The expanded, parallel, and monochromatic x-ray beam of BEaTriX: alignment and characterization

BEaTriX (Beam Expander Testing X-ray) is the compact (18m x 9m) X-ray facility being implemented at INAF for the acceptance tests of the ATHENA Silicon Pore Optics Mirror Modules (MM) working at the two energies of 1.49 and 4.51 keV. It adopts an innovative design based on a collimating mirror and Bragg crystals in proper configuration to provide a large and parallel beam. The 4.51 keV line provides a parallel beam with 170 mm x 60 mm size and it has been calibrated and characterized in term of intensity, uniformity, divergence and stability. This paper traces the path taken for the bestachieved alignment of the different optical components, from the preliminary phases to the final step where the function of merit was obtained directly from the parallel beam itself. The alignment method used a combination of optical and mechanical tools: laser tracker, micro-alignment telescope (MAT), 3D measuring machine (CMM) and self-designed holed plates. The final characterization of the X-ray beam is presented.