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

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 by

Funded by

Publications

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

impulse.mlz-garching.de

Citation templates for users

In all publications based on experiments on this instrument, you must provide some acknowledgements. To make your work easier, we have prepared all the necessary templates for you on this page.