Fine-Resolution Fermi Chopper Spectrometer


Mission Statement

Studying dynamic processes in novel systems

Instrument Description

SEQUOIA is a direct geometry time-of-flight chopper spectrometer with fine energy transfer (ω) and wave-vector (Q) resolution capabilities used for forefront research on dynamical processes in materials. In particular, SEQUOIA allows for unprecedented high-resolution inelastic neutron scattering studies of magnetic excitations and lattice vibrations. 


Condensed matter and materials science experiments cover a wide cross-section of important research areas such as the following:

  • strongly correlated electrons systems
  • high-temperature superconductors
  • colossal magnetoresistive materials
  • quantum and molecular magnetism
  • itinerant magnets and multilayers
  • ferroelectric, piezoelectric, and thermoelectric materials
  • soft condensed matter
  • alloys

SEQUOIA’s flexibility has been advantageous when measuring systems that have never been examined with inelastic neutron scattering techniques. SEQUOIA complements the other main thermal to epithermal SNS chopper spectrometer, ARCS. In general, SEQUOIA is the instrument of choice for experiments that require high Q and ω resolution and large solid angle coverage at low-to-intermediate scattering angles.

To meet the technical requirements of fine resolution in both ω and Q, SEQUOIA has a 5.5 m flight path from the sample to detector bank. This detector bank currently covers scattering angles from -30 to 60° in the horizontal and from -18 to 18° in the vertical in increments of ≈0.3°. Therefore the total solid angle coverage is .863 steradians. To optimize the flux on sample in this high-resolution configuration, the moderator-to-sample distance is as short as possible (i.e., 20 m). SEQUOIA uses the full source spectrum provided by the decoupled water moderator and can therefore be used to study excitations on energy scales ranging from a few millielectron volts up to several electron volts.

A supermirror neutron guide is included on the instrument to further enhance the flux of thermal neutrons on the sample.


Source-sample distance 20.0 m
Mean sample-detector distance 5.53 m
Angular coverage Horizontally -30 to 60 deg.
Vertically: +/- 18
Range of energy resolution 1–5% Ei
Typical incident energy range 8-2000 meV