Design and advancement status of the Beam Expander Testing X-ray facility (BEaTriX)

Abstract

The BEaTriX (Beam Expander Testing X-ray facility) project is an X-ray apparatus under construction at INAF/OAB to generate a broad (200´60 mm 2 ), uniform and low-divergent X-ray beam within a small lab (6´15 m 2 ). BEaTriX will consist of an X-ray source in the focus a grazing incidence paraboloidal mirror to obtain a parallel beam, followed by a crystal monochromation system and by an asymmetrically-cut diffracting crystal to perform the beam expansion to the desired size. Once completed, BEaTriX will be used to directly perform the quality control of focusing modules of large X-ray optics such as those for the ATHENA X-ray observatory, based on either Silicon Pore Optics (baseline) or Slumped Glass Optics (alternative), and will thereby enable a direct quality control of angular resolution and effective area on a number of mirror modules in a short time, in full X-ray illumination and without being affected by the finite distance of the X-ray source. However, since the individual mirror modules for ATHENA will have an optical quality of 3-4 arcsec HEW or better, BEaTriX is required to produce a broad beam with divergence below 1-2 arcsec, and sufficient flux to quickly characterize the PSF of the module without being significantly affected by statistical uncertainties. Therefore, the optical components of BEaTriX have to be selected and/or manufactured with excellent optical properties in order to guarantee the final performance of the system. In this paper we report the final design of the facility and a detailed performance simulation.

Manufacturing and testing of the X-ray collimating mirror for the BEaTriX facility

“…It is worth to mention that in the first version of the optical design [10], we had estimated that a maximum tolerable HEW of 3 arcsec was to be reached through the manufacturing process. Afterwards, with the purpose to counterbalance some adjustments of the overall error budget, we turned the manufacturing tolerances stricter, so as to leave the target of divergence tolerance of the BEaTriX beam within 1.5 arcsec.…”

“…The BEaTriX (Beam Expander Testing X-ray) facility is a new type of beamline for mirror acceptance testing and calibration, under realization at INAF-Brera Astronomical Observatory [8], and funded by ESA, AHEAD, ASI and INAF. BEaTriX was designed to provide a broad (170 mm × 60 mm) and uniform X-ray beam with 1.5 arcsec HEW residual divergence, at either 1.49 keV or 4.51 keV energy [9,10]. The BEaTriX facility aims at performing the acceptance test (Point Spread Function, PSF, and effective area) of the ATHENA SPO MM's at the fast rate of 3MM/day.…”

Performance simulations for the ground-based, expanded-beam x-ray source BEaTriX

“…These motivations urged us to design and develop the BEaTriX (Beam Expander Testing X-ray facility) system [7] with the specific purpose of performing the functional tests of SPO modules prior to their integration into the mirror assembly of ATHENA. Following a number of updates over years, [8][9] [10] BEaTriX has been finalized (Figure 1) in its design [11] and, owing to a number of grants (ESA, AHEAD, ASI, INAF), it is now in advanced status of completion at INAF-Brera, Merate. [12] BEaTriX will generate a 17 cm ´ 6 cm parallel (» 2 arcsec) beam at either 1.49 keV or 4.51 keV.…”

BEaTriX (Beam Expander Testing X-ray facility) for testing ATHENA's SPO modules: advancement status

“…The 60 mm height will fully cover the 54 mm entrance pupil of the MM, and the 4 mm width will be expanded by the asymmetric cut crystal. We have already procured two mirrors [16] from Zeiss in fused quartz HOQ 310, one in a preliminary lapped status (shape: PV < 5 µm, roughness: rms < 0.5 µm), the second one just grinded (shape: PV < 15 µm, roughness: rms < 2 µm). The polishing and final figuring will be done in house, aiming at achieving a maximum tolerable HEW of 0.5 arcsec.…”

“…However, the large volume to be evacuated makes it impossible to perform the functional tests at the MMs production rate of 3 MM/day [12]. To overcome these limitations, we started in 2012 to design a facility aimed at generating a broad (170 x 60 mm 2 ), uniform and low-divergent (1.5 arcsec HEW) X-ray beam within a small lab (∼ 9  18 m 2 ) [13,14,15,16]. This will be possible thanks to an X-ray microfocus source (30 m focal spot FWHM) in the focus of a paraboloidal mirror, a monochromation system with symmetrically cut crystals and an asymmetrically-cut crystal for beam expansion.…”