X-ray beam diagnostics at the BEaTriX facility

Abstract

In the framework of NewATHENA x-ray space telescope, BEaTriX (Beam Expander Testing X-ray) is the novel ground support equipment designed to perform the Silicon Pore Optics Mirror Modules (SPO MMs) acceptance tests in terms of point spread function and effective area. As of today, the facility built at INAF-Brera Astronomical Observatory in Merate has a first operative beamline at the energy of 4.51 keV. The 170 mm × 60 mm x-ray beam, created by an innovative optical setup, is able to fully illuminate a complete SPO MM in a single exposure with a parallel and monochromatic X-ray beam. The optical chain includes a paraboloidal mirror, with an x-ray source in its focus, that collimates and expands vertically the beam, a monochromatic stage composed by a set of symmetrically cut silicon crystals (the Channel Cut Crystals), and an asymmetrically cut silicon crystal (the Beam Expander) that expands the beam horizontally. To achieve the expected x-ray beam quality in terms of collimation, number of photons and uniformity, the BEaTriX optical components need to be properly aligned. The result of several measurements confirms the theoretical predictions on the behavior of each optical element. This paper describes the work performed to quantify the x-ray beam properties with the adoption of different types of detectors, and alignment sequence, providing the outlook for further optimizations.