The SiC primary mirror of the EUCLID telescope

Bougoin, M.; Lavenac, Jérôme; Gerbert-Gaillard, Alexandre; Pierot, Dominique

doi:10.1117/12.2296073

Cited by 3 publications

(1 citation statement)

References 3 publications

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“…Regarding mirrors made of SiC material, Reosc and Boostec recently reported the fabrication of a 1.54 by 0.49 m SiC primary mirror, achieving a final processing result of 9 nm RMS [12]. The SiC primary mirror of the EUCLID Telescope, with an aperture of 1.25 m, has a targeting precision of 9 nm [13]. The Herschel Telescope's primary mirror, previously the largest SiC material reflector, attained a surface form accuracy of 3 micrometers RMS [14].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of a 4 m SiC Aspheric Mirror Using an Optimized Strategy of Dividing an Error Map

Liu,

Li,

et al. 2024

Photonics

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This paper introduces an optimization strategy for fabricating large aspheric mirrors. We polished a large SiC aspheric mirror, 4 m in diameter, achieving a surface error of 1/40λ RMS. To the best of our knowledge, this is the first instance of such a result for a mirror of this material and size combination. Due to the various performance settings of different tools, achieving optimal polishing results with a single setting is challenging. We evaluated the performance of various tool settings and developed an optimization strategy, dividing error maps to enhance efficiency in large-aperture aspheric mirror fabrication. We established the relationship between tool size and its error control capability. The residual error map of the mirror was divided into two parts using Zernike polynomial expansion based on the frequency order of the error map. Here, we used the first 36 terms of the Zernike polynomial fit to define a low-order error map, and the residual error was used to define a high-order error map. Large tools were used to correct the low-order frequency error map, whereas small tools were used to correct the high-order frequency error map. Therefore, the original residual error map could be corrected with significantly high efficiency. By employing this strategy, we fabricated a 4 m SiC aspheric mirror in 18 months, achieving a final surface error better than 0.024λ RMS.

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Section: Introductionmentioning

confidence: 99%

Fabrication of a 4 m SiC Aspheric Mirror Using an Optimized Strategy of Dividing an Error Map

Liu,

Li,

et al. 2024

Photonics

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New candidate substrate materials for space mirror optics

Hsu

Chang

Huang

et al. 2019

Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems IV

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Additive manufacturing in ceramics: targeting lightweight mirror applications in the visible, ultraviolet and x-ray

Atkins,

Chahid,

Lister

et al. 2024

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI

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Additive manufacturing (AM; 3D printing), which builds a structure layer-by-layer, has clear benefits in the production of lightweight mirrors for astronomy, as it can create optimised lightweight structures and combine multiple components into one. AM aluminium mirrors have been reported that demonstrate a 44% reduction in mass from an equivalent solid and the consolidation of nine parts into one. However, there is a limit on the micro-roughness that can be achieved using AM aluminium at ∼5 nm RMS (root mean square; Sq), therefore, to target applications at shorter wavelengths alternative AM materials are required. New capabilities in AM ceramics, silicon carbide infiltrated with silicon (SiC + Si) and fused silica, offer the possibility to combine the design benefits of AM with a material suitable for visible, ultraviolet and X-ray applications. This paper will introduce the different printing methods and post-processing steps to convert AM ceramic samples into reflective mirrors. The samples are flat disks, 50 mm diameter and 5 mm in height, with three samples printed in SiC + Si and three printed in fused silica. Early results in polishing the SiC + Si material demonstrated that a micro-roughness of ∼2 nm Sq could be achieved. To build on this study, the 50 mm SiC + Si samples had three different AM finishing steps to explore the best approach for abrasive lapping and polishing, the reflective surfaces achieved demonstrated micro-roughness values varied between 2 nm and 5 nm Sq for the different AM finishing steps. To date, the printed fused silica material has heritage in lens applications; however, its suitability for mirror fabrication was to be determined. Abrasive lapping and polishing was used to process the fused silica to reflective surface and an average micro-roughness of <1 nm Sq achieved on the samples.

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The SiC primary mirror of the EUCLID telescope

Cited by 3 publications

References 3 publications

Fabrication of a 4 m SiC Aspheric Mirror Using an Optimized Strategy of Dividing an Error Map

Fabrication of a 4 m SiC Aspheric Mirror Using an Optimized Strategy of Dividing an Error Map

New candidate substrate materials for space mirror optics

Additive manufacturing in ceramics: targeting lightweight mirror applications in the visible, ultraviolet and x-ray

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