Design and performance of BOREAS, the beamline for resonant X-ray absorption and scattering experiments at the ALBA synchrotron light source

The optical design of the BOREAS beamline operating at the ALBA synchrotron radiation facility is described. BOREAS is dedicated to resonant X-ray absorption and scattering experiments using soft X-rays, in an unusually extended photon energy range from 80 to above 4000 eV, and with full polarization control. Its optical scheme includes a fixed-included-angle, variableline- spacing grating monochromator and a pair of refocusing mirrors, equipped with benders, in a Kirkpatrick-Baez arrangement. It is equipped with two endstations, one for X-ray magnetic circular dichroism and the other for resonant magnetic scattering. The commissioning results show that the expected beamline performance is achieved both in terms of energy resolution and of photon flux at the sample position.