A post-monochromator is installed in tandem with the main monochromator in order to further improve the X-ray beam energy resolution. High-resolution is mandatory for high energy resolution in spectroscopy experiments (for instance high resolution HAXPES). High stability and precision are guaranteed, since the system is mounted/supported on a huge granit block. The Post-monochromator is  identical to the main monochromator, a pseudo channel-cut type based on a double crystal scheme (DCM)  with two fixed Si(220) crystals moved together by a simple goniometer circle, in the (-n,+n) configuration. The first crystal, with dimension of ~120 mm x 80 mm x 60 mm (L x W x P), is fixed to the rotation table. Both crystalls are keep at room temperature. Such a configuration provides an intrisic energy resolution of 5.8x10-5. Hence, a beam bandwidth of 870 meV at a photon energy of 15 keV is  achieved. The photon bandwidth at 5 keV is further reduced to 300 meV.  High Miller indices Si crystal could be installed in order to improve even more the beamline energy resolution.