Instrument Description

CORELLI is a statistical chopper spectrometer with energy discrimination. It's designed and optimized to probe complex disorder in crystalline materials through diffuse scattering of single-crystal samples. The momentum transfer ranges from 0.5 to 12 Å-1, and the energy of incident neutrons ranges from 10 to 200 meV.

This instrument combines the high efficiency of white-beam Laue diffraction with energy discrimination by modulating the beam with a statistical chopper. A cross-correlation method is used to reconstruct the elastic signal from the modulated data. Accurate modeling of the short-range order associated with the diffuse scattering requires measurements over large volumes of three-dimensional reciprocal space, with sufficient momentum resolution to distinguish the diffuse signal from the strong Bragg peaks.

Applications

  • Material science, including colossal magnetoresistance materials, ferroelectric relaxors, and fast ion conductors
  • Condensed matter physics, including high-temperature superconductors, geometrically frustrated systems, and quantum critical phenomena
  • Molecular systems, including molecular solids and microporous framework systems

Specifications

Moderator Ambient H2O decoupled poisoned
Source- to-sample distance 20 m
Sample- to-detector distance 2.5 m
Anular coverage -21.9 to +148.2° horizontally ±28.5°vertically
Energy resolution ΔE/Einc ~0.9% (FWHM) at Einc=25 meV
Momentum resolution ΔQ/Q ≤ 7x10-3at 90oat Q=10 Å-1
Incident energy range 10–200 meV
Momentum transfer 0.5 - 16 Å-1
Beam size at sample position ~8 mm/width x 12mm/height
Minimum solid angle coverage 2.0 sr