Study and implementation of a soft X-ray 100 eV -20 keV fixed exit monochromator system

We describe a “built in house” X-ray monochromator which produces a fixed exit X-ray beam tunable in the fullenergy range 0.1 - 20 keV. The system is based on a double diffraction on two large size parallel crystals positionedusing a remotely controlled micropositioning system in order to keep the position of the monochromatic beamfor any chosen energy. Up to six different diffracting elements can be selected without breaking the vacuum.This allows to cover the full energy range of interest. The system is part of an upgrading project of the XACTfacility at the Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Palermo G.S. Vaiana, and will beemployed for the testing and calibration of filters, detectors and optics at X-ray wavelengths.