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.