Monochromator crystals
Monochromators
The monochromator is the first and most important optical component of most ILL instruments.
While many cold-neutron instruments use pyrolytic graphite which is commercially available with a controlled mosaic, monochromators and analysers for thermal and hot neutrons have had to be developed and produced in-house.
The ILL has acquired world-leading skills in the production of large copper and Heusler alloy crystals with controlled mosaic.
We also modify home-grown and commercially available germanium crystals to obtain specific values of curvature and mosaic.
The Monochromator Team
Jérémie Baudin-Cavallo, Roland Hehn, Philipp Gausmann, Catherine Menthonnex, Benoît Mestrallet
Crystal Growth
Recent progress in the growth of large copper single crystals at ILL has resulted in the production of copper crystals with a very narrow and uniform mosaic spread in the range of 20 seconds to 1 arc-minute. We have also succeeded in growing high-quality germanium single crystals with a neutron mosaic spread of up to 0.1° and Heusler single crystals with a specific mosaic.
Crystal Preparation
Double-focusing monochromator
High-flux three-axis spectrometer
λ = 1.5Å
flux = 4.6 108 n.cm-2S-1
Δd/d = 10-3
flux ~ 107 n.cm-2S-1
A gamma-ray Laue lens
High quality copper single crystals can be used to make a gamma-ray Laue lens for astrophysical applications
Three-axis spectrometer Polarised Neutrons
λ = 1.5 Å
flux = 8 107 n.cm-2S-1
How to control the mosaic
Controlling the mosaic
Plastic deformation
Single crystals can be produced with a desired mosaic spread using high-temperature plastic deformation techniques
