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DNS

Diffuse scattering neutron time of flight spectrometer

DNS scheme DNS scheme

DNS is a versatile diffuse scattering cold neutron time-of-flight spectrometer with polarization analysis. It 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 optimized as a high intensity instrument with medium Q- and E- resolution.

New chopper and position sensitive detector systems are to be installed at DNS. This is expected to largely improve possibilities for single-crystal time-of-flight spectroscopy with efficient measurements in all 4 dimensions of S(Q,E). With its unique combination of single-crystal time-of-flight spectroscopy and polarization analysis, DNS is also complimentary to many modern polarized cold neutron triple-axis spectrometers.

Typical Applications

With the increased flux and efficiency at FRM II, DNS becomes ideal for the studies of complex spin correlations, such as in highly frustrated magnets and strongly correlated electrons, as well of the structures of soft condensed matter systems, such as the nanoscale confined polymers and proteins, via polarization analysis. The exploration of unusual magnetic properties can also be efficiently undertaken on single-crystal samples by reciprocal space mapping. In addition to the separation of magnetic cross section from nuclear and spin-incoherent ones, polarization analysis also allows to distinguish in detail the anisotropy of spin correlations. It has also been well demonstrated that polarized powder diffraction on DNS is complementary to standard neutron powder diffraction and may be extremely useful for magnetic structure refinements, 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 summarized as the follows,

  • Magnetic, lattice and polaronic correlations: geometrically frustrated magnets, strongly correlated electrons, emergent materials
  • Single-crystal and powder time-of-flight spectroscopy: single-particle excitations, magnons and phonons
  • Soft condensed matters: separation of coherent scattering from hydrogenous materials, polymer, liquids and glasses
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 field up to 5 T)
Technical Data

Monochromator

  • Neutron guide NL6-S
  • Horizontal- and vertically adjustable
  • double-focusing
  • PG (002), d = 3.355 Å
  • Crystal dimensions: 2.5 × 2.5 cm2 (5 × 7 crystals)
  • Wavelengths range: 2.4 Å < λ < 6 Å

Double chopper system

  • Chopper frequency: ≤ 300 Hz
  • Repetition rate: ≤ 900 Hz
  • Chopper disks: Titanium, 3 slits, Ø = 420 mm

Flux at sample

  • Non-polarized ~ 108 n cm-2 s-1
  • Polarized ~ 5 · 106 – 107 n cm-2 s-1
  • (polarizer: m = 3 supermirror benders)

Detector banks for non-polarized 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° < 2θ ≤ 135°

Detector banks for polarized neutrons

  • 24 detection units:
  • Polarization 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:
    • λi = 2.4 Å (Ei = 14.2 meV): 4.84 Å-1
    • λi = 6 Å (Ei = 2.28 meV): 1.93 Å-1

Energy resolution

  • λi = 2.4 Å (Ei = 14.2 meV): 1 meV
  • λi = 6 Å (Ei = 2.28 meV): 0.1 meV

Instrument Scientists

Dr. Yixi Su
Phone: +49.(0)89.289.10714
E-Mail:

Dr. Kirill Nemkovski
Phone: +49.(0)89.289.10779
E-Mail:

DNS
Phone: +49.(0)89.289.14339 /.14876

Operated by

JCNS

Gallery

DNS
DNS

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich