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20 September 2007 Carbon overcoatings for soft x-ray reflectivity enhancement
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In X-ray astronomical telescopes, the focalization of the radiation is achieved by means of grazing incidence Wolter I (parabola + hyperbola) optics in total reflection regime. In general, high density materials (e.g. Au, Pt, Ir, W) are used as reflecting coatings, in order to increase as much as possible the cut-off angles and energies for total reflection. However these materials present an important reduction of the reflectivity between 0.2 and 5 keV, due to the photoabsorption, and this phenomenon is particularly enhanced in correspondence of the M absorption edges (between 2 and 3.5 keV). In general, this determines a strong decrease of the telescope effective area. To overcome the problem we suggested in previous works the coating of the mirror surface by a low-density material such as carbon. Mirror samples with different coatings made by high density materials: Au, Ir, Pt, and W with a carbon overcoating were manufactured and reflectivity data in the soft X-ray band (100-2000 eV), performed both at the XACT facility in Palermo (Italy) and at BSRF synchrotron in Beijing (China), are showed. In this paper we present some of the first results concerning the measurements carried out at the photon energies of 200 eV (i.e. below the carbon K absorption edge) and 1280 eV (i.e. the region just below the heavy material M absorption edge).
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
V. Cotroneo, D. Spiga, M. Barbera, R. Bruni, K. Chen, C. Marcelli, G. Pareschi, S. Romaine, Y. D. Zhao, L. Zheng, and Z. Y. Wu "Carbon overcoatings for soft x-ray reflectivity enhancement", Proc. SPIE 6688, Optics for EUV, X-Ray, and Gamma-Ray Astronomy III, 66880U (20 September 2007);


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