{"id":612,"date":"2020-05-05T19:17:36","date_gmt":"2020-05-05T17:17:36","guid":{"rendered":"http:\/\/ahead.astropa.inaf.it\/?page_id=612"},"modified":"2022-07-02T11:03:54","modified_gmt":"2022-07-02T09:03:54","slug":"beatrixinaf-oab-ahead-2020","status":"publish","type":"page","link":"http:\/\/ahead.astropa.inaf.it\/index.php\/infrastructures-ahead-2020\/beatrixinaf-oab-ahead-2020\/","title":{"rendered":"BeaTriX@INAF\/OAB"},"content":{"rendered":"

BEaTriX, Merate, Lecco, Italy<\/p>\n

BEaTriX (Beam Expander Testing X-ray facility) is a laboratory present at <\/span>INAF-Osservatorio Astronomico Brera in its premises of Merate. It is a unique pathfinder facility characterized by a <\/span>broad (170 <\/span>\u00d7<\/span> 60 mm<\/span>2<\/span><\/sup>), uniform and parallel X-ray beam (divergence <\/span>\u223c<\/span> 2 arcsec HEW) <\/span>at the energy of 4.51 keV<\/span>, highly monochromatic (FWHM = 30-50 eV). A second beam line is going to be added at the energy of 1.49 keV.<\/span><\/p>\n

The system is very compact (9 \u00d7 18 m2), positioned on a stable foundation (gray in Figure 1) designed and built to isolate the beam line from vibrations. The facility works at a vacuum level of 10-3 mbar, easily evacuated in a short time. The vacuum pumping system is entirely based on magnetic turbo pumps, and oil-free pre-vacuum and backing pumps, to avoid optics contamination. The small size of the facility also contributes to reduce the evacuation time with respect to bigger X-ray facilities. Moreover, the modular compartments design, guaranties that the vacuum can be broken independently in the different sectors, enabling to replace the optics under test in a short time: simulations have shown that the experimental chamber (F in Figure 1) can be evacuated in about 30min. The experimental chamber opens into an ISO5 clean tent, to allow samples to be loaded and unloaded in a clean environment. Venting is performed in all the system with dried dehumidified air. A thermal box is also present therein (Figure 3), to radiatively heat the X-ray optics under test, at temperature ranging from -10 to +50 \u00b0C; some gradients can also be applied. A software based on the NI Labview platform allows all the BEaTriX operations.<\/p>\n

BEaTriX prime goal is to prove that it is possible to perform the acceptance tests (PSF and Aeff) of the ATHENA Silicon Pore Optics (SPO) Mirror Modules (MM) at the production rate of 3 MM\/day. Nevertheless, the facility can also be used to test other X-ray optics: the limit in size is 365 \u00d7 365 \u00d7 600 mm, given by the thermal box structure; the limit in weight is 5kg, interfacing structure included (for the SPO case, the interface is 2.6 kg), given by the hexapod maximum load (see later).<\/p>\n\n\n\n
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Figure 1. Left: the mechanical design of the facility in the laboratory. Right: the optical design<\/em><\/p>\n

The source is a micro-focused X-ray emitter (A) with focal spot size of 35 \u00b5m <\/span>\u00d7 35 \u00b5m<\/span>. The 4.51 keV line is emitted by a Ti anode. The source is in UHV environment, separated by a 100 <\/span>\u00b5<\/span>m thick Be window. It can be aligned with mechanical adjustments in air. <\/span>The flux of the Ti source was measured to be 6 \u00d7 10<\/span>11<\/span><\/sup> ph\/sec\/sterad. <\/span><\/p>\n

The beam is propagated through the short arm (B) onto the Optical Chamber (rectangular tank in Figure 1), where the optical components for the beam moderation are present. The parabolic mirror (C) is used for beam collimation; diffraction on 4 symmetrically cut crystals (D) have the function to monochromate the beam, while the asymmetrically cut crystal (E) expand the beam and reflect it at about 90 deg. The emerging beam has then a size of 170 mm in the horizontal direction and 60 mm in the vertical direction. <\/span><\/p>\n

An Si-PIN detector (Amptek, X123 with 25mm<\/span>2<\/span><\/sup> area \/ 500 <\/span>\u00b5<\/span>m thickness \/ 25 <\/span>\u00b5<\/span>m Be window) in present in front of the last crystal to monitor the flux and the alignment stability (Fig. 2 right).<\/span><\/p>\n

The monochromation system (D) can optimize either the horizontal divergence or the flux. Two different configurations can be adopted one in which the <\/span>vertical divergence only is optimized (max flux), and one in which both vertical and horizontal divergences play a key role and need to be optimized. This is obtained with a rotation of the second CCC (yellow motor in Fig. 2 left). The <\/span>performance of BEaTriX in the t<\/span>wo different configurations were simulated as follows, with <\/span>t<\/span>he experimental results well in line with the<\/span> expectations<\/span>:<\/span><\/p>\n