Journal of large-scale research facilities, 1, A30 (2015) http://dx.doi.org/10.17815/jlsrf-1-38 Published: 19.08.2015 SPHERES: Backscattering spectrometer Heinz Maier-Leibnitz Zentrum Forschungszentrum Jülich, Jülich Centre for Neutron Science Instrument Scientists: - Michaela Zamponi, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 10793, email: m.zamponi@fz-juelich.de - Marina Khaneft, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 11676, email: m.khaneft@fz-juelich.de Abstract: SPHERES (SPectrometer for High Energy RESolution), operated by JCNS, Forschungszen- trum Jülich, is a third-generation neutron backscattering spectrometer with focussing optics and a phase-space-transform chopper. It enables the investigation of atomic and molecular dynamics with an energy resolution of about 0.65 µeV in a dynamic range of ± 31 µeV. 1 Introduction The high energy resolution of a backscattering spectrometer is achieved by Bragg re�ection from per- fect monochromator and analyzer crystals under angles close to 180°. Due to this geometry a primary beam de�ector and a duty-cycle chopper is needed. At SPHERES, both functions are realised in one by a chopper with de�ector crystals on its circumference. As an additional advantage, the fast motion of the de�ector crystals achieves a phase-space transformation of the primary spectrum, thereby enhancing the usable �ux at the monochromator. A schematic view of this compact spectrometer layout is shown in Figure 2. The principal �gures of merit qualify SPHERES as one of the best of its class (Wuttke et al., 2012). Count rates and signal-to-noise ratio have been improved by �lling the instrument housing with argon, thereby avoiding air scattering in the secondary spectrometer. Another gain in �ux will be achieved by a more e�cient phase-space transform chopper which is in the commissioning phase. The new designed chopper will be more e�cient due to optimised rotation speed and higher re�ectivity and mosaicity of the graphite crystals. The resolution of the small angle detectors have been improved by reducing the azimuth angle range of the analyzers (Wuttke & Zamponi, 2013). 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-1-38 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 1, A30 (2015) http://dx.doi.org/10.17815/jlsrf-1-38 Figure 1: View inside SPHERES: the large array of Si(111) analyzer crystals covers a solid angle of about 2.5, which is 20 % of 4 π (Copyright by A. Heddergott, TUM). As a multi-detector instrument with relaxed angular resolution, SPHERES is particularly suited for studying tagged-particle motion by incoherent scattering. Typical applications include for example dynamical processes in polymers and biological systems (Gallat et al., 2012). The high resolution and sensitivity of the spectrometer allows to investigate the dynamics of water in con�ned geometry and deep in the supercooled state (Doster et al., 2010). The high count rates allow inelastic temperature scans (Häußler et al., 2011) and real-time kinetic experiments (Léon & Wuttke, 2011). Further applications are hyper�ne splitting in magnetic materials (Chatterji et al., 2008) and rotational tunneling (Bator et al., 2013). 2 Typical Applications • Hyper�ne splitting • Molecular reorientations and rotational tunneling • Dynamic signature of phase transitions • Hydrogen di�usion • Liquid dynamics • Polymer relaxation • Protein aggregation 2 http://dx.doi.org/10.17815/jlsrf-1-38 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-1-38 Journal of large-scale research facilities, 1, A30 (2015) Figure 2: Schematic drawing of SPHERES. 3 Sample Environment • Cryofurnace 3...700 K • Dilution inset 20 mK • Furnace 4 Technical Data 4.1 Primary beam • Neutron guide: NL6-S • Neutron wavelength: 6.27 Å • Neutron energy: 2.08 meV 4.2 Main parameters • Resolution FWHM 0.62 – 0.65 µeV • Dynamic range ± 31 µeV • Q range 0.2 – 1.8 Å-1 • Flux after selector 1010 s-1 • Flux at sample 1.8 · 106 s-1 • Illuminated area 40 x 30 mm2 3 http://dx.doi.org/10.17815/jlsrf-1-38 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 1, A30 (2015) http://dx.doi.org/10.17815/jlsrf-1-38 References Bator, G., Sobczyk, L., Sawka-Dobrowolska, W., Wuttke, J., Pawlukojć, A., Grech, E., & Nowicka-Scheibe, J. (2013). Structural, spectroscopic and theoretical studies on 3,4,7,8- tetramethyl-1,10-phenantroline complex with picric acid. Chemical Physics, 410, 55-65. http://dx.doi.org/10.1016/j.chemphys.2012.10.012 Chatterji, T., Schneider, G. J., & Galera, R. M. (2008). Low-energy nuclear spin excitations in NdMg3 and NdCo2. Physical Review B, 78, 012411. http://dx.doi.org/10.1103/PhysRevB.78.012411 Doster, W., Busch, S., Gaspar, A. M., Appavou, M.-S., Wuttke, J., & Scheer, H. (2010). Dynamical Transition of Protein-Hydration Water. Physical Review Letters, 104, 098101. http://dx.doi.org/10.1103/PhysRevLett.104.098101 Gallat, F.-X., Brogan, A. P. S., Fichou, Y., McGrath, N., Moulin, M., Härtlein, M., . . . Weik, M. (2012). A Polymer Surfactant Corona Dynamically Replaces Water in Solvent-Free Protein Liquids and Ensures Macromolecular Flexibility and Activity. Journal of the American Chemical Society, 134, 13168-13171. (PMID: 22853639) http://dx.doi.org/10.1021/ja303894g Häußler, W., Holderer, O., Unruh, T., & Wuttke, J. (2011). High-Resolution Neutron Spectroscopy at the FRM II. Neutron News, 22, 24-30. http://dx.doi.org/10.1080/10448632.2011.598804 Léon, A., & Wuttke, J. (2011). Hydrogen release from sodium alanate observed by time-resolved neutron backscattering. Journal of Physics: Condensed Matter, 23, 254214. http://dx.doi.org/10.1088/0953- 8984/23/25/254214 Wuttke, J., Budwig, A., Drochner, M., Kämmerling, H., Kayser, F.-J., Kleines, H., . . . Staringer, S. (2012). SPHERES, Jülich’s high-�ux neutron backscattering spectrometer at FRM II. Review of Scienti�c Instruments, 83, 075109. http://dx.doi.org/10.1063/1.4732806 Wuttke, J., & Zamponi, M. (2013). Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES. Review of Scienti�c Instruments, 84, 115108. http://dx.doi.org/10.1063/1.4831815 4 http://dx.doi.org/10.17815/jlsrf-1-38 http://dx.doi.org/10.1016/j.chemphys.2012.10.012 http://dx.doi.org/10.1103/PhysRevB.78.012411 http://dx.doi.org/10.1103/PhysRevLett.104.098101 http://dx.doi.org/10.1021/ja303894g http://dx.doi.org/10.1080/10448632.2011.598804 http://dx.doi.org/10.1088/0953-8984/23/25/254214 http://dx.doi.org/10.1088/0953-8984/23/25/254214 http://dx.doi.org/10.1063/1.4732806 http://dx.doi.org/10.1063/1.4831815 https://creativecommons.org/licenses/by/4.0/ Introduction Typical Applications Sample Environment Technical Data Primary beam Main parameters