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85748 Garching

TOFTOF

Cold neutron time-of-flight spectrometer

This instrument is focussed on cold neutrons. All parameters given here are valid during the current operation of FRM II. Please get in touch with the instrument team well in advance for all further details (length of experiment etc.).

Insrumentscheme TOFTOF Insrumentscheme TOFTOF

TOFTOF is a direct geometry disc-chopper time-of-flight spectrometer located in the Neutron Guide Hall West. It offers an excellent signal-to-background ratio and a variable energy resolution. Adaptable for a wide range of sample environments, TOFTOF is ideal for investigations of 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.

A cascade of seven fast rotating disc choppers which are housed in four chopper vessels is used to prepare a monochromatic pulsed beam which is focussed onto the sample by a converging supermirror section. The scattered neutrons are detected by 1000 3He detector tubes with a time resolution up to 50 ns. The detectors are mounted at a distance of 4 m and cover 12 m2 (or 0.75 sr). The high rotation speed of the chopper system (up to 22 000 rpm) together with a wavelength range of 1.4 -~5 Å allows free tuning of the energy resolution between 3 meV and ~100 µeV.

The prototype of a new focussing neutron guide has been installed recently, as alternative option in the last section of the guide system. The existing linearly tapered neutron guide yields a beam spot size of 23 × 47 mm2. Using the focussing guide, an intensity gain up to a factor of 3 (wavelength dependent) is observed on a sample area of 10 × 10 mm2.

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 sample environment
  • CCR Cryostat (4 – 600 K)
  • 3He insertion device (down to 0.5 K)
  • Circulation thermostat furnace (255 – 450 K)
  • High temperature furnace (300 – 2100 K)
  • 2.5 T magnet
Sample environment provided by collaborators
  • Electromagnetic levitator
  • Electrostatic levitator
  • Hydraulic pressure cells (up to 3.5 kbar)
  • Clamp pressure cells (few GPa)
  • In-situ raman spectroscopy (in combination with neutron spectroscopy)
Technical Data
Primary Beam
  • Neutron guide: NL2a-u
  • Number of chopper discs: 7
  • Chopper frequency range: 400 min-1 – 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
Main Parameters
  • Adjustable range of incident neutrons: 1.4 – ~5 Å
  • Elastic energy resolution: ~100 µeV – 3 meV
  • Range of energy transfers: -30 meV – 50 meV
  • Angular range of the detector bank: -15° to -7° and 7° to 140°

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 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
TOFTOF

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
Elastic resolution
Elastic resolution

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

Dynamic range of the TOFTOF spectrometer
Dynamic range of the TOFTOF spectrometer

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

Expected neutron flux (simulated)
Expected neutron flux (simulated)

Fig. 3: Expected incident differential white neutron flux at the sample position (simulated).

© 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: