First light of BEaTriX, the new testing facility for the modular X-ray optics of the ATHENA mission

Abstract

Aims. The Beam Expander Testing X-ray facility (BEaTriX) is a unique X-ray apparatus now operated at the Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Brera (OAB), in Merate, Italy. It has been specifically designed to measure the point spread function (PSF) and the effective area (EA) of mirror modules (MM) of the Advanced Telescope for High-ENergy Astrophysics (ATHENA) X-ray telescope, based on the silicon pore optics (SPO) technology, for acceptance before integration into the mirror assembly. To this end, BEaTriX generates a broad, uniform, monochromatic, and collimated X-ray beam at 4.51 keV. The beam collimation is better than a few arcseconds to ensure reliable tests of the ATHENA MMs, in their focus, at a 12 m distance. Methods. In BEaTriX, a micro-focus X-ray source with titanium anode is placed in the focus of a paraboloidal mirror, which generates a parallel beam. A crystal monochromator selects the 4.51 keV line, which is expanded to the final size by a crystal asymmetrically cut with respect to the crystalline planes. An in-house built Hartmann plate was used to characterize the X-ray beam divergence, observing the deviation of X-ray beams from the nominal positions, on a 12 m-distant CCD camera. After characterization, the BEaTriX beam has the nominal dimensions of 60 mm × 170 mm, with a vertical divergence of 1.65 arcsec and an horizontal divergence varying between 2.7 and 3.45 arcsec, depending on the monochromator setting on either high collimation or high intensity. The flux per area unit varies from 10 to 50 photons/s/cm 2 from one configuration to another. Results. The BEaTriX beam performance was tested using an SPO MM, whose entrance pupil was fully illuminated by the expanded beam, and its focus was directly imaged onto the camera. The first light test returned a PSF and an EA in full agreement with the expectations. As of today, the 4.51 keV beamline of BEaTriX is operational and can characterize modular X-ray optics, measuring their PSF and EA with a typical exposure of 30 minutes. Another beamline at 1.49 keV is under development and will be integrated into the current equipment. We expect BEaTriX to be a crucial facility for the functional test of modular X-ray optics, such as the SPO MMs for ATHENA.

X-ray tests of the ATHENA mirror modules in BEaTriX: from design to reality

“…5 right). More details can be found in [26]. The intensity in this case was estimated as 50 ± 5 ph/s/cm 2 , slightly lower than the expected 60 ph/s/cm 2 .…”

“…A first optically representative SPO mirror module (MM-0042) was measured in BeaTriX [26]. It consists of two identical XOUs, made of bare Si/SiO2 plates, with an on-axis incidence angle of about 0.3 deg, sufficiently small to reflect at 4.5 keV without the coating.…”

The VERT-X calibration facility: development of the most critical parts

“…13 To quantify the tolerable roughness and figure errors at different spatial scales, we started from the final polishing state of the BEaTriX mirror PSD as reference. 5 We assumed a similar polishing level at high frequencies, but a much smoother behaviour at midand low frequencies. This would correspond to a better figure error.…”

“…The mirror will be built using the ESA Silicon Pore Optics (SPO) technology which provides large effective area with excellent angular resolution. 4 While test and integration procedures of the single mirror modules (MM) have been well established [5][6][7] , the verification and calibration of the entire MA are particularly challenging. In this paper we describe the design and the state of the development phase of the VERTical X-ray raster-scan facility (VERT-X) which has been designed to accomplish this task.…”

The BEaTriX x-ray facility at work: activities and future development

“…Several facilities are being considered for the integration and calibration of the ATHENA telescope: the synchrotron facilities XPBF 2.0 at the BESSY II facility in Berlin (Germany) [4] and MINERVA at the ALBA facility near Barcelona (Spain) [5]; conventional-source existing X-ray facilities such as PANTER near Munich (Germany) [6] and the NASA XRCF in Huntsville (Alabama, USA) [7]; the new X-ray facility BEaTriX near Milano (Italy) [8] and the UV [9] and X-ray facilities VERT-X [10] under development at MediaLario S.r.l also near Milan (Italy). Among these facilities, BEaTriX, the Beam Expander testing X-ray facility, will play the role of testing each MM for acceptance before integration into the Mirror Module Assembly (MAM), with a fast and precise X-ray screening.…”