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Lichtenbergstr.1
85748 Garching

TOFTOF

Cold neutron time-of-flight spectrometer

This instrument is focussed on cold neutrons. Therefore, please carefully check the “Technical data WITHOUT cold source” section. Deviating parameters are in bold. The instrument team is happy to answer any further questions!

Insrumentscheme TOFTOF Insrumentscheme TOFTOF

TOFTOF is a direct geometry disc-chopper time-of-flight spectrometer. Offering an excellent signal-to-background ratio and a variable energy resolution, it is also adaptable to a wide range of sample environments. TOFTOF is ideal for investigating fundamental concepts and challenges in physics and materials science.

TOFTOF is suitable for both inelastic and quasi-elastic neutron scattering, and the scientific questions addressed range from the dynamics in disordered materials in hard and soft condensed matter systems (such as polymer melts, glasses, molecular liquids, or liquid metal alloys), properties of new hydrogen storage materials to low-energy magnetic excitations in multiferroic compounds, and molecular magnets.

The neutron spectrum from the cold source is guided over a total length of ~60 m to the sample via an S-bended neutron guide. The S-shape of the neutron guide efficiently suppresses the fast neutron background and the excellent signal-to-noise. Within the primary spectrometer, the neutron guide tapers linearly. After the last chopper pair, an exchangeable neutron guide is installed, which can adjust the beam size illuminating the sample. Thus, an extended, homogenous beam spot with little divergence (23 × 47 mm2) or a focussed beam (10 × 10 mm2) offering a wavelength-dependent intensity gain up to a factor of 2.5 with some cost in terms of angular resolution can be used.

The broad energy neutron beam is transformed into a pulsed monochromatic by a cascade of seven fast-rotating chopper disks. After the sample, the scattered neutrons are detected by 1000 3He detector tubes with a time resolution of up to 50 ns. A sample-to-detector distance of 4 m is essential to achieve a good TOF resolution. Together with the high rotation speed of the chopper system (up to 22 000 rpm) and a high neutron flux in the wavelength range of 1.4 – 14 Å, this configuration enables a tuneable energy resolution.

Typical applications
  • Diffusion in liquid metals and alloys
  • Hydrogen dynamics in soft matter systems such as molecular liquids, polymer melts or colloids
  • Molecular magnetism, quantum criticality in heavy fermion compounds, low energy excitations in multiferroic materials and novel magnetic phases
  • Dynamic properties of energy storage materials, such as solid-state hydrogen storage materials, electrolytes for batteries and fuel cells, or gas storage materials
  • Energy-resolved quasi-elastic neutron scattering on proteins, vesicles, and biological materials
  • Kinetic studies of hydrogen binding, e.g. in concrete
  • Aging effects in disordered media and low-frequency dynamics in glasses
  • Biological activity and functionality of proteins and cells under pressure
Sample environment
Standard
  • CCR Cryostat: 4 – 500 K
  • 3He insertion device: down to 0.5 K
  • Dilution insert device: down to 50 mk
  • Circulation thermostat furnace: 274 – 400 K
  • High-temperature furnace: 300 – 2100 K
  • Magnet: 2.5 T
  • Hydraulic pressure cell: up to 400 MPa
  • Hydrogen gas handling equipment and pressure cell: 7 MPa H2, 50 – 400 K
  • LASER/LED illumination/ excitation of samples
Provided by collaborators
  • Electromagnetic levitator
  • Electrostatic levitator
  • Clamp pressure cell: few GPa
  • In-situ Raman spectroscopy: in combination with neutron spectroscopy
  • Variable gas phase sample environment: combination with Raman spectroscopy is possible
Technical data WITHOUT cold source
Primary spectrometer
  • Neutron guide: NL2a-u
  • Adjustable range of incident neutrons: 1.4 – ~5 Å
  • Number of chopper discs: 7
  • Chopper frequency range: 400 – 22000 min-1
  • Diameter of chopper disc: 600 mm
  • Cross section of neutron guide
    • At the entrance: 44 × 100 mm2
    • 20 cm in front of sample position: 23 × 47 mm2
    • Cross section of focussing guide: minimal 12 × 25 mm2
Secondary spectrometer
  • Sample-to-detector distance: 4 m
  • 1000 3He detector tubes
    • Angular range of the detector bank: -15° to -7° and 7° to 140°
    • Solid angle coverage: 12 m2 (0.75 sr)
  • Time resolution down to 50 ns
  • Elastic energy resolution: ~60 µeV – 3 meV
  • Range of energy transfers: -30 – 50 meV
Technical data WITH cold source
Primary spectrometer
  • Neutron guide: NL2a-u
  • Adjustable range of incident neutrons: 1.4 – 14 Å
  • Number of chopper discs: 7
  • Chopper frequency range: 400 – 22000 min-1
  • Diameter of chopper disc: 600 mm
  • Cross section of neutron guide
    • At the entrance: 44 × 100 mm2
    • 20 cm in front of sample position: 23 × 47 mm2
    • Cross section of focussing guide: minimal 12 × 25 mm2
Secondary spectrometer
  • Sample-to-detector distance: 4 m
  • 1000 3He detector tubes
    • Angular range of the detector bank: -15° to -7° and 7° to 140°
    • Solid angle coverage: 12 m2 (0.75 sr)
  • Time resolution down to 50 ns
  • Elastic energy resolution: ~2 µeV – 3 meV
  • Range of energy transfers: -30 – 50 meV

Instrument scientists

Dr. Marcell Wolf
Phone: +49 (0)89 289-14881
E-mail: marcell.wolf@frm2.tum.de

Dr. Christopher Garvey
Phone: +49 (0)89 289-12697
E-mail: christopher.garvey@frm2.tum.de

TOFTOF
Phone: +49 (0)89 289-14881

Operated and funded by

TUM

Publications

Find the latest publications regarding TOFTOF in our publication database iMPULSE:

impulse.mlz-garching.de

Citation of the instrument

Heinz Maier-Leibnitz Zentrum. (2015). TOFTOF: Cold neutron time-of-flight spectrometer. Journal of large-scale research facilities, 1, A15. http://dx.doi.org/10.17815/jlsrf-1-40

For citation please always include the DOI.

Instrument control

Gallery

TOFTOF_01
TOFTOF_01

Top view of the CCR Cryostat inserted into the TOFTOF sample chamber. The blue panelling visible is the exterior of the detector housing.

© W. Schürmann, TUM
TOFTOF_02
TOFTOF_02

Figure 1: Elastic resolution as a function of the incident neutron wavelength for selected chopper rotational frequencies.

© MLZ
TOFTOF_03
TOFTOF_03

Figure 2: Dynamic range of the TOFTOF spectrometer for different
incident wavelengths

© MLZ
TOFTOF_04
TOFTOF_04

Neutron flux

© MLZ

MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Hereon> Helmholtz-Zentrum Hereon
Forschungszentrum Jülich> Forschungszentrum Jülich

MLZ is a member of:

LENS> LENSERF-AISBL> ERF-AISBL

MLZ on social media: