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Proceedings Paper • Open Access

Design and development by direct polishing of the WFXT thin polynomial mirror shells
Author(s): L. Proserpio; S. Campana; O. Citterio; M. Civitani; H. Combrinck; P. Conconi; V. Cotroneo; R. Freeman; E. Mattini; P. Langstrof; R. Morton; G. Motta; O. Oberle; G. Pareschi; G. Parodi; C. Pels; C. Schenk; R. Stock; G. Tagliaferri

Paper Abstract

The Wide Field X-ray Telescope (WFXT) is a medium class mission proposed to address key questions about cosmic origins and physics of the cosmos through an unprecedented survey of the sky in the soft X-ray band (0.2-6 keV) [1], [2]. In order to get the desired angular resolution of 10 arcsec (5 arcsec goal) on the entire 1 degrees Field Of View (FOV), the design of the optical system is based on nested grazing-incidence polynomial profiles mirrors, and assumes a focal plane curvature and plate scale corrections among the shells. This design guarantees an increased angular resolution also at large off-axis positions with respect to the usually adopted Wolter I configuration. In order to meet the requirements in terms of mass and effective area (less than 1200 kg, 6000 cm2 @ 1 keV), the nested shells are thin and made of quartz glass. The telescope assembly is composed by three identical modules of 78 nested shells each, with diameter up to 1.1 m, length in the range of 200-440 mm and thickness of less than 2.2 mm. At this regard, a deterministic direct polishing method is under investigation to manufacture the WFXT thin grazing-incidence mirrors made of quartz. The direct polishing method has already been used for past missions (as Einstein, Rosat, Chandra) but based on much thicker shells (10 mm ore more). The technological challenge for WFXT is to apply the same approach but for 510 times thinner shells. The proposed approach is based on two main steps: first, quartz glass tubes available on the market are ground to conical profiles; second the pre-shaped shells are polished to the required polynomial profiles using a CNC polishing machine. In this paper, preliminary results on the direct grinding and polishing of prototypes shells made by quartz glass with low thickness, representative of the WFXT optical design, are presented.

Paper Details

Date Published: 20 November 2017
PDF: 7 pages
Proc. SPIE 10565, International Conference on Space Optics — ICSO 2010, 105652N (20 November 2017); doi: 10.1117/12.2309176
Show Author Affiliations
L. Proserpio, INAF-OAB Astronomical Observatory of Brera (Italy)
Univ. dell’Insubria (Italy)
S. Campana, INAF-OAB Astronomical Observatory of Brera (Italy)
O. Citterio, INAF-OAB Astronomical Observatory of Brera (Italy)
M. Civitani, INAF-OAB Astronomical Observatory of Brera (Italy)
Univ. dell’Insubria (Italy)
H. Combrinck, ZEEKO Ltd. (United Kingdom)
P. Conconi, INAF-OAB Astronomical Observatory of Brera (Italy)
V. Cotroneo, INAF-OAB Astronomical Observatory of Brera (Italy)
R. Freeman, ZEEKO Ltd. (United Kingdom)
E. Mattini, INAF-IASF (Italy)
P. Langstrof, Heraeus Quarzglas GmbH & Co. (Germany)
R. Morton, ZEEKO Ltd. (United Kingdom)
G. Motta, INAF-OAB Astronomical Observatory of Brera (Italy)
O. Oberle, Heraeus Quarzglas GmbH & Co. (Germany)
G. Pareschi, INAF-OAB Astronomical Observatory of Brera (Italy)
G. Parodi, BCV Progetti S.r.l. (Italy)
C. Pels, Heraeus Quarzglas GmbH & Co. (Germany)
C. Schenk, Heraeus Quarzglas GmbH & Co. (Germany)
R. Stock, Heraeus Quarzglas GmbH & Co. (Germany)
G. Tagliaferri, INAF-OAB Astronomical Observatory of Brera (Italy)


Published in SPIE Proceedings Vol. 10565:
International Conference on Space Optics — ICSO 2010
Errico Armandillo; Bruno Cugny; Nikos Karafolas, Editor(s)

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