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All variants are found to produce an effective area at 1 keV of around 1.24 m2, well beyond the scientific requirement of 1.1 m2. All variants are shown, when assuming a perfectly shaped and aligned mirror that is perfectly smooth, to have an intrinsic PSF that is an order of magnitude below the scientific requirement. Comparing these intrinsic PSF’s, the secondary polynomial performs best at energies below 7.5 keV. Above this energy, the equal polynomial variant performs best. A phenomenon is also shown where shifting destructive interference causes periodic peaks and troughs in the PSF HEW of individual rings of the optics, though this effect is not seen in the PSF HEW of the entire optics.
XRR scans provide detailed insights into thin film properties, however, the dependence on accurate a priori knowledge necessitates a robust model for solving the inverse problem. Addressing this limitation, XPS proves invaluable in revealing the chemical composition of thin films, improving the accuracy of the XRR model. Combined characterization through OM and XRR is very useful to find visual insights into surface contamination-induced changes when mirrors are stored for long periods in a clean room environment, as might be the case for some astronomical missions. The synergy among these techniques is pivotal for evaluating coating quality for high-energy astronomical telescopes, with a specific focus on NewAthena and upcoming missions. This research not only advances methodologies in this field but also highlights the collaborative power of XRR, XPS, and OM in providing a comprehensive understanding of thin film coatings, emphasizing the importance of pre-coating mirror quality and mitigating contamination effects throughout the optics production process to ensure optimal performance.
A key aspect of the thin film coating development for the NewATHENA X–ray optics, is to determine the adhesion efficiency and the residual stress limitation of the coatings on silicon substrates. To do so, we magnetron sputtered different layer thicknesses of chromium layers underneath iridium/carbon bilayer and linear graded multilayer coatings. The samples were characterized using X–ray Reflectometry (XRR) to derive the thickness and micro–roughness. The residual stress was assessed by profilometry using a Dektak 150 stylus profilometer. The curvature of the samples before and after coating, along with the total film thickness derived from XRR, was used to evaluate the residual stress.
ESA’s Athena mission will use silicon pore optics, in which the optics assembly consists of pairs of mirror plates stacked into mirror modules. This paper presents a study of the angular resolution of Athena, using several candidate variants of mirror curvature and wedging. Results were achieved by ray-tracing these variants of Athena’s optics with the ray-tracing software SPORT.
The study shows that all polynomial variants yield a PSF below 1” on-axis, at all energies between 0.1 and 12 keV. The secondary-only polynomial variants perform best, for both on- and off-axis point sources. Of these variants, the wedging 0/2 variant is shown to generally yield superior angular resolution at higher energies, the -1/1 variant at lower energies.
A ray-tracing analysis using the Crab Nebula as an observation target was also performed. A 2D Fourier analysis was applied to the resulting focal plane responses to determine their angular resolution. This analysis indicates the angular resolution of all polynomial variants to be below 1”, at all but the highest energies. It also shows, though to a lesser extent, that the secondary-only polynomial variants perform best in most circumstances. Nevertheless, this second analysis requires further investigation for a more conclusive outcome.
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