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Proceedings Paper

Soft (0.1 - 10 keV) and hard (>10 keV) x-ray multilayer mirrors for the XEUS astronomical mission
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Paper Abstract

The XEUS X-ray mission is currently being studied by ESA. It will be based on a huge (10 m of aperture diameter) grazing-incidence mirror unit with 50 m focal length, realized by a two separate satellites system, one dedicated to host the mirror module and the other for the detector. The current baseline foresees a single reflecting layer of Gold for the full set of 562 mirror shells of the XEUS telescope (296 shells of the first stage of the project, named XEUS I, with a maximum diameter of ~ 4 m, plus 266 shells of the second phase, named XEUS II, that will be activated after about 5 years). However, the use of multilayer mirrors instead of Au for XEUS-I (i.e. where the incidence angles of the mirror shells series are smaller) is an interesting alternative, already recently proposed by other authors, to extend the XEUS operative range in the hard X-ray region (up to 80 keV). In this work we applied a global optimization approach based on an “Iteraded Simplex Procedure” to optimize the sequence of bi-layers of depth-graded multilayer films, in order to get the best achievable response by the XEUS-I mirrors in the hard X-ray region. In addition, we theoretically evaluated the performances of the XEUS-II mirrors after the introduction of constant d-spacing multilayers with a thin (100 Å) overcoating of Carbon instead of Au. In this case the main advantage is given by an enhancement of the telescope effective area in the soft X-ray region (0.1-10 keV). The role of the Carbon top layer is to reduce the photoelectric absorption effect in the total-reflection regime, with an important improvement of the reflection efficiency with respect the usual mirrors based on high density materials like, e.g., Au, W, Ir and Pt.

Paper Details

Date Published: 29 January 2004
PDF: 12 pages
Proc. SPIE 5168, Optics for EUV, X-Ray, and Gamma-Ray Astronomy, (29 January 2004); doi: 10.1117/12.509470
Show Author Affiliations
Giovanni Pareschi, Osservatorio Astronomico di Brera (Italy)
Vincenzo Cotroneo, Osservatorio Astronomico di Brera (Italy)

Published in SPIE Proceedings Vol. 5168:
Optics for EUV, X-Ray, and Gamma-Ray Astronomy
Oberto Citterio; Stephen L. O'Dell, Editor(s)

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