Forty years of ZERODUR mirror substrates for astronomy: review and outlook

Döhring, Thorsten; Jedamzik, Ralf; Thomas, Armin; Hartmann, Péter

doi:10.1117/12.788936

Cited by 20 publications

(16 citation statements)

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“…Only the mirror faces were highly precise as result of long-lasting and painstaking polishing processes. 2 Applications outside astronomy emerged soon after the production of the first ZERODUR mirrors. Its combination of very low thermal expansion and very low Helium permeability made it a perfect substrate for ring laser gyroscopes.…”

Section: From Simple To Sophisticated Shapesmentioning

confidence: 99%

“…Only the combination of all these aspects and the capability to achieve such quality with high reproducibility enabled the material to find very successful applications in astronomical telescopes and in high-tech industry. 2,3 Since 2005, roughly speaking, further progress led to astonishing improvements in several aspects of high importance for leading edge applications.…”

Section: Introductionmentioning

confidence: 99%

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Glass ceramic ZERODUR®: Even closer to zero thermal expansion: a review, part 2

Hartmann

Jedamzik

Carré

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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Observational astronomy has sought better telescopes with higher resolution from its beginning. This needs ever-larger mirrors with stable, high-precision surfaces. The extremely low-expansion glass ceramic ZERODUR ® has enabled such mirrors for more than 50 years with significant improvements in size and quality since then. We provide a survey of the progress achieved in the last 15 years. Equally important as the thermal expansion coefficient CTE is its homogeneity. The CTE variation in 4-m mirror blanks lies below 5 ppb∕K in radial and axial directions on large and short scales. Improved measurement capabilities allow reduced bias, which in the past made variations look greater than they were. Isotropy and uniformity of ZERODUR are outstanding. A method for lifetime calculation increases reliability considerably with respect to mechanical loads. The production and metrology capability and capacity are greatly extended. Surface figure and texture of large blanks allow starting directly with polishing. Filigree structures with up to 90% weight reduction are well-suited for space mirrors. The progress with low thermal expansion and its measurement, the insensitivity of ZERODUR against ionizing radiation in space, and outstanding application examples are presented in the first part of our review. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: From Simple To Sophisticated Shapesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Glass ceramic ZERODUR®: Even closer to zero thermal expansion: a review, part 2

Hartmann

Jedamzik

Carré

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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“…1,9 Due to the initiative of the astronomer Hans Elsässer from the Max-Planck-Institute for Astronomy in Heidelberg, Germany, SCHOTT developed ZERODUR in 1968 for mirror substrates to meet the requirements of the lowest possible and homogenous CTE together with a high Young's modulus. 1,2,10 They should be easy to be inspected and polished and coated with aluminum or silver many times.…”

Section: Discovery Of Low Thermal Expansion Glass Ceramicmentioning

confidence: 99%

“…Only the combination of all of these aspects and the capability of achieving such quality with high reproducibility enabled the material to find very successful applications in earth-bound and space-borne astronomical telescopes and in the high-tech industry. 2,3 In the last decade, further progress has led to astonishing improvements in several aspects that are of high importance for leading-edge application.…”

Section: Introductionmentioning

confidence: 99%

Glass ceramic ZERODUR®: Even closer to zero thermal expansion: a review, part 1

Hartmann

Jedamzik

Carré

et al. 2021

J. Astron. Telesc. Instrum. Syst.

Self Cite

View full text Add to dashboard Cite

Observational astronomy has striven for better telescopes with higher resolutions from its start. This needs ever-larger mirrors with stable high precision surfaces. The extremely low expansion glass ceramic ZERODUR ® enables such mirrors with more than 50 years of significant improvements in size and quality since its development. We provide a survey of the progress achieved in the last 15 years. The narrowest coefficient of thermal expansion (CTE) tolerance is now AE7 ppb∕K. It is possible to adapt the material for lowest expansion to temperature-time courses given for special environments. At cryo temperatures, expansion is low and adaptable. Improved measurement capabilities allow for absolute CTE uncertainty of 3 ppb∕K and reproducibility of 1 ppb∕K (2σ). The influence of ionizing radiation on the surface figure integrity is subject to new investigations. Improved measurement capabilities increase the reliability of structure designs. Some outstanding examples are given for applications of ZERODUR in astronomy and in the very important high technology industry. The progress of thermal expansion homogeneity, the mechanical strength of ZERODUR, production capabilities in melting, precision machining, light-weighting, and dimensional metrology is presented in the second part of the paper. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…The mirror is in Zerodur, this material has been chosen for its low Coefficient of Thermal Expansion, ideal for a space use [16]. The system dimensions have been optimized in order to meet the correction specifications but also to ensure the system mechanical strength.…”

Section: B Optimization With Finite Element Analysismentioning

confidence: 99%