Journal of large-scale research facilities, 3, A121 (2017) http://dx.doi.org/10.17815/jlsrf-3-161 Published: 22.11.2017 TREFF: Re�ectometer and instrument compo- nent test beamline at MLZ Heinz Maier-Leibnitz Zentrum Technische Universität München Forschungszentrum Jülich, Jülich Centre for Neutron Science * Instrument Scientists: - Egor Vezhlev, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 11654, email: e.vezhlev@fz-juelich.de - Stefan Mattauch, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 10709, email: s.mattauch@fz-juelich.de - Andreas Ofner, Heinz Maier-Leibnitz Zentrum, Technische Universität München, Garching, Ger- many, phone: +49(0) 89 289 14677, email: andreas.ofner@frm2.tum.de - Peter Link, Heinz Maier-Leibnitz Zentrum, Technische Universität München, Garching, Germany, phone: +49(0) 89 289 14622, email: peter.link@frm2.tum.de Abstract: TREFF is a high resolution polarized neutron re�ectometer and instrument component test beamline resulting in a highly modular instrument providing a �exible beam line for various applica- tions. 1 Introduction Serving for both purposes – high resolution polarized neutron re�ectometer and instrument component test beamline, TREFF has been consequently built to provide a modular and �exible set-up. A pyrolytic graphite (PG) monochromator (2) is re�ecting the the lower part of the neutron guide NL5- S (1) with a cross section of 29 × 100 mm2 under a �xed scattering angle of 2ΘM = 90° resulting in neutron beam with two monochromatic wavelengths of of λ = 4.73 Å (002) and λ /2 = 2.37 Å (004). The second monochromator (5) is redirecting the neutron beam back, parallel to the NL5-S neutron guide direction. Both of them are inside radiation shielding housings. A neutron guide element with m=2 supermirrors on the top and bottom faces (3) is placed between the two monochromators in order to *Cite article as: Heinz Maier-Leibnitz Zentrum et al.. (2017). TREFF: Re�ectometer and instrument component test beamline at MLZ. Journal of large-scale research facilities, 3, A121. http://dx.doi.org/10.17815/jlsrf-3-161 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-3-161 http://dx.doi.org/10.17815/jlsrf-3-161 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 3, A121 (2017) http://dx.doi.org/10.17815/jlsrf-3-161 increase the transported intensity in the vertical direction. The second shielding includes the cooled Be- �lter setup (4) and a beam monitor (6). The Be-�lter e�ectively scatters out neutrons with wavelength less than 4.05Å, thus serving here as �lter for the λ /2 = 2.37Å neutrons. Between 2nd monochromator and sample stage the primary beam collimation is realized by two remote controlled slits (8 & 10) with a distance of 1820mm. Further a Fe-Si supermirror can be moved into the beam path as polarizer (7) allowing together with the adiabatic rf resonant spin �ipper (9) polarized neutron experiments. Figure 1: Schematic layout of TREFF. The sample table (12) consists of stages for tilt φ (±7°) and χ (±20°) and rotation ω (±180°) with on top translation stages for x (±7 cm), y (±7 cm) and z (±7 cm). The sample may be pre-oriented by a laser. The sample table can carry loads up to 300 kg. The default detector arm for re�ectometry and di�raction is attached to a high precision bearing at the sample table. Motorized by a friction wheel scattering angles between -15°< 2Θ < 120° are accessible. It can easily be removed to give space for alternative setups, for instance a detector test bench or a Neutron Depth Pro�ling spectrometer. The 2D scintillation detector (16) is mounted at a distance of 1.9 m from the sample position at the end of a �ight tube, which can be �lled with He to reduce air scattering. Inside the tube as further components a beamstop (13), a spin �ipper (14) and the polarization analyzer (15) are placed. The magnetic guide �eld reaches to the analyzer position. The beamstop blocks the direct beam at small scattering angles to reduce detector background. It consists of a Li polymer with a cadmium stripe for a sharp edge and can be moved inside or outside the beam with a precision better than a detector pixel width. The polarization analyzer is a radial supermirror stack originally designed for HADAS (Rücker et al., 2000). A Mezei spin �ipper consisting of two Al coils with perpendicular winding is used to �ip the neutrons in front of the analyzer. The detector itself is a 2D scintillation detector with an active area of 80 mm in diameter, with a pixel size of 0.4 mm and a FWHM resolution of 1.2 mm. At the typical sample to detector distance of 1.9 m it covers an angular range of ∆2Θ = 2.4°. TREFF is operated using the MLZ standard control software NICOS. Scan data is written to plain text 2 http://dx.doi.org/10.17815/jlsrf-3-161 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-3-161 Journal of large-scale research facilities, 3, A121 (2017) �les containing the full instrument setup information and the scan data table. Further the detector images per scan point are saved as 256*256 pixel intensity information into separate �les. 2 Typical Applications The main purpose of TREFF is to serve as a development and test instrument for new instrument com- ponents and methods. Major applications are characterization and performance measurements of all kind of neutron detectors, di�raction measurements of the re�ectivity and mosaicity of monochroma- tor crystals and re�ectivity measurements ensuring quality control of supermirror coatings or even Neutron Depth Pro�ling measurements. 3 Sample Environment Standard holders for re�ectometry samples including a vacuum suction holder are available. Further an electromagnet (0.3 T without pole shoes, maximum sample height 13 cm, 0.7 T with pole shoes, maximum sample height 5 cm) and the corresponding closed cycle cryostat (T ≥ 3.5 K, maximum sample height 2 cm, including an electric �eld setup for up to 500 V), is available besides other devices from the MLZ sample environment pool. 4 Technical Data 4.1 Primary Beam • Located at the neutron guide NL5-S • Monochromator: PG(002) double monochromator • Wavelength: 4.73 Å / 2.37 Å (PG 002/004) • vertical sample, horizontal scattering plane 4.2 Distances and Angles • 1820 mm distance S1 – S2 (collimation) • 400 mm distance S2 – sample • 50 mm x 40 mm (w x h) max. opening S2 • 1910 mm distance sample – detector • -15° to 120° maximum detector angle 4.3 Polarisation Analysis • FeSi transmission polarizer • rf spin �ipper before sample position • Mezei type spin–�ipper after sample position • remanent FeCoV / TiN supermirror analyzer 4.4 Detector • 2D Scintillation detector • active area Ø 80 mm • pixel size 0.4 mm • FWHM resolution 1.2 mm 3 http://dx.doi.org/10.17815/jlsrf-3-161 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 3, A121 (2017) http://dx.doi.org/10.17815/jlsrf-3-161 References Rücker, U., Alefeld, B., Bergs, W., Kentzinger, E., & Brückel, T. (2000). The new polarized neutron re- �ectometer in Jülich. Physica B: Condensed Matter, 276-278, 95 - 97. http://dx.doi.org/10.1016/S0921- 4526(99)01257-0 4 http://dx.doi.org/10.17815/jlsrf-3-161 http://dx.doi.org/10.1016/S0921-4526(99)01257-0 http://dx.doi.org/10.1016/S0921-4526(99)01257-0 https://creativecommons.org/licenses/by/4.0/ Introduction Typical Applications Sample Environment Technical Data Primary Beam Distances and Angles Polarisation Analysis Detector