ANNUAL REPORT 2005 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) Cover Image: Quartz Test Sample at the Single Crystal Diffractometer RESI Contents Iii

$ANNUAL REPORT 2005 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) Cover Image: Quartz Test Sample at the Single Crystal Diffractometer RESI Contents Iii$

ANNUAL REPORT 2005 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) cover image: Quartz test sample at the single crystal diffractometer RESI Contents iii

Contents

Directors’ report 1

The Year in Pictures 2

1 Central services 5 1.1 FRM II in Routine Operation ...... 5 1.2 Neutron ﬂux values and spectra ...... 6 1.3 Reduced Enrichment for FRM II ...... 9 1.4 Detector and Electronics Lab ...... 11 1.5 Sample Environment ...... 12 1.6 IT Services ...... 12 1.7 HELIOS ...... 15 1.8 Hot Neutron Source ...... 16 1.9 Neutron Optics ...... 18

2 Instruments 21 2.1 NEPOMUC ...... 21 2.2 TOF-PAES ...... 22 2.3 PAES ...... 23 2.4 MEPHISTO ...... 24 2.5 MIRA ...... 25 2.6 Simulations for a new neutron guide switch ...... 26 2.7 REFSANS ...... 27 2.8 SPODI ...... 29 2.9 STRESS-SPEC ...... 31 2.10 RESI ...... 33 2.11 Irradiation ...... 34 2.12 SPHERES ...... 37 2.13 PANDA ...... 38 2.14 MAFF ...... 40 2.15 N-REX+ ...... 41 2.16 PUMA ...... 43 2.17 NECTAR ...... 44 2.18 SANS-1 ...... 46 2.19 ANTARES ...... 48 2.20 Fission Neutron Source ...... 50 2.21 RESEDA ...... 51

3 Scientiﬁc Highlights 53 3.1 Magnetic-ﬁeld induced instability in MnSi ...... 53 3.2 CDBS:Measurements on Mg-Alloys ...... 54 3.3 Stroboscopic Neutron Imaging ...... 55 3.4 Small-angle scattering effects in radiography ...... 57 3.5 TOFTOF: Dynamics of melts ...... 59 3.6 TRISP:Phonon Linewidths in Pb ...... 60 iv Contents

4 Facts and Figures 62 4.1 User Program ...... 62 4.1.1 User support ...... 63 4.2 Public relations ...... 65 4.3 Committees ...... 68 4.4 Staff ...... 74 4.5 Publications ...... 77

Imprint 79 Directors’ report 1

Directors’ report

Successful Start of Routine Operation at FRM II

The outstanding event of the past come from the cold source through the outstation was started. In early January year was certainly the beginning of neutron guides to the positions at the 2006 the 1800 m2 large base concrete the routine operation of FRM II. Af- instruments have been characterized in plate was cast at a Bavarian winter tem- ter having completed the nuclear com- great detail. Some of them are the perature of about -10° C. The first oc- missioning in 2004 the Bavarian reg- most intensive ones world wide. By the cupants are expected to move in dur- ulator gave the permission for rou- end of 2005, 14 beam instruments were ing December 2006. This building was tine operation of FRM II on April in operation. We expect 5 further in- also in the centre of a dispute with our 22, 2005. As a consequence, the struments to start routine operation in antagonists accusing FRM II of illegally Technische Universität München took 2006. 278 proposals were submitted in drilling holes into the outer reactor wall over FRM II from the general con- 2 proposal rounds in 2005. Beam time in order to feed particle beams into the tractor Siemens/Framatome ANP on was overbooked by a factor of 2 on the new experimental hall. In late Decem- April 25, 2005. We would like to ex- average. About 32 % of the beam re- ber, during a visit to the location, the press our sincere thanks to the staff of quests came from research groups out- Mayor of Garching and the members Siemens/Framatome ANP that has built side of Germany. of the City Parliament convinced them- a safe and extremely powerful neutron The silicon doping, the pneumatic selves that all of these accusals would source. At the same time the general rabbit system and other irradiation fa- withstand a verification. contractor was released from his nu- cilities are routinely serving our indus- Prof. Schreckenbach, who had be- clear co-responsibility, which went over trial clients by a very pure thermal neu- gun to structure the operation group in exclusively into the hands of the Tech- tron spectrum and suppression of fast 1999 and become the successor of the nische Universität München up from neutron flux by factors between 103 project manager Dr. Axmann in 2002, this date. Immediately after, the 2nd - 105. Single crystalline silicon rods finished the construction and started fuel element was put into the core po- of a diameter of 20 cm to 50 cm in FRM II successfully. On December 31, sition. On Tuesday, May 2, FRM II height show the demanded homoge- 2005 the term of Prof. Klaus Schreck- reached its nominal power of 20 MW neous doping needed by the semicon- enbach as Technical Director of FRM II and the first neutrons were delivered to ductor industry. Industry also booked ended. Routinely he handed over the the users. Altogether, FRM II operated experimental time at beam instruments steering wheel to Dr. Ingo Neuhaus. for 3 full cycles in 2005. The 52-day- like the strain scanner StressSPEC and Dr. Ingo Neuhaus studied Mechanical rhythm for each cycle was only inter- the radiography station ANTARES. The and Nuclear Engineering at the RWTH rupted for a short period, among oth- Centre for Industrial Applications (IAZ) Aachen, received his PhD for studying ers due to two extremely strong thun- welcomed its first lodger in 2005. Of- plutonium reduction by using thorium derstorms, which interrupted the cur- fices and laboratories will be used for based fuel in PWR. Before joining the rent supply in the region around Garch- the production of radio pharmaceuti- FRM-II staff in April 2005 Dr. Neuhaus ing. The regular maintenance interval cals. was responsible for the nuclear opera- after the 3rd cycle was finished in due Furthermore FRM II participated in tion of the Jülich heavy water research time. At the very end of 2005 the 5th fuel the open house on the Garching cam- reactor. element was loaded into the core in or- pus last year. As usual a maximum of Colleagues, users and friends of FRM II der to start the 5th cycle on January 5, 500 visitors were guided through the wish to express their thanks to Prof. 2006. nuclear and experimental facilities. Schreckenbach on the occasion of a The neutron fluxes at the instru- In June 2005 the construction work Farewell Colloquium which will take ments are fulfilling more than our ex- for the combined experimental and of- place on May 15, 2006. pectations. The neutron beams which fice building housing for the FZ-Jülich

Guido Engelke Winfried Petry Klaus Schreckenbach 2 The Year in Pictures

The Year in Pictures

14 April 05: The Centre for Industrial Users (IAZ) has been com- 3 June 06: ANTARES receiving visitors from the Bavarian Ministry pleted. of Culture, Research and Arts, MD Ulrich Wilhelm and Dr. Ul- rike Kirste, and the ﬁrst scientiﬁc user at ANTARES: Dr. Meneske Bastürk, Atomic Institute, Vienna (center); group left: Veronika Vitzthum, ANTARES staff, Prof. Schreckenbach, Technical Direc- tor FRM II, Dr. Ingo Neuhaus, designated Technical Director, and Dr. Burkhard Schillinger, head of ANTARES.

6 May 05: The very ﬁrst users at FRM II: Dr. Klaus Habicht / BENSC (far left) and Pegor Aynajian, Diploma student at MPI Stuttgart (far right) at the NRSE-TAS instrument together with Prof. Petry (FRM II) and Kathrin Buchner, MPI. 17 March 2005: Visitors from the Federal Ministry of Education and Research (BMBF): Dr. Beatrix Vierkorn-Rudolph and State Secre- tary W.-M. Catenhusen (right). The Year in Pictures 3

25 April 05: Siemens handing over the Neutron Research facility to the Technische Universität München: Prof. Schreckenbach, Technical Director FRM II, Mr. Eisenbeiß, Head of the Admin- 24 November 05: Inauguration of N-REX+ operated by the Max- istration ZA1, and Mr. Engelke, Administrative Director FRM II, Planck-Institute Stuttgart: Prof. Petry; Prof. Dosch, MPI Stuttgart; signing the transfer documents. Dr. Ulrike Kirste, Bavarian Ministry of Science, Research and Arts; Dr. Rainer Gastl, Max-Planck-Society; Dr.-Ing. Kuch, Manage- ment TUM.

27 April 05: Celebrating the successful transfer: MDgt. Dr. Brandmair, Bavarian Ministry for Environment, Health and Con- sumer Protection; Prof. Schilling, University Management ; Prof. Schreckenbach, Technical Director FRM II; Mr. Grolle, Fram- atome ANP; Mrs. Marzin, Administration TUM; Prof. Petry, Sci- entiﬁc Director, Mr. Eisenbeiß, Head of the Administration at Garching; Mr. Donath, Mr. Gyr, Mr. Falke, Mr. Bergmann, Fram- 20 December 05: Prof. Petry guiding the members of the Garching atome ANP (2nd row, from left to right); Mr. Novak und Mr. Land- town council through the research reactor: On his right Mayor graf, Framatome ANP GmbH (1st row). Manfred Solbrig and Mayor Hannelore Gabor (far right) and Wal- ter Kratzl (far left), Manfred Kick and Annette Knott.

7 October 05: Freunde und Förderer der TU München visiting the FRM II(from left to right): Dr. Eva Sandmann, Dipl.-Ing. Wolfgang Kling, Robin Kling, Dr. Volker Jung, Heide Jung, (from left ro right) and Dr. Horst Nasko, Johannes Ortner, Maximilian Grauvogl

20 December 05: Prof. Dr. Dr. hc. mult. W. A. Herrmann, president of the TUM, welcomes members of the Garching town council at the FRM II 4 The Year in Pictures 1 Central services 5

1 Central services

1.1 FRM II in Routine Operation

K. Schreckenbach 1 1Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU München

Following the successful nuclear provements. rience of 2005 we are quite optimistic start-up of the FRM II in 2004 with one that 5 full reactor cycles are technically full reactor cycle, extensive reports on Following the approval for routine possible in 2006. A new fuel element the results were prepared and submit- operation the second fuel element was was already placed in December 2006 ted to the regulatory body (StMUGV). immediately placed in the operational for the early start of the fifth cycle in In addition, various technical improve- position. After start-up tests full power 2006. ments were carried out especially at the was achieved on May 2, 2005. Three beam tubes, the neutron guides and full reactor cycles (52 days at 20 MW) At the end of 2005 Prof. K. Schreck- the operation of the cold source. Based were scheduled for 2005. This goal was enbach finished his term as the first on these reports, the completion of the accomplished on December 19, 2005 technical Director of the FRM II. He technical improvements and the ful- when the forth reactor cycle was fin- had started at FRM II in May 1999 with filment of obligations arising from the ished. The three cycles were running organisation of the reactor operation operation licence the StMUGV granted from group and passed through the difficult the approval for routine operation on 2/5 to 24/6/2005, period of the licence for nuclear opera- April 22, 2005. 12/7/ to 8/9/2005, and tion and the nuclear start-up of the FRM 26/10/ to 19/12/2005. II. The designated successor in the re- During the construction and the nu- sponsibility as Technical Director, Dr. clear start-up TUM and the general There were only short interruptions Ingo Neuhaus, came to the FRM II in contractor Siemens/Framatome were within the cycles. They were caused by April 2005 for a learning period at the the common holder of the nuclear li- two strong thunderstorms with a break facility, a period which is anyhow oblig- cence and the nuclear responsibility of the external power supply. Other in- atory due to the nuclear regulations. for the FRM II. After the approval for terruptions were due to planned short I. Neuhaus brought with him a dedi- routine operation Siemens/Framatome stops and minor problems with mea- cated experience from his former job left this responsibility on April 14, 2005. surement units. as head of the Jülich research reactor Further on TUM is the only holder of DIDO. Based on his experience at Jülich the nuclear licence and is working on The long reactor shutdown from and his new experience at the FRM II its own responsibility. The change over September 9, 2005 to October 15, 2005 the regulatory body readily granted him was worked out smoothly and the con- was used for the extensive maintenance the agreement for his new responsibil- tractor remained on-site only for the program and for work at neutron guides ity. completion of still open technical im- and radiation shielding. With the expe- 6 1 Central services

1.2 Neutron ﬂux values and spectra at operating FRM II

A. Röhrmoser 1 1ZWE FRM II, TU München

In April 2005 routine operation of eration of FRM II to the upper position Including fast spectrum corrections FRM II started. Flux measurements of rest or in the region of the strongly derived from the calculated data one 14 2 1 were made in addition to those already absorbing Cd-nose of the vertical beam gets again 1.8 10 cm− s− . · performed during the nuclear commis- tube SR11. Further there are some re- The flux measurements in the HFRP sioning phase with the first fuel element gions of re-thermalisation to lower or positions were also undertaken in order in 2004 at different power steps. This re- higher temperature in the D2O. Those to calibrate the absolute thermal power port presents a comparison of the mea- areas are restricted to the cold and hot during the commissioning phase. Two surements and the accompanying cal- source regions. critical items determine the accuracy culations. The measurements and calculations of this procedure. Firstly, the gold foil These measurements were done in mentioned now are done with very low activation measurements in the HFRP and outside the D2O-moderator vessel. background of fast flux with exception position have an accuracy of about 10 30 cm distant from the fuel element of the converter beam tube SR10 as dis- %, secondly the computer simulations, the neutron spectrum is quite well ther- cussed later. which make the link between the mea- malised and the very huge part of the sured flux at the HFRP position and the vessel serves no more as a moderator Irradiation positions in the maximum neutron fluxes in the moder- but as a storage for the neutrons, the ator, have to rely on the precise 3-D in- D2O vessel best one we can have. So the name put of all kind of devices in the modera- ’moderator’ is only half of the truth. Power determination through flux tor vessel. There are several positions in the measurement in the ‘high flux It turned out that despite of the error D2O vessel where the usually very well rabbit pipe’ (HFRP) bars for the gold foil activation analysis defined thermal neutron spectrum is this calibration of the absolute power heavily disturbed, e.g. around strong The flux at the position in the high was of great help for power determina- absorbers as there are the shut down flux rabbit pipe HFRP, at 8 cm above tions at low power loads. We further rods, which are withdrawn during op- mid plane and at a radius of 45 cm, asked the question whether the com- was calculated being perturbed by all parison of measured and calculated flux other installations in the vessel to 3.6 values at the HFRP position can be used 14 2 1 · to determine the maximum flux level in 10 cm− s− . The unperturbed flux at the same position was calculated to the moderator vessel. Here, it turned 14 2 1 out that a much more reliable deter- 5 10 cm− s− . But the most impor- · tant flux depression for the point of mination of the maximum neutron flux measurement originates from the HFRP stems from reactivity measurements of pipe itself. Including this, the absolute the reactor in comparison to the predic- flux for the HFRP position at 20 MW tions by the 3D- simulations of the neu- thermal power was calculated to [1]: tronics in the D2O vessel. Considering all the information the maximum thermal flux values are HFRP 14 2 1 Φ 1.84 10 cm− s− n = · The first flux measurements came max 14 2 1 Φth 8.0 10 cm− s− unperturbed from gold activation in the high flux = · rabbit pipe (HFRP) at 10 kW, 160 kW, 2 MW and 5 MW power steps of FRM II Figure 1.1: Horizontal cut through the D2O max 14 2 1 Φ 6.4 10 cm− s− perturbed vessel and the core, 20 cm above core mid during nuclear start up. When extrap- th = · plane; the positions of interest are shown, olating the measured values to 20 MW . as the (HFRP) pipe and the SDA, which thermal power by means of a final com- The perturbed value is of course an come vertically from the top. Two fingers prehensive analysis of all power data, average value because perturbation is of the KBA are fed inclined from the top one can derive a best value of measured rather unisotropic around the fuel ele- and reach down to this depth. Both are thermal flux: cut at the bottom lid in the picture. Some ment due to the different inserts in the other installations, like the supply chim- moderator vessel. neys of the cold and hot source, can be HFRP 14 2 1 Φn 1.7 10 cm− s− perceived. = · . 1 Central services 7

Rabbit systems bit system RPA there have already ex- isted more detailed calculations and the Fig. 1.2 shows the calculated perturbed self shielding by the pipes is drastically flux profile Φth at irradiation positions lower than in the described cases HFRP along the two fingers of the KBA. All and KBA. So, the officially exhibited val- flux values are calibrated to a thermal ues should be rather good [3]. reactor power of 20 MW. Each finger provides five irradiation positions, for Silicium doping facility SDA which the average values are given. For the topmost two positions there also The silicon doping facility SDA is lo- exist measured data [2]. A remark- cated in the D2O vessel at a distance of ably good agreement between mea- 1 m from the core center. In order to surements and calculations has been achieve homogeneous doping over the found for all four measured (2*2) top whole volume of single crystals with a positions. height of 50 cm and a variable diame- Figure 1.4: n-current jn(E) at SR4 end po- According to the calculations the ter between 4 to 8 inch, it is necessary sition; comparison of measured (red fast neutron flux is suppressed by two to shape the neutron flux profile. With- points) and 3d-calculated (blue dots) decades at the bottom position 1 and out such measures gradients in flux of spectra. three decades at the end position 5. at least 10 % would occur between the Measuring the fast flux is clearly more mid height of a cylinder and its two difficult and in this case it gave merely extremes. This flux homogenizing is Flux values at beam tubes half of the calculated values for the top obtained by a Ni-cylinder surrounding positions. The calculations are judged the silicon blocks having an optimized FRM II is furnished with a series of to be reliable. thickness profile. The here presented beam tubes for the scientific usage. For the somewhat comparable irradi- calculations are of considerably higher Three beam tubes (SR 1,2,4) are fed by ation positions of the pneumatic rab- precision than those performed in the the cold source (CNS) of FRM II at 40 cm licensing phase of FRM II. As a conse- distance to the core central axis. The quence vertical homogeneity could be biggest beam tube SR1 supplies six neu- considerably improved. tron guides which feed the neutrons The now optimized Ni-liner has a into an external experimental hall. The trapezium shape and is better covering other two cold beam tubes lead into the the entire silicon blocks to overcome reactor hall. the overall trend of the flux depression at the ends. Figure 1.3 shows the axial Cold Spectrum at SR4 flux profiles in a 6“-Si-block, which is now much flatter over the whole block Beam tube SR4 allows measurements of height. the spectrum at an end position with Since the Ni-layer is really thin and direct view onto the cold source sur- shaped, the question can be risen, how face. The measurements were done at Figure 1.2: Φth at KBA position along the precise it can be fabricated. The calcu- full power of FRM II close to the end of two fingers after a 3D-calculation. For lations clearly show that the tolerances the nuclear commissioning phase. Fig- the two top positions exist measurements for the thickness have to be less than ure 1.4 shows the measured and the cal- (light colored dots). 0.2 mm (preferred 0.1 mm) in order to culated spectra for this end position. achieve homogeneity. Fig. 1.4 shows an excellent agreement Very last results showed that an eas- between the measured and calculated ier solution could be regarded dismiss- spectrum over three decades in energy; ing any thin and shaped absorber layer. the calculated values extend even one When shaping the width of the H2O extra decade down to 0.1 meV. To reach channel, surrounding the silicon block, that perfect agreement several parame- a comparable flux shaping can be ob- ters had to be fine-tuned in an iterative tained without changes to the overall procedure. The most important ones geometry of the SDA facility. The man- were the exact geometry and the filling ufacturing would be quite uncompli- of the cold source. For instance, the cated, having no questions about the cold source apparently was filled to a Figure 1.3: calculated axial flux shape in a 6“- achievable precision or any absorber level of 12 cm, the displacer was empty Si-block in the SDA facility. burn up. and a density of 93% was assumed for 8 1 Central services

the liquid D2. Together with these pa- For the extreme low power case 1) rameter studies, measurements of the (blue curve) the distribution is very spectrum at SR4 may serve to precisely asymmetrical. Under more usual oper- characterize the filling conditions of the ational conditions (viola curve) the dis- cold source. Fig. 1.4 also clearly reveals placer in the CNS is evaporated and the the characteristic undermoderation of cold SR1 neutrons at the nose arrive the FRM II cold source. more symmetrically and more from the Measured data turn out to be less re- center of the CNS. This nicely confirms liable below neutron energies of 1 meV. the idea of a flux gain due to the ‘cavity In this area and even down to far lower effect’. Normalized to the same nominal energies only calculations provide reli- power case 2) delivers 32 % more neu- able data. Because the calculations so trons in comparison to case 1). nicely meet the spectral measurements at SR4, it is concluded that the calcu- Converter facility SKA lations are of similar reliability for the two other cold beam holes SR1 and SR2, Figure 1.5: Distribution of cold neutrons en- A comparable neutron and also γ tering the nose SR1 with flight direction where measurements are not feasable. source file was generated in beam tube towards the exit in the case of 200 kW re- These calculations are the basis for a SR10 for the converter facility SKA. Em- actor power with 13 l D2 in the CNS. prediction of the flux properties at the phasis was put on the exact incorpora- output side of the cold beam tubes and tion of the complex geometry of a con- complex neutron guide systems of op- One can recognize in figure 1.5 and verter facility. The total thermal power erating FRM II. curve ‘FSt +2 cm’ in figure 1.6 that the of the SKA is now calculated to about 70 lower part of the nose is better illumi- kW. Further calculations which concen- Source flux for the neutron guide nated by cold neutrons than the upper trate on dose values at a phantom at the hall part. The tracks are summed up hori- beam exit use this source files as parti- zontally and lead to the distributions of cle start data. For further calculations an interface figure 1.6 over the nose height for both These calculations are now an impor- was constituted in form of a source file, cases. tant input for the qualification of the tu- which provides all the specific particle mor therapy by fast neutrons required tracks as start data. In this case the gen- by the German rules for medical facili- erated source file is a collection of neu- ties. tron tracks entering SR1 with flight direction towards the exit. Each single [1] FRM II. Zu erwartende Neutronen- track is stored with exact position, di- Messsignale während der nuk- rection, energy and weight. The calcu- learen Inbetriebsetzung (IBS) des lations were run for more than a week FRM II,OPA313. on a dedicated computer,so the statis- tical variance is really low. Figures 1.5 [2] Annual Report FRM II 2003, 66. and 1.6 show the distribution of the cold [3] Annual Report FRM 2004, 63. neutrons entering SR1 from such files for particular fill levels of the NCS: 1. The extreme case of a fill level FSt of the NCS of only 1.6 cm above center at a very low power of 200 Figure 1.6: Calculated density distribution of kW. Due to insufficient heating cold neutrons entering SR1 with flight di- the displacer volume is not evap- rection towards the exit as function of the orated. The NCS contains 13 l D2. height position on the nose for the two operational cases but normalized to the 2. A more usual operational case same reactor power and begin of cycle. with a fill level of the NCS of 10 cm Caused by the density step between vapor above center. to liquid D2 surfaces a sharp decrease is observed in both cases. 1 Central services 9

1.3 Reduced Enrichment for FRM II

A. Röhrmoser 1, W. Petry 1, N. Wieschalla 1 1ZWE FRM II, TU München

In 2001 an ‘Agreement between the tors) group at Argonne presented al- tual HEU case. The total U mass is 21.6 Federal Republic of Germany and the ternative fuel element designs with re- kg instead of 8.0 kg now. The important Free State of Bavaria on the Conversion duced enrichment. These calculations value of the radial form factor is clearly of FRM II was written down and finally confirmed that a conversion to LEU was less opportune with the MEU fuel. Par- signed after the final operating license impossible for FRM II without severe ticularly the maximum of the heat load was granted in May 2003. This compro- geometry changes even with the theo- in the outer zone is much higher than mise is part of the final nuclear license retical limit of uranium metal densities actually and can not be accepted for and aims for the development of a new of 19 g/cm3. a final design. At the same time this medium enriched fuel element until the Any scenario to convert the FRM II would lead to increased values of the end of the year 2010 (MEU, not more has to keep the reactor power constant maximum of the fission density (FD) in than 50% U-235; at the present high en- at 20 MW, to guarantee a duration of the fuel. Test irradiations have to show riched fuel with 93% U-235 is used.). the fuel cycle of 52 days and to yield what fission densities the new fuel can The TUM has established an interna- only marginal losses in the neutron flux withstand under conditions compara- tional working group to meet this target. and quality. For an enrichment of 50% ble to those in a reactor like FRM II. The planning is split into three periods: an advanced fuel with high density is The thermal flux is depressed by 1. Search for the fuel type, perform required when maintaining the dimen- about 8.0% when compared to the ac- irradiations of fuel plates sions of the HEU compact core fuel el- tual HEU fuel. 2. Further test irradiations, final de- ement. It is clear that some penalties With the availability of UMo mono- cision on the fuel type and design arise from any reduced enrichment de- lithic fuel the density would be in- of the fuel element sign for the users, some of which are creased again a reasonable step for- 3. Fabrication of the fuel element more obvious, like some loss in flux val- ward. Despite of the technical prob- and licensing ues or less obvious ones as an increase lems to produce large fuel plates with It goes without saying that all the phases in the production of Pu from 11g to gradients in fuel density and curved have to be accompanied by extensive about 100 g with the less enriched vari- shape first calculations were performed calculations on a MEU fuel, to decide ants. with monolithic fuel of uranium den- on the necessary uranium density for sity of 15.1 g/cm3. From a theoretically a conversion, to do parameter studies Calculations with UMo/Al point of view the higher density could and to search for possible alternative dispersive and monolithic be used to further reduce the enrich- pathways. The first 2 1/2-year period is fuel, actual results ment for the unchanged core geome- ending with the year 2005. For phase 1 try. As it can be derived from the cal- it was intended to be able to do a pres- culations with UMo-Al dispersive fuel Uranium-molybdenum dispersion fuel election of the fuel for a MEU fuel ele- the mass of 235-U cannot be regarded (UMo-Al) was and is under research ment. Activities had to be performed in to stay constant under the given condi- worldwide up to a density of 8.5 the following fields: tions. Instead the harmful loss of neu- gU/cm3. Our neutronics calculations • Calculations for the high density trons in the 238-U has to be largely over- were executed with the same numerical fuel(s) for FRM II geometry compensated for constant FRM II ge- scenario and procedures that led to the • Irradiations of MEU fuel plates of ometry. And this compensation fac- HEU design of FRM II, where the fuel is full size tor will even raise stronger when fur- U Si and has a maximum density of 3 • Active participation in inter- 3 2 ther reducing the enrichment. This is gU/cm3 to achieve 1040 MWd of opera- national research programs for shown in the figure 1, where the mass of tion with some reserve. dense fuel. 235U is drawn as a function of the en- For UMo/Al dispersive fuel the re- richment in the current geometry. The sult is that the uranium density in the horizontal line at density 19 g/cm3 in- Calculations with high fuel must be at least 7.75 g/cm3 with an dicates the physical limit with metallic density fuels 235-U enrichment of 50%. When tak- uranium. The calculations for 20% en- ing into account other aspects like the richment demands a hypothetical den- First enrichment studies for a new FRM less fortunate power density distribu- sity of about 40 g/cm3. were performed by TUM during the de- tion (s. below) some parameter range sign phase in the 80’ies; one decade for corrections is needed and the min- later at beginning of the construction imum density can hardly be below 8.0 phase for FRM II the RERTR (reduced g/cm3. In total the core contains then enrichment for research and test reac- 10.8 kg 235-U instead of 7.5 kg in the ac- 10 1 Central services

bilities in the search for a balance be- chanically thickness scans are done in tween the contradicting demands of de- situ after each cycle to measure the lo- creasing enrichment and highest opera- cal swelling of the plates. tional quality of a neutron source. This could mean a better burn up ratio or in Cooperation in UMo other words longing for a longer cycle monolithic fuel research length for the given FRM II geometry, to compensate the penalty of a lower flux The alternative of monolithic UMo fuel value of 8-10% in the case of 50% en- is presently under study at the RERTR richment. A raise in the power level Program. One of the main challenges is very difficult to achieve because of with this very high density fuel is the Figure 1.7: Mass of 235-U and U-total (re- the less opportune power distribution fabrication of full size plates. So far spectively the corresponding U density, in the reduced enrichment case. only two test irradiations of small mini- right scale) necessary in FRM II to obtain plates have been performed. In Au- a cycle length of 52 days. In the calcu- Fuel irradiation in phase I lations particular enrichments have been gust 2005 TUM and CEA/CERCA have chosen (see dots) and the uranium den- signed a contract for ’Cooperation in sity has been treated as a variable. For Phase I it was decided to irradi- develop-ment for UMo-monolithic fuel ate four test plates of full size at the plates’. As soon as plates with this MTR reactor OSIRIS/Saclay. For this monolithic fuel can be fabricated a In the case of 34% enrichment, which purpose six plates were produced by common TUM/CEA/CERCA irradiation corresponds to the density of UMo CERCA with UMo-Al dispersive fuel (8% experiment will be launched at OSIRIS. monolithic fuel the mass of uranium wt. Mo). The uranium densities are 7 in the fuel element would be about 40 and 8g/cm3. Two of the 8g/cm3 plates Metallographic studies kg instead of 8 kg now, thus five times contain a Si additive, a possible "diffu- higher. The mass of 235-U would be in sion blocker". Before starting irradia- TUM contributes to high density fuel the order of 14 kg instead of 7.5 kg now, tion OSIRIS needed an extension of its research. Actually the build up of thus nearly doubled. The radial form license for heat flux values in the or- the harmful UMo-Al interdiffusion layer factor rises even higher than already 2 der of 300 W/cm for the TUM plates during irradiation has to be better ex- in the UMo/Al dispersive fuel case and to reach a targeted cladding surface plained. In a new approach TUM ir- further density gradients would have to temperature of 100°C. After some de- radiates UMo samples by a heavy ion be introduced. A fuel element of that lay with this French licensing the irra- beam in order to simulate irradiation kind still burns not more than 1.3 kg diation could finally start 15.9.05 with 4 induced diffusion as it takes place dur- 235-U, i.e. only 9.6% of 235-U would be plates in two different IRIS devices. It ing fuel burn up. This study should used, an unacceptable burn-up value. is predicted that the aimed density of reveal whether the diffusion is mainly The loss in thermal neutron flux will 21 3 2.3 10 fissions/cm can be reached at caused by the fission product projec- be clearly more than 10%. The lat- · first after 3½ cycles for the front plates tiles or rather stems from the thermal ter results are real penalties, more than of each IRIS-device and later for the sec- treatment during irradiation and could marginal ones. ond plate each device. The 3. cycle in general allow rather cheap metallo- On the other side the high density of (start 15.12.05) shall be finished with graphic studies. UMo monolithic fuel opens new possi- the beginning of the year 2005. Me- 1 Central services 11

1.4 Detector and Electronics Lab

I. Defendi 1, S. Egerland 1, A. Kastenmüller 1, M. Mühlbauer 1, M. Panradl 1, T. Schöffel 1, K. Zeitelhack 1 1ZWE FRM II, TU München

The main activities of the lab in 2005 counting, Time-of-Flight measurement collimators or monochromators is of were governed by the commissioning or pulse height analysis using the M- great importance for the performance of new scientific instruments. A vari- module standard [2]. It has been ex- of the scientific instruments. Continu- ety of detectors and readout systems as panded by new modules specifically de- ing a development of the tomography well as electronic components for the veloped for the thermal single crys- group at FRM II [4], we designed a com- instrument control were brought into tal diffractometer RESI and the single pact neutron sensitive camera for on- operation. A few examples are reported. crystal diffractometer for hot neutrons line beam inspection, which covers the The Detector and Electronics Lab is HEiDi. The boards allow multiframe neutron flux range 105 108 n/cm2/s. − strongly involved in the neutron flux counting controlled by the detector arm The camera is based on a 0.3 mm thick calibration and the study of neutron movement and include an angular nor- 6LiF/ZnS scintillator with optical CCD- beam quality at the individual instru- malization. readout. Its field of view is 98 × ments. In this framework a scintillator Within the Joint European NMI3- 65 mm with a resolution of approxi- based neutron camera for sample and JRA2 (MILAND) project the lab par- mately 0.15 mm. Fig 1.8 shows the cam- neutron optical component adjustment ticipates in the development of a fast era and the associated power supply. has been developed presented in sec- medium resolution ( 1 mm) neutron First measurements with neutron beam ' tion 2. detector. One important difficulty to are scheduled for January 2006. Apart from service and maintenance deal with is the unprecedented density the study of new developments and of readout channels to be implemented [1] Rummel, S. Diplomarbeit, technologies is regarded as an impor- in a limited space. We therefore eval- Physikdepartment E18, Technis- tant task of the lab. With the Physics uate the possible use of integrated cir- che Universität München. Department (E18) of the TU München, cuits (ASICs) for an individual readout the lab collaborates in the development of single wires/strips. In a survey on [2] Zeitelhack, K., et al. FRM-II annual report, 6–7. of a N2 based 2d-position sensitive neu- ASIC’s applicable to MILAND four inter- tron beam monitor for high flux appli- esting candidates were identified and [3] Mühlbauer, M. Diplomarbeit, cation [1]. In addition, the lab enforced investigated [3]. Physikdepartment E21, Technische its activities within the NMI3-JRA2 (MI- Universität München. LAND) project with the investigation of Detectors an ASIC based individual channel read- [4] Guerard, B., et al. NMI3-JRA2 "‘MI- out for MWPC or MSGC. A proper adjustment of neutron opti- LAND"’ annual report. cal components like focusing guides, Instrument Control and Readout Electronics

A new power supply and control system for the guiding ﬁeld magnets of the beam line was developed and installed at the positron beam facility NEPO- MUC. The system contains 60 voltage controlled high current sources (I = 0 - 10 A, Umax = 2.3 V), which can be individually accessed by a microcontroller. The system can be operated completely remote controlled or in a manual mode. The backbone of the FRM II data acquisition hardware for single neutron detectors is built by a whole fam- ily of PCI/cPCI-based DAQ-boards for Figure 1.8: 6LiF/ZnS scintillator based neutron camera with optical CCD-readout. 12 1 Central services

1.5 Sample Environment

J. Peters 1, H. Kolb 1, A. Schmidt 1, A. Pscheidt 1, J. Wenzlaff 1 1ZWE FRM II, TU München

In 2005 the sample environment cial available thermostat (-20°C < T < group faced its ﬁrst year character- 200°C). ized by routine operation. Standard FRM II sample environment equipment like closed cycle top loading cryostats (CCR) and high temperature furnaces were successful in operation. A CCR combined with a 3He-insert developed at the FRM II stood the test in a high- pressure experiment on the Triple Axis Neutron Resonance Spin Echo Instru- ment. In addition to the support of instru- mentalists and users intensive work was done on the further development, improvement and completion of our sample environment equipment. Dedi- cated to the TOF TOF spectrometer a medium temperature furnace was designed and manufactured for applications like investigation of colloidal Figure 1.9: Medium Temperature Device drug delivery systems using a commer-

1.6 IT Services

H. Wenninger 1, L. Bornemann 1, J. Dettbarn 1, J. Ertl 1, S. Galinski 1, H. Gilde 1, C. Herbster 1, S. Kreyer 1, J. Krüger 1, J. Mittermaier 1, R. Müller 1, J. Pulz 1, C. Rajczak 1, S. Roth 1, M. Stowasser 1, B. Wildmoser 1 1ZWE FRM II, TU München

Overview NICOS, TACO and TACO appli- tem is connected via SCSI-U320 to the cations server. The network connection of the The IT Services groups provide and • further efforts of making NeXus server is a Gigabit Fiber Channel line di- maintain the software and network in- available for the instruments rectly to the main switch. Client access frastructure used at the FRM II. to the storage is provided by means of Major efforts and achievements New file server NFS, CIFS [3], SFTP [4] and FTP. made in 2005 are In addition to UNIX permission bits, • the new file server “hektor” In 2004, we reached the capacity limit fine grained access control for files and • improvements of the DHCP of our main file server more than once. directories is supported by POSIX.1e server As this is the central data storage point ACLs. Backups of the storage system are • a new printing system the proper operation of our client sys- taken every night and are transferred to • the new firewall controlling the tems very much relies on it. To provide a the TSM system at the “Leibniz Rechen- network between internal net- stable solution with capacity and speed zentrum”. The whole system is very sta- works and the DMZ that matches our today’s requirements, ble and reliable and turned out to be a • the user room located at the we replaced the old system in the first complete success. project building week of 2005. • the migration of our Windows The new system consists of a dual DHCP failover 2000 Servers to Windows Server CPU server provided by Fujitsu- 2003 Siemens Computers [1] and a transtec In the FRM II network, nearly all client • continuous development of [2] RAID storage system with a gross computer systems get their IP address capacity of 6.4 TByte. The storage sys- by querying our DHCP server. As re- 1 Central services 13 ported in the last annual report, we grate failover mechanisms utilizing two Upgrade from Windows 2000 have done a lot of testing to build DHCP or more CUPS servers and CUPS printer Server to Windows Server servers with failover functionality and classes. 2003 LDAP based configuration backend. Due to the encouraging test results New Firewall At the FRM II, the operating network is with the ISC DHCP distribution [5] we based on an Active Directory structure decided to set up the new servers in The Symantec Enterprise Firewall [7] running on Windows 2000 Server. Due 2005. We could finally put the system became fully operational at the begin- to limited support of Windows 2000 we into operation in the first half of 2005. ning of 2005. It runs on a Sun Enterprise decided to upgrade all domain con- So far we did not encounter any prob- E250 and Solaris [8] as operating sys- trollers and raise the functional level to lems. The risk of a DHCP service out- tem. It separates the internal networks Windows Server 2003 [16]. age is significantly reduced. The con- of the FRM II from the DMZ, and there- The benefits of the Windows Server figuration for the DHCP service is cur- fore controls all network traffic which 2003 environment are improved secu- rently still stored in a file as we want to leaves or comes into the internal net- rity, easier to use management services test and investigate the LDAP backend a works. and the ability to rename the Active Di- little bit more. The main purpose of the firewall is to rectory domain which we did later that guarantee security to the networks and year. The upgrade and rename process New print server to provide network address translation was completed sucessfully without any (NAT) of the private IP addresses used bigger problems. As printing is a great demand we have to in the internal networks to gain access provide a reliable solution which is able to the internet. Additional features are Database for the FRM II to handle the different types of network the application level proxies, which al- Main Entrance printers, their connection methods and low protocol inspection transparent to device specific options. Our old Line the user. At the main entrance of the FRM II Printer Daemon protocol based system many events like the allocation and re- was not able to cope with all these re- User Room turn of keys, cars entering and leaving quirements. the reactor compound or the change of We decided to use the Common The new user room set up in the FRM II the guards have to be recorded. Until UNIX Printing System (CUPS) [6]. CUPS project building is intended for quick February 2005 this was done on paper. uses the Internet Printing Protocol and easy network access for scien- It was decided to switch to a network (IPP), described in RFC 2910 and RFC tific users visiting the FRM II. Currently based client/server system. 2911, for managing printers, print jobs, it consists of six Pentium4 computers On the client’s side the guard can use queues and printer classes. Net- with 17" TFT monitors. a web browser to connect to the server. work printer browsing allows CUPS to The operating system used is A PHP [17] script provides the frontend send printer announcements and offers FreeBSD [9], a UNIX derivative. Soft- to a MySQL [18] database on the server, available printers to requesting clients. ware installed on the systems includes in which all events are stored. This solu- CUPS uses PostScript Printer Descrip- the window manager WindowMaker tion allows backup, archiving and easy tion (PPD) based printing options for [10] and the web browsers Mozilla [11], access to stored data. device specific parameters. Backward Opera [12] and Firefox [13]. The office compatibility is achieved by cups-lpd, suite OpenOffice [14] and the image TACO a server that supports legacy LPD pro- manipulation program Gimp [15] are tocol clients. The LPD protocol is de- available. In 2005 we focused on improving and scribed in RFC 1179. To simplify maintenance of the op- stabilizing the TACO based system [19] Access to the new print server for erating system and all other software, (in close cooperation with the software Windows clients is provided by Samba everything is installed at a single loca- development group of the ESRF) as [3]. Samba offers a mechanism called tion for all systems. The computers well as on the development of new de- point-n-print to the Windows client in boot from network by means of PXE and vice servers for new instrument control the same way a Windows server itself mount all necessary directories utiliz- hardware. is doing it. Using this feature, we are ing the network file system (NFS). The Improvements made on the TACO able to provide easy access to our print- user PCs can be used by every person distribution: ers and to maintain all printer drivers with a FRM II network account. and device specific configurations di- • use of fully qualified host names rectly on the print server. Clients with inside TACO to allow the use of a different operating system can use TACO device servers across differ- it without any manual driver installa- ent DNS zones tion. In the future we plan to inte- • installation and startup of the system itself 14 1 Central services

Due to the stabilization and the im- NICOS to be adapted to satisfy the needs of the provements of the system, more and experimentators on the one hand and more instruments at the FRM II switch Our main goal of the developments to retain NeXus compliance as far as to a TACO based instrument control made on NICOS was the improvement possible on the other hand. Up to now, system. At the moment the instruments of the NICOS client usability. In co- the instruments MIRA, TOFTOF, HEiDi, PUMA, PANDA, HEiDi, RESI, MIRA, operation with the responsible instru- PUMA and PANDA can deliver NeXus RESEDA and REFSANS are using TACO. ment scientists and engineers as well files as an option. The modularity of TACO enables us as the instrument users working with to respond quickly to new requirements NICOS we implemented the following [1] Fujitsu-Siemens Computers. of the instruments. A lot of device improvements: http://www.fujitsu-siemens. drivers were written in 2005. By the help • A syntax check before executing de/. of our own development tool “tacode- commands as well as scripts to vel” we were able to implement and avoid runtime errors of long run- [2] transtec AG. http://www. test new devicedrivers in a timely man- ning scripts (typically over night transtec.de/. ner. It took us only some hours up to runs). [3] Tridgell, A., et al. The Samba some days, depending on the complex- • A plot window to display the cur- Project. http://www.samba. ity of the hardware, the quality of doc- rently measured data was devel- org/. umentation and hardware details to in- oped. tegrate a new device server into the in- • The user interface was simplified. [4] The OpenBSD Project. OpenSSH. strument control software. Most of the The main activities of the user can http://www.openssh.org/. time (about 70 %) was required for test- now be done in a single window, ing the software and fixing problems and the users may see the current [5] Internet Systems Consortium. Dy- with hardware (mal-)functions. state of the instrument and the namic Host Configuration Proto- progress of their experiment. col distribution. http://www. TACO Diagnostics Due to the satisfying experience with isc.org/sw/dhcp/. the client/server concept of NICOS [6] Easy Software Products. Common The purpose of TACO Diagnostics is to more instruments will be outfitted with UNIX Printing System. http:// conveniently monitor all parameters of- the system in the course of 2006. www.cups.org/. fered by a TACO [19] server. The program shows the actual values NeXus [7] Symantec Enterprise Firewall. delivered by the TACO server (see fig- http://www.symantec.com/ ure 1.10). Different states of a TACO de- With the scope of the standard neutron Products/enterprise?c= vice are shown by different colours of data format and the appropriate tools prodinfo\&refId=853. the digits. Originally the program was continuously evolving, the support and [8] Solaris Enterprise System. http: developed in the Linux environment, usage of NeXus [21] at FRM II has been //www.sun.com/software/ but it can be ported without problems extended likewise. Two different ap- solaris/index.jsp. to other operating systems like *BSD, proaches have been followed to generate NeXus files. First the “anything-to- [9] The FreeBSD Project. FreeBSD. NeXus” converter NXtranslate was used http://www.freebsd.org/. in conjunction with instrument specific template files to produce NeXus data [10] others, A. K. Window Maker. from the existing ASCII files. For that http://www.windowmaker. purpose the appropriate retrieval plu- org/. gins, which actually do the translation [11] Mozilla Foundation. Mozilla job, have been written. Suite. http://www.mozilla. Alternatively data of the NICOS scan org/products/mozilla1.x/. routines can be directly written into NeXus structures utilizing the NeXus [12] Opera Software ASA. Opera. http: python API developed at FRM II. In this //www.opera.com/. case according to the NICOS routines a generic class deals with writing raw [13] Mozilla Foundation. Firefox. scan data whereas instrument specific http://www.mozilla.com/ Figure 1.10: Screenshot of TACO Diagnostics data is output by corresponding sub- firefox/. MacOS or Windows, as it is written in classes. [14] Sun Microsystems. OpenOf- C++ and using the Qt3 library [20] which In both cases, the NeXus instrument fice.org. http://www. is available on all major platforms. definitions had to be designed and had openoffice.org/. 1 Central services 15

[15] The GIMP Team. The GIMP. Preprocessor. http://www.php. [20] Trolltech AS. Qt. http: http://www.gimp.org/. net/. //www.trolltech.com/ products/qt/index.html. [16] Microsoft Corporation. Win- [18] MySQL AB. MySQL RMDB. http: dows Server 2003. http: //www.mysql.com/. [21] NeXus International Advi- //www.microsoft.com/ [19] Götz, A., et al. TACO dis- sory Committee. NeXus windowsserver2003/default. tributed control system. Data Format for Neutron, mspx. http://sourceforge.net/ X-ray & Muon Science. [17] The PHP Group. PHP: Hypertext projects/taco. http://www.nexus.anl.gov/.

1.7 Polarized 3He gas on the way to neutron instruments at the FRM II

S. Masalovich 1, O. Lykhvar 1, G. Borchert 1, W. Petry 1,2 1ZWE FRM II, TU München 2TU München, Physik Department, E13

In January 2005 HELIOS (IC- Cells 2005. These NSF are based on the Automation GmbH), the facility for quartz cells built in 2004, which were large-scale production of highly po- Polarization of the gas stored in the cell now thoroughly cleaned up and coated larized 3He gas, has been put into op- decreases with time as: with pure metallic cesium (Fig. 1.11). eration at the FRM II. The measure- Cesium in one cell was then acciden- t ments that have been done during the P (t) P (0) e− T1 tally oxidized. With the aim to compare, He = He · year 2005 confirmed the reproducible the relaxation time has been measured This results from steady-state 3He polarization of about for both cells: • magnetic interaction of atoms 78% and about 27 bar litre/day produc- • Cell #1 (Cs-coated, accidentally · with magnetic impurities (what- tion rate at 72% gas polarization. oxidized) T (75 3)h; ever they are) on the surface and 1 = ± With the aim to utilize this highly po- • Cell #2 (Cs-coated) T (267 in the bulk of the cell, 1 = ± larized 3He gas at the neutron instru- 17)h. • inhomogeneous magnetic guid- ments, gas can be compressed up to Cell #2 shows the relaxation time ing field (field gradient), 5.3 bar into detachable cells and trans- comparable with the best relaxation • dipole-dipole interaction. ported to the experiment. The main time reported by other groups for the Thus the total relaxation rate (inverse tasks in 2005 therefore were: quartz cells. relaxation time, T1) can be written as a • to get the experience in pro- The neutron transmission for the empty sum: duction of cells capable to keep cells (quartz windows with 8mm total gas polarization for a long time 1 1 1 1 thickness) has been measured to be: wall gr dd (days); T1 = T + T + T • T 0.84 at λ 1.5Å; 1 1 1 n = = • to build the transporter with • T 0.90 at λ 9.7Å. Here the relaxation rate related to the n = = a highly homogeneous magnetic Next cells will be built according to interaction with inhomogeneous mag- field. the requirements of the neutron instru- netic guiding field and dipole-dipole in- ments. teraction can be estimated with the following formulas: Transporter Ã ~ !2 1 4 B 1 1 gr 1.7 10 ∇| ⊥| To preserve gas polarization while T [h] = · B0 [cm] · p [bar] 1 transporting it from the HELIOS lab to and a neutron instrument the special trans- 1 p [bar] porter has been developed and built dd ≈ 800 T1 [h] in 2005. The transporter (Fig. 1.12) is while the relaxation rate related to the based on a circular solenoid powered interaction with the walls is entirely the with two battery cells 4.5V each. result of a proper choice of the cell The parameters of the solenoid were material and the quality of the surface chosen to provide a homogeneous mag- Figure 1.11: NSF cell coated with metallic Cs. cleaning. netic field in the central area (sized to Two neutron spin filters (NSF) have cover the volume of the NSF cell) with been prepared and tested in the year 16 1 Central services homogeneity of around of the assembled transporter has been on the neutron beam revealed the gas checked with a homemade magnetic polarization 65% at the instrument. ¯~ ¯ ¯B ¯ 4 1 ∇ ⊥ 7 10− cm− mapping system. The final check-up B0 ' · has been performed with polarized 3He that could ensure the relaxation time gas stored in the transporter. The to- related to the magnetic field inhomo- tal relaxation time has been measured geneity about T 100h. to be T1 [h] (110 8) p [bar] . 1 ' = ± · This solenoid is shielded with mumetal tube against the environmental First application to neutron magnetic fields. The parameters of the experiments tube were also chosen to ensure the best homogeneity in the central area when The first application of polarized 3He acting together with activated magnetic gas at the FRM II has been performed field in the solenoid. The solenoid can at the reflectometer MIRA in November be pulled out of the mu-metal tube and 2005. Gas polarized at HELIOS has been placed in the guiding field of HELIOS to used in the test measurements with the ensure the loss-free replacement of the new device developed and built at ILL 3 NSF cell with newly polarized He gas (France). This device, based on po- into the solenoid. larized 3He gas, combines two tools, The whole magnetic system is as- neutron polarizer (analyzer) and spin- sembled on a PVC base and protected flipper, into one unit. The test measure- against mechanical deformation with ments confirmed the high efficiency of Figure 1.12: Transporter for polarized 3He outer PVC tube. The total weight of the this device and, at the same time, veri- gas. transporter is 11 kg and thus one man fied the ability to provide a highly polar- can carry it with ease. ized 3He gas for neutron experiments at The required magnetic homogeneity the FRM II. The very first measurement

1.8 Hot Neutron Source

C. Müller 1, E. Gutsmiedl 1, M. Meven 1 1ZWE FRM II, TU München

The beam tube SR9 is directed to the The moderator and the insulation of the sensor. It measures the white vessel of the hot neutron source (HNS) are enclosed in two vessels made of noise of the electrical resistance and de- and provides a single crystal diffrac- Zircaloy 4 [2]. The small space between termines the absolute temperature. The tometer called HeiDi [1] with hot neu- both vessels is filled with helium gas of noise sensor was developed and tested trons of energies between 0.1 to 1 eV. 3 bars. The helium pressure is perma- at the Technische Universität München. The HNS shifts the thermal neutron nently monitored. Hence there are two The data acquisition system of the noise spectrum from the reactor to higher barriers, which safely separate the hot thermometer was delivered from the energies. This will be achieved by a moderator from air and water. hot moderator, which is placed in the Figure 1.13 shows a cross section of D O reflector tank close to the thermal the hot neutron source vessel, the hot 2 − neutron flux maximum. moderator and the thermal insulation. A cylinder made out of nuclear-grade Due to the extremely harsh environ- graphite is the essential part of the mental conditions (e.g. high graphite HNS. This graphite moderator will be temperature, chemical reactivity and heated by gamma radiation of the reac- nuclear radiation), the temperature of tor core to temperatures above 2000 °C. the hot moderator is very difficult to To achieve these high temperatures, measure. Thermocouples and pyrome- several layers of carbon fiber and a rigid ters are not suitable in this case. There- hemisphere of bounded carbon fiber fore a purpose-built noise thermometer thermally insulate the moderator. Both was installed to measure the tempera- Figure 1.13: Cross section of source vessel types of insulation also have the task to ture of the hot graphite (figure 1.13). A with graphite cylinder and carbon insula- fix the hot moderator in the center to noise thermometer [3] is a contact ther- tion. avoid the contact with the "cold" walls. mometer and is not affected by changes 1 Central services 17

Forschungszentrum Jülich, ZEL in Ger- Heat-Up effect of the hot ture of 1900 °C and the counts raised many. neutron source to 2300 neutrons per second. This Further design details of the hot neu- demonstrates the task of the hot neutron source can be found in [4]. The relative long time needed to reach tron source to shift thermal neutrons to temperature was used to measure the higher energies. Temperature transients of heat-up effect of the hot neutron source It is intended to repeat these mea- the hot moderator (Figure 1.15). At the beginning of the surements on full reactor power measurements the reactor was powered (20MW) and with different wave- At full reactor power (20 MW) the mod- up to 19 MW and then kept constant. lengths. These measurements are sup- erator reaches a maximum temperature The temperature of the hot moderator posed to start with the "cold" HNS at 0 of 2030 °C (3690 °F). The following figure reached 700 °C and a monitor counted MW. 1.14 will give an idea how long it takes 1700 neutrons per second at a wave- By doing that, we expect to get a more to get the maximal temperature and to length of 0.552 Angström. Six hours detailed overview of the spectral effi- cool down. later, the source reached a tempera- ciency / gainfactor of the HNS, which is expected to be about 7 at its maximum.

[1] Meven, M., Hibsch, F.,Heger, G. An- nual Report 2003 ZWE FRM-II.

[2] Gutsmiedl, E., A., S. In Proceed- ings of the IGORR 8 Meeting (Mu- nich, 2001).

[3] Brixy, H. Noise Thermometers in Sensors, volume 4 (VCH Verlag, 1990).

[4] Müller, C., Gutsmiedl, E. Annual Re- port 2003 ZWE FRM-II.

Figure 1.14: Temperature transients of the hot moderator measured by noise thermometer at 20 MW reactor power. The maximum temperature will be achieved within 12 hours (red curve). After shutting down the reactor, it takes more than 20 hours to cool down to room temperature (blue curve).

Figure 1.15: Heat-Up effect of hot neutron source at 19MW reactor power 18 1 Central services

1.9 The new Neutron Guide of FRM-II: NL 4a, NL 4b and NL 2a-o

Ch. Breunig 1, E. Kahle 1, R. Schwikowski 1, G.L. Borchert 1, H. Türck 1, D. Hohl 2, S. Semecky 3, A. Ioffe 4, M. Monkenbusch 4, O. Holderer 4 1ZWE FRM-II, TU München 2Technische Dienstleistungen, München 3Kommunikationstechnik, München 4IFF,Forschungszentrum Jülich

The new Neutron Guides NL ing of top and bottom plates from iron, 4a and NL 4b connected by columns of permanent magnets NbFeB to maintain a guiding In continuation of the work reported in field of about 30mT (see Fig. 1.17). The Annual Report 2004, pages 11 ff. we continuation of the NG is a straight sec- accomplished the construction of the tion of 4m that ends at a selector unit. It neutron guide (NG) NL4a between the is coated with Ni58, m=1.2 and enclosed high speed shutter close to the case- by a magnetic cage similar to that inside mate wall and the selector gap in the the casemate but with a field strength NG hall (see Fig. 1.16), and the accord- of 5mT. Along the last meter of the NG ing section of NG NL4b between the fast before the selector the magnetic field shutter and the entrance of the PGAA is rotated from transversal to longitudi- bunker (see Fig. 1.16). nal by means of a magnetic coil with in- In both cases the NG had to penetrate creasing winding density (see Fig. 1.18). the wall between the casemate and the NG hall. Therefore the wall had to be opened and the heavy concrete blocks were rearranged to give passage for the NGs. The glass elements of the NGs have been mounted on top of the corresponding steel bars. The adjustment of the NG was performed by means of theodolites reaching high mechanical Figure 1.16: View of NGs NL4a (to the right) tolerances. Maximum displacement of and NL4b (to the left) in the NG hall dur- two consequent glass elements is less ing the installation period. NL4a is com- than 10µm, angular mismatch less than pletely enwrapped with lead ending at 15arcs and less than 45arcs in horizon- the position of the selector. For NL4b the tal and vertical direction, respectively. glass elements have been adjusted above As in this section the glass NGs have the bottom lead plate by means of the ad- Figure 1.17: The first part of the NG NL2a-o to be vacuum tight all consequent glass justment frames. in the casemate. The glass elements are tube elements were glued together. The jacketed by the magnetic cage. The top final element was equipped with an The new polarising Neutron and bottom plates from soft iron are con- Al window that withstands the vacuum Guide NL 2a-o nected by rectangular magnetic columns pressure and is transparent for neu- maintaining a magnetic field of 30mT. For trons. All NGs could be shown to keep This new NG has been designed by the the first element the NG is already en- the vacuum up to 2x10-2mbar. members of the Jülich Centre for Neu- housed with 10cm thick PE plates. In the casemate region, the NGs were tron Science (JCNS). It takes the up- enclosed in 10 cm thick borated PE per part of the former NL2a cross sec- plates, in the NG hall they have been tion, BxH=44x60mm2 at the fast shut- jacketed by a sandwich of 5 mm borated ter. Within the casemate it has a ra- epoxy and 9cm thick lead (see Fig. 1.16). dius of curvature of 160m horizontally and stays in the casemate section close to NL2a-u so that both NGs had to be coupled to one unit. The coating of the outer wall is FeSi with m=3 while that of the other walls is Ni58, m=1.2. The NG is enclosed in a magnetic cage consist- 1 Central services 19

Figure 1.18: The last part of the NG NL2a- o before the selector gap during the installation period. The glass elements are surrounded by the magnetic coil wind- ings. The NG directly behind the NL2a- o is already enhoused with 10cm thick PE plates. 20 1 Central services 2 Instruments 21

2 Instruments

2.1 First Experiments at the Positron Beam Facility NEPOMUC

Christoph Hugenschmidt 1,2, Thomas Brunner 2, Stefan Legl 2, Jakob Mayer 2, Christian Piochacz 1, Reinhard Repper 1, Martin Stadlbauer 2, Klaus Schreckenbach 2,1 1ZWE FRM II, TU München 2TU München, Physics Department, E21

The mono-energetic positron ceeded to extract a low-energy positron Positron Experiments at beam of high intensity at beam at 15 eV with the world highest NEPOMUC intensity of 4 107 moderated positrons NEPOMUC · per second. The positron beam is extracted at 1 keV In 2005 several positron experiments The positron beam facility was ex- for the CDB-spectroscopy, where the were performed at the high intensity tended by several components: µ-metal beam is focused to 1 mm at the sample positron beam facility at NEPOMUC shielding at the straight sections of the position. Several material systems were (NEutron induced POsitron source MU- beam line, a new adjustable aperture studied – partially with external users – niCh). After adjustment of the positron and an adiabatic beam switch in order in order to investigate the chemical sur- beam the beam parameters such as di- to divide the beam line into five sub- rounding at atomic defects: GaAs(Zn), ameter and intensity were determined sections. With this new switch up to Fe and Fe-alloys, and Mg-alloys. at the first accessible position outside five different positron experiments can The low-energy beam (15 eV) is re- the biological shield. The positron yield be connected to the evacuated beam fa- quired for PAES-experiments with low was improved to a maximum beam in- cility. This beam switch works in the positron induced electron background. tensity of 5 108 at a positron energy of energy range of 15 eV to 1 keV without With this novel spectrometer positron · 1 keV. The diameter in the longitudinal considerable intensity loss. annihilation induced Auger-electron magnetic guide field of 6 mT was found emission was investigated at the surface to be less than 15 mm. We also suc- of single crystalline silicon and polycrystalline copper. Within a diploma thesis a completely new time-of-flight configuration was connected to the beam line in order to enable PAES- measurements with much higher efficiency, that would lead to two orders of magnitude lower measurement time . This year an apparatus for the production of the negatively charged positronium (Ps−) was transferred from the Max-Planck-Institute of Nuclear Physics to the FRM II. Recently this experimental set up was connected to the open beam port of the positron beam line in order to determine the diameter of the 500 eV positron beam at the position of the (Ps−) production target. The present arrangement of the experiments is shown in figure 2.1.

Figure 2.1: Overview of the positron beam facility NEPOMUC and the ﬁrst installed experiments. CDB spectrometer and the PAES set ups are built and operated by E21/TUM. The (Ps−) is operated by the Max-Planck-Institute for nuclear physics. 22 2 Instruments

Outlook brightness. This will enhance the (UniBW) and TUM. In addition, a performance of the scanning positron pulsed positron beam system from Besides the presented experiments it microscope that will be transferred the UniBW will be connected to the is planned to install a remoderation to the FRM II in a collaboration be- positron beam facility NEPOMUC. device in order to improve the beam tween the University of the Bundeswehr

2.2 Time of ﬂight spectroscopy of positron induced auger electrons

Stefan Legl 2,1, Christoph Hugenschmidt 1,2, Reinhard Repper 1 1ZWE FRM II, TU München 2TU München, Physics Department, E21

Auger electron spectroscopy was first built at the University of Texas The inhomogeneous magnetic field by A. Weiss. [2] between the sample and the trochodial Auger electron spectroscopy (AES) is a filter has two important functions. widely used method in surface physics. Experimental setup Positrons leaving the filter are cap- X-rays or high energy electrons are used tured and adiabatically focussed onto to excite core electrons of a material. Positrons entering the flight tube are the sample. The second and much These electrons are emitted into vac- deflected in a trochodial ExB-filter up- more important effect is that all emit- uum. When electrons from higher wards (fig. 2.3). When they leave the ted auger electrons from a solid angle shells take their places, binding energy filter their longitudinal momentum lies of 2π (!) are focussed towards the filter. is released and can be transferred to exactly on the axis of the flight tube Hence each emitted electron can reach a valence bond electron which is also where also the sample is placed. Addi- the micro channel plate. The physical emitted into vacuum. This so called tional the positrons are focussed onto explanation for this is the following: auger electron has a specific kinetic en- the sample by the magnetic field gradi- Due to conservation of the magnetic ergy. By analyzing these energies one ent caused by a strong NdFeB2 perma- moment and conservation of energy, in can determine the elemental composi- nent magnet that is placed behind the an inhomogeneous magnetic field lon- tion of the toplayers of the sample. sample. When a positron annihilates gitudinal momentum is converted into Positron induced auger electron with a core electron two gamma quanta transversal momentum (flight direc- spectroscopy (PAES) uses low energy are created (511keV ) and simultane- tion towards the stronger field) and vice positron annihilation (15eV ) instead of ously the auger electron is emitted. If versa (flight direction towards smaller X-rays or high energy electrons to create one of these gamma quanta hits the field). the e− hole in the inner shell. The fol- B aF2-detector the timing is started. This two effects guarantee a high lowing e− emission process is the same The auger electron travels through the count rate and together with the ability as in AES. trochodial filter in the opposite direc- to measure a large energy range simul- To analyze the energy of the auger tion of the positron trajectories. There- taneously we expect a measuring time electrons mostly hemispherical energy fore the e− is deflected upwards where it for a auger spectrum of less than one analyzers are used. Due to their small hits a micro channel plate (MCP) when hour. solid angle (typically 0,1%) and the it leaves the filter. This MCP creates the ≥ necessity to scan over certain energy stop signal for the timing. The recorded Conclusion and Results ranges in 0.1eV steps one needs sev- TOF spectrum can be transferred into ≥ eral hours (using an intense positron an energy spectrum of the auger elec- So far the experimental setup has been source like NEPOMUC at the FRM II) trons. completed and first measurements at or even weeks (at the lab with a β+- emitter) to get an auger spectrum [1]. In order to reduce this measurement time v B to less than one hour we developed a B B0 transversal,0 = new spectrometer using a time of flight v B method for analyzing the auger ener- transversal 0 gies. In this spectrometer the count rate of auger electrons is much larger than in Vtransversal,0 Vtransversal conventional analyzers and also a large β energy spectrum can be measured simultaneously. A similar spectrometer Figure 2.2: Momentum in an inhomogeneous magnetic field. 2 Instruments 23

showed that electrons emitted from the START STOP 1,3 m sample reach the MCP. Presently, the BaF -Detector 2 electronics is adjusted in order to record B (30 Gauss) E MCP first TOF-spectra. e- e+ NdFeB- flight tube with trochodial filter [1] Strasser, B. Aufbau einer Anlage Magnet (2000 Sample zu positroneninduzierten Auger- Gauss) Elektronenspektroskopie. Ph.D. thesis, Technische Universtiät Figure 2.3: Experimental setup of the TOF-PAES. München (2002). [2] Jiang, N. Design and model- the intense positron source NEPOMUC second hitting the sample, the inten- ing of a positron annihilation in- were performed this year. Focussing sity of the positron beam is also in duced auger electron spectrometer positrons on the sample was optimized this range. Therefore, it is concluded with time-of-flight energy analyzer. in a first step. Our measurements that the beam guiding system works ex- Ph.D. thesis, University of Texas at showed a number of 107 positrons per tremely efficient. In a second step we Arlington (1999).

2.3 First PAES-measurements at the Positron Beam Facility NEPOMUC

Christoph Hugenschmidt 1,2, Stefan Legl 2, Jakob Mayer 2, Reinhard Repper 1, Martin Stadlbauer 2, Benno Straßer 2, Klaus Schreckenbach 2,1 1ZWE FRM II, TU München 2TU München, Physics Department, E21

Principle of PAES positron induced secondary electron Measurements and results background at E E due to the low e− > e+ Auger Electron Spectroscopy (AES) is a kinetic energy of the positrons. Sec- There have already been ﬁrst success- commonly used technique in surface ondly, tightly bound adsorbates at the ful measurements and the results are science. Since in AES the Auger pro- surface are barely destroyed by the in- shown below. The surface sensitiv- cess is induced by high energy (1keV ) cident e+-beam. The greatest advan- ity of the method can be seen at the electrons or X-rays, the spectra con- tage of PAES is the extremely high sur- single-crystal Si-sample (Fig. 2.5). With tain a large secondary electron back- face sensitivity since most of the slow only one monolayer of copper on it, ground. Hence it is very difﬁcult to positrons ( 90%) annihilate with elec- the Auger-peak of the Si completely > identify Auger peaks in the low-energy trons of the topmost atomic layer. vanishes. The other spectrum (Fig. region. The challenge in PAES is to produce 2.6) shows polycrystalline copper (Ar- A new method to initiate the Auger a e+-beam of high intensity. Since sputtered). process is the annihilation of low en- usual laboratory e+-sources provide The measurement time for all spectra ergy (some 10eV ) positrons with elec- 4 e+ shown was 13 hours and the pressure in only about 10 s , measurement times 9 trons. PAES (Positron annihilation in- of 20 days per spectrum or more are the chamber was about 10− mbar . Un- duced Auger Electron Spectroscopy) necessary. fortunately, the background was higher has several advantages compared to conventional AES: Firstly, there is no Experimental setup at

5 0 0 0 S i , s p u t t e r e d NEPOMUC S i w i t h 1 M L C u

4 0 0 0 The new positron-beam NEPOMUC at V

e 3 0 0 0

the research reactor FRM II provides s t n

7 u o

a low energy-beam of 5 10 moder- c 2 0 0 0 · ated positrons per second at the anal- 1 0 0 0 ysis chamber. Due to the high beam- intensity the measurement time is re- 0 4 0 6 0 8 0 1 0 0 1 2 0 duced to several hours. The existing e n e r g y [ e V ] spectrometer (Fig. 2.4) was transferred Figure 2.4: A drawing of the PAES-facility at to the reactor in the end of 2004. the FRM II. Figure 2.5: Si with PAES. 24 2 Instruments than expected, that might be attributed to other experiments nearby and insuf- ﬁcient shielding. 7 0 0 0 C u , s p u t t e r e d Outlook 6 0 0 0

In the following year, the aim is to ﬁnd the true surface sensitivity (qualita- 5 0 0 0 tively) for different samples and coatings and to reduce the background. 4 0 0 0 V e

Besides a better shielding, coinci- /

dent measurement (Auger-electron and s t

n 3 0 0 0 annihilation-radiation) of the electrons u o would be the best way to get a better c signal/noise-ratio. 2 0 0 0

1 0 0 0

0 4 0 6 0 8 0 1 0 0 1 2 0 e n e r g y [ e V ]

Figure 2.6: Cu with PAES.

2.4 MEPHISTO – a measuring facility for particle physics with cold neutrons

D. Rich 1, H.-F.Wirth 2, O. Zimmer 2 1ZWE FRM II, TU München 2TU München, Physik Department, E 18

Scientific design • Low backgrounds is typically collimated to a size appropriate to the given experiment, with Experiments using cold neutrons ad- Current status additional shielding designed accord- dress a diverse array of issues in nu- ingly, to minimize the backgrounds at clear physics, particle physics, astro- Neutron guide and shielding the detectors and in the surrounding physics, and cosmology. The purpose environment. of MEPHISTO is to provide a versatile Experiments at MEPHISTO are installed facility at which one may conduct such at the end of a 30 m, supermirror- Polarizer experiments. The bulk of the instru- coated neutron beamguide, which mentation for each experiment is pro- conducts a neutron fluence of A supermirror polarizer is available, but vided and installed by the user (in col- Φ = 6.8 109n/cm2/sec (measured by not yet installed, as the experiments × laboration with the MEPHISTO team at gold-foil activation in April, 2005) to conducted in 2005 did not require po- the FRM II). The instrument itself is de- the experiment. To our best knowledge larized beam. It is anticipated that the signed to optimize the following condi- this is the most intense cold neutron polarizer will be installed, and the neu- tions for the users: beam for the purpose of fundamental tron beam polarization accurately de- • Maximized neutron fluence physics. The guide itself is shielded by termined, in 2006. • High neutron polarization (as a combination of polyethylene, lead, needed) and concrete. After the guide, the beam 2 Instruments 25

Experiments leased in the neutron decay. A previous ment saw beam for the first time any- measurement at the ILL using the same where in 2005 at MEPHISTO. The runs Two experiments received significant instrument [1] set an upper bound on to date have been largely development beamtime at MEPHISTO in 2005. The this decay branch. A first ever obser- runs, and it is anticipated that the first first, designated RASPAD (Russian for vation of this decay was the goal of the production runs will be conducted early “decay”), ran for 1.5 cycles. The second, measurement at MEPHISTO. Data anal- in 2006. designated aSPECT (a SPECTrometer to ysis is still underway. measure the little ’a’ coefficient in neu- [1] Beck, M., Byrne, J., Khafizov, R. U., tron beta decay), also received 1.5 cy- aSPECT Kozlov, V. Y., Mostovoi, Y. A., Rozh- cles of measuring time. nov, O. V., Severijns, N., Solovei, V.A. The experiment aSPECT was designed JETP Letters, 76, (2002), 392–396. RASPAD to measure the little ’a’ coefficient in neutron beta decay, corresponding to [2] Glück, F., Baessler, S., Byrne, J., The experiment RASPAD was designed the neutrino-electron angular correla- van der Grinten, M. G. D., Hart- to measure the rare radiative branch in tion coefficient. This is achieved by the mann, F.J., Heil, W., Konorov, I., Pet- neutron beta decay. This is achieved by very precise measurement of the en- zoldt, G., Sobolev, Y., Zimmer, O. detection of a triple coincidence among ergy spectrum of recoil protons from Eur. Phys. J. A, 23, (2005), 135–146. the proton, electron, and photon re- neutron beta decay [2]. This instru-

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

R. Georgii 1, N. Arend 2, P.Böni 2, H. Fußstetter 1, D. Lamago 1, S. Mühlbauer 2, R. Schwikowski 1 1ZWE FRM II, TU München 2TU München, Physik-Department, E21

MIRA is a versatile instrument for a 3D-goniometer for sample orienta- very cold neutrons (VCN) using neu- tion. The scattered neutrons are de- trons with a wavelength λ 8 Å (see Fig. tected either by means of a 3He detec- > 2.7) . It is situated at the cold neutron tor or 2-dimensional position sensitive guide NL6b in the neutron guide hall detector (PSD). A slit system of 4 aper- of the FRM II. As the instrument set-up tures before and behind the monochro- can be changed quickly, MIRA is ideally mator and the sample position is used suited as a testing platform for realising to define the momentum resolution of new instrumental set-ups and ideas. In MIRA. An optical bench allows quickly particular, MIRA is unique in its possi- changing the different instrumental set- bilities of combining different neutron ups. scattering methods as: Figure 2.7: Mira equipped with a magnet Furthermore, after the monochroma- • Polarized or non-polarized reflec- and a cryostat. In order to reduce scat- tor the neutrons may be polarised. They tometry. tering by air, the neutrons travel in evac- are guided in a guide field of 60 Gauss • Polarized or non-polarized small uated tubes before and after the sample. provided by permanent magnets. Mul- angle scattering (SANS). tilayer bender with a polarization effi- • Classical NRSE (Neutron Reso- MIRA to about 8 Å. The monochroma- ciency of 95 % are used for determining nance Spin Echo) setup as well as tor mechanics at the end of the guide the polarisation of the neutrons before using the MIEZE principle. is situated inside a massively shielded and after scattering. All moving parts, drum. The multilayer monochromator the NRSE electronics and the readout of Design of the instrument presently used (m = 4.3) allows choos- the detectors are fully automated and ing wavelengths between 8 Å and 30 controlled by the experiment software. The instrument is located at the end of Å. After monochromatisation the neu- In 2005 MIRA was successfully taken a 8 m long curved 58Ni neutron guide trons are then guided through a vac- into user operation. In total, 6 propos- (R = 84 m) with a cross section of 10 uum tube to the sample position, with als, several test and service measure- mm x 120 mm. The instrument is the desired sample environment (e.g. ments were performed, for example a 3 fed by means of a wavelength sensitive low temperatures, magnetic fields). The test of a switchable polarization He switch from neutron guide NL6. The ra- reflection geometry is vertical, so that spin filter for the ILL. 2 diploma the- θ 2θ scans can be performed. Fur- dius of curvature of the guide and its − ses (The flux line lattice of Niobium by coating limit the critical wavelength of ther, the sample table is equipped with Sebastian Mühlbauer (E21), Entwick- 26 2 Instruments lung eines positionsempfindlichen De- tektors für intensive Neutronenstrahlen Table 2.1: Instrument parameters of MIRA Wavelength range 8 Å- 30 Å by Stefan Rummel, E18) and one Ph.D. 5 1 1 2 Monochromatic flux 4 10 Å− s− cm− at 10 Å thesis (Small angle scattering on MnSi · 1 1 Momentum transfer 0.005 Å− Q 1.1 Å− by Daniel Lamago (FRM II) were fin- 6 < < Largest observable length 0.4 10− m ished using mainly data form MIRA. · o Also major parts of the beam time went Angular Resolution 0.05 in another Ph.D. thesis for the develop- Temperature range 180 mK - 2000 K Available magnets B 0.5 T vertical, horizontal ment of a double MIEZE spectrometer < B 10 T vertical (Nikolas Arend, E21), which will be fin- < ished in 2006. Polarization analysis 2 multilayer benders Detector 180 mm x 180 mm PSD resolution 1 mm x 2 mm; single 3He detector

2.6 Simulations for a new neutron guide switch for the instrument MIRA

Sebastian Mühlbauer 1, Peter Böni 1, Robert Georgii 1,2 1TU München, Physics Department, E21 2ZWE FRM II, TU München

Intention guide NL6-b and is coated with Ni 58 straints as shown in fig. 2.9 the guide for the first quarter, supermirror m 2 switch can be shifted by several meters Ni = The instrument MIRA is located at the [Θc ] for the second quarter and super- end of the neutron guide 6B, which is mirror m 3 [ΘNi ] for the second two = c connected to the cold neutron guide quarters of its length. The radius of cur- switch NL6-b by means of a wavelength sen- vature of the guide is 85 m, the super- Neutron guide 6A Ni sitive switch. The neutron flux at the mirror coating is m 2 [Θc ]. Both, the = Guide 6B sample position of MIRA was measured inclination of the neutron guide NL6-b MIRA 5 2 1 recently to be 4 10 cm− s− . In or- and the silicon wafer, as well as the ra- · der to improve the neutron flux, several dius of curvature of the guide are limit- 3° deviation (Si-wafer, m=1-3) simulations for a new, improved neu- ing the cutoff wavelength of the system tron guide switch were performed, us- to 7.7 Å. The maximum of the cold neu- ing the program package McStas [1]. A tron flux of the FRM II cold source is lo- 6cm 2cm gain factor of 10 can be reached without cated at 4 Å, therefore only a small frac- 6° deviation R=85m the usage of neutron focusing devices. tion of the neutrons can be used at the m=2 Furthermore, by adding neutron focus- instrument. ing devices, gains of 100 compared to Figure 2.8: Current geometry of the neutron the actual flux are achievable. In order Improved neutron guide guide switch for NL6/B. to calculate the losses in neutron flux switch for the NL6 after the rebuilt switch, ad- Shifting of the switch towards reactor Neutron guide 6A ditional simulations were performed. Improving the neutron flux without Guide 6B changing the cross section of the neu- MIRA Current neutron guide switch tron guide (120 10 mm) makes it nec- × essary to shift the cutoff wavelength of tangential deviation The first issue to be considered is the the guide system to a smaller wave- actual geometry of the guide switch, as length, i.e. 4 Å. To achieve this goal, shown in fig. 2.8. A silicon wafer, tilted both the guide and the switch have to 6cm 1cm at an angle of 3◦ relative to the beam be redesigned. The simulations con- axis is deflecting the neutrons into the tained several different geometries of R=65-85m neutron guide NL6-b (cross section 120 varying inclination angles of the neu- m=2.5-3.5 10 mm), which is inclined towards tron guide, different radii of curva- × the guide 6 at an angle of 6◦. The sili- ture of the guide and different coatings. Figure 2.9: Improved geometry of the neu- con wafer reaches 2 cm into the neutron Within the bounds of geometrical con- tron guide switch for Nl6/B. 2 Instruments 27 towards the reactor, as well as the in- [1] Nielsen, K., Lefmann, K. Physia strument itself can be moved by 35 cm B, 238. McStas webpage: towards the NL6. The results of the sim- http://neutron.risoe.dk/mcstas. ulations are presented in fig. 3.

Losses for the neutron guide NL 6 1 . 0 1 . 0 ]

. 0 . 8 u

In order to make assumptions for the . a [ losses of ﬂux of the NL6, the neutrons 0 . 8 x 0 . 6 u l

deﬂected by the switch were subtracted F

] . n 0 . 4 u from the ﬂux inside NL6. As only 1 cm o . r t a u [ of the cross section of NL6 is shadowed, 0 . 6 e 0 . 2 x

1 N u the maximum loss can be 6 . Addition- l F 0 . 0

ally, the divergence of the neutron beam n 0 5 1 0 1 5 2 0 2 5 o r after the switch was analyzed. t 0 . 4 Wavelength [Å] u e Results N 0 . 2 As shown in fig. 2.10, a gain factor in neutron flux of 10 can be reached, shift- 0 . 0 ing the cutoff to shorter wavelengths, 0 5 1 0 1 5 2 0 2 5 while losing only about 12 percent of Wavelength [Å] neutron flux inside the NL6 (shown in the inset of fig. 2.10). Furthermore, shorter wavelengths would give direct Figure 2.10: Gain factor for a suggested geometry of the new neutron guide switch (tangen- access to atomic resolution on MIRA, tial deviation, R 80 m, m 2.5 [ΘNi ], cutoff 4 Å. The inset shows the losses in the guide which is not yet possible with 10 Å. = = c NL6 for the upper geometry.

2.7 Horizontal ToF-Neutron Reﬂectometer REFSANS at FRM II Munich/Germany: First Tests and Status

R. Kampmann 1, M. Haese-Seiller 1, V. Kudryashov 1, C. Daniel 2, B. Nickel 3, J. Rädler 3, A. Schreyer 1, E. Sackmann 2 1GKSS Forschungszentrum, Institut für Werkstoffforschung, Geesthacht, Germany 2TU München, Physik Department, E22 3Ludwig-Maximilians-Universität, München, Germany

Introduction REFSANS and its main components In 2005 the horizontal reflectometer REFSANS at FRM II in Mu- The main demands made on REFSANS nich/Germany has successfully been are to provide excellent conditions for put into operation. It is dedicated to i) specular reflectivity, ii) grazing in- the comprehensive analysis of the air cidence (GI-)-SANS and iii) to allow / water interface by means of specular comprehensive investigations on the air and off-specular reflectivity as well as / water interface for biological applica- GISANS measurements [1, 2]. tions [1, 2]. To meet these demands novel and expensive components have been developed for this horizontal ToF- reflectometer.

Figure 2.11: View of neutron guide elements (NGE), master chopper and slave chopper in the chopper chamber. 28 2 Instruments

The instrument starts with the master chopper (MC) in the chopper chamber in which the slave chopper (SC) can be positioned in neutron guide gaps at distances between 5 cm and 2.1 m ≈ ≈ from the MC. Both choppers have double discs to adjust the transmission window between 0° and 120°(Fig. 2.11). They are operated with windows of equal height and the SC opens at the time t0 when the MC closes with the result that at t0 the neutron guide between both choppers is filled with neutrons with wavelengths λ λ [3]. This < 0 expensive design (Fig. 2.12) is needed to meet the demands of specular reflectivity and of GI-SANS comprising high and low λ-resolution. Figure 2.12: Schematic view of the horizontal focusing of up to 13 beams in the detector Neutron guide elements of REFSANS plane. The beam is pre-collimated in the radial collimator (lower channels in the 0.6m as well as their mechanical support in and 1m long NGE-3 and -4). the chopper and in the beam guide chamber are designed for realizing very different beam geometries. Stan- consists of a damping table, a temper- dard reflectivity measurements are perature controlled film balance and a set Status formed with a horizontally slit height- of translational tables (x, y, z) together smeared beam and incidence angles with a three-axis goniometer (χ,φ,Ω). REFSANS has successfully been put into of the primary beam of 3, 12 and A 2D-position sensitive area detec- operation, all components (chopper ± 48 mrad (main beam settings in REF- tor with an active area of 500 mm system, neutron optics, sample envi- × SANS). The beam may be guided to- 500 mm and a position resolution of ronment, 2D-detector, shielding, scat- ≈ wards the sample surface from the air or 2 mm 3 mm has successfully been put tering tube with lifting system and data × through the substrate [1, 2]. into operation. With its high quan- acquisition system) meet or even sur- GISANS geometry demands to colli- tum efficiency for neutrons and its very pass their requirements. Test beams mate the beam horizontally and verti- low one for gammas the detector meets have already been guided to the sam- cally. In this geometry the intensity can all requirements for measuring low re- ple demonstrating that the shielding is strongly be increased by means of fo- flectivity and weak GISANS contribu- sufficiently thick. First measurements cusing 13 partial beams in the detector tions [4]. Together with a new data will be performed at REFSANS in spring plane at a distance of 9 m from the acquisition based on the P7888 card 2006 after repairing of some broken ele- ∼ sample (Fig. 2.12). This focusing is per- from FAST ComTec GmbH the delay- ments of neutron guide NL-2b. formed by means of pre-collimating the line based 2D-detector allows of maxi- 6 beams in radially collimating neutron mum count rates of 10 n/s. ∼ Acknowledgements guide channels in the chopper cham- In the scattering tube the 2D- ber (NGE-3 and -4) and by comb-like detector can be positioned at distances The great contribution of the techni- diaphragms which can be moved into between 2 m and 12 m from the ≈ ≈ cal department of GKSS to constructing the beam in between of neutron opti- sample. The scattering tube can be and manufacturing of REFSANS com- cal bodies (Fig. 2.12 and 2.13) prevent- lifted such that the specularly reflected ponents is gratefully acknowledged. ing mixing of neutrons in different par- beam passes its centre for incidence The development of REFSANS has been tial beams. angles between 0 and 100 mrad ∼ ∼ supported by the German Federal Min- The sample environment is designed (Fig. 2.11). istry of Education, Research and Tech- for experiments at the air / water inter- nology (BMBF) under contracts 03- face as well as at the air / solid and liq- KA5FRM-1 and 03-KAE8X-3. uid / solid interface. In all cases one can make use of a microscope in upright [1] Kampmann, R., Haese-Seiller, M., or inverted position either for prepara- Marmotti, M., Burmester, J., De- tion purposes or as a complementary riglazov, V., Syromiatnikov, V., Oko- measuring option (e.g. fluorescence rokov, A., Frisius, F., Tristl, M., Sack- techniques). The further equipment mann, E. Applied Physics A, 74, 2 Instruments 29

(2002), 249–251.

[2] Kampmann, R., Haese-Seiller, M., Kudryashov, V., Deriglazov, V., Syro- miatnikov, V., Tristl, M., Toperverg, B., Okorokov, A., Schreyer, A., Sack- mann, E. Physica B, 335, (2003), 274–277.

[3] van Well, A. A. Physica B, 180-181, (1992), 959–961.

[4] Kampmann, R., Marmotti, M., Haese-Seiller, M., Kudryashov, V. Nuclear Instruments and Methods A, 529, (2004), 342–347.

Figure 2.13: View of neutron optical bodies (NOB) ready for being mounted into the beam guide chamber (NGE, UC and LC: neutron guide element and its upper (UC) or lower channel (LC); GFC: guide ﬁeld coil; ID: interim diaphragms).

2.8 Structure Powder Diﬀractometer SPODI

M. Hoelzel 1, A. Senyshyn 1, R. Gilles 2, B. Krimmer 2, F.Elf 3, H. Boysen 4, H. Fuess 1 1TU Darmstadt, Material- und Geowissenschaften 2TU München, ZWE FRM II 3Universität Bonn, Mineralogisch-Petrologisches Institut 4Ludwig-Maximilians-Universität, Depart. für Geo- und Umweltwissenschaften, München

Introduction area detector at various distances be- ready in the first reactor cycle, a detec- tween 0.5 and 3 m behind the slit. Be- tor calibration file could be established The Structure Powder Diffractometer side the image plate detector of SPODI which was implemented in a new de- SPODI (fig. 2.14) is designed for high (belonging to the small-angle scatter- tector read-out software. The applica- resolution powder diffraction. The gen- ing apparatus), also the CCD camera tion of the detector calibration file on eral concept of SPODI and descriptions made by Martin Muehlbauer has been the raw data yields the intensity distri- of its components have already been applied for detection. For adjusting bution of neutrons vs. scattering angle published [1, 2, 3, 4, 5]. In this report, the monochromator, all 17 crystals have and detector height. the commissioning of the instrumental to be aligned individually according to The different transmissions of the components as well as measurements three axis (i) translation (ii) tilting for during first proposal cycles in 2005 are vertical focussing and (iii) rotating in summarized. the scatting plane. The observed intensity distributions of the spots displayed Results and Discussion on the detector were used as a measure for the alignment of the monochroma- At the beginning of the second reactor tor crystals. cycle, significant improvements in the For each of the 80 detectors, which adjustment of the Ge(551) monochro- are position sensitive in the vertical di- mator have been achieved. Neutron rection, the correlation between the po- radiography images of the monochro- sition along the detector height and the mator crystals have been taken using detector channel number has to be de- a small circular slit (about 1 mm di- termined individually. Based on long- Figure 2.14: Diffractometer SPODI in the Ex- ameter) at the sample position and an time vanadium scans carried out al- perimental Hall of FRM II 30 2 Instruments detector collimators as well as the dif- During this period, the high- Acknowledgement ferent efficiencies of the detectors re- temperature furnace as well as the cold- The support of this project by the Ger- quire an intensity correction value for head cryostat have been set into opera- man BMBF is gratefully acknowledged. each of the 80 collimator-detector pairs. tion at SPODI. These intensity correction values have A new data analysing software has [1] Gilles, R., Artus, G., Saroun, J., Boy- been derived from various vanadium been developed to integrate the data sen, H., Fuess, H. Physica B, 276- scans at different positionings of the de- along the Debye-Scherrer cones using 278, (2000), 87. tector array. the full detector height while taking into In addition to the intensity correc- account the instrumental corrections. [2] Gilles, R., Saroun, J., Boysen, H., tion, also corrections for the scattering Figure 2.15 illustrates a section of the Fuess, H. Proc. HERCULES X Euro angles have to be determined for each intensity distribution (counts vs. de- Conference, 282. of the 80 collimator-detector pairs. This tector height and scattering angle) for a [3] Gilles, R., Krimmer, B., Saroun, J., is necessary because small mismatches measurement of Al2O3 standard. In fig- Boysen, H., Fuess, H. Mat. Sci. For., between the orientations of the detec- ure 2.16 corresponding diffraction pat- 378-381, (2001), 282. tor collimators towards the sample po- terns are shown, obtained by differ- sition or the detectors cause a deviation ent way: (i) by integration along the [4] Gilles, R., Krimmer, B., Boysen, H., of the effective scattering angle from Debye-Scherrer cones over the full de- Fuess, H. Appl. Phys. A 74 (Suppl.), the nominal scattering angle. To detector height, (ii) by integration along 74, (2002), S148. termine the offset in the scattering an- the vertical direction over the full detec- gle for each collimator-detector pair, se- tor height and (iii) by integration along [5] Hoelzel, M., Gilles, R., Schlapp, M., quences of measurements of standard the vertical direction over 100 mm de- Boysen, H., Fuess, H. Physica B, 350, samples have been carried out. In these tector height. The comparison shows (2004), e671. sequences, the positionings of the de- that high resolution diffraction along tector array have been varied in the fol- with high intensities can be achieved at lowing way: 0°, -2°, .... up to -60°. SPODI. From these data, diffraction patterns for Recently, the small-angle scatter- the individual collimator-detector pairs ing apparatus of the Structure Pow- have been derived. The diffraction pat- der Diffractometer has been set into terns of each detector have been anal- operation. For this purpose, a new ysed by Rietveld refinement to get a Cu(111) monochromator has been in- zero-shift value (= offset in scattering stalled, yielding 4.08 Angstroems at a angle) for each collimator-detector pair. monochromator take-off angle of 155°. Various standard samples have been After adjustment of the monochromatic used to achieve enough statistics for the beam, first test measurements have scattering angle correction for each of been performed using circular slits for the 80 collimator-detector pairs. the collimation and a cooled beryllium From the end of the second reactor filter to cut off lambda-half contribu- cycle and throughout the third reactor tions. cycle, measurements of users have been carried out at SPODI.

Figure 2.15: 2D intensity distribution for Al2O3 standard. 2 Instruments 31

Figure 2.16: Diffraction patterns obtained from the intensity distribution given in ﬁg 2.15, by (i) integration along the Debye-Scherrer cones over the full detector height, (ii) integration along the vertical direction over the full detector height and (iii) integration along the vertical direction over 100 mm.

2.9 STRESS-SPEC Materials Science Diﬀractometer

M. Hofmann 1, U. Garbe 2, G.A. Seidl 1, R. Schneider 3, J. Rebelo-Kornmeier 3, R.C. Wimpory 3 1TU München, ZWE FRM II 2GKSS, Geesthacht 3BENSC, Hahn-Meitner-Institut, Berlin

Introduction tion damage and improve long term sta- ple position was determined with cali- bility of the beam line. The interlock brated monitors for all three monochro- The Materials Science diffractometer system to restrict access to the experi- mators at selected wavelengths and Stress-Spec is located at the thermal mental area while the neutron beam is monochromator to sample distances beam tube SR3 and is optimized for open was finalised and tested to work (see table 2.2 and figure 2.17). The residual stress analysis and texture according to specifications. measurements of new materials and engineering components. Its main Commissioning experiments 3 . 5 x 1 0 7 ]

characteristics and components have s / 2 7 m 3 . 0 x 1 0 c been described elsewhere [1, 2] and /

In the ﬁrst reactor cycle of 2005 we n [

e l here only the most relevant develop- continued with the commissioning of p m 7

a 2 . 5 x 1 0

s ments of 2005 will be reviewed. t the instrument. The ﬁrst experi- a

x u l

F 7 ments included new gold foil mea- 2 . 0 x 1 0 n o r

t Si(400) multiwafer New Hardware surements at the monochromator po- u e optimal focusing condition N sition. The measured thermal flux at 1 . 5 x 1 0 7 1 . 4 1 . 5 1 . 6 1 . 7 1 . 8 1 . 9 2 . 0 9 The new primary collimators with iron the monochromator is approx. 9x10 Wavelength λ [Å] foils were installed and aligned prior to n/cm2/s with a small contribution of the 2nd reactor cycle. They replaced fast neutrons (E > 0.3 eV) determined Figure 2.17: Neutron flux at the sample po- the existing High Performance Thermo- through comparison with gold foils sition for optimised focusing of the Si plastic foil collimators to avoid radia- shielded by Cd. The flux at the sam- monochromator. 32 2 Instruments

Monochromator λ [Å] Reflection Flux [n/cm2/s] diffractometer TEX-2 [5]. Our exper- Si (400) 1.548 (400) 3.2x107 iments, however, show that in future PG (002) 1.47 (004) 9.2x107 due to the high neutron flux at STRESS- Ge (511) 1.516 (511) 1.4x107 SPEC in combination with the area detector it will be possible to decrease the Table 2.2: Measured neutron flux at the sample position of STRESS-SPEC. The data acquisition time for such experi- monochromator-sample distance was LMS = 1.8 m. ments by at least a factor of 3. A software tool to handle and analyse the data 3 focussing options of the Ge and Si gauge volume of 2x2x2 mm was used. of the two dimensional detector was de- monochromators were also directly in- Other experiments included determi- veloped. It also allows to evaluate pole vestigated using a camera setup bor- nation of the strain values in the VA- figures of phase mixtures. rowed form the tomography group. MAS Round Robin Ring and Plug sam- Moreover we used a perfect Si(100) sin- ple [3], where excellent agreement with Outlook gle crystal to check the homogeneity of tabulated and calculated strain values all three monochromators and to deter- was achieved in comparably short mea- In 2006 tests and upgrading of the in- mine their respective resolution func- surement times. It was possible to strument will continue with the aim to tions. This revealed that in case of the achieve experimental uncertainties in speed up the alignment procedure of 4 PG monochromator some of the crys- strain values ² of 1x10− = 100 µ² in this the slits for strain measurement using a tals seem to have moved during the in- Al sample in less than 3 minutes per newly developed automated procedure. stallation procedure which will be rec- strain direction using gauge volumes For texture measurements the time to 3 tified at the first possible opportunity down to 2x2x2 mm . position samples has to be decreased. in 2006. In addition the resolution of This can be done by adapting the in- the Si(400) and the Ge(511) monochro- Texture strument software to take data continu- mator was measured using Al2O3 and ously while rotating the sample around annealed Fe samples at wavelength λ = The first pole figures (figure 2.19) mea- the rotation angle phi. 1.81 Å and 1.516 Å, respectively, show- sured on STRESS-SPEC using standard ing good agreement with expected val- samples show that global texture analy- ues. Values of ∆d/d =∆θS /tanθS down sis [4] is easily feasible. The results and 3 to 2·10− can be achieved on STRESS- also the time required to measure the SPEC. pole figures are at least comparable to measurements at the dedicated texture Residual Strain

Apart from the start of the user program (see Experimental Reports), several experiments using either Round 1 5 0 0 Robin samples or samples extensively measured at other neutron sources were conducted to compare STRESS- 1 0 0 0 SPEC with other neutron strain scan- ners and texture diffractometers. Fig- m ure 2.18 shows a comparison of two of / 5 0 0 m

ferritic steel repair weld round robin µ

samples, which were measured within i a the frame work of the NET European r 0 t S Network (Network on Neutron Tech- A 2 P e t t e n niques Standardization for Structural A 3 M u n i c h Integrity), lead by the Joint Research - 5 0 0 p l a s t i c z o n e Centre - Institute for Energy (JRC-IE) in Petten, NL. The specimens are nomi- nally the same and indeed the strain, - 1 0 0 - 5 0 0 5 0 1 0 0 here in the out-of-plane normal direc- P o s i t i o n i n m m tion, shows excellent agreement. For this measurement, the Si (400) perfectly bent crystal monochromator was selected, with a scattering angle of 2θ Figure 2.18: Comparison of JRC Petten and STRESS-SPEC measurements on repair weld S ≈ 88.3° using the Fe (211) reﬂection. A round robin samples. 2 Instruments 33

[1] Hofmann, M., Seidl, G., Schneider, R. Ann. Report FRM II.

[2] Hofmann, M., Schneider, R., Seidl, G., Garbe, U., Rebelo-Kornmeier, J., Brokmeier, H. Physica B. In press.

[3] Webster, G. In Proceedings ICRS- 6, volume 1, 189–196 (Oxford, Insti- tute of Materials, 2000).

[4] Bunge, H., Wenk, H., Pannetier, J. Texture Microstruct., 5, (1982), 153.

[5] Brokmeier, H.-G., Zink, U., Schnieber, R., Wittassek, B. Mat. Sci. Forum, 273-275, (1998), 277.

Figure 2.19: Comparison of the (110) - pole ﬁgure of the standard Cu sample measured on STRESS-SPEC and TEX-2. Note the better resolved pole ﬁgure due to higher resolution in orientation space of STRESS-SPEC.

2.10 RESI – The Single Crystal Diﬀractometer

B. Pedersen 1, G. Seidl 1, W. Scherer 2, F.Frey 3 1ZWE FRM II, TU München 2Universität Augsburg, Institut für Physik 3Ludwig-Maximilians-Universitat München, Sektion Kristallographie, GeoDepartment,

Introduction tow-circle goniometer with either a tilt- era” for neutrons, we were able to focus ing head or an eulerian craddle was in- the monochromatic beam on an area The year 2005 has been the first year stalled and is currently being commis- of about 20 30 mm, thereby increasing × with real user service on RESI. The in- sioned. the flux density on the sample position strument was further adjusted, the sec- The sample environment available by approx. a factor of 5 (compared to ond monochromator was successfully at RESI was expanded by an Ox- flat monochromator) to approx. 1 106 n 2 1 · commissioned and measurements to ford Cryosystems Cryojet open-flow ni- cm s− for the copper monochromator 6 2 1 characterise the instrument were car- trogen cooler (operating temperature and 4 10 n cm s− for the germanium · ried out. range RT-100K) and an Oxford Diffrac- monochromator. tion Helijet open-flow helium cooler To determine the resolution function New components (operating temperature range 100K - of the instrument, we measured a small 15K). piece of a perfect germanium crystal The main new component installed in with fine slicing (rotation scan,omega 2005 was the Ge-511 monochromator Instrument characterisics scan width 0.1° per image) using the Cu- for a wavelength of 1.5 Å. It uses stacks 422 at 1 Å. From the rocking width of of elastically bend Ge-wafers in the The highly sophisticated monochroma- the reflections, we find the expected be- same focusing system as the Cu-422 tor mechanics, which allow adjustment havior, with a minimum at 90° theta, monochromator. of the individual crystals in three de- where the resolution is 12’. This corre- In the end of 2005 also the second go- grees of freedom have proven to be very sponds to the divergence of the focus- niometer option consisting of a heavy useful. Using the image plate as a “cam- ing neutron guide. For reflections not 34 2 Instruments in the diffraction plane, the resolution slightly decreases due to a combination of the curvature of the Ewald sphere and 0.35 the larger vertical divergence of the incident beam. 0.3

0.25

0.2

rocking width/degrees 0.15

0.1

0.05 3 3.5 4 4.5 5 5.5 6 6.5 Q/AA-1

Figure 2.20: Resolution (rocking width, FWHM) of a perfect Ge single crystal, determined from different reﬂections covering the active detector area.

2.11 Irradiation Facilities

H. Gerstenberg 1, X. Li 1, G. Langenstück 1, M. Oberndorfer 1, A. Richter 1 1ZWE FRM II, TU München

General Table 2.3: Irradiations at the FRM II in 2005 position PRA KBA SDA AS RS total After the successful taking into opera- irradiation No. 52 77 7 3 1 140 tion during the nuclear start-up in 2004, the irradiation service of the FRM II Table 2.4: Neutron ﬂux in some irradiation channels at the FRM II (status 2005) has begun its routine operation starting 2 2 2 from the second reactor cycle in spring channel Φth(1/cm s) Φepi (1/cm s) Φf ast (1/cm s) 2005. In addition to the following main RPA1 3.6 1013 6.7 109 2.0 109 × × × facilities: RPA2 1.5 1013 3.2 109 4.1 108 × × × • the pneumatic rabbit system RPA, RPA3 4.8 1012 7.6 108 7.2 107 × × × • the capsule irradiation facility RPA4 7.3 1013 2.4 1010 5.6 1011 × × × KBA, RPA5 3.9 1013 1.2 1010 5.9 109 × × × • the test rig of the silicon doping RPA6 7.1 1012 1.2 109 1.5 108 × × × facility SDA, KBA1-1 1.3 1014 2.6 1011 3.9 1011 × × × • the transport rabbit system TRP KBA1-2 9.3 1013 9.9 1010 2.0 1011 × × × serving as quick connection be- KBA2-1 1.1 1014 7.5 1010 2.1 1011 × × × tween FRM II and the Institute for KBA2-2 7.7 1013 3.9 1010 1.0 1011 × × × Radiochemistry (RCM), SDA2 1.6 1013 1.0 1011 1.0 1010 × × × two other new irradiation positions AS 1.2 1013 1.0 109 1.5 1010 × × × were set into operation in 2005. These RS 1.8 1014 are: × 2 Instruments 35

• the position for short term irra- For a very special research purpose diations of medium volume sam- in the geoscience (fission track analy- ples (AS) and sis), a series of stone samples were ir- • the high flux irradiation position radiated at a low reactor power of 300 in the central control rod (RS). kW or 900 kW, so that a desired relatively Altogether 140 irradiations were car- low neutron fluency could be reached ried out during the three reactor cycles in a reasonable irradiation time. Ac- in 2005. Table 2.3 shows the irradiation cording to the different neutron fluen- numbers on each system. cies the irradiation times were between Neutron fluxes were measured again 9 and 98 minutes. The reactor ran at this by using the standard flux monitors (Al, low power step normally for only sev- Co, Zr, U, Ni) at the beginning of the eral hours. Altogether 19 low fluency ir- routine operation in the second reac- radiations of this kind were carried out tor cycle. The new flux data are very using the KBA in 2005. The longest irra- comparable to the values which were diation on the KBA at full reactor power measured during the nuclear commis- of 20 MW was 48 hours for a production sioning of the reactor in 2004. The de- of 177Lu. Table 2.5 shows irradiations tailed results of the neutron flux mea- on the KBA at different reactor powers surements are shown in table 2.4. in 2005. Three new operators have joined the irradiation team in 2005. Position for Short Term Irradiations of Medium Pneumatic Rabbit System Volume Samples (AS) (RPA) This new irradiation position was used The pneumatic rabbit system consists for the first time in 2005, so that irradia- of six independent irradiation chan- tions of larger volume samples or those Figure 2.21: Design of the irradiation device nels, which are suited to be loaded by requiring a low neutron fluency can also for the fishing irradiation position. identical polyethylene capsules. Due be performed at nominal reactor power to their different positions within the at 20 MW. The distance from the centre using Au Al (1%) wires and Ni-foil heavy water moderator tank these ir- − of the irradiation position to the reac- (99.8%) as flux monitors. radiation channels offer different ther- tor core is exactly 100 cm. The irradia- mal neutron flux densities, what means tion pipe is parallel to the fuel element. Irradiation position in the flexible irradiation conditions for the In comparison to the KBA, the thermal users. Beside the irradiations of sam- neutron flux here is about one order of central control rod (RS) ples for the neutron activation analy- magnitude lower. In principle the lo- sis, some interesting isotopes for the cal neutron flux at the position of the During the 3rd reactor cycle a neutron 177 nuclear pharmacy such like Lu and sample can easily be lowered further by flux measurement was carried out for 188 Re were also produced using this sys- varying the irradiation position in the the first time in the irradiation position tem. vertical axis in the irradiation pipe be- in the control rod, which was optimized cause of the change of the vertical neu- mainly to provide a high fast neutron Capsule Irradiation Facility tron flux distribution within the mod- flux. It can, however, only be loaded (KBA) erator tank. Figure 2.21 shows the de- and unloaded when the reactor is shut sign of this irradiation device, which is down, i.e. after completion of its 52-day cycle. For the flux measurement, the The capsule irradiation facility is a pool mounted on the handling bridge dur- monitors were loaded in an Al-capsule water driven rabbit device to be used for ing the operation. The position of the mounted at the end of the control rod in long term irradiations. It exhibits two ir- sample container can be defined by the the central channel of the reactor. The radiation channels both of which can be length of the nylon string just like fish- fast neutron flux was determined via the loaded by up to five Al irradiation cap- ing. Neutron flux was measured by reaction 54Fe(n,p)54Mn. The result is sules. shown in Tab. 2.4. The fast neutron flux is less than expected. The reason could reactor power 300 kW 900 kW 20 MW total be the shielding effect of the control rod irradiation No. 5 14 58 77 itself. The typical monitor Ni for the de- irradiation time 21-98 min 9-35 min 100s-20d termination of fast neutron flux is here not suitable due to the burn-up effect in Table 2.5: irradiations on the KBA at different reactor powers in 2005. 36 2 Instruments a very high thermal flux. The determi- test doping rig mounted with the first nation of thermal and epithermal neu- nickel liner. The neutron flux distribu- tron fluxes could not be performed in tion behind the nickel liner was deter- this cycle for technical reasons but will mined again. be done in one of the next reactor cycles Flux monitors were mounted at 24 as soon as possible. positions in a test ingot with a diameter Some possible applications in this of 6 inches and a length of 500 mm. The position are for example the produc- results in figure 2.24 show that the ax- tion of the positron source 58Co or the ial difference between the middle level isotope 188Re for the nuclear medicine. and the both edges of the test ingots is The isotopes will be produced via the less than 5%. The total neutron flux is following reactions: reduced by about 6% as compared to 58Ni(n,p)58Co(T 78d), (fast the use of the pure Al tube due to the 1/2 = neutron reaction) absorption by the nickel coating. Test 186 187 188 W (n,γ) W (n,γ) W (β−)(T silicon ingots with diameters of 4 and 1/2 = 69d)187Re(T 17h) (double neutron 6 inches from two manufactures were 1/2 = capture with thermal neutrons). irradiated in the test doping rig with Test samples will be irradiated in the the Ni-liner to check the doping homo- next reactor cycles in 2006. geneity. According to the feed-backs of the Silicon doping Facility (SDA) clients, the first doping results were extremely positive. Radial resistivity vari- The neutron flux profile within the sili- ation is less than 4% 5%. Axial vari- ∼ con ingots in the doping position were ation is below 3% 4% and seems to ∼ successfully determined by using a sim- be completely hidden in measurement plified test rig of the doping facility noise. The minority carrier lifetime in (SDA-opt) during the system start-up Si is high, around 400-700 microsec- in 2004. Based on the values of the onds, what means a low content of irra- flux measurements, the shape of the diation defects. After adjustment of the Ni-absorber being necessary to reduce Figure 2.23: top) Ni-liner after the coating, calibration factors connecting the irra- the axial inhomogeneity of the neu- bottom) Test doping rig mounted with diation dose to the target resistivity the tron flux within the ingot below 5% was the first nickel liner after an irradiation in irradiations met the conditions of the calculated and optimised by means of the reactor pool. doping specifications very well. The rel- Monte-Carlo calculation. Figure 2.22 ative axial resistivity deviations within a shows the cut view of the optimised 6 inches test ingot is shown in figure shape of the Ni-liner. Two nickel coating samples were analysed by the governmental Material Test Office for Engineering. Above all, the connection between the very thin nickel coating layer and the aluminium carrier was intensively checked through bending test and metallurgical analysis. After the positive examination, a prototype of the nickel absorber pipe was made by the company Leistner in the summer of 2005. Figure 2.23 shows the

Figure 2.22: cut view of the optimised Ni- liner shape.

Figure 2.24: Neutron ﬂux proﬁle behind Ni-liner in a 6" ingot. 2 Instruments 37

2.25. The first doping batch of 6" Si- ingot for a commercial production was already irradiated before the Christmas 2005. Up to 500 kg Si ingots will be irradiated by using the current manual doping system in the next reactor cycle at the beginning of 2006. The concept of the final Si doping facility offering a semi automatic operation was already verified by the TÜV Süd in summer of 2005. The installation of important parts has already begun. The final system will be completely installed in the moderator tank in 2006.

Figure 2.25: Relative axial resistivity deviation within a 6 inches test ingot.

2.12 Status of the Backscattering Spectrometer SPHERES

P.Rottländer 1, J. Wuttke 1, W. Bünten 1, M. Prager 1, D. Richter 1 1Institut für Festkörperforschung, Forschungszentrum Jülich

At first, we wish to announce that in October 2005, Joachim Wuttke joined ing. Additional shielding measures the backscattering spectrometer has our team as instrument responsible. were also taken for the convergent neu- been renamed from RSSM to SPHERES Early in the year, the instrument tron guide (Fig. 2.27). (SPectrometer with High Energy chamber finally has been closed and the For the phase-space transformation RESolution). On a more technical side, polyethylene and cadmium shielding chopper, the good news is that we now in the course of the year 2005, the in- has been attached to the inside walls. have a working device which enables strument has made the transition from Paint gave a brighter look to the instru- us to proceed with commissioning of assembly to the early commissioning ment (Fig. 2.26). the instrument. We had to give up the phase. The gap between the primary neu- idea of a magnetic bearing because of SPHERES is the first instrument of tron guide and the instrument-specific still unsolved resonance problems. The the Jülich Centre for Neutron Science convergent neutron guide has been control circuit of the bearings produces (JCNS) with personnel permanently on filled with the temporary instrument rather well-defined frequencies which site in Garching. In autumn 2004 and beam shutter, and the selector. Both could not be damped away. The con- spring 2005, Peter Rottländer and Wil- components were successfully tested ventional bearing, originally thought of helm Bünten moved to Garching, and before they were surrounded by shield- as backup solution, proved to be more successful: For a short time, it was possible to operate the wheel at full speed (4800 rpm). After a week or so, however, the bearing began to show signs of wear. With replaced bearings, we therefore decided to operate the wheel at 1600 rpm. At this speed, all timing conditions with respect to the neutron times of flight are fulfilled, thus per- mitting normal operation of the instrument. The phase-space transformation effect will be halved thus giving an in- Figure 2.27: The last neutron guide element tensity increase by a factor of two in- Figure 2.26: The instrument chamber. is inserted. stead of four. We still pursue the plan 38 2 Instruments

detectors 13 14 15 16 4000

3000

2000

neutrons / sec 1000

0 0 100 200 300 chopper phase

Figure 2.28: The detectors as mounted in the Figure 2.29: Correlation of chopper position and neutron intensity. instrument chamber. On the left there is the chopper vacuum chamber. Wiring of the instrument and instal- shown an integral neutron intensity of of a better performing chopper wheel. about 1 1010 neutrons per second at the lation of media supply has been partly · No serious problem was encountered done and will be completed in 2006, to- end of the convergent neutron guide, when starting operation of the Doppler gether with the installation of the re- just in front of the chopper. The neu- monochromator. The vibrations of the maining parts of the safety instrumen- trons are spatially homogeneous dis- Doppler drive were minimal even at tation and other components. The de- tributed with a current density of 1.8 9 2 · the maximum velocity amplitude of 4.7 tector banks have been installed, and 10 neutrons per second and cm . First m/s. wired (Fig. 2.28). Data acquisition elec- neutron measurements show opening All components being installed, the tronics also has been installed and it has and closing of the chopper wheel (Fig. instrument was optically aligned to been demonstrated that it takes detec- 2.29). On the other hand, it was not yet about a tenth of a degree with help of a tor counts and angular information of possible to detect the elastic peak of a laser beam and mirrors. the chopper wheel and the position and vanadium sample. The reason is a too velocity of the Doppler monochromator high background of neutrons. Reduc- properly. tion of the background will be the fore- A gold foil activation analysis has most problem to solve in 2006.

2.13 PANDA – The Cold Three-Axis Spectrometer

P.Link 1, A. Schneidewind 2, D. Etzdorf 1, M. Loewenhaupt 2 1ZWE FRM II, TU München 2TU Dresden, Institut für Physik

Introduction on June 22nd. The succeeding exper- In addition, first successful experiments iments were also used to further im- using the 15T cryomagnet were per- The last year led us from commission- prove the instrument. The obtained re- formed. ing of the cold three-axes spectrometer sults showed that PANDA has the ex- PANDA to first user experiments. Fol- pected performance at least for the con- lowing the start-up of the reactor in May figurations tested so far. 2005 we completed the magnetic field During cycles 3 and 4 (second half of shielding and did a first spectrometer the year), we run a total number of 12 alignment. We were able to measure user experiments delivering 75 days of the first inelastic signal from a sample beamtime (51 days for external users). 2 Instruments 39

ment IN14 at ILL using a comparable 120 instrument set-up. This has been con- ﬁrmed with Gold foil activation mea- 100 surements, which yielded a maximum monochromatic ﬂux of about 5.5 107 80 2 × n/cm s at the sample position for ki = eV)

µ 1 2.662Å− with a 6cm PG ﬁlter and hav- 60 ing the monochromator in the vertically

FWHM ( focused mode. Concerning the reso- 40 lution datasets obtained from a Vana-

20 dium standard also fulfil the expecta- tions (see fig. 2.30). Besides the config-

0 uration for the small wave vector / high 1 1,1 1,2 1,3 1,4 1,5 1,6 energy resolution mode we also worked -1 kf (Å ) at incident wave vectors ranging from 2 Å-1 to 3.5 Å-1 to realize medium energy transfers / medium resolution. As a test phonons of a Pb single crystal have been measured in this configuration as Figure 2.30: Energy resolution obtained from Vanadium scans with flat analyser and shown in figure 2.31. monochromator Outlook 1 During the year 2006 the PANDA team

-1 will complete the characterisation of 0,8 kf = 2.662A PG Filter the instrument with PG monochroma- TA Q=(ξ,2,2) T=300K tor and analyzer and start the instal- 0,6 sample size 0.8cm³ lation of the Heusler monochromator 400cts/sec. typical 350 and analyser for experiments with po-

(THz) 300 ν larised neutrons and polarisation anal- 0,4 250 Q=(0.15,2,2) 200 ysis. Responding to the high demand 150 100 of the community for PANDA we want 0,2 50 cts / monitor *1e3 monitor / cts to keep the high level of available beam 0 0 0,2 0,4 0,6 0,8 time for external users under the given ν (THz) conditions. 0 0 0,1 0,2 0,3 0,4 0,5 0,6 ξ (r.l.u.)

Figure 2.31: test measurement of Pb acoustic phonons.

field magnet as dedicated sample en- Commissioning and first vironment. Before inserting the PG002 results of the instrument monochromator we did a Au foil measurement of the white beam flux at the characterisation monochromator position. This resulted in a value of 3.5(5)·109 n/cm2s almost PANDA had been designed to match exactly matching the predictions of the two main aspects of cold TAS perfor- MC simulations with MCNP and Mc- mance, a high flux at the sample po- Stas. From user experiments (as an Figure 2.32: Example of inelastic data: spin- sition and a most flexible set-up con- example of data obtained with PANDA wave dispersion of a S=1/2 2D square lat- cerning resolution and choice of wave see figure 2.32) we concluded the per- vector. Further emphasis has been tice Heisenberg antiferromagnet (cour- formance of PANDA being about the tesy of M. Kenzelmann and H. Ronnow). laid on the usage of the 15T vertical same as the up to now leading instru- 40 2 Instruments

2.14 MAFF – Munich Accelerator for Fission Fragments

D. Habs 1,3, R. Krücken 2,3, R. Stoepler 3, M. Groß 1,3, W. Assmann 1,3, T. Faestermann 2,3, R. Großmann 1,3, Ph. Jüttner 4, H.-J. Maier 1,3, P.Maier-Komor 2,3, F.Nebel 2,3, M. Schumann 1,3, J. Szerypo 1,3, P.G. Thirolf 1,3, F.-L.Tralmer 4, E. Zech 2,3 1Dept. f. Physik der LMU München 2Physik-Department E12, TU München 3Maier-Leibnitz-Laboratorium f. Kern- u. Teilchenphysik 4ZWE FRM II, TU München

MAFF, the Munich Accelerator for sign, especially when it comes to the • Failure simulations Fission Fragments, is a reactor based trolley bodies and the traction system. Still in progress are tests concerning: RIB facility, planned to be set up at the This system is used regularly at the • Long term tests FRM II by the group for experimental source side and leaves little to no tol- • Electrical contacting nuclear physics (Prof. Habs) of the LMU erance to failure. Therefore the trac- • Failure simulations and the TUM physics department E12 tion system of the trolley and every- The performed tests have shown the (Prof. Krücken). thing related, like the adjustment sys- feasibility of the concept and have been MAFF aims at providing very intense tem for the trolley and the lock for se- valuable to gain deeper insight on pos- beams of neutron-rich isotopes to a curing the trolley in its final position as sible failures and their respective prob- broad range of nuclear physics exper- well as the supporting structure have abilities. Design enhancements based iments as well as applied physics and been designed and constructed over the on the gained operating experience nuclear medicine [1, 2, 3]. In a first past years and are currently tested. It could be made. Upcoming test will be step (MAFF First Beam) the beam will is planned to use the majority of the devoted to long term tests, investigation have an energy of 30 keV (low-energy constructed parts, in case of successful of the electrical contacting concept and 3 beam), and only 10− of the final beam tests, later on for the MAFF project. To enhanced failure simulations. intensity will be available in order to avoid concerns from the TÜV, intricate start the experiment with a minimum material tracing has been performed for Neutron-flux measurement of investment costs. In a second step all crucial components. the full beam intensity corresponding Among the tests carried out are: A neutron-flux measurement in the 14 to 10 fissions/s will be made available • Mechanical integrity neutron guide tunnel was carried out (MAFF-I) before also the high-energy • Traction system performance during the 4th power-cycle, to gain bet- beamline will be set up, where the • Adjustment possibilities ter knowledge about the neutron dis- ions are post-accelerated to energies • Comparison of different traction tribution in the neutron guide tunnel adjustable in the range 3.7–5.9 MeV/u. concepts during reactor operation. This informa- • Comparison of different lubri- tion is important for MAFF to estimate Project management and cants system engineering

Since June 2005 our team is strength- ened by a project manager with experience from industry. In the second half of 2005 we solicited quotations for the basic engineering of the main components of MAFF . Several companies submitted a quote and the orders were placed in October. The results shall be delivered until March 2006, provid- 3 1 ing the basis of the speciﬁcations re- 7 5 2 quired for the authorisation procedure 11 9 4 that will be opened subsequently. 6 10 8 Trolley Tests

Lens and source trolley are the heart of the MAFF I physics program enabling the production and extraction of rare Figure 2.33: Positions of Co and Au samples for determination of the neutron-flux in the isotopes. Both trolleys are similar in de- neutron guide tunnel. 2 Instruments 41 the amount of neutron induced γ- After the end of the reactor cycle the neutron guide tunnel especially close activation to metal components. The samples have been removed and the to the reactor wall must be objected. decision if and where stainless steel neutron-flux at the sample positions A substantiated calculation of the neu- or aluminium can respectively must be has been determined by measuring the tron induced γ-activity of MAFF com- used will be strongly influenced by the γ-activity of the samples. ponents can now be performed. outcome of this measurement. Preliminary results indicate an av- The integral neutron-flux over the erage neutron-flux of 1 105 to 5 [1] Habs, D., et al. MAFF – Physics Case 6 2 1 · · whole reactor cycle was determined by 10 n cm− s− and hint towards a and Technical Description. placing 59Co (0,1 g to 1 g) samples on maximum neutron-flux of 2 105 to 5 7 2 1 · · [2] Habs, D., et al. NIM B, 204, (2003), top of neutron guide 1 (NL1) and on the 10 n cm− s− . floor in alignment with the beam tube 6 The neutron-flux is highest next to 739–745. (SR6) as shown in Fig. 2.33. the reactor shielding and drops towards [3] Faestermann, T., et al. Nucl. Phys. A, In addition to the Co samples gold the end of the neutron guide tunnel, by 746, (2004), 22c–26c. foils ( 200 µg) have been placed in the one to two orders of magnitude. ≈ same locations, to determine the flux From the results can be seen that the during the last days of the power cycle. extensive use of stainless steel in the

2.15 N-REX+ – The Materials Science Neutron/X-Ray Reﬂectometer

A. Rühm 1, U. Wildgruber 1, M. M. Nülle 1, F.Maye 1, J. Franke 1, J. Major 1, H. Dosch 1 1Max-Planck-Institut für Metallforschung, Stuttgart

During the year 2005 the commis- on silicon substrate. These measure- for the investigation of dewetting pro- sioning of the neutron reflectometer ments are part of a project aimed at cesses in polymer films. Understand- with add-on X-ray option, N-REX+, proving the suitability and new poten- ing and controlling the dewetting pro- (Figure 2.34) has been started and is ex- tial of the SERGIS (spin-echo resolved cess of polymer films is important as pected to be finished in the second half grazing incidence scattering) technique the polymer-island morphology gener- of 2006. The instrument has reached a state in which the basic operation mode of unpolarized neutron reflectivity measurement on solid samples is 10 1 available for first in-house test experi- 100 Å film ments. N-REX+ was officially inaugu- 0 rated on November 24th, 2005. 10 1 h toluene exposure Figure 2.35 shows a first set of neutron reflectivity data obtained on a 10 -1 500 Å dPS (deuterated polystyrene) film 10 -2

10 -3

Reflectivity [a.u.] Reflectivity 10 -4

10 -5 0.0° 0.5° 1.0° 1.5° 2.0° 2.5° 3.0° α i

Figure 2.34: The neutron/X-ray reflectome- Figure 2.35: Reflectivity curve obtained from 2D detector images on a dPS film on Si sub- 5 ter N-REX+ in its present state. The strate. The accessible dynamic range for reflectivity measurements is currently 10− . open structure between monochromator, This must be improved by one order of magnitude in 2006. A major improvement should sample and detector allows adoption of be achievable by an enhancement of the current neutron flux of 2 104 neutrons/cm2s to · extended beam conditioning equipment, the expected optimum value of 3 106 neutrons/cm2s (according to the measured white · e.g. a SERGIS set-up. beam characteristics and MCSTAS simulations). 42 2 Instruments ated in the dewetting process can be ex- ploited to grow nanostructures on sur- Table 2.6: The basic N-REX+ instrument parameters (for liquid/horizontal sample mode, faces. In the present case, the dewet- HOPG monochromator, 20 MW reactor power) ting process is most easily initiated by wavelength range 2-6 Å exposing the samples to toluene atmo- max. incidence angle 5◦ sphere [1, 2]. The sample chamber used max. exit angle 20◦ for this purpose at N-REX+ is shown in 1 max. out-of-plane q (specular) 0.55 Å− Figure 2.36. It allows to expose the sam- 1 max. q (within the reflection plane) 1.35 Å− ples to the vapor of the polymer solvent 1 max. in-plane q (grazing angle >5.4 Å− in a computer controlled way, thus en- diffraction) abling in-situ reflectivity measurements total flux at monochromator 4 109 neutrons/cm2s during the dewetting process. The · maximum flux at monochromator 4 108 neutrons/cm2sÅ (at 4 Å) chamber exhibits two aluminum and · monochromatic flux for reflectome- 3 106 neutrons/cm2s (estimated) two kapton windows, which will later · try at sample also enable simultaneous neutron/X- ray experiments. The first two neutron reflectivity curves displayed in Figure polymer film as a consequence of sol- tasks to be completed are: complete in- 2.35 show the effect of swelling of the vent incorporation into the film. After stallation of all 33 HOPG (highly ori- exposure to toluene atmosphere for 1 ented pyrolithic graphite) monochro- hour, the first minimum in the reflectiv- mator crystals (at present only 7 are in- ity curve has shifted to smaller grazing stalled), flux and background optimiza- incidence angles αi, indicating an in- tion, improvement of the control soft- crease of the film thickness. These mea- ware, improvement of the preliminary surements shall be amended by GISANS radiation shielding, installation of radi- (grazing incidence small angle neutron ation safety electronics, completion of scattering) and especially SERGIS ex- the motor, encoder, and detector instal- periments at a later stage of the com- lations. For quantitative instrument pa- missioning of N-REX+ to unravel the rameters of the N-REX+ reflectometer lateral morphology of dewetted poly- see the Table 2.6 mer films. Figure 2.36: Vacuum/vapor sample chamber Figure 2.37 shows the compact X-ray [1] Müller-Buschbaum, P., Gutmann, for simultaneous neutron/X-ray charac- source unit of the add-on X-ray reflec- J. S., Stamm, M., Cubitt, R., Cunis, terization. The chamber comprises two tometer at N-REX+. This unit integrates S., von Krosigk, G., Gehrke, R., Petry, aluminum and two kapton windows at a a Cu-Kα sealed tube X-ray source, a W. Physica B, 283, (2000), 53–59. 90◦ angle. focussing mirror optics, a germanium (220) channel-cut monochromator, a [2] Müller-Buschbaum, P., Bauer, E., slit unit to define the beam size, as Wunnicke, O., Stamm, M. J. Phys.: well as two vertical translation stages Condens. Matter, 17, (2005), S363– to adjust the incidence angle of the X- S386. ray beam onto the sample surface. A [3] Felcher, G. P., te Velthuis, S. G. E., very similar detector unit, which can Major, J., Dosch, H., Anderson, C., adopt a scintillation counter or a CCD Habicht, K., Keller, T. In Ander- camera, is already in the manufacturing son, I. S., Guérard, B., editors, Ad- process. The X-ray reflectometer will vances in Neutron Scattering In- thus be completed and available for ex- strumentation, Proceedings of SPIE, periments in summer 2006. Polariza- 164–174 (SPIE Optical Engineering tion equipment will become available at Press, Bellingham, WA, USA, 2002). about the same time. This includes two polarizing mirrors, a bender in com- [4] Major, J., Dosch, H., Felcher, G. P., bination with a collimator, and a 3He Habicht, K., Keller, T., te Velthuis, S. cell. In combination with spin-echo set- G. E., Vorobiev, A., Wahl, M. Physica up from the EVA reflectometer (Insti- B, 336, (2003), 8–15. tut Laue Langevin, Grenoble), SERGIS experiments (spin-echo resolved graz- Figure 2.37: The compact-source unit of the ing incidence scattering) will then be add-on X-ray reflectometer (EFG, Berlin). possible at N-REX+ [3, 4]. Current This machine can deliver Cu-Kα radiation of variable divergence. The beam is rotated around the sample by means of two vertical translation stages. There- fore neutron and X-ray characterization can be performed simultaneously without mutual interference. 2 Instruments 43

2.16 PUMA – the thermal triple axis spectrometer

K. Hradil 2, H. Schneider 2, J. Neuhaus 1, G. Eckold 2 1ZWE FRM-II, TU München 2Inst. f. Physikal. Chemie, Universität Göttingen

During the year 2005 the three axes strated the efficiency of this design. The camera pictures with the McStas sim- sprectrometer PUMA started its com- positioning of the beamstop as an ad- ulations which are in very good agree- missioning phase and performed first ditional axis is implemented within the ment. ’friendly user’ experiments. Problems control software in order to assure the First and preliminary flux measure- due to the inefficient primary shield- radiation protection requirements. ments have been performed at sam- ing could be solved by mounting addi- For the first experiments the PG(002) ple position with horizontal and verti- tional shielding elements made from PE monochromator bending device build cal entrance slits of 10 mm and 130 mm, in combination with B4C in vulcanized in cooperation with the FRM II and op- respectively, using a calibrated moni- rubber. The flux of unwanted epither- timised in the workshop of the Univer- tor along with gold foils. Both methods 8 2 1 mal neutrons outside the monochro- sity Göttingen was available. Figure 2.39 yielded a flux of 2.4 *10 n cm− s− for mator drum could be reduced by a fac- shows the device within the exchange 1.8 Å neutrons in good agreement with tor of 250. The first measurements unit in the monochromator drum. The McStas simulations. for characterisation revealed that the mechanical tests yielded an excellent During the adjustment of the instru- performance of the instrument corre- accuracy and reproducibility of the hor- ment with neutrons a vanadium sam- sponds (extremely) well to the predic- izontal and vertical bending. ple was used to measure the energy res- tions from simulations. For optical tests a conventional diver- olution for different incident energies Figure 2.38 shows the instrument in gent halogen lamp was used. Reflection for the PG(002) monochromator (figure its current status with the mounted of light from the PG(002) crystals reveal 2.41). As expected the results for dE/E additional shielding arround the an excellent performance of both ver- are in the range between 2 to 4%. monochromator drum. The shielding tical and the horizontal focussing. Af- After only 1 1/2 cycle, all abso- consists of 26 individual elements that ter mounting the device within the pri- lute encoders within the monochro- remove efficiently radiation leaks as mary shielding and the adjustment with mator shielding were not working any well as unwanted background. Whereas neutrons, the beam profils were mea- longer due to radiation damage. Con- the range of the monochromator is not sured with a CCD camera. Figure 2.40 sequently, a new concept for the read- affected by the additional shielding, represents the comparison of the CCD out of the positions for the respective the sample scattering angle range is now limited to a maximum of 120 degrees. Moreover, additional shielding elements around the sample as well as at the entrance of the analyser system helped a lot to further reduce the background counting rate. An efficient shielding of the experimental area made from a composite structure (iron, PE, B4C in vulcanized rubber, lead) allows for a sufficient radioprotection of the surrounding acessible area. Due to the high flux in the focussing mode of the instrument, the beamstop for the direct beam could not be mounted directly at the sample table. Rather it was placed on a separate unit on air pads that can be automatically positioned according to any particular combination of monochromator and scattering angles. The beamstop is made as a sandwich of 3mm LiF, 30cm boron enriched PE and 10 cm lead. Additionally, 5 cm thick lead plates surround the PE Figure 2.38: View on the triple axes spectrometer PUMA within the experimental hall of part. Test measurements in different in- FRM-II. strument configurations have demon- 44 2 Instruments axes was required and implemented ments not only from new external users within short time in order to continue proofed the excellent performance of the user operation. The subsequent re- the instrument. Detailed information adjustment and tests of the encoding on results of these experiments can be sytems revealed that the required po- found within the experimental reports. sitioning accuracy of 0.005° was main- tained. Despite all the problems during com- misioning phase of the instrument, not only first characterisation measurements and inelastic test experiments Figure 2.40: Comparision of the beam pro- on phonons from a quartz crystal (not file for the PG(002) monochromator for shown here), but also approximately 40 the horizontal/vertical focussed device days of cycle 2 and 3 have been assigned (left) and the collimator configuration to external friendly users. The scientific (right) with McStas simulations. results obtained and the amount of pro- Figure 2.39: PG(002) monochromator within posed scientifically high quality experi- the change unit in the primary shielding.

Figure 2.41: Energy resolution curve of the PG(002) monochromator for the double focussing mode.

2.17 NECTAR - Neutron Computer Radiography and Tomography facility

T. Bücherl 1, M. Mühlbauer 1, Ch. Lierse von Gostomski 1 1Institut für Radiochemie, TU München

General neutrons for radiography and tomogra- Activities phy measurements. The available beam The NECTAR facility is set up at the con- time has to be shared with the facil- Begin of 2005, the complete hardware verter facility in the experimental hall ity for medical applications (MEDAPP), of NECTAR, i.e. the manipulator for (beam tube SR 10). It is using ﬁssion also located at SR 10. the samples, the manipulator for the 2 Instruments 45

Applications

For industrial purposes studies on the applicability of neutron radiography on large gear boxes (side lengths up to 40 cm), motors (diameter larger then 12 cm) and on large turbine blades (ca. 20 cm in height and up to 12 cm in depth) have been performed, especially the latter very successfully. The NECTAR facility was also used by Figure 2.42: Photograph of the NECTAR fa- an external client for the testing of elec- cility. Left: Manipulator for the samples. tronic components on fast neutron sen- Right: Detector system based on a liquid sitivity. nitrogen cooled CCD camera.

Figure 2.43: Normalized radiograph of a step Outlook detector systems and the new con- wedge made of lead, iron, aluminium and structed beam stop, was set up again af- polyethylene (from left to right). The With the availability of fission neutrons ter the installation of the overhead trav- depth of the each step increases by 5 mm, the measurements of the system pa- elling crane, including a precise adjust- i.e. the maximum depth is 50 mm. rameters will continue with higher pre- ment of all components. The control cision as well as the optimization of cabin housing detector electronics and the radiography mode, specially the im- working place was positioned on the investigated in more detail in the next provement of detection efficiency. The back wall of the bunker, the control unit reactor periods. main focus in 2006 will be the installa- for the manipulator system close to it. The fission neutron flux available at tion of the tomography mode for rou- Due to problems in the control elec- the measuring position was estimated tine application. tronics of the shutters and filters of by taking into account the modified the converter facility, no measurement permanent filter and the collimator 6 2 1 time was available for several months with L/D =118 to about 4.9 10 cm− s− . · in 2005. But some measurements for the determination of system parame- Radiography Mode ters, for the optimization of the radiography mode and of first users could be The actual challenge in optimization performed. the radiography (and tomography) At the end of the year the set up of the mode is the improvement of the detec- second detector system based on 4 sin- tion efficiency of the fission neutrons. gle beam detectors was started. It will Due to the low cross sections of scintil- be mainly used for tomography. lator and converter materials and their limited applicable thicknesses only a System Parameters small fraction of the incoming fission neutrons contribute to the signal in One important parameter of a radiog- the detector. Furthermore, when using raphy system is the L/D value, where L scintillators moderated neutrons (e.g. is the distance between collimator and when passing the sample) may super- Figure 2.44: Intensity plot of the individual sample position and D the diameter of impose this signal resulting in distorted materials of the step wedge (small pho- the circular collimator outlet window. and often useless radiographs. tography) derived from the normalized It is a measure of the available resolu- First investigations of different scin- radiograph. tion. It was determined experimentally tillators and converters for the opti- by using an iron cylinder (diameter 5 mized conversion of incoming fission cm, height 2.56 cm) fixed at the sample neutrons in visible light while being manipulator and varying the distance highly insensitive for neutrons with between the cylinder and the detector lower energies have been performed. system. A first estimation resulted in Actually a pp-converter gives the best L/D 233 16. The relatively large results, but further improvement might = ± standard deviation may be caused by be possible. the contribution of scattered neutrons in the cylindrical object. This has to be 46 2 Instruments

Figure 2.45: Left: Photograph of a motor. Right: Normalized ﬁssion neutron radiograph of the motor.

2.18 The new small-angle scattering instrument SANS-1 at the FRM II

R. Gilles 1, B. Krimmer 1, A. Ostermann 1, C. Schanzer 2, O. Nette 3, A. Vogel 3, R. Kampmann 3, A. Schreyer 3, W. Petry 1 1ZWE FRM II, TU München 2Paul Scherrer Institut, Villigen, Switzerland 3GKSS Forschungszentrum, Geesthacht

The new small-angle scattering in- plications - maximum sample to detec- for S-shaped neutron guides if similar strument SANS-1, a project of the Tech- tor distance 20 m, - detector area 1 x 1 flux at the sample position is compared nische Universität München and the m2, lateral movement 0.5 m - Q-range: (see fig. 2.47). The latter neutron guide 2 1 1 GKSS in Geesthacht is currently build Qmin 10− nm− , Qmax 16 nm− provides a sharp wavelength cut off at < at the new Foschungs-Neutronenquelle A comparison of different neutron λ 3 Å for a collimation part with neu- < Heinz Maier-Leibnitz (FRM II)[1, 2, 3]. guide systems (single curved and S- tron guide and apertures as well. Single This contribution describes the concept shaped types) shows a few advantages curved neutron guides forward these and the technical features of the instrument. The first task was to implement the instrument in the park of other instruments in the neutron guide hall of FRM II. Monte Carlo simulations with the program McStas were performed to optimize the neutron guide system and the positioning of the instrument according the available space. The design of the instrument allows it to include additional components in the future in a flexible way. Parameters of the new SANS-1 instrument (Fig. 2.46): - cross section of neutron guide 50 x 50 mm2 - vertically S-shaped neutron guide, R = 480 m (second part of S- shaped neutron guide is curved in horizontal with R = 2100 m) - supermirrors with m = 1.2 - 2.0 - collimation length of 20 m: a) neutron guide, b) slit system, c) polarisation option, d) focusing elements e) chopper option for future ap- Figure 2.46: Schematic drawing of the new SANS-1 instrument 2 Instruments 47 useless neutrons below 3 Å to the se- The set up of the S-shaped neutron lector position which results in a higher guide (Fig. 2.50) was the main task of background. Fig. 2.48 and fig. 2.49 this year and was done by the neutron show the intensity and divergence dis- optic group (Prof. G. Borchert, C. Bre- tribution for the two types of neutron unig, E. Kahle) and H. Tuerck as well as guides. The difference in the intensity by the company GHS. At the same time distribution is small with slightly higher the construction and building of the se- intensity (5%) at the sample position for lector tower and the instrument shutter the S-shaped neutron guide. The asym- was done by the construction group of metry in the intensity distribution after F. Tralmer and the workshop of the TU the collimation section (Fig. 2.48) due Munich. to the curvature is very similar for both Figure 2.50: End position of the S-shaped guide systems. A more pronounced dif- neutron guide NL 4a for the SANS-1 in- ference is visible in the divergence pro- strument. files. The standard single curved guide shows a clear asymmetry between the Recently a co-operation with GKSS horizontal and vertical divergence in (the group of Prof. A. Schreyer) has comparison to the S-shaped neutron started. GKSS takes over the construc- guide. tion and building of the collimation sys- Another advantageous consequence tem. The collimation system consists of of the vertical S-shaped neutron guide four tracks for optic elements and a po- is an increase of the height of the neu- lariser at the beginning. A chopper sys- tron beam centre to 1.5 m, which allows tem is foreseen in the collimation part a higher degree of freedom for differ- Figure 2.48: Intensity distribution at the end as an option for future. ent sample environments. Last but not of the collimation system with guide (19 least only the vertical S-shaped guide m) of a horizontal single curved neu- [1] Gilles, R., Schanzer, C., Petry, W., allows an adequate positioning of the tron guide (open circles) and of a vertical Eckold, G. In Proceedings of Ger- instrument in the neutron guide hall. S-shaped neutron guide (closed circles). man Neutron Scattering Conference Left: Sum along the horizontal direction (Dresden, 2004). for the S-shaped guide and the vertical direction for the single curved guide. Right: [2] Gilles, R., Schanzer, C., Petry, Sum along the vertical direction for the W., Eckold, G. In Proceedings of S-shaped guide and along the horizontal CANSAS-IV Meeting (RAL: Chilton, direction for the single curved guide. A Didcot, Oxfordshire, England, wavelength of 4.7 Å was used in the simu- 2004). lation. [3] Gilles, R., Ostermann, A., Schanzer, C., Krimmer, B., Petry, W. Physica B. In print.

Figure 2.49: Divergence distribution at the end of the collimation system with guide 19 m of a horizontal single curved neu- Figure 2.47: Comparison of intensity ver- tron guide (left) and of a vertical S-shaped sus wavelength between a single curved neutron guide (right) for the horizontal (open circles) and an S-shaped (closed divergence (triangles, dashed line) and circles) neutron guide. Top: The collima- the vertical divergence (circles, solid line). tion part (19m) contents a neutron guide A wavelength of 4.7 Å was used in the sim- of Ni58. Bottom: The collimation part ulation. contents 50 x 50 mm2 apertures. 48 2 Instruments

2.19 Multiple radiation measurements at the radiography facility ANTARES

Burkhard Schillinger 1,2, Elbio Calzada 1,2, Martin Mühlbauer 2, Michael Schulz 2 1ZWE FRM II, TU München 2TU München, Physics Department,E21 3Institut Laue-Langevin, Grenoble, France

Although the neutron radiography and tomography facility ANTARES is designed for measurements with thermal and cold neutrons, the use of additional ﬁlters and an X-ray tube allows for measurements with epithermal neutrons, with 300 kV X-rays and with gamma.

Thermal and cold neutrons

ANTARES (Fig. 2.51) is situated at the Figure 2.53: Thermal/cold neutron radiogra- beam line SR4b, facing the cold source phy of a pressure reducer. of the reactor. A vertical secondary Figure 2.55: The selector wheel with the shutter contains two steel collimators of Cadmium filter. 1m length and roughly 20 mm and 40 mm diameter to optimize between high resolution and high flux (Fig. 2.52). Fig. 2.53 shows a neutron radiography of a pressure reducer. Thermal and cold neutrons are ideally suited to penetrate thick layers of Aluminium and to show organic compounds like sealants, O-rings and adhesives. Fig. 2.54 shows a neutron radiography of an oil-filled pump. The oil layer is practically im- Figure 2.54: Thermal/cold neutron radiography of an oil-filled pump. Figure 2.56: Epithermal neutron radiography of the pump. penetrable for cold neutrons, and also the steel parts show a lot of attenuation. a factor of ten. In Fig. 2.55, the steel Figure 2.51: Vertical cross section of the On the top left, a plastic plug is visible parts show better penetration, and ANTARES facility. in a valve. some outlines are visible through the oil. Epithermal neutrons Gamma radiation After the secondary shutter, a filter wheel with different pinhole di- Between the secondary shutter and the aphragms is installed. One of the filter wheel, a pneumatic fast shut- positions is equipped with a 2mm ter (Fig. 2.57) is installed to shut off Cadmium sheet (Fig. 2.54), which the thermal and cold flux during short will absorb all neutrons with ener- breaks such as repositioning or rotat- gies below 0.4 eV. The scintillation ing of the sample or data readout times screen employed in the detection sys- in order to keep the sample activa- tem is sufficiently sensitive for ep- tion as low as possible. It consists of Figure 2.52: Vertical cross section of sec- ithermal neutrons as well, although a container filled with boron carbide. ondary shutter. the measuring time increases by The shutter will absorb all cold and 2 Instruments 49 thermal and a wide range of epither- X-ray tube mal neutrons, but can be easily pen- etrated by fast neutrons and gamma For standard measurements, a remov- radiation originating from the reactor able 320kV X-ray tube (fig. 2.59 has core and from the neutron absorption been mounted on a sliding system be- in the beam tube nozzle. The prompt tween the filter wheel and the flight gamma radiation from neutron capture tube. in Aluminium has a very high energy With the X-ray scintillation screen up to 8 MeV. If the neutron scintillation mentioned above, high-quality X-ray screen is replaced by a standard med- images can be obtained in about 30 sec- ical X-ray scintillation screen made of onds measuring time. Fig. 2.60 shows a Gadolinium oxisulfide, we can obtain ski boot as an example. The positioning gamma radiographies with a very high of the tube in the beam path in 12m dis- penetration also for steel (Fig. 2.58). tance wastes a lot of X-ray intensity, but Figure 2.61: Photo of a computer board. The efficiency of the screen drops to- assures exactly the same quasi-parallel wards high energies, due to the expo- beam geometry as for neutrons. Images sure time is in the order of minutes. recorded that way can be superposed Fig. 2.58 shows high penetration even to neutron images without the need for for the steel body of the pump, the plas- any adjustment or registering. Fig. 2.61, tic body in the valve is faintly outlined, 2.62 and 2.63 show a photo, a neutron probably due to some remaining sensi- and X-ray radiography of a printed cir- tivity for fast neutrons, the oil filling is cuit board, Fig. 2.64 shows the X-ray im- virtually invisible. Some fingerprints on age subtracted from the neutron image. the scintillation screen were removed only after the measurement.

Figure 2.62: X-ray radiography.

Figure 2.59: The X-ray tube in the beam path.

Figure 2.57: The Boron Carbide fast shutter. Figure 2.63: Neutron radiography.

Figure 2.60: X-ray radiography of a ski boot. Figure 2.58: Gamma radiography of the pump. 50 2 Instruments

Conclusion

ANTARES offers a multitude of possibilities for measurement with different radiations, which can be selected according to the problem at hand. While the instrument is of course optimized for thermal and cold neutrons, a lot of additional information can be obtained with different radiations. All images are perfectly congruent and can be superposed without further adjustment.

Figure 2.64: The X-ray image subtracted from the neutron image.

2.20 The Fission Neutron Source (Converter facility)

F.M. Wagner 1, A. Kastenmüller 1, B. Loeper 1, S. Kampfer 1, W.Waschkowski 1 1ZWE FRM-II, TU München

During the whole year 2005, the irra- water phantom, a data set for the ir- diation facility at beam tube SR10 was radiation of patients has been worked optimized with respect to the modelling out. Complementary measurements of of the beam and the functional safety of some special features of the treatment shutters, collimator, and other compo- beam, i.e., the spectral flux distribution, nents. The beam filters and the 40-leaf have been prepared. collimator have been completed, docu- Figure 2.65 shows the medical irradi- mented as parts of a medical product, ation room with the collimator exit and and successfully tested. the treatment couch. In comparison The facility was examined according with the former therapy facility at FRM, to the Medical Devices Act, MPG, with the advantages of the new facility are respect to the functional, mechanical, • a large cross section of the beam and electrical safety and other criteria up to 20x30 cm, with external experts in order to furnish • a higher dose rate, it with the CE safety mark. The expected • easier patient positioning due to successful completion of this procedure the height of the beam and the in early 2006 will allow to apply formally larger irradiation room for a license for medical use in radiation • a second irradiation room for the cancer therapy. radiography and tomography fa- The development of a new filter com- cilities (see NECTAR). Figure 2.65: The medical irradiation room bination for therapy, and the evalua- External clients have used the beam with the collimator exit and the treatment tion of the beam quality by extensive for the systematic testing of the radi- couch. MCNP calculations with the as-built ation sensitivity of electronic compo- data have been accomplished. By use nents. of dose measurements in an automatic 2 Instruments 51

2.21 First Spin Echo Signal at RESEDA

W. Häußler 1, D. Streibl 1, R. Schwikowski 1, H. Wagensonner 1, P.Böni 2 1ZWE FRM-II, TU München 2TU-München Physik Department E21

Despite meager manpower (1 scien- tests were performed showing that the tist, half-time technician) when com- beam polarization is lower than prepared with such a demanding instru- dicted, most likely due to polarization ment, we succeeded to produce the losses in the Ni/Ti-neutron guide. Neu- first spin echo signal at the quasielastic tron spin echo (NSE) coils containing Neutron Resonance Spin Echo spectro- neutron guides made of float glass, were meter RESEDA in November 2005. put on stream, and first NSE polar- Commissioning of RESEDA was de- ization showed that beam polarization layed until then, because of high ra- was partially lost also in the attenu- diation background. Neutron guide ation/monitor zone between the neu- and selector housing are shared with tron guide and the mumetal shielding the instrument NOSPEC which is not of RESEDA. The guide field in this re- Figure 2.66: The image shows the two sec- yet built, in contrast to previous plans. gion was hence modified in the reactor ondary spectrometer arms of RESEDA. We therefore had to build an additional pause of September and October, and The open mumetal shielding gives free shielding, in order remove an open- the attenuator shielding was improved. view on the NSE and NRSE coils. ing in the selector shielding, which had At the same time, the RF circuits were been foreseen for NOSPEC. We con- finished and put into operation with cent tests gave hints that the polariza- structed the shutters for both instru- the new RF amplifiers. The impedance tion is decreasing with increasing diver- ments which are made out of boron and the resonance frequencies of the gence. containing absorber plates and added RF circuits were tested under differ- In 2005, the progress at RESEDA also a new concrete shielding. In ad- ent conditions, and the software con- was again very remarkable, as in 2004. dition to this unforeseen work, we fi- trolling the RF parameters was adapted Within less than 2 years essential parts nally improved the radiation shielding to the amplifiers. In November, the of the instrument have been modi- of the polarizing part of the neutron Neutron Resonance Spin Echo (NRSE) fied, including neutron guide shielding, guide NL 5b (total length 65 m, polariz- coils were put into operation, and the selector housing, beam shutters and ing part 40 m, bending radius 1640 m), first NRSE echo groups could be de- attenuators, NRSE coils, cooling and to the total thickness of 14.5 cm, in or- tected. Though the beam polarization security systems, complete cabling of der to reduce the gamma background is not perfect, the NRSE data - a typi- the instrument, completely new instru- level sufficiently. In the meantime, a cal echo group plot is shown in Fig. 2.67 ment control software etc. Commis- gamma shutter, a beam monitor, and demonstrate that all the components of sioning of RESEDA will presumably take three movable attenuators have been RESEDA work properly. The mean neu- some time still in 2006. constructed and fixed at the end of the tron wavelength of the primary beam, neutron guide in front of the spectro- as extracted from the NRSE data, is meter. High radiation background pro- 5.3 Å in good agreement with the value duced in the first spectrometer arm, predicted from the selector frequency, however, prevents until now measure- and the width of the wavelength band ments with the full beam. amounts to 13% (FWHM). We finally in- By using the first neutrons being vestigated the dependence of the NRSE available at the instrument in August polarization from several parameters, 2005, the primary spectrometer arm as the magnetic fields in the coupling of RESEDA was aligned with respect coils and the solenoids fixed at the mu- Figure 2.67: A typical NRSE echo group. The to the straight neutron beam, and ad- mental shielding, and as a function of RF frequency in the first spectrometer justed to its vertical position. The 3He- the RF frequency. Besides the predomi- arm is fixed to 189.5 kHz. The RF fre- detector was put into operation, and nantly expected results from these tests, quency in the second arm is scanned first measurements of the shape and in- it turned out that the polarization de- around the same value. The mean neu- tensity of the neutron beam were per- pends on the position of the neutron tron wavelength extracted from the fit formed. The estimated intensity of the guide hall crane, and on the set value with the theoretical function is 5.3 Å, the straight beam, measured by using beam of the FRM-II sample oven. Further test width of the wavelength band is 13 % attenuators of well-known attenuation measurements, especially of the polar- (FWHM). strengths, is in agreement with theo- ization as a function of the beam diver- retical predictions. First polarization gence, are in preparation, because re- 52 2 Instruments 3 Scientific Highlights 53

3 Scientiﬁc Highlights

3.1 Magnetic-ﬁeld induced instability in the A-Phase of MnSi: Bulk and SANS measurements

D. Lamago 2,1, R. Georgii 2,1, P.Böni 1, C. Pﬂeiderer 1 1Physics Department, E21, TU München, 2ZWE FRM II, TU München

MnSi develops itinerant-electron B = 160 mT magnetism below T 29 K that sup- c = ports a long wavelength helical modulation. In recent years the properties of MnSi have attracted great scientific interest [1, 2]. Motivated by recent efforts [3] we revisit reorientational processes of the helical modulation in MnSi at ambient pressure as function of field. We combine small-angle neutron scattering with AC susceptibility data. This B = 0 mT provides unexpected new insights into the nature of the helical modulation and its possible connection to the NFL phase and the partial magnetic order at high pressure [2]. The AC susceptibility of a single crystal of MnSi have been measured by means of a 9 T Quantum Design PPMS System. SANS-experiments were carried out at the diffractometer MIRA at FRM II in Garching. Figure 3.2: Neutron SANS intensity of MnSi at T 28.5 K (just below Tc ) recorded Fig. 3.1(a) shows typical AC- = at the diffractometer MIRA at FRM- II. susceptibility data as measured in the Lower panel: data at B 0. Four = A-phase used for determining the phase resolution-limited spots are characteris- boundaries of the A-phase. As function tic of long-range helical order, consistent of magnetic field, the AC susceptibility with previous work. Upper panel: data at displays an abrupt change of slope and 0.16 T, where only a ring of scattering in- a minimum that signifies the A-phase. tensity appears. The onset of this minimum has been mapped out as function of temperature corresponding to Q , that was not and is shown in the phase diagrams in | | present at B 0. Fig. 3.1(b), (c) and (d). = Typical small-angle neutron scatter- The appearance of this ring of intensity is only gradual from the B 0- ing data are shown in Fig. 3.2. At a = temperature T 28.5 K, just below T , phase into the A-phase. Interestingly, c Figure 3.1: (a) AC susceptibility as measured = we observe the same qualitative be- we observe well defined spots of he- in the A-phase of MnSi using a magnetic haviour also for B 110 and B 111 lical magnetic order (lower panel) as field with B 100 . The data for B 110 ∥ 〈 〉 ∥ 〈 〉 ∥ 〈 〉 ∥ 〈 〉 reported in numerous studies before. and 111 are qualitatively similar. Panels (not shown). 〈 〉 With increasing magnetic field, we ob- (b), (c) and (d) show the phase boundary Therefore, the behaviour is isotropic serve as an additional feature a ring of the A-phase for B 100 , 110 , and and not related to a particular initial di- ∥ 〈 〉 〈 〉 of scattered intensity with a radius 111 , respectively. 〈 〉 54 3 Scientific Highlights rection of the helical order that is en- microscopic nature of the reorientation doh, Y. Phys. Rev. Lett., 88, (2002), forced at low T by lattice anisotropies. transition in MnSi. The results indi- 237204. The distinct change of slope of the cate the appearance of a new form of AC susceptibility as well as the sharp magnetic ordering that may be inter- [2] Pfleiderer, C., Reznik, D., peaks in the specific heat(not shown) preted in terms of skyrmions. Presently, L.Pintschovius, Löhneysen, H., indicate a well defined phase transition a device for 3-dimensional polarisation Garst, M., Rosch, A. Nature, 427, into the A-phase that shows up in the analysis, MuPAD, is being installed at (2004), 227. SANS-experiments as a ring of scatter- MIRA and will help to resolve the mi- [3] Okorokov, A., Grigoriev, S., ing intensity. croscopic magnetic structure in the A- Chetverikov, Y., Maleyev, S., Georgii, Our experiments show that combin- phase of MnSi and distinguish between R., Böni, P., Lamago, D., Eckerlebe, ing SANS measurements at the new the various models. H., Pranzas, K. Physica B, 356, diffractometer MIRA at FRM II with (2005), 259. bulk measurements helps resolving the [1] Roessli, B., Böni, P., Fischer, W., En-

3.2 Measurements on Mg-Alloys with the Coincident Doppler Broadening Spectrometer CDBS

M. Stadlbauer 2, C. Hugenschmidt 1, K. Schreckenbach 1, P.Böni 2 1ZWE FRM II, TU München 2 TU München, Physikdepartment E21

Experimental Setup Characterization of the The sharp edges of the borders be- Focus tween aluminum and tungsten become During 2004 a new coincident Doppler smooth transitions in the S-parameter broadening spectrometer (CDBS) was In order to investigate the focus param- picture since the beam diameter shows set into operation at the high in- eters at the sample position, an alu- a certain extension. The area of this tense positron source NEPOMUC. The minum sample with glued on tungsten transitions allows to estimate the beam positron beam is guided in a longitudi- stripes was investigated with the CDBS diameter in the x and y direction. Figure nal magnetic field to the analysis cham- since aluminum and tungsten have very 3.3 shows clearly a beam diameter of ber and nonadiabatically released from different electron momentum distribu- about 2 mm. By inserting an additional this field by a magnetic field termina- tions. The S-parameter - a quantity that aperture, a focus of 1 mm was achieved. tion. After passing an aperture of 3 mm measures the width of the annihilations diameter, electrical lenses focus the di- line - was recorded depending on the Measurements on Mg-Alloys vergent positron beam onto the sam- position of the positron beam spot on ple where a focus diameter of 1 mm was the sample at a potential of -20 kV. The Mg-alloys experience an increasing in- achieved. result is shown in figure 3.3. terest for industrial applications due to Since the high momenta of the elec- their very low specific weight, high elas- trons in the sample endue high mo- ticity and mechanical strength. The menta compared to the thermalized CDBS is an ideal tool for investigating positrons, the 511 keV annihilation ra- the behaviour of the alloy constituents, diation is Doppler shifted. By measur- i.e. aluminum and zinc. If the concen- ing this Doppler shift with high purity tration of one of the alloy constituents germanium detectors, the electron mo- changes in the vicinity of open volume mentum distribution at the annihila- defects, the structure of the annihilation site can be investigated. At high tion line should change in the high mo- Doppler shifts, i.e. regions of the an- mentum region. First measurements nihilation line with very low count rate, were recorded of the pure and annealed information about the chemical sur- Figure 3.3: S-parameter vs. position of the metals aluminum, zinc and magnesium rounding of the annihilation sites - for focused positron beam on an aluminum in order to get reference spectra. These example open volume defects - can be sample with glued on tungsten stripes. annihilation lines were compared with revealed [1]. Therefore, the CDBS is This picture was recorded at a sample po- AZ31, a diecast Mg-alloy consisting of equipped with two facing germanium tential of 20 kV with a focal diameter of 1% wt. zinc and 3% wt. aluminum detectors in coincidence in order to re- 2 mm and normalized to magnesium (see fig- duce background. ure 3.4). 3 Scientific Highlights 55

The lines of the pure elements can be clearly separated from each other. Especially zinc shows a large deviation compared to magnesium and aluminum at high momenta. The structure of the AZ31-line is clearly shifted towards the line of zinc due to the 1% wt. zinc atoms in the sample. Conse- quently even in defect free samples zinc can be detected.

[1] Asoka-Kumar, P.,Alatalo, M., Ghosh, V. J., Krusemann, A. C., Nielsen, B., Figure 3.4: Annihilation lines of annealed Lynn, K. G. Phys. Rev. Let., 77, aluminum, zinc, magnesium and AZ31- (1996), 2097–2100. samples, normalized to magnesium. The line of AZ31 is shifted towards the line of zinc, which proofs that even in defect free material, 1% wt. of zinc can be detected.

3.3 A study of oil lubrication in a rotating engine using stroboscopic neutron imaging

Burkhard Schillinger 1,2, Johannes Brunner 1,2, Elbio Calzada 1,2 1TU München, Physics Department, E21 2ZWE FRM II, TU München

Even at modern high-flux neutron a collimation ratio of L/D=400. Con- to a 2kW electro motor with a trans- sources, the required exposure time for sidering a time window as long as one mission belt. The spark plugs were re- one neutron radiography image with millisecond and a scintillator detection moved, so that the engine would not high counting statistics is in the order of efficiency of 30%, only 3.3 x 105n/cm2s generate compression in its cylinders. one second. Continuous time-resolved are detected on a square centimeter. If Only this way, the comparatively weak imaging of objects in motion is thus an area of 0.3 mm x 0.3 mm is imaged electro motor was capable of turning very limited in time resolution and sig- onto one pixel of the detector, only 300 the engine at low rotation speeds, and nal dynamics. However, repetitive mo- are detected on a single pixel. This sig- due to the reduced heat production, tions can be recorded with a strobo- nal is not sufficient for a useful radio- the water cooling could be omitted. scopic technique: A trigger-able accu- graphy image with attenuations from Instead of using the sparc distributor mulating detector is triggered for many zero to a factor of 1000. The only way to generate a synchronization signal, identical time windows of the cyclic to increase the counting statistics is to we mounted a hall sensor close to the motion until sufficient fluence is accu- use a stroboscopic imaging technique transmission wheel on the camshaft. mulated for one image. The image is to record a periodic motion. The signal The generated pulse was used to trigger read out, the delay for the time window of may time windows identical within the image intensifier of a cooled CCD is shifted and the recording repeated the cycle of the examined motion is ac- camera. With the camera electronics until a complete movie of the cyclic mo- cumulated on a trigger-able detector and software, the trigger signal could be tion can be put together. We report before the signal is digitized and read delayed in order to shift the time win- about a study of oil flux in a running, out, until sufficient counting statistics dow within the cycle of the engine. electrically driven BMW engine out of is achieved. current production. Measurements at ANTARES Experimental setup Introduction The detection system was an Andor iS- For our studies, we obtained a NG4 tar MCP intensified CCD camera with The neutron radiography facility BMW engine out of current production. 1024 x 1024 pixels [1, 2]. Of special ANTARES at FRM II of TU München The engine was stripped of the intake interest is the visualization of the oil delivers a cold flux of 108 n/cm2s at and exhaust system and was coupled cooling of the piston bottoms. Since 56 3 Scientific Highlights

visible along with the horizontal pressure tube. The area between the pistons contains the vertical tubes for the pressure-free backflow of oil from the camshaft on top to the oil pan at the bottom of the engine. In the car, these tubes are mostly empty, because the engine is mounted at a 30 degree tilt angle. On our test stand, the engine was mounted vertically, resulting in a fill-up of these tubes. Fig. 3.5 shows a static radiography of the engine, showing valves, pistons, piston rods, piston pins and piston rings, Figure 3.8: Dynamic neutron radiography with the pressure tubes and backflow cutout. Figure 3.5: Static neutron radiography image channels empty. Fig. 3.6 shows one sin- of the engine. gle frame of the engine in motion, view- ing different cutouts. An oil blob is visi- the camshaft bearings would also have ble on its way to the piston bottom, the been of interest, but the engine has a the pistons are only connected to the horizontal pressure tube for the supply plastic cover on top which obstructs the engine body via the piston rings with of the oil ejection nozzles and the verti- neutron view to this area. Further tests very low heat dissipation, a continuous cal backflow tubes are filled up. will be performed with an Aluminium oil jet is directed from below at the pis- Fig. 3.7 and 3.8 show a static and dy- replacement cover. ton bottoms, lowering the piston tem- namic cutout for comparison. The ver- perature by more than 200 degrees C. tical backflow tubes which are mounted Outlook Because of the limited flux, the time on the outside of the engine block ex- window was selected as high as one tend beyond the edges of the cylinder Stroboscopic neutron radiography has millisecond, the rotation speed was se- bore and cover the edges of the pistons, proved its potential for further exam- lected as 600 rpm, which is well below making impossible to observe the oil inations of the lubrication of running the nominal idle speed of the engine. film on the pistons in motion in this 90 engines. In a realistic experiment The images thus show motion unsharp- degree view. with compression, heat generation will ness, but good definition on the station- In the running engine, the trans- cause difficulties, as filling the cooling ary parts. At this rotation speed, the oil mission through the free areas besides system with water will obstruct part of pump did not produce its nominal pres- the crankshaft is only half of the static the view. A partial solution may be the sure, the oil pressure was pulsed and transmission, meaning non-repetitive use of heavy water in the cooling sys- produced blobs in the cooling oil jet. oil splashes and foams obstruct the tem. To avoid exhaust fumes in the re- In the field of view of 25 cm x 25 cm, view. As repetitive phenomenon, cur- actor hall, an external electro motor will the nozzles for the cooling oil jets were tains of oil are visible flowing down be required which must equal the nom- the cylinder walls. The lubrication of inal power of the engine to drive it at high rotational speeds.

[1] iStar. www.andor.com.

[2] Schillinger, B., Brunner, J., Calzada, E. Physica B. Acc. pub.

Figure 3.7: Static neutron radiography image Figure 3.6: Dynamic neutron radiography cutout. image of the engine. 3 Scientiﬁc Highlights 57

3.4 Small-angle scattering eﬀects in neutron radiography and tomography

Burkhard Schillinger 1,2, Elbio Calzada 1,2, Roland Gähler 3, Hongyun Li 1,4, Martin Mühlbauer 1,2, Michael Schulz 1,2 1TU München, Physics Department, Institute E21 2ZWE FRM II, TU München 3Institut Laue-Langevin, Grenoble,France 4Northwest Institute of Nuclear Technology, Xi’an, P.R. China

Due to the very parallel beam colli- path. The effect is not visible in mation at the neutron radiography fa- standard radiography with the detector cility ANTARES, the distance between close to the sample. If the sample to de- sample and detector can be increased tector distance is increased to 0.5 to 2 up to two meters distance while still ob- meters, even faint effects become visi- taining unblurred images. At these large ble in a radiography or tomography. distances, small angle scattering effects in otherwise homogeneous and plane Radiographic examination of samples build up to intensity variations smooth-polished car chassis that can be detected in a radiography numbers in steel plates image. We have examined different Alu- minium and steel samples with texture The German Federal Police brought us variations induced by plastic deforma- Figure 3.10: Standard neutron radiography. test samples of steel plates which had tion. contained car chassis numbers ham- mered into the metal. Fig. 3.9 shows a Motivation photo of the steel plates with a size of about 5 cm. The plates were grinded Quantitative stress measurements to a smooth surface, no trace of the are performed with the Stress- chassis numbers is visible by eye. Fig. Spectrometer STRESS-SPEC, where 3.10 shows a standard neutron radiog- crystal lattice reﬂexes can be examined raphy with a few centimeters distance to a depth of several centimeters. By to the detector, revealing nothing but using small diaphragms, the incoming homogeneous material. The distance and outgoing neutron beam is focused was then increased to two meters, the to a measuring volume of about one cu- collimation ratio to 2300. Fig. 3.11 bic millimeter. By scanning the sample and 3.12 show enhanced images of the volume, the internal stress is mapped plates with most of the original im- Figure 3.11: Large distance radiography. due to shift of the reﬂexes compared printed numbers visible. to the unperturbed material. Scanning of a large volume may take hours up to days. With neutron radiography and tomography, it is intended to do a qualitative scan of the sample as a whole and to determine regions of interest to be scanned quantitatively by STRESS- SPEC.

Working principle

The beam at ANTARES has a very high Figure 3.12: False colours of the radiography parallel collimation ratio of L/D=800. image. With the use of a selector wheel with Figure 3.9: Photo of the sanded steel plates. pinhole apertures, this collimation can Tomographic examination of be increased to 2300 up to 16000. Small a cold-expanded rivet hole in texture changes in an otherwise flat and Aluminium homogeneous sample will lead to lo- cally increased small angle scattering, Aircraft parts are riveted, not welded to- deviating neutrons from their straight gether. The rivet holes are subjected 58 3 Scientific Highlights to high stress during operation. To increase their stability, holes are drilled to less than the required diameter, then cold expanded by about 4% by a man- drel. This process introduces plastic deformation and a negative pre-stress into the hole edges.If pulling forces are introduced by the rivets during aircraft operation, the negative stress is first compensated before positive stress may lead to cracks. As a test sample, we examined a rolled-out Aluminium sheet with a cold expanded hole with neutron computed tomography. The sample was put in a distance of half a meter to the detector. The computed tomography returns a certain range of attenuation values or grey values for the mate- Figure 3.15: Increased attenuation at the rial Aluminium. For three-dimensional hole edges. visualisation, we set most of that greyvalue range to transparent and examined only the most attenuating upper greyvalue range. Fig. 3.13 show a standard view of the Aluminium sheet, Fig. 3.14 shows the same sheet with only the most attenuating parts set visible.

Figure 3.14: Only the most attenuating areas visible.

The Figures 3.16, 3.17and 3.18 show better that it is a true 3D tomography. Ordinary holes in the same samples were drilled later and re-examined. Figure 3.16: This image proves that it is a true They did not show the increased at- 3D tomography. tenuation at the edge. This measurement was performed at at time when the above-mentioned pinhole selector wheel had not yet been available. The experiment will be repeated with even Figure 3.13: Standard tomographic view of higher collimation soon. the Aluminium sheet. The tomography ﬁrst reveals a wave structure originating from the rolling- out of the metal sheet. Furthermore, the edge of the cold-expanded hole shows a signiﬁcant increase in attenuation compared to the surrounding material (Fig. 3.15).

Figure 3.17: Another 3D view with the wave structure invisible. 3 Scientiﬁc Highlights 59

Conclusion

A very high collimation of the neutron radiography beam allows for the examination of small-angle scattering effects in neutron radiography and tomography and thus extends the range of examination methods considerably. More experiments will be done soon.

Figure 3.18: All hard structures together.

3.5 Mechanisms of mass transport in multicomponent melts

A. Meyer 1, F.Kargl 1, S. Mavila Chathoth 1, T. Unruh 2 1Physik Department E13, TU München 2ZWE FRM II, TU München

We investigate the atomic motion of 40 mm gives a count rate of 2900 cps liquid Fe Ni in multicomponent metallic and oxi- summed over all 640 detectors. 90 10 1855 K dic melts with inelastic neutron scatter- Beside surface energies, the precise ) -1 ing in order to clarify the microscopic knowledge of diffusion coefﬁcients rep- 10-1 transport mechanisms. The high- resents an important input for a mod- ) (meV resolution energy and momentum in- elling of the solidiﬁcation of multicom- ω

formation emerging from inelastic neu- ponent materials and hence a virtual S (q, tron scattering experiments allows to materials design. However, especially study the interplay between intermedi- due to convection effects diffusion co- 1.0 A-1 -2 ate range structure, viscous flow and the efficients are in general not known in 10 0 2 4 atomic diffusion of particular compo- high melting alloys. Since with inelas- hω (meV) nents. With a high neutron flux on the tic neutron scattering atomic motion is sample, an excellent energy resolution probed on a 10 picosecond time scale Figure 3.19: Quasielastic neutron scattering and an outstanding signal to noise ra- at interatomic distances, convection ef- on a Fe90Ni10 melt at 1855 K. tio, the neutron time-of-flight spectro- fects that cause a macroscopic flow on meter TOFTOF is especially suited for microsecond time scales, do not alter Nickel is slightly smaller than in dense the investigation of atomic diffusion in the quasielastic signal. packed pure liquid Nickel[1] or Nickel high temperature melts where measur- Figure 3.19 shows the quasielastic rich NiAl alloys[2]. ing times are limited due to sample signal of a liquid Fe90Ni10 alloy at In multicomponent hard sphere like evaporation and/or interdiffusion be- 1855 K. For the measurements the alloy viscous metallic melts, where diffusion tween sample and sample holder. was melted in an alumina can that pro- coefficients of the various components On TOFTOF an incident neu- vides a hollow cylindrical sample geom- exhibit similar values above the melting 1 tron wavelength of λ 5.4Å− in etry with 1.2 mm sample wall thickness. point, the relaxational dynamics is in = combination with choppers rotat- The line represents a fit with a Lorentz quantitative agreement with the univer- ing at 12.000 rpm yields an accessi- function. Below the first structure fac- sal mode coupling scaling functions[3] ble wavenumber range at zero energy tor maximum the signal is governed by and mixing effects only play a mi- 1 transfer of q 0.2 2.2Å− and an en- the contribution of the incoherent scat- nor role for the mass transport[1]. In = − ergy resolution of 85µeV (FWHM) at tering on the Nickel atoms. From the q sodium silicates[4] and sodium borates 90◦ scattering angle. A hollow cylindri- dependence of the width of quasielas- the time scales for the Na α relaxation cal Vanadium standard with a diameter tic line a Ni self diffusion coefficient and the Si(B)-O network structural re- of 23 mm, a Vanadium wall thickness of can be obtained on an absolute scale. laxation are separated. The long range 9 2 0.88 mm ( 10 % scatterer) and a height Interestingly with 3.4 0.1 10− m /s atomic transport of sodium is faster by ' ± · the resulting self diffusion coefficient of orders of magnitude as compared to 60 3 Scientific Highlights

used a Platinum sample can that pro- a function of temperature extrapolates Na2O 4 B2O3 vides a hollow cylindrical sample ge- to one Tc value for all q. Since toward ometry with a sample wall thickness of small q the signal is dominated by inco- 1.2 1.2 mm. With these sample dimensions herent scattering on the sodium atoms, multiple scattering is negligible. In the the resulting q dependence of the am-

S (q,t) low q-region incoherent neutron scat- plitude h demonstrates that sodium 1060 K q 1.0 1100 K tering on sodium is the dominant con- contributes to the fast relaxation pro- 1140 K 1180 K tribution to the signal, whereas around cess. Therefore, the Na ion diffusion 1220 K the first sharp diffraction peak at q in sodium borates is prepared by a fast 1.4 A-1 1260 K 1 ≈ 1.5 Å− coherent scattering on B and β relaxation process as described by 0.1 1 10 O dominates. Therefore, the q depen- Mode Coupling Theory (MCT). Time (ps) dence of amplitude and time scale of a Figure 3.20: Density correlation function of fast β relaxation process should display [1] Chathoth, S. M., Meyer, A., Schober, a viscous sodium tetra borate melt ob- the coupling to the two distinct α relax- H., Juranyi, F. Appl. Phys. Lett, 85, tained by quasielastic neutron scattering. ation processes. (2004), 4881. The lines are fits with the β scaling func- Figure 3.20 shows density correlation of mode coupling theory. tion functions. The lines are fits with [2] Das, S. K., Horbach, J., Koza, M. M., the mode coupling β scaling law. The Chathoth, S. M., Meyer, A. Appl. the transport of the silicon (boron) and full set of data can consistently be de- Phys. Lett., 86, (2005), 011918. oxygen atoms. scribed with a temperature and q in- [3] Meyer, A. Phys. Rev. B, 66, (2002), In an experiment on TOFTOF we independent line shape parameter λ and 134205. vestigated sodium tetra borate in or- a q independent cross over time tσ as der to address the question how far the found in one component viscous liq- [4] Meyer, A., Horbach, J., Kob, W., relaxational dynamics in such a sys- uids. The amplitude hq of the fast relax- Kargl, F.,Schober, H. Phys. Rev. Lett., tem can be described with universal ation is found to be in phase with static 93, (2004), 027801. mode coupling scaling functions. We 2 structure factor for all q. hq plotted as

3.6 Inﬂuence of the superconducting energy gap on phonon linewidths in Pb – a high resolution study at TRISP

P.Aynajian 1, K. Buchner 1, K. Habicht 2, T. Keller 1,3, M. Ohl 1, B. Keimer 1 1Max-Planck-Institut für Festkörperforschung, Stuttgart 2BENSC, HMI Berlin 3ZWE FRM II, TU München

spectrometer TRISP at the FRM-II. The the whole phonon spectrum (tunneling electron-phonon (ep) interaction is re- spectroscopy). Allen [1] first derived sponsible for the formation of Cooper- a simple relation between the phonon pairs in conventional BCS supercon- linewidth and the ep coupling param- ductors. Therefore detailed knowl- eter, but he also pointed out that ex- edge of the ep coupling parameters cept for some rare cases where phonon is required to understand fundamen- linewidth broadening is exceptionally tal properties of these materials. The large, the energy resolution of neutron ep interaction provides a decay channel spectrometers is generally too low to re- for phonons and broadens the phonon solve these phonon linewidth effects. linewidth (shortens the phonon life- In early studies, conventional triple Figure 3.21: The spin echo triple axis time). Thus phonon linewidth mea- axis spectrometers were used to investi- spectrometer TRISP at the FRM-II surements using neutron spectroscopy gate ep interaction in the superconduc- obviously offer direct access to the tors Nb3Sn [2, 3] and Nb [4], which show ep coupling parameters of each single such unusually large phonon linewidth The broadening of the linewidths of phonon and thus can extend the range broadening. As the phonon linewidth transverse phonons resulting from the of conventional spectroscopy methods, is also broadened by other decay pro- electron-phonon interaction in super- which are restricted to phonons at cesses such as phonon-phonon scat- conducting Pb was resolved for the the center of the Brillouin zone (light tering or by instrumental effects and first time at the triple axis neutron scattering) or take an average over sample imperfections, in general thor- 3 Scientific Highlights 61 ough data analysis is required to sepa- a cylindrical single crystal ( 3 5cm3, ; × rate the electron-phonon contribution cylinder axis along [100]) with a low mo- Γep from the total phonon linewidth. saic spread of 4.20. The temperature Axe and Shirane [2, 3] used an ele- dependence of the phonon linewidth gant approach to directly extract Γep . was determined by measuring the po- The basic principle of their method larisation for six different values of τ. is that phonons with energy smaller The linewidth is obtained by fitting ex- than the width of the superconduct- ponentials to these data points (Fig. ing energy gap, 2∆(T ), cannot decay by 3.23). The typical counting time for one breaking Cooper-pairs and thus have a linewidth was 4 hours. smaller linewidth (longer lifetime) than Two sample scans are shown in Fig. phonons with energy above 2∆. By 3.23. The data in the plot were taken for scanning the temperature, 2∆(T ) is var- a [2.32 1.68 0]T1 phonon with an energy ied across the phonon energy, and the of 2.37meV (horizontal line) at the tem- Figure 3.23: Spin echo linewidth data for a change in phonon linewidth directly peratures 3.7 and 6K indicated by the [0.32 0.32 0]T1 phonon in superconduct- gives the electron-phonon contribution vertical arrows in Fig. 3.22. As the su- ing Pb. The slope of the curves is pro- Γep . Using conventional triple axis perconducting energy gap is tempera- portional to the linewidth. An additional spectrometers under favorable focus- ture dependent, the phonon energy lies broadening of 7 1µeV appears when ± ing, typical Γep in the order of 1meV for below 2∆ at 3.7K and above at 6K . The the gap energy 2∆ gets smaller than the transverse acoustic phonons in Nb3Sn additional broadening of the phonon phonon energy. and 200µeV in Nb were observed. For linewidth of 7 1µeV (a smaller slope ± superconducting Pb, Γep is in the or- of the data in Fig. 3.23 indicates a nar- [1] Allen, P. B. Phys. Rev., B6, (1972), der of 5µeV , which is far beyond the rower linewidth), which occurs when 2557. resolution limits of conventional neu- the gap energy 2∆ crosses falls below tron spectrometers. Attempts to resolve the phonon energy, can be identified [2] Axe, J., Shirane, G. Phys. Rev. Lett., Γe phon triple axis spectrometer thus with influence of the electron-phonon 30, (1972), 214. − failed [5]. part Γ of the phonon linewidth. ep [3] Axe, J., Shirane, G. Phys. Rev., B8, Using the high-resolution spectro- Changes of the phonon linewidth re- (1973), 1965. meter TRISP [6] at the FRM-II, we were sulting from phonon-phonon scatter- for the first time able to observe the mo- ing are negligible at these low temper- [4] Shapiro, S., Shirane, G., Axe, J. mentum and temperature dependence atures. Phys. Rev., B12, (1975), 4899. of the linewidths of transverse acoustic Detailed linewidth data was also col- phonons around T 7.2K and to ex- lected for other transverse branches in [5] Youngblood, R., Noda, Y., Shirane, c = tract the electron-phonon broadening Pb [10]. This allows a comparison with G. Sol. State Comm., 21, (9178), Γep . TRISP is a triple axis spectrometer modern ab-inito calculations, which 1433. with polarized incident beam and po- are able to predict Γ for each single ep [6] Keller, T., Habicht, K., Klann, H., larisation analysis of the scattered beam phonon branch. Ohl, M., Schneider, H., B.Keimer. combined with a resonance spin echo We thank H. Kolb and J. Peters for get- Appl. Phys. A, 74, (2002), S332. (NRSE) spectrometer. The NRSE uses ting the cryogenics running and C.T. Lin small radio frequency (RF) spin flippers for preparing the Pb crystal. [7] Golub, R., Gähler, R. Phys. Lett., to define precession regions in the in- A123, (1987), 42. cident and scattered beam[7, 8]. By rotating the RF spin flip coils with respect [8] Golub, R., Gähler, R. J. Phys. to the neutron beam and proper setting (Paris), 49, (1988), 1195. of the frequencies, the spin echo reso- [9] Habicht, K., Golub, R., Mezei, F., lution function is tuned to the phonon Keimer, B., Keller, T. Phys. Rev., group velocity and energy (for details, B69, (2004), 104301. see [9] and references therein). If the phonon has zero linewidth, the polari- [10] Keller, T., Aynajian, P., Habicht, K., sation of the scattered beam vs. the ap- Boeri, L., Bose, S., Keimer, B. To be plied RF stays constant as function of published. the spin echo time. A finite linewidth Figure 3.22: Temperature dependence of the Γ results in a decay of the polarisa- superconducting energy gap in Pb. The tion, where for a Lorentzian lineshape horizontal line corresponds to the energy the polarisation decays exponentially of the [0.32 0.32 0]T1 phonon, the arrows P(τ) exp( Γ τ). τ is the spin echo indicate the two temperature points cor- = − · time, which is proportional to the ap- responding to the data in Fig. 3.23. plied RF. For the present experiment, we used 62 4 Facts and Figures

4 Facts and Figures

4.1 Experiments and user program

J. Neuhaus 1, U. Kurz 1, B. Tonin-Schebesta 1, W. Wittowetz 1, E. Jörg-Müller 1 1Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU München

The user office ments. We received 160 proposals de- in-house has proven to be a reliable and manding for 1236 days of beam time. user friendly system. Continuous im- In the year 2005 the user office has In total 638 days could be distributed in provement of the functionality is still started routine operation in parallel the second round. The proposals origi- going on. The underlying content man- with the neutron source. Right from nate from 16 different countries, where agement system, however, has shown the beginning external users were us- by far the most (62%) stem from Ger- several significant limits for the future ing the neutron and positron beams at many. About one third of the propos- development. We therefore decided to the FRM II. The first call for proposals originate from European countries make a major break and rewrite the als was launched already in November which are eligible for funding within the software for the system typo3. By this 2004, experiments started in May 2005. 6th frame work program of the EU, i.e. we will merge our public Internet pages After serving the first friendly users the access program of the NMI3 consor- with the user office system in order to we made the second call for proposals tium. further improve the usability for inter- with deadline in July 2005. The referee The experiments for the first two calls nal and external users. meeting took place in September. Here for proposals could be performed in the Proposals can be submitted twice a we could establish 3 scientific groups reactor cycles 2 to 5. Here 235 exper- year. In order to spread out the dead- evaluating the proposals. This scientific iments were taken all together using lines in relation to other European neu- classification will be more fine grained 1543 days of beam time. These exper- tron centers the future deadlines will be in the future with an increasing num- iments include the internal use of the mid January and mid August every year. ber of instruments in routine opera- instrument groups as well as the beam The deadlines for 2006 are January 20 tion. Already in the second round we time for industrial use. and August 11. The referee meetings could ask for proposals for 15 instru- The user office software developed will take place about 4 weeks later.

The proposal submission is done online in the user office system (http://user.frm2.tum. de). Each proposer has to register for a personal account in the system. Using the module Proposal the user is guided through a questionnaire concerning the experimental parameters. In addition a written scientific motivation in form of a pdf file with a length of maximal two A4 pages is required. A detailed guide line for proposal submission is given in the section user guide in the online system. In addition to the proposal submission the user office system collects experimental reports which are requested for each experiment. The reports can be uploaded in form of a pdf file up to two written pages. In addition questions concerning the user satisfaction can be filled in. The experimental re- Figure 4.1: Usage of beam time in cycles 2-5. 4 Facts and Figures 63 ports will be published online on our In- Instrument position operated by experiments ternet pages. Experimental hall Panda SR2 (17) TU Dresden 26, 140 days Instruments Stress-Spec SR3 (18) HMI 20, 140 days Antares SR4b (19) TU München 44, 115 days In the year 2005 commissioning and Trisp SR5b (21) MPI Stuttgart 14, 205 days testing of the instruments dominated Puma SR7 (22) Univ. Göttingen, TU München 16, 108 days the scientific work to a large extend. Spodi SR8a (23) TU Darmstadt, LMU München 26, 98 days This took place to a large extend si- Resi SR8b (24) Univ. Augsburg, LMU München 12, 57 days multaneously during the first experi- Heidi SR9b (25) RWTH Aachen 17, 122 days ments. A large number of the 19 instru- Nectar SR10h (26) TU München 11, 62 days ments (positron source Nepomuc with Medapp SR10v (27) TU München commissioning 3 experiment places is counted as one Nepomuc∗ SR11 (28) TU München, Univ. Bundeswehr 17, 130 days instrument) presented at the FRM II Neutron guide hall could already demonstrate their perfor- N-Rex+ NL1 (1) MPI Stuttgart commissioning mance, delivering fully scheduled ex- TofTof NL2au (3) TU München 14, 104 days periments. The number given in table Refsans NL2b (4) GKSS, LMU München commissioning 4.1, column position corresponds to the Mephisto NL3a (5) TU München 2, 208 days∗∗ position number in figure 4.3. PGAA NL4b (10) Univ. Köln, TU München commissioning Reseda NL5ao (11) TU München commissioning 4.1.1 User support Spheres NL6 FZ-Jülich commissioning Mira NL6 (16) TU München 29, 184 days The user office helps to organise the stay at the FRM II for external visitors. If Table 4.1: List of instruments at the FRM II in December 2005. Experiment in cycles 2-5 until March 2006. ( Nepomuc 3 Instruments, including setup of the experiments) required support for hotel booking and ∗ ∗∗ organisational help is provided. A central e-mail ([email protected]) and phone number (+49 899 289 14313) is In order to provide working space to reachable during normal office hours. our external users, we have installed a Unfortunately a guest house is avail- terminal room for public use. In the for- able on site up to now. mer seminar room of the Projekthaus All visitors are asked to register their 6 personal computers are available 24h stay within the online user office system a day. The user gets a temporary ac- (module Arrival_Departure). Here, spe- count to use these computers. Here In- cial requirements can be asked for. The ternet access via different browsers and users are normally contacted by e-mail. office programs are available. Own mo- As well, bookings of hotel rooms and bile computers can be connected by an others can be seen in the online system, Ethernet cable. which is helpful in case an e-mail gets Figure 4.2: Terminal room for users. lost. 64 4 Facts and Figures E D / / & 1 1 8 3 5 3 0 $ , $ 7 2 ' ' , 3 & ( ( ( ( 1 0 1 + R D X D / , 1 / 3 $ ' , 1 6 0 6 , 2 E ( 8 3 5 5 6 3 7 / X 1 D D D / / / 1 1 & 1 ( 3 6 6 R ( 6 E D $ 6 5 6 / $ ' $ ( / 1 7 3 1 1 5 1 7 $ 2 E $ 7 6 3 / 1 / 1 E ( 5 / $ , ( 1 $ 5 6 + 5 , $ 1 3 ' 0 6 0 & $ H W ( ' W 3 $ ( 6 D 6 $ 6 1 P ( 2 * $ H V 5 1 3 6 D . O R W H V Q L Q K 6 6 6 X S 5 5 7 H : : : 6 6 . . . 0 5 6 5 6 V E 6 W E ) Q 1 2 5 H $ 5 7 ; 6 6 6 5 P ( D E ) ) ( 6 D X 5 5 U ( 6 2 W 5 6 5 5 7 1 Q 5 V 6 6 6 Q ,

Figure 4.3: Position of the instruments in the experimental and neutron guide hall. 4 Facts and Figures 65

4.2 Public relations and visitor service at the FRM II

J. Neuhaus 1, U. Kurz 1, B. Tonin-Schebesta 1, I. Scholz 2 1Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU München 2Presse & Kommunikation, TU München, Bereich Garching

The high demand to visit the FRM II The presentation of the FRM II was is still a good indicator for the public in- completed by 3 talks in the lecture hall terest in our institute. Due to the heavy of the physics department. Winfried overload of duties for our staff members Petry explained in two sessions how we had to restrict the visits for general neutrons are used for scientific and in- groups to 3 days a week. Nevertheless, dustrial purposes. First experiments in the year 2005 we could welcome 2535 taken at the FRM II, especially those visitors among them 326 pupils and 203 for applied sciences fascinated the au- students from universities all over Ger- dience. In another talk Klaus Schreck- many. Especially the guided tours for enbach explained how to operate a neu- students hopefully create an interest to tron source, which at that time had just use neutron beams for their own fu- started the routine service. ture research. On the other hand we are strong engaged to demonstrate the Figure 4.5: Registration desk with heavy fascination of science for our youngest overload on the day of open doors. visitors, namely pupils in higher classes Already in the early morning a long close the final secondary-school exami- queue was built up to register for the nations. guided tour through the reactor. In addition an exposition on natural radioactivity and measuring instruments to monitor radioactivity was organised by our radiation protection group. Lively discussions and a continuous run during the whole day clearly demonstrated the interest of the general public for this Figure 4.7: Fascinating the public with neu- issue. During the discussions our ex- trons. perts could explain the security mea- Besides the personal visits a large sures of our installation to minimise the number of press releases concerned the release of activity to the environment. FRM II and special experiments which are of public interest. A short impres- sion is given on the next pages where a collection of headlines were put together. Figure 4.4: Visitors in 2005. A highlight for our public relations A highlight for the visitors is clearly was clearly the film of the Bavarian tele- the annual day of open doors which vision on the FRM II, which was broad- took place on October 22nd in 2005. To- casted on the 21st of February. In the gether with the institutes of the campus weekly series α-Campus a 30-minute- in Garching several thousand people presentation on the building of the neu- came to Garching. As usual the demand tron source as well on selected instru- to visit the FRM II was larger than the ments were presented. The film covered number of people we could welcome. the scientific use as well as the indus- In total this day 491 visitors came to Figure 4.6: Our radiation protection group trial applications of the neutron beams. see the reactor installations and the sci- explaining how to measure natural activ- entific instruments in the experimental ity. and neutron guide hall. 66 4 Facts and Figures

Figure 4.8: Headlines of articles in public journals and news papers. 4 Facts and Figures 67

Figure 4.9: Headlines of articles in public journals and news papers. 68 4 Facts and Figures

4.3 Committees

Strategierat FRM II

Chairman

Prof. Dr. Gernot Heger Institut für Kristallographie RWTH Aachen

Members

MRin Dr. Ulrike Kirste Prof. Dr. Helmut Schwarz Bayerisches Staatsministerium für Wissenschaft, Forschung Institute of Chemistry und Kunst Technische Universität Berlin

Dr. Rainer Koepke Prof. Dr. Dr. Michael Wannenmacher Bundesministerium für Bildung und Forschung Radiologische Klinik und Poliklinik Abteilung Strahlentherapie Prof. Dr. Georg Büldt Universität Heidelberg Institut für Biologische Informationsverarbeitung Forschungszentrum Jülich Dr. Heinz Voggenreiter Director Prof. Dr. Dosch Institute of Structures and Design Max-Planck-Institut für Metallforschung German Aerospace Center (DLR) Stuttgart

Prof. Dr. Dieter Richter Prof. Dr. Götz Eckold Institut für Festkörperphysik Institute of Physical Chemistry Forschungszentrum Jülich Universität Göttingen (Speaker Instrumentation Advisory Board) Prof. Dr. Dirk Schwalm Max-Planck-Institut für Kernphysik, Heidelberg

Honorary Member

MDgt i.R. Jürgen Großkreutz

Guests

Prof. Dr. Dr. h.c. mult. Wolfgang A. Herrmann Prof. Dr. Winfried Petry Präsident der Technischen Universität München ZWE FRM II Technische Universität München Dr.-Ing. Rainer Kuch Hochschulleitung Prof. Dr. Klaus Schreckenbach Technische Universität München ZWE FRM II Technische Universität München Dr. Michael Klimke Hochschulleitung Technische Universität München Guido Engelke ZWE FRM II Technische Universität München 4 Facts and Figures 69

Instrumentation Advisory Board (Subcommittee of the Strategierat)

Chairman

Prof. Dr. Götz Eckold Institute of Physical Chemistry Georg-August-Universität Göttingen

Members

Prof. Dr. Dieter Habs Prof. Dr. Wolfgang Scherer Sektion Physik Lehrstuhl für Chemische Physik Ludwig-Maximilian-Universität München Universität Augsburg

Prof. Dr. Peter Böni Dr. habil. Dieter Schwahn Physik Department E21 Institut für Festkörperforschung Technische Universität München Forschungszentrum Jülich Prof. Dr. Dirk Dubbers Physikalisches Institut Prof. Dr. Markus Schwaiger Universität Heidelberg Lehrstuhl für Nuklearmedizin Technische Universität München Dr. Hans Graf Abteilung NE Prof. Dr. Andreas Türler Hahn-Meitner-Institut, Berlin Institut für Radiochemie Technische Universität München Prof. Dr. Andreas Magerl Chair of Crystallography and Structural Physics Dr. habil. Regine Willumeit Friedrich-Alexander-Universität Erlangen-Nürnberg GKSS Forschungszentrum, Geesthacht Prof. Dr. Gottfried Münzenberg Gesellschaft für Schwerionenforschung mbH, Darmstadt

Guests

Dr. Michael Klimke Prof. Dr. Winfried Petry Referent der Hochschulleitung ZWE-FRM II Technische Universität München Technische Universität München

Dr. Klaus Feldmann Guido Engelke BEO-PFR ZWE FRM II Forschungszentrum Jülich Technische Universität München

MRin Dr. Ulrike Kirste Prof. Dr. W. Press Bayerisches Staatsministerium für Wissenschaft, Forschung Institut Laue Langevin und Kunst Grenoble, France

Prof. Dr. Gernot Heger Prof. Dr. Klaus Schreckenbach Institut für Kristallographie ZWE FRM II RWTH Aachen Technische Universität München

Dr. Jürgen Neuhaus Prof. Dr. Tasso Springer ZWE-FRM II Technische Universität München 70 4 Facts and Figures

Secretary

Dr. Peter Link ZWE FRM II

Committee for Industrial and Medical Use (Subcommittee of the Strategierat)

Members

Automobile Industry Dr.-Ing. Maik Broda Dr.-Ing. Rainer Simon Ford Forschungszentrum Aachen BMW AG München

Aerospace Industry Chemistry and Environment Dr.-Ing. Rainer Rauh Dr. Jens Rieger Airbus Deutschland Bremen BASF AG Ludwigshafen

Dr. Ralph Gilles Dr. Heinz Voggenreiter TU München ZWE FRM II German Aerospace Center (DLR) Stuttgart http://wwwnew.frm2.tum/en/industry.html

Scientiﬁc Committee - Evaluation of Beamtime Proposals (Subcommittee of the Strategierat)

Members

Prof. Dr. Hartmut Abele Prof. Heinz-Günther Brokmeier Ruprecht-Karls-Universität Institut für Werkstoffforschung Heidelberg GKSS - Forschungszentrum Geesthacht

Prof. Dr. Matthias Ballauf Prof. Dr. Thomas Brückel Universität Bayreuth IFF FZ-Jülich Prof. Dr. John Banhart Dr. Olwyn Byron Hahn-Meitner-Insitut Div. of Infection and Immunity Berlin University of Glasgow

Dr. Philippe Bourges PD Mechthild Enderle Laboratoire Léon Brillouin Institut Laue Langevin CEA Saclay Grenoble

Prof. Markus Braden Prof. Nikolaus Froitzheim Physikalisches Institut Geologisches Institut Universität zu Köln Universität Bonn

Dr. Hermann Heumann MPI für Biochemie Martinsried bei München 4 Facts and Figures 71

Prof. Jan Jolie Prof. Dr. Joachim Rädler Institute of Nuclear Physics Department für Physik Universität zu Köln Ludwig-Maximilians-Universität München

Prof. Bernhard Keimer Dr. Louis-Pierre Regnault Max-Planck-Institut für Festkörperforschung CEA Grenoble Stuttgart Dr. Rodriguez-Carvajal Prof. Dr. Andreas Magerl Institut Laue-Langevin LS für Kristallographie und Strukturphysik Grenoble Universität Erlangen Prof. Günther Roth Prof. Karl Maier Institut für Kristallographie Helmholtz-Institut für Strahlen- und Kernphysik RWTH Aachen Bonn Prof. Michael Ruck Dr. Joël Mesot Institut für Anorganische Chemie ETH Zürich & PSI TU Dresden Villigen, Schweiz Prof. Wolfgang Scherer Prof. Dr. Kell Mortensen Institut für Chemische Physik Risoe National Laboratory Universität Augsburg Danish Polymer Center Denmark Prof. Wolfgang Schmahl LS für Strukturforschung Prof. Dr. Krause-Rehberg Ludwig-Maximilians-Universität München Department of Physics Universität Halle Prof. Jeremy Smith Fachbereich Computational Molecular Biophysics Dr. Stéphane Longeville Universität Heidelberg Laboratoire Léon Brillouin Laboratoire de la Diffusion Neutronique Prof. Dr. Manfred Stamm CEA Saclay Institut für Polymerforschung Dresden Prof. Dr. Andreas Meyer Physik-Department E13 Prof. Bernd Stühn TU München Institut für Festkörperphysik TU Darmstadt Prof. Michael Monkenbusch Institut für Festkörperforschung Prof. Monika Willert-Porada Forschungszentrum Jülich Lehrstuhl für Werkstoffverarbeitung Universität Bayreuth Prof. Werner Paulus Structures et Propriétés de la Matière PD Katharina Theis-Bröhl Université de Rennes 1 Festkörperphysik Ruhr-Universität Bochum Dr.-Ing Anke Pyzalla Institut für Werkstoffkunde und Materialprüfung TU Wien 72 4 Facts and Figures

Scientiﬁc Secretaries

Dr. Christoph Hugenschmidt Dr. Martin Meven ZWE FRM II ZWE FRM II

Dr. Peter Link Dr. Tobias Unruh ZWE FRM II ZWE FRM II

TUM Advisory Board

Chairman

Prof. Dr. Ewald Werner Lehrstuhl für Werkstoffkunde und -mechanik Technische Universität München

Members

Prof. Dr. Peter Böni Prof. Dr. Bernhard Wolf Physik Department E21 Heinz Nixdorf-Lehrstuhl für medizinische Elektronik Technische Universität München Technische Universität München

Prof. Dr. Andreas Türler Prof. Dr. Arne Skerra Institut für Radiochemie Lehrstuhl für Biologische Chemie Technische Universität München Technische Universität München

Prof. Dr. Markus Schwaiger represented by Prof. Dr. Senekowitsch-Schmidtke Nuklearmedizinische Klinik und Poliklinik Klinikum Rechts der Isar Technische Universität München

Guests

Dr. Michael Klimke Prof. Winfried Petry University Management ZWE FRM II Technische Universität München Technische Universität München

Guido Engelke Prof. Klaus Schreckenbach ZWE FRM II ZWE FRM II Technische Universität München Technische Universität München 4 Facts and Figures 73

Scientiﬁc Steering Committee

Chairman

Dr. Hans Boysen Prof. Dr. Dieter Richter Sektion Kristallographie IFF FZ-Jülich Ludwig-Maximilians-Universität München Prof. Dr. Winfried Petry Prof. Dr. Bernhard Keimer ZWE FRM II MPI für Festkörperforschung Stuttgart TU München 74 4 Facts and Figures

4.4 Staﬀ

Board of Directors

Scientiﬁc Director Technical Director Administrative Director Prof. Dr. W. Petry Prof. Dr. K. Schreckenbach G. Engelke

Experiments

Head K. Lorenz Detectors and electronic Prof. Dr. W. Petry R. Lorenz Dr. K. Zeitelhack A. Mantwill Dr. I. Defendi Secretaries F.Maye (MPI-Stuttgart) S. Egerland W. Wittowetz T. Mehaddene Dr. A. Kastenmüller E. Jörg-Müller Dr. M. Meven D. Maier Coordination S. Mühlbauer M. Panradl Dr. J. Neuhaus Qi Ning (Visiting Scientist from China) Th. Schöffel M. Nülle (MPI-Stuttgart) H. Türck Sample environment H. Bamberger Dr. A. Ostermann Dr. J. Peters Dr. B. Pedersen H. Kolb Instruments C. Piochacz A. Pscheidt P.Aynajian (MPI-Stuttgart) Dr. J. Rebelo-Kornmeier (HMI Berlin) A. Schmidt Dr. S. Bayrakci (MPI-Stuttgart] Dr. A. Radulescu (JCNS) J. Wenzlaff J. Brunner R. Repper K. Buchner (MPI-Stuttgart) Dr. D. Rich Neutron optics M. Bröll(MPI-Stuttgart) J. Ringe Prof. Dr. G. Borchert W. Bünten (JCNS) Dr. P.Rottländer (JCNS) C. Breunig E. Calzada Dr. A. Rühm (MPI Stuttgart) H. Hofmann Chr. Daniel (LMU München) A. Sazonov E. Kahle D. Etzdorf Dr. B. Schillinger O. Lykhvar J. Franke (MPI-Stuttgart) Dr. M. Schlapp (TU Darmstadt) Dr. S. Masalovich Dr. U. Garbe (GKSS) H. Schneider (Univ. Göttingen) A. Ofner Dr. A.-M. Gaspar Dr. A. Schneidewind (TU Dresden) A. Urban Dr. R. Georgii R. Schwikowski R. Valicu Dr. R. Gilles Dr. A. Senyshyn (TU Darmstadt) Dr. M.Haese-Seiller (GKSS) G. Seidl IT Services Dr. W. Häußler C. Smuda J. Krüger F.Hibsch M. Stadlbauer H. Wenninger Dr. M. Hofmann B. Straßer L. Bornemann Dr. M. Hölzel (TU Darmstadt) Dr. T. Unruh J. Ertl Dr. K. Hradil (Univ. Göttingen) H. Wagensonner J. Dettbarn Dr. C. Hugenschmidt F.M.Wagner S. Galinski Dr. V. Hutanu (RWTH Aachen) Dr. W. Waschkowski H. Gilde S. Kampfer Dr. U. Wildgruber (MPI-Stuttgart) J. Mittermaier R. Kampmann (GKSS) Dr. R. Wimpory (HMI Berlin) R. Müller Dr. T. Keller (MPI-Stuttgart) Dr. H.-F.Wirth J. Pulz Dr. V. Kudryaschov(GKSS) Dr. Joachim Wuttke (JCNS) C. Rajaczak B. Krimmer Prof. O. Zimmer S. Roth D. Lamago M. Stowasser Dr. P.Link B. Wildmoser Dr. Loeper-Kabasakal Konstruktion C. Loistl K. Lichtenstein 4 Facts and Figures 75

Administration

Head B. Bendak I. Scholz (ZV TUM) G. Engelke B. Gallenberger A. Schaumlöffel I. Heinath Secretary Visitorservice K. Lüttig C. Zeller U. Kurz R. Obermeier Dr. B. Tonin-Schebesta Members Public relations

Reactor operation

Head R. Binsch A. Wirtz Prof. Dr. K. Schreckenbach H. Gampfer Reactor projects Dr. Ingo Neuhaus, W. Glashauser Dr. J. Meier designated Technical Director J. Groß M. Schmitt G. Guld Secretaries M. Ullrich B. Heck M. Neuberger N. Hodzic Documentation S. Rubsch M. Kleidorfer V. Zill Management W. Kluge J. Jung Dr. H. Gerstenberg (irradiation and H. Kollmannsberger Instrument Safety sources) J.-L. Kraus R. Lorenz Dr. J. Meier (reactor projects) R. Maier Dr. C. Morkel (reactor operation) K. Otto Technical design A. Schindler Shift members F.-L. Tralmer R. Schlecht jun. J. Fink F.Gründer J. Schreiner H. Fußstetter A. Bancsov C. Strobl J. Jüttner A. Benke G. Wagner K. Lichtenstein M. Danner A. Weber J.-M. Favoli J. Wetzl Workshops M. Flieher N. Wiegner C. Herzog H. Groß C. Ziller U. Stiegel L. Herdam A. Begic F.Hofstetter Electrics and electronics M. Fuß K. Höglauer R. Schätzlein A. Huber T. Kalk G. Aigner A. Scharl G. Kaltenegger W. Buchner R. Schlecht sen. U. Kappenberg Ü. Sarikaya M. Tessaro F.Kewitz H. Schwaighofer M. G. Krümpelmann U. Wildgruber Radiation protection Dr. H. Zeising J. Kund Irradiation and sources A. Lochinger S. Dambeck Dr. H. Gerstenberg G. Mauermann W. Dollrieß Dr. E. Gutsmiedl A. Meilinger H. Hottmann Dr. X. Li M. Moser B. Neugebauer C. Müller L. Rottenkolber D. Kugler M. Oberndorfer G. Schlittenbauer H.-J. Werth D. Päthe S. Wolff Technical services W. Lange N. Waasmaier G. Langenstück Chemical laboratory K. Pfaff V. Loder Dr. F.Dienstbach J. Aigner A. Richter U. Jaser D. Bahmet H. Schulz C. Auer F.-M. Wagner R. Bertsch 76 4 Facts and Figures

Reactor physics

Prof. Dr. K. Böning N. Wieschalla R. Jungwirth Dr. A. Röhrmoser C. Bogenberger Security department

L. Stienen J. Stephani 4 Facts and Figures 77

4.5 Publications

[1] Schneidewind A., Link P., Etzdorf D., Schedler R., Rotter M., Loewenhaupt M. PANDA: ﬁrst results from the cold three axes spectrometer at FRM-II, (proceedings of ICNS 2005). Physica B. In press.

[2] Affouard F., Cochin E., Danede F., Decressain R., Descamps M., Häussler W. Onset of slow dynamics in diﬂuorotetra- chloroethane glassy crystal. Journal of Chemical Physics, 123/8, (2005), 084501.

[3] Brunner M., J. Engelhardt, Frei G., Gildemeister A., Lehmann E., A. H., Schillinger B. Characterization of the image quality in neutron radioscopy. Nucl. Instr. & Meth., A542, (2005), 123–128.

[4] Böning K. The New FRM-II Research Reactor in Munich. The 2005 Frederic Joliot/Otto Hahn Summer School on Nuclear Reactors , Karlsruhe (Germany) August 24 - September 2, 2005, Proceedings of the Summer School, 14 pages.

[5] Cadogan J., Moze O., Ryan D., Suharyana, Hofmann M. Magnetic ordering in DyFe6SN6. Physica B. In press.

[6] Calzada E., Schillinger B., F.G. Construction and assembly of neutrons radiography and tomography facility ANTARES at FRM-II. Nucl. Instr. & Meth., A 542, (2005), 38–44.

[7] Fei Y., Kennedy S., Campell S., Hofmann M. Neutron polarisation analysis of nanostructured ZnFe2O4. Physica B, 356, (2005), 264.

[8] Gapinski J., Wilk A., A. P.,Häussler W. Diffusion and microstructural properties of solutions of charged nanosized proteins: Experiment vs Theory. Journal of Chemical Physics, 123 (5), (2005), 054708.

[9] Gilles R. Neutron scattering, a powerful tool in material science exemplary on superalloys. Zeitschrift für Metallkunde, 96, 4, (2005), 325–334.

[10] Gilles R., Schlapp M., Hölzel M., Krimmer B., Boysen H., Fuess H. SPODI - the new Structure Powder Diffractometer at the FRM-II. Zeitschrift für Kristallographie - Suppl., 22, 45.

[11] Grigoriev S., Maleyev S., Okorokov A. I., Chetverikov Y. O., Georgii R., Böni P.,Lamago D., Eckerlebe H., Pranzas K. Critical ﬂuctuations in MnSi near Tc : A polarized neutron scattering study. Physical Review, B 72, (2005), 134420–1–5.

[12] Gutsmiedl E., Petry W., Schreckenbach K. Status of the new research reactor FRM-II. Proceedings of the International Symposium on Research Reactor and Neutron Science - In Commemoration of the 10th Anniversary of HANARO Daejeon, Korea, April 2005.

[13] Hofmann M., Campell S., Link P.,Fiddy S., Goncharenko. Valence and Magnetic Transitions in YbMn2Ge2 - Pressure and Temperature. Physica B. In press.

[14] Hofmann M., Schneider R., Seidl G., Kornmeier J., Wimpory R., Garbe U., Brokmeier H. The New Materials Science Diffractometer STRESS-SPEC at FRM-II. Physica B. In press.

[15] Hugenschmidt C., Mayer J., Stadlbauer M. Investigation of the near surface region of chemically treated and Al-coated PMMA by Doppler-broadening spectroscopy. Radiat. Phys. Chem. In press.

[16] Hugenschmidt C., Schreckenbach K., Stadlbauer M., Straßer B. First positron experiments at NEPOMUC. Appl. Surf. Sci., 252, (2006), 3098 – 3105.

[17] Hugenschmidt C., Schreckenbach K., Stadlbauer M., Straßer B. Low energy positrons of high intensity at the new positron facility NEPOMUC. Nucl. Instr. Meth., A 554, 1-3, (2005), 384–391.

[18] Häussler W., Schmidt U. Effective ﬁeld integral subtraction by the combination of spin echo and resonance spin echo. Physical Chemistry Chemical Physics, 7/6, (2005), 1245 – 1249.

[19] Jarousse C., Lemoine P.,Petry W., Röhrmoser A. Monolithic UMO Full Size Prototype Plates Manufacturing Development. The International Meeting on Reduced Enrichment for Research and Test Reactors RERTR, Boston (Mass. USA), November 6-10, 2005; to be published in the RERTR 2005 Proceedings.

[20] Jobic H., Karger J., Krause C., Brandani S., Gunadi A., Methivier A., Ehlers B., G.and Farago, Häussler W., Ruthaven D. Diffusivities of n-alkanes in 5A zeolite measured by neutron spin echo, pulsed-ﬁeld gradient NMR, and zero length column techniques. Adsorption Journal of the International Adsorption Society, 11, Suppl. 1, (2005), 403–407. 78 4 Facts and Figures

[21] Köper I., Bellissent-Funel M.-C., Petry W. Dynamics from picoseconds to nanoseconds of trehalose in aqueous solutions as seen by quasielastic neutron scattering. J. of Chemical Physics, 122, (2005), 014514–1–6.

[22] Lamago D., Georgii R., Böni P. Magnetic susceptibility and speciﬁc heat of the itinerant ferromagnet MnSi. Physica, B 359, (2005), 1171–1173.

[23] Masalovich S., Ioffe A., Schlapp M., von Seggern H., Küssel E., Brückel T. Optimization of a neutron image plate detector with low gamma-sensitivity. Nuclear Instruments and Methods in Physics Research, A 539, (2005), 236–249.

[24] Mühlbauer M., Calzada E., Schillinger B. Development of a system for neturon radiography and tomography. Nucl. Instr. and Meth., A 542, (2005), 324–328.

[25] Nienhaus K., Ostermann A., Nienhaus G., Parak F.,Schmidt M. Ligand migration and protein ﬂuctuations in myoglobin mutant. Biochemistry, 44, (2005), 5095–105.

[26] Okorov A., Grigoriev S., Hugenschmidt C., Chevertikov Y., Maleyev S., Georgii R., Böni P., Lamago D., Eckerlebe H., Pranzas K. The effect of the magnetic ﬁeld on the spiral spin structure in MnSi studied by polarized SANS. Physica, B 356, (2005), 259–263.

[27] Ostermann A., Parak F. Hydrogen Atoms and Hydration in Myoglobin: Results from High Resolution Protein Neutron Crystallography. in: Hydrogen- and Hydration Sensitive Structural Biology, ISBN4-87805-061-6 C3045, 111–122.

[28] Röhrmoser A., Petry W., Wieschalla N. Reduced Enrichment Program for the FRM-II, Status 2004/05. Proceedings ’9th International Meeting on Reduced Enrichment for Research and Test Reactors (RERTR)’, Budapest, April 10 - 13, 2005.

[29] Schillinger B., Abele H., Brunner J., Frei G., Gähler R., Gildemeister A., Hillenbach A., Lehmann E., Vontobel P. Detection systems for short-time stroboscopic neutron imaging and measurements on a rotating engine. Nucl. Instr. and Meth., A542, (2005), 142–147.

[30] Schillinger B., Brunner J. Stroboscopic and continuous fast imaging with neutrons. Internal Publication of PSI on the occasion of the International Workshop ’Imaging with cold neutrons’ held on Oct 13th -14th, 2005 at Paul-Scherrer- Insti- tute.

[31] Schillinger B., Brunner J., Calzada E. A study of oil lubrication in a rotating engine using stroboscopic neutron imaging. Physica B. In press.

[32] Schillinger B., Calzada E. Proposed combination of CAD data and discrete tomography for the detection of coking and lubricants in turbine blades of engines. Electronic Notes in Discrete Mathematics; Proceedings of the Workshop on Discrete Tomography and its Applications, 20, (2005), 493–499.

[33] Schreckenbach K. Nukleare Inbetriebnahme des FRM-II (Jahrestagung Kerntechnik, 10.-12. Mai 2005, Nürnberg, 2005).

[34] Schreckenbach K., Gerstenberg H. Status Report on the Nuclear Start-up of FRM-II. ENS RRFM Transactions - 9 th International Topic Meeting on Research Reactor Fuel Management, Budapest, 10-13 April 2005, 114 – 118.

[35] Stadlbauer M., Hugenschmidt C., Schreckenbach K., Straßer B. Spatially Resolved Investigation of Thermally Treated Brass with a Coincident Doppler-Spectrometer. Appl. Surf. Sci., 2006, (2005), 3269 – 3273.

[36] Stampanoni M., Borchert G., Abela R. Progress in Microtomography with the Bragg Magniﬁer at SLS. Radiation Physics and Chemistry. In press.

[37] Stampanoni M., Borchert G., Abela R. Nanotomography employing asymmetrical Bragg diffraction. Nucl. Instr. Meth., A 551.

[38] Wieschalla N., Böning K., Petry W., Röhrmoser A., Böni P., Bergmaier A., Dollinger G., Grossmann R., Schneider J. Heavy Ion Irradiation of U-Mo/Al Dispersion Fuel. The International Meeting on Reduced Enrichment for Research and Test Reactors RERTR, Boston (Mass. USA), November 6-10, 2005; to be published in the RERTR 2005 Proceedings.

[39] Zeitelhack K., Schanzer C., Kastenmüller A., Röhrmoser, Daniel C., Franke J., Gutsmiedl E., Kudryashov V., Maier D., Päthe D., Petry W., Schöffel T., Schreckenbach K., Urban A., Wildgruber U. Measurement of neutron ﬂux and beam divergence at the cold neutron guide system of the new Munich research reactor FRM-II. Nuclear Instruments and Methods in Physics Research A. In press. Imprint

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