Welcome
BEaTriX (Beam Expander Testing X-ray facility) is a laboratory installed at INAF-OAB / Merate (Lecco, Italy). It is a unique pathfinder facility for X-ray tests at the energies of 4.51 and 1.49 keV, providing a collimated (2 to 4 arcsec HEW, depending on the energy), uniform, monochromatic, polarized (for the 4.51 keV), and wide (up to 170 x 60 mm²) beam.
The first line at 4.51 keV is operational since 2022. The second line at 1.49 keV is now under installation. Its commissioning is expected to be completed by early 2027.
BEaTriX was designed with the main objective to perform the acceptance tests (PSF and Effective area) of the hundreds of optical components of the NewAthena telescope, at their production rate (3MM/day). It also offers the possibility to perform measurements of the optics under tests at different thermal conditions in the range 20±20 °C.
The facility has been upgraded (BEaTriX+) in 2026 to extend its operational versatility from the fixed NewAthena focal length of 12 m to a tunable focal length in the range 1.4 ÷ 14 m, opening calibration capabilities to a much wider class of X-ray optics and detectors.

The calibration challenge for NewAthena and the BEaTriX solution
ATHENA (Advanced Telescope for High-ENergy Astrophysics) is the second Large mission selected by ESA within the Cosmic Vision Program, with launch foreseen in late 2030s. The optics consists of a large aperture X-ray mirror (diameter ∼ 2.5 m), Effective Area > 1.1 m² at 1 keV, and Half Energy Width (HEW) < 9 arcsec at 1 keV
The ambitious requirements of the ATHENA mission can only be met with a novel X-ray optics technology.
The X-ray optics of this future space observatory are based on the Silicon Pore Optics (SPO) technology, developed at Cosine (https://www.cosine.nl/, The Netherlands). To create the aperture of such a large X-ray telescope, a modular approach is foreseen, where each step of the process has to be followed by dedicated tests and calibration procedures.
In a typical SPO manufacturing process, 38 silicon plates with rectangular grooves are stacked, with dedicated robotic machines, to form a HPO (high performance optics). Two stacks are aligned along the rays and enable two reflections in sequence in each pore, reproducing the Wolter-I geometry, widely used in X-ray telescopes, where the primary and secondary sectors are aligned to form an X-ray Optical Unit (XOU). Two XOUs are combined in one SPO MM, which is therefore composed by four HPO stacks. The alignment of these stacks is performed using synchrotron radiation as the XPBF 2.0 beamline at the BESSY II facility in Berlin (Germany) and the MINERVA beamline at the ALBA facility in Barcelona (Spain). These facilities, together with the 132 m-long PANTER facility of MPE near Munich (Germany), can also characterize the MM in terms of PSF and Effective Area, but their testing throughput is too low to test the 600 MMs for acceptance before integrating them into the Mirror Assembly Module (MAM). The BEaTriX facility was conceived to overcome this limitation, by combining a compact (18 m x 9 m) design with fast vacuum pump-down, and a broad beam to fully illuminate the aperture of the MM under test.