BEaTriX x-ray calibration facility: status of the project

BEaTriX, which stands for Beam Expander Testing X-ray facility, is operated by the INAF-Brera Astronomical Observatory at its premises in Merate, Italy. It serves as ground support equipment for the verification phase of NewAthena, the upcoming L-class X-ray space observatory confirmed by ESA in November 2023 as a flagship mission. BEaTriX will conduct acceptance tests of the Silicon Pore Optics Mirror Modules (SPO MMs), which, when properly assembled, will form the X-ray grazing-incidence optics with a diameter of over 2 meters.

The facility is compact (just 8 m x 14 m). Thanks to an innovative optical design based on an asymmetrical-cut crystal associated with a paraboloidal grazing incidence mirror, it can produce an expanded X-ray beam (170 mm x 60 mm) with low divergence (about 2 arcsec measured for the 4.51 keV beamline) at the two monochromatic energies of 4.51 keV and 1.49 keV. This allows us to calibrate each SPO MM's Effective Area and Point Spread Function precisely.

The first beamline, at 4.51 keV photon energy, is already operational, as the commissioning was completed in Q1-2023. The second beamline, at 1.49 keV energy, is being developed. It presents some more challenging aspects from both the design and implementation points of view. The monochromator stage is based on two Quartz (100); two ADP asymmetric-cut crystals (101) will provide the horizontal expansion of the beam. The X-ray source needs to be very brilliant (5 x 10¹¹ - 10¹² ph/s/sterad) due to the large fraction of photons rejected by the crystals.

This paper describes the ongoing activities. It will present the results of the 4.51 keV X-ray beamline optimization and the tests performed on a coated MM. It will also describe the progress in implementing the 1.49 keV components and discuss the comparison with other X-ray testing facilities.