Journal of large-scale research facilities, 1, A27 (2015) http://dx.doi.org/10.17815/jlsrf-1-33 Published: 19.08.2015 DNS: Di�use scattering neutron time-of-�ight spectrometer Heinz Maier-Leibnitz Zentrum Forschungszentrum Jülich, Jülich Centre for Neutron Science Instrument Scientists: - Yixi Su, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 10740, email: y.su@fz-juelich.de - Kirill Nemkovskiy, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 10779, email: k.nemkovskiy@fz-juelich.de - Sultan Demirdiş, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching, Germany, phone: +49(0) 89 289 10717, email: s.demirdis@fz-juelich.de Abstract: DNS is a versatile di�use scattering instrument with polarisation analysis operated by the Jülich Centre for Neutron Science (JCNS), Forschungszentrum Jülich GmbH, outstation at the Heinz Maier-Leibnitz Zentrum (MLZ). Compact design, a large double-focusing PG monochromator and a highly e�cient supermirror-based polarizer provide a polarized neutron �ux of about 107 n cm-2 s-1. DNS is used for the studies of highly frustrated spin systems, strongly correlated electrons, emergent functional materials and soft condensed matter. 1 Introduction DNS allows the unambiguous separation of nuclear coherent, spin incoherent, and magnetic scattering contributions simultaneously over a large range of scattering vector Q and energy transfer E. With its compact size DNS is optimised as a high intensity instrument with medium Q- and E- resolution. The general view of DNS and instrument layout are shown in Figure 1 and 2. New chopper, neutron velocity selector, and position sensitive detector systems have recently been installed at DNS. This is expected to largely improve possibilities for single-crystal time-of-�ight spec- troscopy with e�cient measurements in all four dimensions of S(Q,E). With its unique combination of single-crystal time-of-�ight spectroscopy and polarisation analysis, DNS is also complimentary to many modern polarised cold neutron three axes spectrometers. 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-1-33 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 1, A27 (2015) http://dx.doi.org/10.17815/jlsrf-1-33 Figure 1: Di�use neutron scattering spectrometer DNS (Copyright by W. Schürmann, TUM). 2 Typical Applications With the increased �ux and e�ciency delivered by the FRM II, DNS becomes ideal for the studies of complex spin correlations, such as in highly frustrated magnets and strongly correlated electrons, as well as of the structures of soft condensed matter systems, such as the nanoscale con�ned polymers and proteins, via polarisation analysis. The exploration of unusual magnetic properties can also be e�ciently undertaken on single-crystal samples by reciprocal space mapping. In addition to the sep- aration of magnetic cross section from nuclear and spin-incoherent ones, polarisation analysis also allows to distinguish in detail the anisotropy of spin correlations. It has also been well demonstrated that polarised powder di�raction on DNS is complementary to standard neutron powder di�raction and may be extremely useful for magnetic structure re�nements, particularly in case of small moments by improving the signal to background ratio. DNS also represents a powerful instrument for the soft condensed matter community for the separation of nuclear coherent scattering from often dominating spin incoherent scattering background. The main applications can be summarised: • Application of polarisation analysis: uniaxial-, longitudinal-, and vector-PA • Magnetic, lattice, and polaronic correlations: geometrically frustrated magnets, strongly correlated electrons, emergent materials • Single-crystal and powder time-of-�ight spectroscopy: single-particle excitations, magnons and phonons • Soft condensed matters: separation of coherent scattering from hydrogenous materials, polymer, liquids and glasses 3 Sample Environment • Top-loading CCR • Closed-cycle cold head • Orange-type cryostat • Cryo-furnace • Dilution 3He/ 4He cryostat insert (∼20 mK) • Cryomagnet (self-shielding, vertical �eld up to 5 T) 2 http://dx.doi.org/10.17815/jlsrf-1-33 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-1-33 Journal of large-scale research facilities, 1, A27 (2015) Figure 2: Schematic drawing of DNS. 4 Technical Data 4.1 Monochromator • Neutron guide NL6-S • Horizontally and vertically adjustable, double-focusing • PG(002), d = 3.355 Å • Crystal dimensions: 2.5 x 2.5 cm2 (5 x 7 crystals) • Wavelength range: 2.4 Å < λ < 6 Å 4.2 Neutron velocity selector • Minimum wavelength: 1.5 Å @ 22000 rpm • Resolution ∆λ /λ : 30 – 40 % 4.3 Chopper • Chopper frequency ≤ 300 Hz • Repetition rate ≤ 900 Hz • Chopper disc: Titanium, 3 slits, Ø = 420 mm 4.4 Flux at sample • Non-polarised: ∼ 108 n cm-2 s-1 • Polarised: ∼ 5 · 106 – 107 n cm-2 s-1 (polariser: m = 3 supermirror benders) 4.5 Detector banks for non-polarised neutrons • 128 position sensitive 3He tubes: Ø = 1.27 cm, height ∼100 cm • Total solid angle covered: 1.9 sr • Covered scattering angles in the horizontal plane: 0° < 2 θ ≤ 135° 3 http://dx.doi.org/10.17815/jlsrf-1-33 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 1, A27 (2015) http://dx.doi.org/10.17815/jlsrf-1-33 4.6 Detector banks for polarised neutrons • 24 detection units: Polarisation analysis by m = 3 supermirror benders 3He detector tubes, Ø = 2.54 cm, height 15 cm • Covered scattering angle in the horizontal plane: 0° < 2θ ≤ 150° • Qmax λ i = 2.4 Å (Ei = 14.2 meV): 4.84 Å-1 λ i = 6 Å (Ei = 2.28 meV): 1.93 Å-1 4.7 Energy resolution • λ i = 2.4 Å (Ei = 14.2 meV): 1 meV • λ i = 6 Å (Ei = 2.28 meV): 0.1 meV 4 http://dx.doi.org/10.17815/jlsrf-1-33 https://creativecommons.org/licenses/by/4.0/ Introduction Typical Applications Sample Environment Technical Data Monochromator Neutron velocity selector Chopper Flux at sample Detector banks for non-polarised neutrons Detector banks for polarised neutrons Energy resolution