SANS experiment planner
Estimate the accessible momentum-transfer range and instrument resolution for a pinhole-collimated small-angle neutron scattering (SANS) geometry. Laboratory frame: x is the direct beam, y horizontal on the detector, z vertical.
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1. Detector geometry
Uses Q = 4π sin(θ)/λ with θ the half scattering angle. Visible Q is bounded by the beamstop (inner radius) and the detector edges (outer radius), measured from the beam position on the detector.
Accessible range
|Q| range
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Real-space distance
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d = 2π / |Q|2θ range
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Scattering geometry
2. Collimation & resolution
Pinhole collimation and wavelength spread contributions to the resolution function.
Instrument resolution vs |Q|
3. Scattering vector of interest
Specify a momentum transfer to evaluate scattering angle, resolution components, and qz. The point is marked on all plots above. Real-space scales from instrumental Q widths use ξ = 1/σ and ξFWHM = 1/FWHMQ, with σ and FWHMQ in Å⁻¹ and ξ in Å.
4. Calculate sample correlation length
Enter the observed peak width in each direction. Instrumental widths from section 3 are subtracted in quadrature: σobs² = σsample² + σinst². Sample correlation lengths use ξ = 1/σsample and ξFWHM = 1/FWHMsample (σ and FWHM in Å⁻¹; ξ in Å).
Configuration
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