Journal of large-scale research facilities, 4, A129 (2018) http://dx.doi.org/10.17815/jlsrf-4-110 Published: 19.03.2018 E2: The Flat-Cone Di�ractometer at BER II Helmholtz-Zentrum Berlin für Materialien und Energie * Instrument Scientists: - Dr. J.-U. Ho�mann, Helmholtz-Zentrum Berlin für Materialien und Energie, Department Quantum Phenomena in Novel Materials, phone: +49(0)30 8062-42185, e-mail: ho�mann- j@helmholtz-berlin.de - Dr. M. Reehuis, Helmholtz-Zentrum Berlin für Materialien und Energie, Department Quantum Phenomena in Novel Materials, phone: +49(0)30 8062-42692, e-mail: reehuis@helmholtz-berlin.de Abstract: The �at-cone di�ractometer E2 at the research reactor BER II is a thermal neutron single- crystal di�ractometer for 3D reciprocal space mapping by using four delay-line area detectors (300 × 300 mm2). Alternatively it is suitable for powder measurements with medium resolution and broad 2-theta scattering range. 1 Introduction The original Flat-Cone Di�ractometer, promoted by D. Hohlwein and W. Prandl (Hohlwein et al., 1986) in 1986, had a banana-type detector. With the Next Generation of the Flat-Cone Di�ractometer E2 at the research reactor BER II we now provide a thermal neutron single-crystal di�ractometer to scan a 3-dimensional part of the reciprocal space in less than �ve steps by combining the “o�-plane Bragg- scattering” and the �at-cone layer concept while using a new computer-controlled tilting axis of the detector bank. Parasitic scattering from cryostat or furnace walls is reduced by an oscillating radial collimator. The datasets and all connected information is stored in one independent NeXus �le format for each measurement and can be easily archived. The software package TVneXus deals with the raw data sets, the transformed physical spaces and the usual data analysis tools (e.g. MatLab). TVneXus can convert to various data sets e.g. into powder di�ractograms, linear detector projections, rotation crystal pictures or the 2D/3D reciprocal space. For single-crystal work the multi detector bank (four 2D detectors 300 × 300 mm2) and the sample table can be tilted around an axis perpendicular to the monochromatic beam to investigate upper layers in reciprocal space (Flat-Cone technique). For powder di�raction studies, the multi detector bank sets on only two positions to measure one powder di�rac- *Cite article as: Helmholtz-Zentrum Berlin für Materialien und Energie. (2018). E2: The Flat-Cone Di�ractometer at BER II . Journal of large-scale research facilities, 4, A129. http://dx.doi.org/10.17815/jlsrf-4-110 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-4-110 http://dx.doi.org/10.17815/jlsrf-4-110 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 4, A129 (2018) http://dx.doi.org/10.17815/jlsrf-4-110 togram covering a scattering range of 80°. On the other hand every detector can be set on an individual position (with gaps between the detectors) for in-situ measurements. Figure 1: Flat-Cone Di�ractometer E2, with the principle geometry axes. (© J.-U. Ho�mann, HZB) Figure 2: Schematic sketch of E2. 2 http://dx.doi.org/10.17815/jlsrf-4-110 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-4-110 Journal of large-scale research facilities, 4, A129 (2018) 2 Flat-Cone Geometry The �at-cone technique is a special case of the Weissenberg techniques which were developed earlier in X-ray di�ractometry using photographic detectors. In these methods a single crystal rotates around the normal vector of the scattering plane, so that we get a �at disc into the reciprocal-space, recorded along straight lines on a cylindrical �lm. If only one line is selected by putting a linear aperture in front of the �lm, then a two-dimensional lattice plane can be mapped on the two-dimensional �lm by coupling the crystal rotation and the �lm translation. The same procedure can be realized with a two-dimensional (electronic) multidetector which is placed along one layer line. For each rotational angle of the crystal a separate measurement has to be made. In comparison, earlier used �lms and linear detector systems have of course a loss in resolution perpendicular to the layer line. On E2 the used two-dimensional detector system can measure a high cylindrical range of the reciprocal space. The sample table is equipped with a special cradle system which allows a turntable (ϕ axis) to be tilted by an angle (0 ≤ µ < 20 °) around the shaft of the lift up system of the detector bank. The detector with its shielding can be tilted by the same amount around the axis which is perpendicular to the direction of the incident beam in most of our experiments. An example to calculate upper layer: With c* vertical, the layer (h,k,x) can be scanned if one inclines the cradle which is parallel to the beam by an angle µ and the detector by lift up the same angle (µ ). The formula in the simplest case is: sin µ = x λ /c with c = 1/c* and the wavelength λ . Figure 3: Flat-Cone Geometry in the reciprocal space. 3 Typical Applications • Representation of complex distributions of superstructure re�ections in the reciprocal space us- ing the Flat-Cone technique (Chmielus et al., 2011) • Determination of commensurate and incommensurate crystal and magnetic structures (Inosov et al., 2009a) • Di�use scattering arising from structural and magnetic short-range order (Kaiser et al., 2009) • Temperature, magnetic and electric �eld, as well as pressure dependent changes of crystal and magnetic structures (Lottermoser et al., 2004) • Investigations of structural and magnetic phase transitions • In-situ kinetics of chemical reactions (Fahr et al., 2001) 3 http://dx.doi.org/10.17815/jlsrf-4-110 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 4, A129 (2018) http://dx.doi.org/10.17815/jlsrf-4-110 4 Data analysis and formats All data sets are stored into the international standard �le format Nexus (Könnecke et al., 2015) for easy data exchanges and converting. In order to handle the sample orientations and instrumental geometry a new software package TVneXus (Windows 64 Application) was developed to transform collected data into the most useful physical space, e.g. 3D-reciprocal space or powder plots (Intensity over q), and including all necessary corrections such as e�ciency of the detector pixels and the integration along Debye-Scherrer cones. The required normalization and merging of data sets are saveable in suitable �le formats, e.g. as needed for other evaluation software packages such as FullProf. The 3D data sets can variously be stored in form of ASCII, HDF4 or Matlab �les, for use with standard visualization and scienti�c analysis tools. TVneXus can work together with the Matlab Server. TVneXus is able to visualize and analyze one and two-dimensional intensity distributions. 5 Sample Environment For measurements di�erent sample environments can be used: Temperatures from 30 mK up to 1700 K, vertical magnetic �elds up to 6.5 T, horizontal magnetic �elds up to 2 T, as well as electric �elds and high-pressure. The �at-cone option in combination with a magnet is limited to a vertical magnetic �eld up to 4.5 T and a maximum tilting angle of µ < 11° 6 Research areas and scienti�c highlights 6.1 Fast ion conductors and battery materials Ionic interactions between charge carriers result in complex short-ranged ordered structures, which de- termine functionality and charging/discharging behavior. Closely related are electrochemical reactions in solid state systems (Kaiser et al., 2009). 6.2 Ferroelectrics Ferroelectrics are technologically a very important class of materials. The properties of these materials have a close analogy to spin models. Further, new approaches to magnetic systems are applicable (Lottermoser et al., 2004). 6.3 Magneto-caloric materials A new research focusses on shape memory alloys for room temperature magnetic cooling as well as frustrated and quantum magnets for low temperature e�ects (Ustinov et al., 2009). 6.4 Novel thermoelectrics Narrow band frustrated metals theoretically can break the limits on the �gure of merit achievable with semiconductors (Roger et al., 2007). 6.5 Multifunctional oxides Multiferroics, CMR e�ects, and short range ordering (Hohlwein et al., 2003). 6.6 Intermetallics and heavy Fermion materials Complex ordering and changes under �eld and pressure. In�uence of site order/disorder e�ects (Inosov et al., 2009b). 4 http://dx.doi.org/10.17815/jlsrf-4-110 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-4-110 Journal of large-scale research facilities, 4, A129 (2018) 7 Technical Data Beam tube R 1B Collimation 15‘, 30‘, 60‘ (open) Monochromator • Cu (220) • Ge (311) • PG (002) Wave length • λ = 0.091 nm [Cu (200)] • λ = 0.121 nm [Ge (311)] • λ = 0.241 nm [PG (002)] Flux 2·10−6n/cm2s (�at PG monochromator without collimation) Range of scattering angles -10° < 2θ Θ < 107° Angle resolution • Horizontal resolution: 0.2° - 0.1° • Vertical resolution: 0.5° - 0.1° • Pixel size 0.1°x0.1° Detector Four 2D delay-line detectors (PSD 300 x 300 mm2) Tilting angle 0° < µ < 18° Instrument options • Single crystal mode • Powder di�raction mode Software TVneXus Table 1: Technical parameters of E2. References Chmielus, M., Glavatskyy, I., Ho�mann, J.-U., Chernenko, V. A., Schneider, R., & Müll- ner, P. (2011). 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V., Kordyuk, A. A., . . . Büchner, B. (2009a). Electronic Structure and Nesting-Driven Enhancement of the RKKY Interaction at the Magnetic Ordering Propagation Vector in Gd2PdSi3 and Tb2PdSi3. Phys. Rev. Lett., 102, 046401. http://dx.doi.org/10.1103/PhysRevLett.102.046401 Inosov, D. S., Evtushinsky, D. V., Koitzsch, A., Zabolotnyy, V. B., Borisenko, S. V., Kordyuk, A. A., . . . Büchner, B. (2009b). Electronic Structure and Nesting-Driven Enhancement of the RKKY Interaction 5 http://dx.doi.org/10.17815/jlsrf-4-110 http://dx.doi.org/10.1016/j.scriptamat.2011.01.025 http://dx.doi.org/10.1109/77.919792 http://dx.doi.org/10.1103/PhysRevB.68.140408 http://dx.doi.org/10.1107/S002188988608946X http://dx.doi.org/10.1103/PhysRevLett.102.046401 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 4, A129 (2018) http://dx.doi.org/10.17815/jlsrf-4-110 at the Magnetic Ordering Propagation Vector in Gd2PdSi3 and Tb2PdSi3. Phys. Rev. Lett., 102, 046401. http://dx.doi.org/10.1103/PhysRevLett.102.046401 Kaiser, I., Boysen, H., Frey, F., Lerch, M., Hohlwein, D., & Schneider, R. (2009). Di�use scattering in quaternary single crystals in the system Zr-Y-O-N. Zeitschrift für Kristallographie - Crystalline Materials, 215(8), 437–440. http://dx.doi.org/10.1524/zkri.2000.215.8.437 Könnecke, M., Akeroyd, F. A., Bernstein, H. J., Brewster, A. S., Campbell, S. I., Clausen, B., . . . Wut- tke, J. (2015). The NeXus data format. Journal of Applied Crystallography, 48(1), 301–305. http://dx.doi.org/10.1107/S1600576714027575 Lottermoser, T., Lonkai, T., Amann, U., Hohlwein, D., Ihringer, J., & Fiebig, M. (2004). Magnetic phase control by an electric �eld. Nature, 430(6999), 541–544. http://dx.doi.org/10.1038/nature02728 Morris, D. J. P., Tennant, D. A., Grigera, S. A., Klemke, B., Castelnovo, C., Moessner, R., . . . Perry, R. S. (2009). Dirac Strings and Magnetic Monopoles in the Spin Ice Dy2Ti2O7. Science, 326(5951), 411–414. http://dx.doi.org/10.1126/science.1178868 Roger, M., Morris, D. J. P., Tennant, D. A., Gutmann, M. J., Go�, J. P., Ho�mann, J. U., . . . Deen, P. P. (2007). Patterning of sodium ions and the control of electrons in sodium cobaltate. Nature, 445(7128), 631–634. http://dx.doi.org/10.1038/nature05531 Ustinov, A., Olikhovska, L., Glavatska, N., & Glavatskyy, I. (2009). Di�raction features due to ordered distribution of twin boundaries in orthorhombic Ni–Mn–Ga crystals. Journal of Applied Crystallog- raphy, 42(2), 211–216. http://dx.doi.org/10.1107/S0021889809007171 6 http://dx.doi.org/10.17815/jlsrf-4-110 http://dx.doi.org/10.1103/PhysRevLett.102.046401 http://dx.doi.org/10.1524/zkri.2000.215.8.437 http://dx.doi.org/10.1107/S1600576714027575 http://dx.doi.org/10.1038/nature02728 http://dx.doi.org/10.1126/science.1178868 http://dx.doi.org/10.1038/nature05531 http://dx.doi.org/10.1107/S0021889809007171 https://creativecommons.org/licenses/by/4.0/ Introduction Flat-Cone Geometry Typical Applications Data analysis and formats Sample Environment Research areas and scientific highlights Fast ion conductors and battery materials Ferroelectrics Magneto-caloric materials Novel thermoelectrics Multifunctional oxides Intermetallics and heavy Fermion materials Technical Data