Speaker
Description
BEaTriX, the Beam Expander Testing X-ray facility, is the X-ray calibration facility at INAF-Brera Astronomical Observatory able to create a wide, monochromatic, and collimated X-ray beam in a compact laboratory (9 x 18 m2). This is possible thanks to an innovative optical design that includes a grazing-incidence paraboloidal mirror, in whose focus the micro-focus source is placed, for collimation and vertical expansion, a monochromatization stage and an expansion stage for the horizontal expansion, both exploiting the diffraction from crystals.
BEaTriX was built specifically for the New Athena mission, the future ESA X-ray space observatory to be launched in 2037. It will be the reference calibration facility for testing the about 500 optical modules that will compose the NewAthena telescope. A project, named BEaTriX+, has started in 2024 to enable X-ray measurements for other missions, giving the possibility to vary the focal length from 1.5 m to 12 m.
The facility hosts two beamlines at 4.51 keV and 1.49 keV energies; the first one is already operative, and the second one will be operational in the Q1-2026. The optical path and component slightly change based on the energy. For the 4.51 keV beamline, a source with Titanium anode is used, two Channel Cut Crystals in Silicon (220) are used as monochromator, and an asymmetrically-cut Si (220) crystal for the expansion stage, obtaining a 17 cm x 6 cm beam (divergence < 2 arcsec). The 1.49 keV beamline instead exploits a source with Aluminum anode, two asymmetrically-cut Quartz (100) crystals for the monochromation stage, and two asymmetrically-cut ADP (101) crystals for the expansion.
The crystal expander constitutes the key element of this design. It is a highly dispersive component, and as consequence, it requires a strong monochromatization, which, in turn, requires a very brilliant source. In the 1.49 keV beamline, all these aspects are more challenging than in the other beamline from several points of view especially, the crystals as the well-known Silicon crystal could not be selected due to its d-spacing not large enough.
The ADP and Quartz crystals characterization highlighted curvatures of the crystalline planes about one order of magnitude smaller of the 22 km requirement, a requirement extremely challenging for any application. The impact of this curvature on the final BEaTriX beam collimation was investigated through simulations performed with both the reference IDL code and the OASYS-SHADOW4. The results of these simulations report an impact on the beam collimation, that will be addressed with a dedicated actuation system for bending the ADP crystals.
