TOFTOF

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, high energy resolution and high neutron flux. 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 high neutron flux in the wavelength range of 1.4 -14 Å allows free tuning of the energy resolution between 3 meV and 2 µeV.

The 60 m primary neutron guide has an s-shape which efficiently suppresses fast neutron background. This enables the investigation of weak signals. 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.