Post Monochromators (OH2)

General Description

Two post-monochromators are installed in the second optical hutch for high energy resolution experiments. Both vessels can contain three sets of crystal pairs. For the moment both post-monochromators are mounted with Si(111), Si(220) and Si(331) channel cut crystals.

Two geometries are available for the post-monochromators setup while keeping the beam height aligned with the next hutches:

1. two post-monochromators with the same crystals surface in a channel-cut setting
2. one post-monochromator close to back-scattering conditions and the other one out of the way.

Channel-cut geometry

Using one or two post-monochromators allow better energy resolution than the one from the monochromator (around 1300meV at 10keV for Si(111)).

Energy resolution

The reflection width of the Si(555) post-monochromator was characterized by a Si(555) channel-cut analyzer crystal to be 19.8 meV at 10 keV which, after deconvolution, corresponds to an energy resolution of 14 meV, in good agreement with the theoretical value of 14.8 meV.