V12a

Bent-crystal Diffractometer (USANS) with Tomography option

Instrument description

An asymmetrically cut perfect Si single crystal monochromator is located is deflecting neutrons of 4.76 Å by (111) Bragg diffraction towards the sample position and the downstream end face of a completely asymmetrically cut analyzer crystal. The asymmetry of the monochromator (α = 41°) changes the beam cross section from 3 x 5 cm2 of the guide to 0.5 x 5 cm2 at the sample side. After penetrating and interacting with a sample the beam passes a 0.3 x 2 cm2 slit, enters the bent perfect Si single crystal analyzer and propagates along its long side. At the spot in the crystal, where the Bragg condition is satisfied, neutrons are deflected through the long side of the crystal towards the position sensitive detector. Neutrons which were scattered by an interaction in the sample will be deflected at a different spot in the analyzer and hence are registered in a different part of the detector than without interaction. By comparison with the empty beam scattering angles of the order of seconds of arc can be resolved on an angular range up to 0.5°.

V12 is complementing small angle scattering machines on the low angle side with overlapping q-ranges. Furthermore equipped with a 2-dimensional position sensitive detector spatial resolved USANS investigations and even tomographies can be performed.

Applications

  • porous materials (i.g. cement, paste, rocks, coal etc.)
  • particles and inhomogeneities on a size range from 50 nm to 10 µm
  • artificial regular structures (e.g. phase gratings) 
  • magnetic domains (e.g. Bloch walls) 

Selected examples

β-carotene

Instrument layout



List of publications
Instrument Data
Neutron guide NL 3B
Collimation
Monochromator Perfect Si single crystal (111), edged, asymmetric alpha
Wave length λ=0.476 nm
Wave length resolution
Flux 2•103 n/cm2
Q range 10-3 nm -1 < Q < 10-1 nm -1
Q resolution ΔQ/Q=1.5·10-4 nm -1
Detector linear PSD (3He)
2D PSD (3He)
Sample-to-detector distance
Polarized neutrons no
Instrument options • spatial resolved USANS (using 2D PSD)
• tomography
Sample environment
Software
Diffraction analyser crystals perfect Si single crystal (111), edged, completly asymmetric