seebach

Experiments

HeadProf. Dr. W. Petry

SecretariesW. WittowetzE. Jörg-Müller

CoordinationDr. J. NeuhausH. Türck

InstrumentsProf. Dr. H. Abele (E18)P. Aynajian (MPI-Stuttgart)Prof. Dr. P. Böni (E21)J. BrunnerK. Buchner (MPI-Stuttgart)Dr. T. BücherlS. BuschH. BreitkreutzDr. H.-G. Brokmeier (GKSS)E. CalzadaL. Canella (Universität zu Köln)D. EtzdorfJ. Franke (MPI-Stuttgart)Dr. U. Garbe (GKSS)Dr. A.-M. Gaspar (Visiting scientist)Dr. R. GeorgiiDr. R. GillesR. HähnelDr. M. Haese-Seiller (GKSS)Dr. W. HäußlerDr. M. HofmannDr. M. Hölzel (TU Darmstadt)W. HornauerDr. K. Hradil (Univ. Göttingen)Dr. C. HugenschmidtDr. V. Hutanu (RWTH Aachen)N. JünkeS. KampferR. Kampmann (GKSS)Dr. T. Keller (MPI-Stuttgart)Dr. W. KleinDr. J. KlenkeP. Kudejova (Universität zu Köln)Dr. V. Kudryaschov (GKSS)Dr. P. LinkDr. B. Loeper-Kabasakal

K. LorenzA. Mantwill (E21)J. Major (MPI-Stuttgart)Dr. M. Major (MPI-Stuttgart)F. Maye (MPI-Stuttgart)T. MehaddeneDr. M. MevenDr. R. MoleDr. P. Moulin (GKSS)S. MühlbauerDr. A. OstermannDr. B. PedersenPh. PikartC. PiochaczDr. J. Rebelo-Kornmeier(HMI Berlin)J. RepperR. RepperJ. RingeDr. A. Rühm (MPI Stuttgart)Ch. SauerA. SazonovDr. B. SchillingerDr. A. Schneidewind (TU Dresden)Prof. Dr. K. Schreckenbach (E21)M. SchulzR. SchwikowskiDr. A. Senyshyn (TU Darmstadt)G. SeidlC. SmudaM. StadlbauerDr. R. Stöpler (E18)B. StraßerDr. T. UnruhF. M. WagnerDr. R. Wimpory (HMI Berlin)Dr. H.-F. WirthProf. Dr. O. Zimmer (E18)

Instruments - JCNSProf. Dr. Dieter Richter (DirectorJCNS)Prof. Dr. Thomas Brückel (DirectorJCNS)Dr. A. Ioffe (Head of outstation atFRM II)

SecretaryS. Mintmans

N. ArendDr. P. BuschA. ErvenDr. H. FrielinghausF. GossenDr. Th. GutberletDr. O. HoldererM. HölzleE. KentzingerTh. KohnkeDr. MattauchDr. R. MittalA. NebelDr. M. PragerDr. V. PipichDr. A. RadelescuH. SchneiderP. StronciwilkDr. Y. SuDr. J. Wuttke

102 8 People

Detectors and electronicsDr. K. ZeitelhackI. DefendiChr. HesseM. PanradlTh. Schöffel

Sample environmentDr. J. PetersP. BiberH. KolbA. PscheidtA. SchmidtJ. Wenzlaff

Neutron opticsProf. Dr. G. Borchert

C. BreunigH. HofmannR. IannucciE. KahleO. LykhvarDr. S. MasalovichA. OfnerR. Valicu

IT servicesJ. KrügerH. WenningerJ. ErtlS. GalinskiF. HänselJ.-P. Innocente

N. IvanovaR. MüllerA. PrellerJ. PulzC. RajczakS. RothA. SchwertnerA. SteinbergerM. StowasserB. WildmoserA. Wimmer

ConstructionK. Lichtenstein

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Administration

HeadDr. K. Seebach

SecretaryC. Zeller

MembersR. ObermeierB. BendakB. GallenbergerI. HeinathK. Lüttig

Public relationsDr. Ulrich Marsch(ZV TUM)A. Schaumlöffel(ZV TUM)

Visitors serviceU. KurzDr. B. Tonin-Schebesta

Reactor operation

HeadDr. Ingo Neuhaus

SecretariesM. NeubergerS. Rubsch

ManagementDr. H. Gerstenberg(Irradiation and fuel cycles)Dr. J. Meier(Reactor operation)R. Schätzlein(Electric and control technology)Dr. A. Kastenmüller(Reactor enhancement)

Shift membersF. GründerA. BancsovA. BenkeM. DannerChr. FeilM. FlieherH. GroßL. HerdamF. HofstetterK. HöglauerT. KalkG. KalteneggerU. KappenbergF. KewitzM. G. KrümpelmannJ. KundA. LochingerG. MauermannA. MeilingerM. MoserL. RottenkolberG. Schlittenbauer

Technical servicesK. PfaffR. BinschA. CziastoH. GampferW. Glashauser

G. GuldS. ManzB. HeckG. WagnerA. WeberM. WöhnerC. ZillerJ. Zöybek

SourcesC. MüllerD. PätheA. Wirtz

Electric and control technologyR. SchätzleinG. AignerW. BuchnerR. KrammerK.-H. MayrÜ. SarikayaH. SchwaighoferJ. Wildgruber

Job safetyH. Bamberger

IrradiationDr. H. GerstenbergJ.-M. FavoliW. FriesDr. X. LiM. OberndorferW. LangeV. LoderJ. MolchA. RichterH. SchulzF.-M. WagnerN. Wiegner

Reactor enhancementW. BüntenF. HenkelR. LorenzB. PollomM. SchmittV. Zill

Technical designF.-L. TralmerJ. FinkH. FußstetterJ. JüttnerS. KüçükK. Lichtenstein

WorkshopsC. HerzogU. StiegelA. BegicM. FußA. HuberA. ScharlR. Schlecht

Radiation protectionDr. H. ZeisingDr. B. WierczinskiS. DambeckW. DollrießH. HottmannD. LewinB. NeugebauerD. SchrulleH.-J. WerthS. WolffD. BahmetW. KlugeA. SchindlerD. Strobl

Chemical laboratoryC. AuerR. BertschP. MüllerS. Uhlmann

Technical safety serviceJ. WetzlR. MaierJ. AignerK. OttoN. HodzicJ. Schreiner

104 8 People

Reactor physics

Dr. A. RöhrmoserC. Bogenberger

R.M. HengstlerR. Jungwirth

W. Schmid

Security department

L. Stienen J. Stephani

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8.3 Partner institutions

GKSS Research Centre GmbHMax-Planck-Straße 121502 GeesthachtGermanyhttp://www.gkss.de/index_e.html

Hahn-Meitner-Institute GmbH (HMI)Glienickerstraße 10014109 BerlinGermanyhttp://www.hmi.de/index_en.html

Jülich Centre for Neutron Science JCNSResearch Centre Jülich GmbH52425 Jülich, GermanyOutstation at FRM II: 85747 Garchinghttp://www.jcns.info

Ludwig-Maximilians-Universität MünchenSektion Kristallographie (Prof. Schmahl)and Sektion Physik (Prof. Rädler)Geschwister-Scholl-Platz 180539 MunichGermanyhttp://www.uni-muenchen.de

Max-Planck-Institut für FestkörperphysikHeisenbergstraße 170569 StuttgartGermanywww.fkf.mpg.de/main.html

Max-Planck-Institut für MetallforschungHeisenbergstraße 370569 StuttgartGermanyhttp://www.mf.mpg.de/de/index.html

RWTH AachenInstitute of CrystallographyJägerstraße 17 - 1952056 AachenGermanyhttp://www.xtal.rwth-aachen.de/index_e.html

Technische Universität DarmstadtMaterial- und GeowissenschaftenPetersenstraße 2364287 DarmstadtGermanyhttp://www.tu-darmstadt.de/fb/matgeo/

Technische Universität DresdenInstitut für Festkörperphysik01062 DresdenGermanyhttp://www.physik.tu-dresden.de/ifp/ifp.php

Universität AugsburgInstitut für PhysikLehrstuhl für Chemische Physik und Materialwis-senschaften86135 AugsburgGermanyhttp://physik.uni-augsburg.de/exp3/home.html

Universität der Bundeswehr MünchenInstitut Angewandte Physik und MesstechnikWerner-Heisenberg-Weg 3985579 NeubibergGermanyhttp://www.unibw.de/lrt2/

Universität GöttingenInstitut für Physikalische ChemieTammannstraße 637077 GöttingenGermanyhttp://www.uni-pc.gwdg.de/eckold/home.html

Universität zu KölnInstitut für KernphysikZülpicherstraße 7750937 KölnGermanyhttp://www.ipk.uni-koeln.de/

106 9 Figures

9 Figures

9.1 FRM II in the Press

9 Figures 107

9.2 Publications

[1] Appavou M.-S., Busch S., Doster W., Unruh T. The Effect of Packing in Internal Molecular Motions of HydratedMyoglobin. MRS Bulletin - Proceedings of the 8th International Conference on Quasi-Elastic Neutron Scattering(QENS2006) held June 14 -17, 2006, Bloomington, Indiana, USA, –, (2007), 83 – 88.

[2] Aynajian P., Keller T., Boeri L., Shapiro S., Habicht K., Keimer B. Energy Gaps and Kohn Anomalies in ElementalSuperconductors. Science, 319, (2008), 1509 – 1512.

[3] Babcock E., Petoukhov A., Andersen K., Chastagnier J., Jullien D., Lelièvre-Berna E., Georgii R., Masalovich S.,Boag S., Frost C., Parnell S. AFP flipper devices: Polarized 3He spin flipper and shorter wavelength neutronflipper; Proceedings of PCMI 2006, Berlin, Germany. Physica B, EU-publication, 397, (2007), 172 – 175.

[4] Balsanova L., Mikhailova D., Senyshyn A., Trots D., Ehrenberg H. Structure and properties of α−AgFe2(MoO4)3.Sol. State Sciences, submitted.

[5] Bouwman W., Plomp J., de Haan V., Kraan W., van Well A., Habicht K., Keller T., Rekveldt M. Real-spacescattering methods. Nuclear Instruments and Methods A, 586, (2008), 9–14.

[6] Boysen H., Lerch M., Stys A., Senyshyn A., Hoelzel M. Oxygen mobility in the ionic conductor mayenite(Ca12Al14O33: a high temperature neutron diffraction study. Acta Cryst. B., 63, (2007), 675 – 683.

[7] Breitkreutz H., Wagner F., Petry W. Spektrale Charakterisierung des Spaltneutronenstrahls der Neutronenther-apieanlage MEDAPP am FRM II. Conference Proceedings of the Three-Country-Convention of the German,Austrian and Swiss Societies of Medial Physics, Bern, Switzerland, 2007, –, (2007), 2.

[8] Brunner T., Hugenschmidt C. Spectrometer for the investigation of temperature dependant Ps formation andmaterial dependent moderation efficiency. Physica status solidi C, 4, (2007), 3989–3992.

[9] Bunjes H., Unruh T. Characterization of Lipid Nanoparticles by Differential Scanning Calorimetry, X- Ray andNeutron Scattering. Advanced Drug Delivery Reviews, 59, (2007), 379 – 402.

[10] Busch S., Doster W., Longeville S., Sakai V., Unruh T. Microscopic Protein Diffusion at High Concentration. MRSBulletin - Proceedings of the 8th International Conference on Quasi-Elastic Neutron Scattering (QENS2006)held June 14 -17, 2006, Bloomington, Indiana, USA, –, (2007), 107 – 114.

[11] Böni P. New concepts for neutron instrumentation. Nuclear Instruments and Methods A, 586, (2008), 1–8.

[12] Böning K., Petry W. Test Irradiations of Full Sized U3Si2−Al Fuel Plates up to Very High Fission Densities.Journal of Nuclear Science, submitted.

[13] Dittrich W., Zeising H. Radio Protection Design of the FRM II. Transactions of the RRFM - IGORR 2007, Lyon,France, March 5 - 11, 2007, –, (2007), 299–303.

[14] Dubbers D., Abele H., Baeßler S., Märkisch B., Schumann M., Soldner T., Zimmer O. A clean, bright,and versatile source of neutron decay products. Nuclear Instruments and Methods in Physics Research.http://arxiv.org/abs/0709.4440.

[15] Eichhöfer A., Wood P., Viswanath R., Mole R. Synthesis, Structure and Magnetic Behaviourof Manganese(II) Selenolate Complexes 1

∞[Mn(SePh)2], [Mn(SePh)2(bipy)2]and[Mn(SePh)2(phen)2](bipy =bipyridyl, phen = phenanthroline). Eur. J. Inorg. Chem., 2007, 30, (2007), 4794–4799.

[16] Eichhöfer A., Wood P., Viswanath R. N., Mole R. A. Synthesis, structure and physical properties of themanganese(II) selenide/selenolate cluster complexes [Mn32Se14(SePh)36(PnPr3)4] and [Na(benzene-15-crown-5)(C4H8O)2]2[Mn8Se(SePh)16]. Chemical Communications, accepted.

[17] Eichhöfer A., Wood P. T., Viswanath R., Mole R. A. Synthesis, structure and physical properties of themanganese (II) selenide/selenolate cluster complexes [Mn32Se14(SePh)36(PnPr3)4] and [Na(benzene−15−crown−5)(C4H8O)2]2[Mn8Se(SePh)16]. Chemical Communications, –, (2008), 1596 – 1598.

[18] Fleischer F., Gwinner G., Hugenschmidt C., Schreckenbach K., Thirolf P., Wolf A., Schwalm D. The negative ionof positronium: measurement of the decay rate and prospects for further experiments. Canadian Journal ofPhysics, submitted.

108 9 Figures

[19] Frotscher M., Klein W., Bauer J., C.-M. F., Halet J.-F., Senyshyn A., Baehtz C., Alberta B. M2B5 or M2B4? AReinvestigation of the Mo/B and W/B System. Z. Anorg. Allg. Chem., 633, (2007), 2626 – 2630.

[20] Gaspar A. Methods for analytically estimating the resolution and intensity of neutron time-of-flight spectrometers.The case of the TOFTOF spectrometer. Electronic publication at www.arxiv.org. http://arxiv.org/abs/0710.5319.

[21] Gaspar A., Appavou M.-S., Busch S., Unruh T., Doster W. Dynamics of well-folded and natively disorderedproteins in solution: a time of flight neutron scattering study. Eur. Biophys. J., published online. http://dx.doi.org/10.1007/s00249-008-0266-3.

[22] Georgii R., Arend N., Böni P., Lamago D., Mühlbauer S., Pfleiderer C. MIRA: Very Cold Neutrons for NewMethods. Neutron News, 18, 2, (2007), 25 – 28.

[23] Georgii R., Böni P., Janoschek M., Schanzer C., Valloppilly S. MIRA - A flexible instrument for VCN. Physica B,397, (2007), 150–152.

[24] Gilles R., Ostermann A., Petry W. Monte Carlo simulations of the new Small-Angle Neutron Scattering instrumentSANS-1 at the Heinz Maier-Leibnitz Forschungsneutronenquelle. J. Appl. Cryst., 40, (2007), s428 – s432.

[25] Grünzweig C., Hils R., Mühlbauer S., Ay M., Lorenz K., Georgii R., Gähler R., Böni P. Multiple Small AngleNeutron Scattering (MSANS): A new Two-dimensional Ultra Small Angle Neutron Scattering Technique. Appl.Phys. Lett., 91, (2007), 203504–1–3.

[26] Hoelzel M., Senyshyn A., Gilles R., Boysen H., Fuess H. The Structure Powder Diffractometer. Neutron News,18:4, (2007), 23 – 26.

[27] Hofmann A., Rebelo-Kornmeier J., Garbe U., Wimpory R., Repper J., Seidl G., Brokmeier H., Schneider R.Stress Spec: Advanced Materials Science at the FRM II. Neutron News, 18:4, (2007), 27 – 30.

[28] Hugenschmidt C. NEPOMUC: The New Positron Beam Facility at the FRM II. Neutron News, 18, 2, (2007), 29 –31.

[29] Hugenschmidt C., Brunner T., Legl S., Mayer J., Piochacz C., Stadlbauer M., Schreckenbach K. Positronexperiments at the new positron beam facility NEPOMUC at FRM II. Physica status solidi C, 4, (2007), 3947 –3952.

[30] Hugenschmidt C., Dollinger G., Egger W., Kögel G., Löwe B., Mayer J., Pikart C., P. Piochacz, Repper R.,Schreckenbach K., Sperr P., Stadlbauer M. Surface and Bulk Investigations at the High Intensity Positron BeamFacility NEPOMUC. Applied Surface Science, in press.

[31] Hugenschmidt C., Mayer J., Schreckenbach K. Surface investigation of Si (100), Cu, Cu on Si (100), and Au onCu with positron annihilation induced Auger-electron spectroscopy. Surface Science, 601, (2007), 2459–2466.

[32] Hugenschmidt C., Mayer J., Stadlbauer M. Investigation of the near surface region of chemically treated andAl-coated PMMA by Doppler-broadening spectroscopy. Radiat. Phys. Chem., 76, (2007), 217–219.

[33] Hugenschmidt C., Pikart P., Stadlbauer M., Schreckenbach K. High elemental selectivity to Sn submonolayersembedded in Al using positron annihilation spectroscopy. Phys. Rev. B, in press, 4.

[34] Hugenschmidt C., T. B., Mayer J., Piochacz C., Schreckenbach K., Stadbauer M. Determination of PositronBeam Parameters by Various Diagnostic Techniques. Applied Surface Science, in press.

[35] Hutanu A., Masalovich S., Meven M., Lykvar O., Borchert G., Heger G. Polarized 3HeSpin Filters for HotNeutrons at the FRM II. Neutron News, 18:4, (2007), 14 – 16.

[36] Hutanu V., Meven M., Heger G. Construction of the New Polarised Hot Neutrons Single Crystal DiffractometerPOLI-HEiDi at FRM-II (Proceedings of PNCMI 2006, Berlin, Germany). Physica B, 397, 1-2, (2007), 135–137.

[37] Hutanu V., Rupp A., Klenke J., Heil W., Schmiedeskamp J. Magnetization of 3He spin filter cells. Journal ofPhysics D: Applied Physics, 40, (2007), 4405–4412.

[38] Hutanu V., Rupp A., Sander-Thömmes T. SQUID measurements of remanent magnetisation in refillable 3Hespin-filtre celles (SFC). Physica B, 397, (2007), 185–187.

9 Figures 109

[39] Häußler W., Gohla-Neudecker B., Schwikowski R., Streibl D., Böni P. RESEDA - the new Resonance Spin EchoSpectrometer using cold neutrons at the FRM II. Physica B, 397, (2007), 112 – 114.

[40] Häußler W., Schwikowski R., Streibl D., Böni P. The Resonance Spin Echo Spectrometer RESEDA at the FRM II.Neutron News, 18:4, (2007), 17 – 19.

[41] Häußler W., Streibl D., P. B. RESEDA: Double and Multi Detector Arms for Neutron Resonance Spin EchoSpectrometers. Measurement Science and Technology - Proceedings ECNS 2007, submitted.

[42] Ioffe A. A new neutron spin-echo technique with time gradient magnetic fields. Nuclear Instruments andMethods A, 586, (2008), 31–35.

[43] Ioffe A., Bodnarchuk V., Bussmann K., Müller R., Georgii R. A new neutron spin-echo spectrometer withtime-gradient magnetic fields: First experimental test. Nuclear Instruments and Methods in Physics Research A,586, (2008), 36–40.

[44] Ioffe A., Bodnarchuk V., Bussmann K., Mueller R. Larmor labeling by time-gradient magnetic fields. Physica BCondensed Matter, 397, 108-111, (2007), 54–55.

[45] Janoschek M., Klimko S., Gähler R., Roessli B., Böni P. Spherical neutron polarimetry wiht MuPAD. Physica B,397, (2007), 125 – 130.

[46] Jarousse C., Lemoine P., Boulcourt P., Röhrmoser A., Petry W. Monolithic UMO Full Size Prototype Plates forIRIS V Irradiation. Proceedings of IGORR - RRFM 2007, March 11 - 15, 2007, Lyon, France, submitted.

[47] Jungwirth R., Petry W., Schmid W., Beck L., Bergmaier A. Progress in Heavy-Ion Bombardement of U-Mo/AlDispersion Fuel. Transactions of the RRFM 2008, Hamburg, Germany, March 2008, –, (2008), 5.

[48] Jungwirth R., Wieschalla N., Schmid W., Röhrmoser A., Petry W., Pfleiderer C. Thermal Conductivity ofHeavy-Ion-Bombarded U-Mo/AL Dispersion Fuel. Proceedings on the 11th International Topical Meeting inResearch Fuel Management (RRFM) 2007, Lyon, –, (2007), 7.

[49] Kampfer S., Wagner F., Loeper B., Kneschaurek P. MEDAPP: Die neue Neutronentherapieanlage am FRM II inGarching. Strahlentherapie, Onkologie, Sondernummer 1, (2007), 72.

[50] Kashem M. A., Perlich J., Schulz L., Roth S., Petry W., Müller-Buschbaum P. Maghemite nanoparticles onsupported diblock polymer nanostructures. Macromolecules, 40, (2007), 5075–5083.

[51] Keller T., Aynajian P., Bayrakci S., Bucher K., Habicht K., Klann H., Ohl M., Keimer B. The Triple Axis-Spin-EchoSpectrometer TRISP at the FRM II. Neutron News, 18, 2, (2007), 16 –18.

[52] Kudejova P., Cizek J., Schulze R., Jolie J., Schillinger B., Lorenz K., Mühlbauer M., Masschaele B., Dierick M.,Vlassenbroeck J. A marker-free 3D image registration for the ANCIENT CHARM project. Case study withneutron and X-ray tomography datasets. Notiziario, Neutroni e Luce di Sincrotrone, 12/2, (2007), 6 – 13.

[53] Köper I., Comet S., Petry W., Bellissent-Funel M.-C. Dynamics of C-Phycocynanin in various deuteratedThrehalose/Water Environments by Quasielastic and Elastic Neutron Scattering. European Biophysical Journal,published online, 10.

[54] Legl S., Hugenschmidt C. A Novel Time-of-flight Spectrometer for PAES. Physica status solidi C, 4, (2007),3981 – 3984.

[55] Lerch M., Boysen H., Rödel T., Kaiser-Bischoff I., Hoelzel M., Senyshyn A. High temperature neutron powderdiffraction study of scandia/nitrogen co-doped zirconia. Z. Kristallogr., 222, (2007), 335 – 340.

[56] Magaddino V., Wagner F. M., Kummermehr J. Preclinical screening of the biological effectiveness of atherapeutic neutron beam at the FRM-II. Proceedings of the 16h symposium "Experimentelle Strahlentherapieund Klinische Strahlenbiologie", Dresden, March 01-03, 2007 (ISSN 1432-864X), –, (2007), 129 – 131.

[57] Martinez Meta N., Schweda E., Boysen H., Haug A., T. C., Hoelzel M. Zr50Sc12O43N50 and Zr3Sc4O43N8 -Synthesis, Neutron Powder Diffraction and Raman Spectroscopy. Z. Anorg. Allg. Chem., 633, (2007), 790 –794.

110 9 Figures

[58] Masalovich S. Method to measure neutron beam polarization with 2 x 1 Neutron Spin Filter. Nuclear Instrumentsand Methods in Physics Research A, 581, (2007), 791–798.

[59] Mayer J., Hugenschmidt C., Schreckenbach K. Study of the surface contamination of copper with the improvedPositron annihilation induced auger electron spectrometer at NEPOMUC. Applied Surface Science, in press.

[60] Mayer J., Hugenschmidt C., Schreckenbach K. Positron annihilation induced Auger electron spectroscopy ofCu and Si. Physica status solidi C, 4, (2007), 3928–3931.

[61] Meven M., Hutanu V., Heger G. HEiDi: Single Crystal Diffractometer at the Hot Source of the FRM II. NeutronNews, 18, 2, (2007), 19 – 21.

[62] Meyer A., Stüber S., Holland-Moritz D., Heinen O., Unruh T. Determination of self-diffusion coefficients byquasielastic neutron scattering measurements on levitated Ni droplets. Phys. Rev. B., 77, (2008), 092201–1–4.

[63] Mukherji D., Del Genovese D., Strunz P., Gilles R., Wiedenmann A., Rösler J. Microstructural characterisation of aNi-Fe-based superalloy by in-situ SANS measurements. J. Phys. Condens. Matter, 20, (2008), 104220–104228.

[64] Mühlbauer S., Böni P., Georgii R., Schmehl A., Schlohm D., Mannhart J. Field and temperature dependence ofthe magnetisation in the ferromagnetic EuO thin films. J. Phys. Condens. Matter, 20, (2008), 4 pp.

[65] Mühlbauer S., Niklowitz P., Stadlbauer M., Georgii R., Link P., Stahn J., Böni P. Elliptic neutron guides - focusingon tiny samples; Proceedings "European Workshop on Neutron Optics", March 5 -7, 2007, Paul-Scherer-Institute, Villingen, Switzerland. Nuclear Instruments and Methods in Physics Research A, 586, (2008), 77 –80.

[66] Müller-Buschbaum P., Ittner T., Mauerer E., Körstgens V., Petry W. Pressure-Sensitive Adhesive Blend Films forLow-Tack Applications. Macromol. Mater. Eng., 292, (2007), 825–834.

[67] Neuhaus J., Petry W. Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II). Neutron News, 18, 2, (2007),13 – 15.

[68] Park S., Senyshyn A., Paulmann C. Increase of ionic conductivity in the microporous lithosilicate RUB-29 byNa-ion exchange processes. Journal of Solid State Chemistry, 180, 12, (2007), 3366 – 3380.

[69] Park S.-H., Hoelzel M., Boysen H., Schmidbauer E. Lithium conductivity in a Li-bearing ring-silicate mineral,sogdianite. J.Sol. State Chem., 180, (2007), 1306 – 1317.

[70] Pedersen B., Frey F., Scherer W. The Single Crystal Diffractometer RESI. Neutron News, 18:4, (2007), 20 – 22.

[71] Peters L., Knorr K., Evan J. S., Senyshyn A., Rahmoun N.-S., Depmeier W. Proton positions in and thermalbehaviour of the phase CaO ∗ 3AL2O3 ∗ 3H2O and its thermal decomposition to < |(OCa4)2|[Al12O24]− SOD,determined by neutron/X-ray powder diffraction and IR spectroscopic investigations. Z. Kristallogr., 222, (2007),365–375.

[72] Petry W., Neuhaus J. Neutronen nach Maß. Physik-Journal, 6/7, (2007), 31–37.

[73] Pfleiderer C., Böni P., Keller U., T. Rößler, Rosch A. Non-Fermi liquid metal without quantum criticality. Science,316, (2007), 1871 – 1874.

[74] Piochacz C., Egger W., Hugenschmidt C., Kögel G., Schreckenbach K., Sperr P., Dollinger G. Implementationof the Munich scanning positron microscope at the positron soucre NEPOMUC. Physica status solidi C, 4,(2007), 4028–4031.

[75] Prager M., Desmedt A., Unruh J., T. und Allgaier. Dynamics and adsorption sites for guest molecules in methylchloride hydrate. J. Phys. Condens. Matter, 20, (2008), 125219 – 6 pp.

[76] Prager M., Grimm H., Natkaniec I., Nowak D., Unruh T. The dimensionality of ammonium reorientation in(NH4)2S2O8: the view from neutron spectroscopy. J. Phys. Condens. Matter, 20, (2008), 125218+11.

[77] Prager M., Pawlukojc A., Wischnewski A., Wuttke J. Inelastic neutron scattering study of methyl group rotationin some methylxanthines. J. Chem. Phys., 127, (2007), 214509.

9 Figures 111

[78] Ranjan R., Senyshyn A., Frey F., Boysen H. Crystal structure of Na1/2Ln1/2TiO3 (Ln : La,Eu,T b). J. Sol. StateChem., 180 (3), (2007), 995–1001.

[79] Ranjan R., Senyshyn A., Vashook V., Niewa R., Boysen H., Frey F. Structural stability of conducting oxideCaRuO3 at high temperatures. Appl. Phys. Lett., 80, (2007), 251913.

[80] Rebelo Kornmeier J., Hofmann M., Schmidt S. Non-destructive testing of satellite nozzles made of carbon fibreceramic matrix composite, C/SiC. Materials Characterization, 58, (2007), 922 – 927.

[81] Repper J., Hofmann M., Krempaszky C., Petry W., Werner E. Influence of microstructural parameters inmacroscopic residual stress analysis of complex materials by neutron diffraction. Proceedings of Meca-SENS,Vienna, 24 - 26 September 2007, –, (2007), 6.

[82] Röhrmoser A., Petry W., Boulcourt P., Chabre A., Dubois S., Lemoine P., Jarousse C., Falgoux J. Status of UMofull size plates irradiation program IRIS-TUM. Proceedings of the RRFM - IGORR 2007, March 11 - 15, 2007,Lyon, –, (2007), 8.

[83] Röhrmoser A., Petry W., Boulcourt P., Chabre A., Dubois S., Lemoine P., Jarousse C., Falgoux J., van denBerghe S., Leenaers A. UMo full plate size irradiation experiment IRIS - TUM - a progress report. Transactionsof the RRFM 2008, Hamburg, Germany, March 2008, –, (2008), 11.

[84] Schmehl A., Vaithyanathan V., Herrnberger A., Thiel S., Richter C., Liberati M., Heeg T., Röckerath M.,Fitting Kourkoutis L., Mühlbauer S., Böni P., Müller D. A., Barash Y., Schubert J., Idzerda Y., Mannhart D. G.,Jochen und Schlom. Epitaxial integration of the highly spin-polarized ferromagnetic semiconductor EuO withsilicon and GaN. Nature Materials, 6, (2007), 882 – 887.

[85] Schmid W., Jungwirth R., Petry W., Böni P., Beck L. Manufacturing of Thick Monolithic Layers by DC-MagnetronSputtering. Transactions of the RRFM 2008, Hamburg, Germany, March 2008, –, (2008), 4.

[86] Schneidewind A., Link P., Etzdorf D., Stockert O., Loewenhaupt M. PANDA: The Cold Three-Axis Spectrometerat FRM II. Neutron News, 18:4, (2007), 9–13.

[87] Senff D., Link P., Aliouane N., Argyriou D., Braden M. Magnetic memory effect and Field dependence ofmagnetic excitations iin multiferroic T bMnO3: a neutron scattering study. PR B: Rapid Communications,accepted.

[88] Senff D., Link P., Hradil K., Hiess A., Regnault L., Sidis Y., Aliouan N., Argyriou D., Braden M. MagneticExcitations in Multiferroic T bMnO3: Evidence for a Hybridized Soft Mode. Phys. Rev. Lett., 98, (2007), 137206–1–4.

[89] Smirnov G., van Bürck U., Arthur J., Brown G. S., Chumakov A., Baron A., Petry W., Ruby S. Currents andfields reveal the propagation of nuclear polaritons through a resonant target. Phys. Rev. A, 76, (2007), 043811.

[90] Smuda C., Busch S., Gemmecker G., Unruh T. Self-diffusion in molecular liquids: medium-chain n−alkanesand coenzyme Q10 studied by Quens. J. Chem. Phys., submitted.

[91] Smuda C., Gemmecker G., Unruh T. Quasi-elastic an inelastic neutron scattering study of methyl group rotationin solid and liquid pentafluoroanisole and pentafluorotoluene. J. Chem. Phys., in print.

[92] Stadlbauer M., Hugenschmidt C., Schreckenbach K. New design of CDB-spectrometer at NEPOMUC forT-dependent defect spectroscopy in Mg. Applied Surface Science, in press.

[93] Stadlbauer M., Hugenschmidt C., Schreckenbach K. Characterization of the chemical vicinity of open volumedefects in magnesium and AZ 31 with coincident Doppler broadening spectroscopy. Physica status solidi C, 4,(2007), 3489–3492.

[94] Stadlbauer M., Hugenschmidt C., Schreckenbach K., Böni B. Investigation of the chemical vicinity of crystaldefects in ion-irradiated Mg and a Mg-Al-Zn alloy with coincident Doppler broadening spectroscopy. Phys. Rev.B, 76, (2007), 174104.

[95] Stampanoni M., Groso A., Borchert G., Abela R. Bragg Magnifier: High Efficiency, High Resolution X-RayDetector. Proc. Syn. Rad. Instr.; Ninth International Conference, CP 879, (2007), 1168 – 1171.

112 9 Figures

[96] Steffens P., Sidis Y., Link P., Schmalzl K., Nakatsuji S., Maeono Y., Braden M. Field-induced paramagnons atthe metamagnetic transitions in Ca1.8Sr0.2RuO4. Phys. Rev. Lett., 99, (2007), 217402–1–4.

[97] Stockert O., Arndt J., Schneidewind A., Schneider H., Jeevan H., Geibel C., Steglich F., Loewenhaupt M.Magnetism and superconductivity in the heavy-fermion compound CeCu2Si2 studied by neutron scattering.Physica B Condensed Matter, 403, 5-9, (2008), 973–976.

[98] Strunz P., Mukherji D., Pigozzi G., Gilles R., Geue T., Pranzas K. Characterization of core-shell nanoparticles bySmall Angle Neutron Scattering. Appl. Phys. A, 88, (2007), 277.

[99] Strunz P., Mukherji D., Rösler J., Gilles R., Näth O., Haug J., Wiedenmann A. In-situ SANS investigation ofsolution treatment of single crystal Ni-base superalloys containing rhenium. tbc, submitted.

[100] Teixeira S., Ankner J., Bellissent-Funel M., Bewley R., Blakeley M., Coates L., Dahint R., Dalgliesh R., Dencher N.,Dhont J., Fischer P., Forsyth V., Fragneto G., Frick B., Geue T., Gilles R., Gutberlet T., Haertlein M., Hauß T.,Häußler W., Heller W., Herwig K., Holderer O., Juranyi F., Kampmann R., Knott R., Kohlbrecher J., Kreuger S.,Langan P., Lechner R., Lynn G., Majkrzak C., May R., Meilleur F., Mo Y., Mortensen K., Myles D., Natali F.,Neylon C., Niimura N., Ollivier J., Ostermann A., Peters J., Pieper J., Rühm A., Schwahn D., Shibata K.,Soper A., Straessle T., Suzuki U.-I., Tanakai I., Tehei M., Timmins P., Torikai N., Unruh T., Urban V., Varvrin R.,Weiss K., Zaccai G. New Sources and Instrumentation for Neutrons Biology. Chemical Physics, 345, (2008),133–151.

[101] Trots D., Senshyn A., Mikhailova D., Knapp M., Hoelzel M., Fuess H., Hofmann M. High-temperature thermalexpansion and structural behaviour of stromeyerite, AgCuS. J. Phys. Condens. Matter, 19, (2007), 136204.

[102] Unruh T. Interpretation of small-angle X-rax scattering patterns of crystalline triglyceride nanoparticles indispersion. J. Appl. Cryst., 40, (2007), 1008 – 1018.

[103] Unruh T., Meyer A., Neuhaus J., Petry W. The Time-of-flight Spectrometer TOFTOF. Neutron News, 18, 2,(2007), 22 – 24.

[104] Unruh T., Neuhaus J., Petry W. The high-resolution time-of-flight spectrometer TOFTOF. Nuclear Instrumentsand Methods in Physics Research A, 580, (2007), 1414–1422 & erratum 585 (2008) 201.

[105] Unruh T., Smuda C., Gemmecker G., Bunjes H. Molecular Dynamics in Pharmaceutical Drug Delivery Systems- The Potential of QENS and First Experimental Results. MRS Bulletin - Proceedings of the 8th InternationalConference on Quasi-Elastic Neutron Scattering (QENS2006) held June 14 -17, 2006, Bloomington, Indiana,USA, –, (2007), 137 – 145.

[106] Wagner F., Bücherl T., Kampfer S., Kastenmüller A., Waschkowski W. Thermal Neutron Converter for Irradiationswith Fission Neutrons. Nuclear Physics and Atomic Energy, 3 (31), (2007), 30–36.

[107] Wagner F., Kneschaurek P., Kastenmüller A., Loeper-Kabasakal B., Kampfer S., Breitkreutz H., Waschkowski W.,Molls M., Petry W. The Munich Fission Neutron Therapy Facility MEDAPP at FRM II. Strahlentherapie undOnkologie (Urban & Vogel), submitted.

[108] Wasmuth U., Meier L., Hofmann M., Mühlbauer M., Stege V., Hoffmann H. Optimisation of Composite Castingsby Means of Neutron-Measurements. Annals of CIRP, 57/1, (2008), 4 pp.

[109] Wimpory R., Mikula P., Saroun J., Poeste T., Li J., Hofmann M., Schneider R. Effiency Boost of the MaterialsScience Diffractometer E3 at BENSC: One Order of Magnitude Due to a Horizontally and Vertically FocusingMonochromator. Neutron News, 19 /1, (2008), 16 – 19.

[110] Zimmer O., Baumann K., Fertl M., Franke B., Mironov S., Plonka C., Rich D., Schmidt-Wellenburg P., Wirth H.-F.,van der Brandt B. Superfluid-Helium Converter for Accumulations and Extraction of Ultracold Neutrons. Phys.Rev. Lett., 99, (2007), 104801–1–4.

Imprint

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Publisher:Technische Universität MünchenForschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II)Lichtenbergstr. 185747 GarchingGermanyPhone: +49 89-289-14966Fax: +49 89-289-14995Internet: http://www.frm2.tum.deemail: mailto://[email protected]

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Editors:J. NeuhausB. PedersenE. Jörg-Müller, TUM

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Photographic credits:All images: TUM, except otherwise noted

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Design:B. Pedersen, TUMJ. Neuhaus, TUME. Jörg-Müller, TUM

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Typesetting(LATEX2ε ):B. Pedersen, TUME. Jörg-Müller, TUM

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