SEQUOIA—Fine-Resolution Fermi Chopper Spectrometer
SEQUOIA detector array
SEQUOIA is a direct geometry time-of-flight chopper spectrometer with fine energy transfer (ω) and wave-vector (Q) resolution 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 fluctuations 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
SEQUOIA is also an outstanding tool for the investigation of novel systems and materials that are currently unknown and complements the other main 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 at low-to-intermediate scattering angles.
To meet the technical requirements of fine resolution in both ω and Q, a 5.5 m flight path from the sample to detector bank is required. This detector bank 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 1.61 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 a couple of electron volts.
A supermirror neutron guide is included on the instrument to further enhance the flux of thermal neutrons on the sample.