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ION BEAM FIGURING OF CVD SILICON CARBIDE MIRRORS
Gailly, Patrick
2004In Warmbein, B (Ed.) Proceedings of the 5th International Conference on Space Optics (ICSO 2004)
 

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Keywords :
ion beam figuring; silicon carbide; space optics
Abstract :
[en] Optical and structural elements made of silicon carbide are increasingly found in space instruments. Chemical vapor deposited silicon carbide (CVD-SiC) is used as a reflective coating on SiC optics in reason of its good behavior under polishing. The advantage of applying ion beam figuring (IBF) to CVD-SiC over other surface figure-improving techniques is discussed herein. The results of an IBF sequence performed at the Centre Spatial de Liège on a 100 mm CVD-SiC mirror are reported. The process allowed to reduce the mirror surface errors from 243 nm to 13 nm rms . Beside the surface figure, roughness is another critical feature to consider in order to preserve the optical quality of CVD-SiC . Thus, experiments focusing on the evolution of roughness were performed in various ion beam etching conditions. The roughness of samples etched at different depths down to 3 m was determined with an optical profilometer. These measurements emphasize the importance of selecting the right combination of gas and beam energy to keep roughness at a low level. Kaufman-type ion sources are generally used to perform IBF but the performance of an end-Hall ion source in figuring CVD-SiC mirrors was also evaluated in this study. In order to do so, ion beam etching profiles obtained with the end-Hall source on CVD-SiC were measured and used as a basis for IBF simulations.
Disciplines :
Aerospace & aeronautics engineering
Author, co-author :
Gailly, Patrick ;  Université de Liège - ULiège > CSL (Centre Spatial de Liège)
Language :
English
Title :
ION BEAM FIGURING OF CVD SILICON CARBIDE MIRRORS
Publication date :
March 2004
Event name :
5ième Conférence Internationale d’Optique Spatiale (ICSO 2004)
Event organizer :
ESA
Event place :
Toulouse, France
Event date :
from 30-03-2004 to 2-4-2004
Audience :
International
Main work title :
Proceedings of the 5th International Conference on Space Optics (ICSO 2004)
Editor :
Warmbein, B
Publisher :
ESA Publications Division, Noordwijk, Netherlands
ISBN/EAN :
92-9092-865-4
Pages :
691-697
Name of the research project :
Usinage ionique
Funders :
DGTRE - Région wallonne. Direction générale des Technologies, de la Recherche et de l'Énergie [BE]
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