General desciption of the ID21 Optics hutch: 

The optical components in this hutch are dedicated for cleaning the beam, i.e. filtering the beam and reducing the power on the downstream optics which may affect its stability. If  the "pink" beam is efficiently "cleaned" and collimated there is no shielding required downstream of the collimator. This strategy  has not only an obvious financial impact upon the beamline design cost but also allows relatively free access to the microscope during the experiments.

This strategy is followed by a 2-mirror device combined with a Bremsstrahlung stop and a collimator downstream of the primary slits. The fixed exit 2-mirror device reduces the maximum integrated power by two reflections from at maximum 700W down to 50W.  90% of the unwanted part of the spectrum is absorbed by the first mirror.  Furthermore the cut-off angle can be tuned from 5 to 20 mrad allowing harmonic rejections better than 10-3 for any energy ranging from 1 to 6 keV. At these small grazing angles the position of the exit beam is effectively fixed.



Separation of the bremsstrahlung radiation from the synchrotron radiation: the combination of the mirror device with a Bremsstrahlung stop and a collimator allows a  tremendous reduction of the shielding required for the downstream beam transport.