Disk chopper time-of-flight spectrometer

How does the IN5B time-of-flight spectrometer work?

IN5 is a typical direct geometry neutron Time-of-flight (ToF) spectrometer. This high precision instrument is used to study low-energy transfer processes as a function of momentum transfer (e.g. quasi-elastic scattering in solids, liquids, molecular crystals and inelastic scattering, etc).
The animation below (HTML5 or Flash ) shows how measurements are performed :

  • the continuous polychromatic neutron flux from the neutron guide H16 is turned into a pulsed monochromatic beam by a set of 6 choppers.
  • the monochromatic neutron bursts are inelastically scattered by the sample, either a liquid, a powder or a single crystal.
  • the scattered neutrons are collected by a huge detectors array  covering 30 m2.
  • the time-of-flight analysis of incoming neutrons from each monochromatic burst results in a three dimensional spectrum x, y (detector position), t (time).

 This gives access to the so-called dynamic structure factor, S(Q,ω), describing the structure and dynamics of the sample at atomic level.